Long-range and short-range dihadron angular correlations in central PbPb collisions at sqrt {{{s_{text{NN}}}}} = 2.76 TeV

October 18, 2017 | Penulis: Malik Jai | Kategori: Javascript
Share Embed


Deskripsi

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

CERN-PH-EP/2011-056 2011/05/12

CMS-HIN-11-001

arXiv:submit/0246512 [nucl-ex] 12 May 2011

Long-range and short-range dihadron angular correlations √ in central PbPb collisions at s NN = 2.76 TeV The CMS Collaboration∗

Abstract First measurements of dihadron correlations for charged particles are presented for central PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV over a broad range in relative pseudorapidity (∆η) and the full range of relative azimuthal angle (∆φ). The data were collected with the CMS detector, at the LHC. A broadening of the away-side (∆φ ≈ π) azimuthal correlation is observed at all ∆η, as compared to the measurements in pp collisions. Furthermore, long-range dihadron correlations in ∆η are observed for particles with similar φ values. This phenomenon, also known as the “ridge”, persists up to at least |∆η | = 4. For particles with transverse momenta (pT ) of 2–4 GeV/c, the ridge is found to be most prominent when these particles are correlated with particles of pT = 2–6 GeV/c, and to be much reduced when paired with particles of pT = 10–12 GeV/c.

Submitted to the Journal of High Energy Physics

∗ See

Appendix A for the list of collaboration members

1

1

Introduction

Measurements of dihadron azimuthal correlations [1–7] have provided a powerful tool to study the properties of the strongly interacting medium created in ultrarelativistic nuclear collisions [8– 11]. An early indication of strong jet-medium interactions at RHIC was the absence of hightransverse-momentum (high-pT ) back-to-back particle pairs in dihadron correlation measurements [1] and the corresponding enhancement of low-pT hadrons recoiling from a high-pT leading, or “trigger”, particle [3]. The recent observations of the suppression of high-pT charged hadrons [12] and of asymmetric energies of reconstructed jets [13, 14] in PbPb collisions at the Large Hadron Collider (LHC) provide further evidence of jet quenching, suggesting a large energy loss for partons traversing the produced medium. At RHIC, extending dihadron azimuthal correlation measurements to larger relative pseudorapidities resulted in the discovery of a ridge-shaped correlation in central AuAu collisions between particles with small relative azimuthal angles (|∆φ| ≈ 0), out to very large relative pseudorapidity (|∆η |) [2, 6]. Although the “ridge” has been qualitatively described by several different models [15–26], its origin is still not well understood. Some models attribute the ridge to jet-medium interactions, while others attribute it to the medium itself. The ridge has been observed for particles with transverse momenta from several hundred MeV/c to a few GeV/c. However, the character of the ridge for even higher-pT particles, as well as its dependence on collision energy, is still poorly understood from the RHIC results [2]. Recently, a striking ridge structure has also been observed in very high multiplicity proton-proton (pp) collisions at a center-of-mass energy of 7 TeV at the LHC by the Compact Muon Solenoid (CMS) Collaboration [27], posing new challenges to the understanding of these long-range correlations. This paper presents the first measurement of dihadron correlations for charged particles produced in the most central (0–5% centrality) PbPb collisions at a nucleon-nucleon center-of-mass √ energy ( s NN ) of 2.76 TeV over a large phase space. The results are presented in terms of the associated hadron yields as a function of pseudorapidity and azimuthal angle relative to trigger particles in different transverse momentum intervals. Traditionally, trigger particles have been utilized to represent the direction of the leading hadron in a jet, and were required to have a higher momentum than all the other associated particles in the jet [2, 6]. However, as shown in Ref. [27], important information can also be obtained by studying the correlation of hadron pairs from the same pT interval, which is particularly useful when addressing the properties of the medium itself. The current analysis employs both approaches. This measurement provides a unique examination of the ridge in the most central PbPb collisions at the highest energies reached so far in the laboratory over a wide range in transverse momentum (2–12 GeV/c) and up to large relative pseudorapidity (|∆η | ≈ 4), imposing further quantitative constraints on the possible origin of the ridge. Details of event readout and analysis for extracting the correlation functions are described in Section 2, the physics results found using the correlations are described in Section 3, and a summary is given in Section 4.

2

Data and Analysis

√ The analysis reported in this paper is based on PbPb collisions at s NN = 2.76 TeV collected during the LHC heavy-ion run in November and December 2010 with the CMS detector. The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter. Within the field volume are the inner tracker, the crystal electromagnetic calorimeter, and the brass/scintillator hadron calorimeter. Muons are measured in gas-ionization detectors embed-

2

2

Data and Analysis

ded in the steel return yoke. In addition to the barrel and endcap detectors, CMS has extensive forward calorimetry. The nearly 4π solid-angle acceptance of the CMS detector is ideally suited for studies of both short- and long-range particle correlations. A detailed description of the CMS detector can be found in Ref. [28]. CMS uses a right-handed coordinate system, with the origin at the nominal interaction point, the x axis pointing to the center of the LHC, the y axis pointing up (perpendicular to the LHC plane), and the z axis along the counterclockwise beam direction. The detector subsystem primarily used for the present analysis is the inner tracker that reconstructs the trajectories of charged particles with pT > 100 MeV/c, covering the pseudorapidity region |η | < 2.5, where η = − ln[tan(θ/2)] and θ is the polar angle relative to the beam direction. The inner tracker consists of 1440 silicon pixel and 15 148 silicon strip detector modules immersed in the 3.8 T axial magnetic field of the superconducting solenoid. The event readout of the CMS detector for PbPb collisions is triggered by coincident signals in forward detectors located on both sides of the nominal collision point. In particular, minimum bias PbPb data are recorded based on coincident signals in the beam scintillator counters (BSC, 3.23 < |η | < 4.65) or in the steel/quartz-fiber Cherenkov forward hadron calorimeters (HF, 2.9 < |η | < 5.2) from both ends of the detector. In order to suppress events due to noise, cosmic rays, double-firing triggers, and beam backgrounds, the minimum bias trigger used in this analysis is required to be in coincidence with bunches colliding in the interaction region. The trigger has an acceptance of (97 ± 3)% for hadronic inelastic PbPb collisions [14]. Events are selected offline by requiring in addition at least three hits in the HF calorimeters at both ends of CMS, with at least 3 GeV of energy in each cluster, and the presence of a reconstructed primary vertex containing at least two tracks. These criteria further reduce background from single-beam interactions (e.g., beam gas and beam halo), cosmic muons, and large-impact-parameter, ultra-peripheral collisions that lead to the electromagnetic breakup of one or both of the Pb nuclei [29]. The reconstructed primary vertex is required to be located within 15 cm of the nominal collision point along the beam axis and within a radius of 0.02 cm relative to the average vertex position in the transverse plane. This analysis is based on a data sample of PbPb collisions corresponding to an integrated luminosity of approximately 3.12 µb−1 [30, 31], which contains 24.1 million minimum bias collisions after all event selections are applied. The energy released in the collisions is related to the centrality of heavy-ion interactions, i.e., the geometrical overlap of the incoming nuclei. In CMS, centrality is classified according to percentiles of the distribution of the energy deposited in the HF calorimeters. The centrality class used in this analysis corresponds to the 0–5% most central PbPb collisions, a total of 1.2 million events. More details on the centrality determination can be found in Refs. [14, 32]. A reconstructed track is considered as a primary-track candidate if the significance of the separation along the beam axis between the track and the primary vertex, dz /σ(dz ), and the significance of the impact parameter relative to the primary vertex transverse to the beam, d xy /σ(d xy ), are each less than 3. In order to remove tracks with potentially poorly reconstructed momentum values, the relative uncertainty of the momentum measurement, σ( pT )/pT , is required to be less than 5.0%. Requiring at least 12 hits on each track helps to reject misidentified tracks. Systematic uncertainties related to the track selections have been evaluated as discussed below. Trigger particles are defined as all charged particles originating from the primary vertex, with trig |η | < 2.4 and in a specified pT range. The number of trigger particles in the event is denoted by Ntrig , which can be more than one per event. Hadron pairs are formed by associating with every trigger particle the remaining charged particles with |η | < 2.4 and in a specified passoc T

3 range. The per-trigger-particle associated yield distribution is then defined by: S(∆η, ∆φ) 1 d2 N pair = B(0, 0) × , Ntrig d∆ηd∆φ B(∆η, ∆φ)

(1)

where ∆η and ∆φ are the differences in η and φ of the pair, respectively. The signal distribution, S(∆η, ∆φ), is the measured per-trigger-particle distribution of same-event pairs, i.e., S(∆η, ∆φ) =

1 d2 N same . Ntrig d∆ηd∆φ

(2)

1 d2 N mix , Ntrig d∆ηd∆φ

(3)

The mixed-event background distribution, B(∆η, ∆φ) =

is constructed by pairing the trigger particles in each event with the associated particles from 10 different random events, excluding the original event. The symbol N mix denotes the number of pairs taken from the mixed event. The background distribution is used to account for random combinatorial background and pair-acceptance effects. The normalization factor B(0, 0) is the value of B(∆η, ∆φ) at ∆η = 0 and ∆φ = 0 (with a bin width of 0.3 in ∆η and π/16 in ∆φ), representing the mixed-event associated yield for both particles of the pair going in approximately the same direction, thus having full pair acceptance. Therefore, the ratio B(0, 0)/B(∆η, ∆φ) is the pair-acceptance correction factor used to derive the corrected per-trigger-particle associated yield distribution. Equation (1) is calculated in 2 cm wide bins of the vertex position (zvtx ) along the beam direction and averaged over the range |zvtx | < 15 cm. To maximize the statistical precision, the absolute values of ∆η and ∆φ are used to fill one quadrant of the (∆η, ∆φ) histograms, with the other three quadrants filled (only for illustration purposes) by reflection. Therefore, the resulting distributions are symmetric about (∆η, ∆φ) = (0, 0) by construction. Each reconstructed track is weighted by the inverse of the efficiency factor, ε trk (η, pT ), as a function of the track’s pseudorapidity and transverse momentum. The efficiency weighting factor accounts for the detector acceptance A(η, pT ), the reconstruction efficiency E(η, pT ), and the fraction of misidentified tracks, F (η, pT ), ε trk (η, pT ) =

AE . 1−F

(4)

Studies with simulated Monte Carlo (MC) events show that the combined geometrical acceptance and reconstruction efficiency for the primary-track reconstruction reaches about 60% for the 0–5% most central PbPb collisions at pT > 2 GeV/c over the full CMS tracker acceptance (|η | < 2.4) and 65% for |η | < 1.0. The fraction of misidentified tracks is about 1–2% for |η | < 1.0, but increases to 10% at |η | ≈ 2.4. The weighting changes the overall scale but not the shape of the associated yield distribution, which depends on the ratio of the signal to background distributions. A closure test of the track-weighting procedure is performed on HYDJET [33] (version 1.6) MC events. The efficiency-weighted associated yield distribution from reconstructed tracks is found to agree with the generator-level correlation function to within 3.3%. In addition, systematic checks of the tracking efficiency, in which simulated MC tracks are embedded into

4

3

Results

data events, give results consistent with pure HYDJET simulations to within 5.0%. The tracking efficiency also depends on the vertex z position of the event. However, this dependence is negligible in this analysis, and its effects are taken into account in the systematic uncertainty by comparing the efficiency-corrected correlation functions for two different zvtx ranges, |zvtx | < 15 cm and |zvtx | < 5 cm, which are found to differ by less than 2.2%. Additional uncertainties due to track quality cuts are examined by loosening or tightening the track selections described previously, and the final results are found to be insensitive to the selections to within 2.0%. An independent analysis, using a somewhat different but well-established methodology [34, 35] in constructing the mixed-event background is performed as a cross-check, where 10 trigger particles from different events are selected first and combined to form a single event, and then correlated with particles from another event. It yields results within 2.9–3.6% of the default values (3.6% for |∆η | < 1 and 2.9% for 2 < |∆η | < 4), with a slight dependence on ∆η and ∆φ. The other four sources of systematic uncertainty are largely independent of ∆η and ∆φ. Table 1 summarizes the different systematic sources, whose corresponding uncertainties are added in quadrature becoming the quoted systematic uncertainties of the per-trigger-particle associated yield. Table 1: Summary of systematic uncertainties. Source Tracking weighting closure test Tracking efficiency Vertex dependence Track selection dependence Construction of the mixed-event background Total

3

Systematic uncertainty of the per-trigger-particle associated yield (%) 3.3 5.0 2.2 2.0 2.9–3.6 7.3–7.6

Results

The measured per-trigger-particle associated yield distribution of charged hadrons as a func√ tion of |∆η | and |∆φ| in the 0–5% most central PbPb collisions at s NN = 2.76 TeV is shown in trig

Fig. 1a for trigger particles with 4 < pT < 6 GeV/c and associated particles with 2 < passoc < T 4 GeV/c. To understand the effects of the hot, dense medium produced in the collisions, this distribution can √ be compared to that from a PYTHIA 8 MC simulation [36] (version 8.135) of pp collisions at s = 2.76 TeV, shown in Fig. 1b. This transverse momentum range, one of several studied later in this paper, is chosen for this figure since it illustrates the differences between correlations from PbPb data and PYTHIA 8 pp MC events most clearly. The main features of the simulated pp MC distribution are a narrow jet-fragmentation peak at (∆η, ∆φ) ≈ (0, 0) and a back-to-back jet structure at |∆φ| = π, but extended in ∆η. In the 0–5% most central PbPb collisions, particle correlations are significantly modified, as shown in Fig. 1a. The away-side pairs (∆φ ≈ π) exhibit a correlation with similar amplitude compared to PYTHIA 8, although the structure in PbPb data is much broader in both ∆φ and ∆η so that it appears almost flat. On the near side (∆φ ≈ 0), besides the common jet-like particle production in both pp and PbPb at (∆η, ∆φ) ≈ (0, 0) due to jet fragmentation, a clear and significant ridge-like structure is observed in PbPb at ∆φ ≈ 0, which extends all the way to the limit of the measurement of

3.1

Associated Yield Distributions versus ∆φ

5

|∆η | = 4. In relativistic heavy-ion collisions, the anisotropic hydrodynamic expansion of the produced medium is one possible source of long-range azimuthal correlations, driven by the event-byevent initial anisotropy of the collision zone [7, 37]. For non-central collisions, these correlations are dominated by the second-order Fourier component of the |∆φ| distribution, usually called elliptic flow or v2 . Measurements of dihadron correlations at RHIC have frequently attempted to subtract or factorize the elliptic flow contribution based on direct v2 measurements, in order to reveal other features of particle correlations that may provide insight into the interactions between the jets and the medium. However, recent theoretical developments indicate that the interplay between initial-state fluctuations and the subsequent hydrodynamic expansion gives rise to additional Fourier components in the azimuthal particle correlations [25, 26, 38– 42]. These components need to be treated on equal footing with the elliptic flow component. In particular for the 0–5% most central PbPb collisions, the elliptic flow contribution to the azimuthal correlations is not expected to be dominant [43]. Therefore, the original unsubtracted correlation functions are presented in this paper, containing the full information necessary for the comparison with theoretical calculations. (b) CMS Simulations

6.6 6.4

6.6 6.4 6.2 6.0 5.8 4

6.2

-2

∆η

4 4

0

0

0.2

∆2φ

2

φ

0.3

0.4 0.3 0.2 0.1

4 6.0

∆2

0.4

PYTHIA8 pp MC s = 2.76 TeV

pair

pair

1 d2N Ntrig d∆η d∆φ

PbPb sNN = 2.76 TeV, 0-5% centrality

pair

-1

1 d2N Ntrig d∆η d∆φ

∫ L dt = 3.1µb

2 pair 11dN d2N Ntrig d ∆ η d ∆ Ntrig d∆η dφ∆φ

(a) CMS

2 0

5.8

0.1

0 -2

∆η

-4

-4

Figure 1: Two-dimensional (2-D) per-trigger-particle associated yield of charged hadrons as a trig function of |∆η | and |∆φ| for 4 < pT < 6 GeV/c and 2 < passoc < 4 GeV/c from (a) T √ 0–5% most √ central PbPb collisions at s NN = 2.76 TeV, and (b) PYTHIA 8 pp MC simulation at s = 2.76 TeV.

3.1

Associated Yield Distributions versus ∆φ

To quantitatively examine the features of short-range and long-range azimuthal correlations, one dimensional (1-D) ∆φ correlation functions are calculated by averaging the 2-D distributions over a limited region in ∆η from ∆ηmin to ∆ηmax : 1 dN pair 1 = Ntrig d∆φ ∆ηmax − ∆ηmin

Z ∆ηmax ∆ηmin

1 d2 N pair d∆η. Ntrig d∆ηd∆φ

(5)

The results of extracting the 1-D ∆φ correlations for the 0–5% most central PbPb collisions are shown in Figs. 2 and 3. The associated yield per trigger particle in the range of 2 < passoc < T trig 4 GeV/c is extracted for five different pT intervals (2–4, 4–6, 6–8, 8–10, and 10–12 GeV/c) and

6

3

Results

two ranges in ∆η. Figure 2 gives the short-range pseudorapidity result, i.e., averaged over the region |∆η | < 1. Figure 3 shows the same comparison for long-range correlations, √ i.e., averaged over the region 2 < |∆η | < 4. A comparison to PYTHIA 8 pp MC events at s = 2.76 TeV is also shown, with a constant added to match the PbPb results at ∆φ = 1 in order to facilitate the comparison. In this projection, only the range 0 < ∆φ < π is shown, as the ∆φ correlation function is symmetric around ∆φ = 0 by construction.

6.5

6.5

6.0

6.0

0

1

|∆φ|

1

|∆φ|

2

trig

8 < pT < 10 GeV/c 7.0

6.5

6.0

6.0

3 0

1

|∆φ|

2

3 0

trig

10 < pT < 12 GeV/c

pair

7.0

6.5

6.0

3 0

2

6 < pT < 8 GeV/c

1 d2N Ntrig d∆φ

PYTHIA8 pp s = 2.76 TeV

6.5

trig

7.0

1 d2N Ntrig d∆φ

4 < pT < 6 GeV/c

sNN = 2.76 TeV, 0-5%

1 d2N Ntrig d∆φ

PbPb

∫ L dt = 3.1 µb-1 pair

trig

7.0

pair

pair

2 < pT < 4 GeV/c

CMS

pair

trig

7.0

1 d2N Ntrig d∆φ

2 < passoc < 4 GeV/c T

1 d2N Ntrig d∆φ

0 < |∆η| < 1

1

|∆φ|

3 0

2

1

|∆φ|

2

3

Figure 2: Short-range (|∆η | < 1) per-trigger-particle associated yields of charged hadrons as √ a function of |∆φ| from the 0–5% most central PbPb collisions at s NN = 2.76 TeV, requiring trig

2 < passoc < 4 GeV/c, for five different intervals of pT . The PYTHIA 8 pp MC results (solid T histograms) are also shown, shifted up by a constant value to match the PbPb data at ∆φ = 1 for ease of comparison. The error bars are statistical only and are too small to be visible in most of the panels. The systematic uncertainty of 7.6% for all data points is not shown in the plots.

6.2

6.0

6.0

0

1

|∆φ|

2

3 0

6.2

6.0

5.8

5.8

6.4

trig

6 < pT < 8 GeV/c

|∆φ|

2

3 0

6.2

|∆φ|

2

3 0

6.2

5.8

5.8

1

trig

10 < pT < 12 GeV/c

6.0

6.0

5.8

1

6.4

trig

8 < pT < 10 GeV/c pair

PYTHIA8 pp s = 2.76 TeV 5-term Fourier fits

pair

pair

6.2

sNN = 2.76 TeV, 0-5%

1 d2N Ntrig d∆φ

pair

1 d2N Ntrig d∆φ

PbPb

trig

4 < pT < 6 GeV/c

2 < pT < 4 GeV/c

∫ L dt = 3.1 µb-1 1 d2N Ntrig d∆φ

trig

CMS

6.4

pair

6.4

1 d2N Ntrig d∆φ

6.4

2 < passoc < 4 GeV/c T

1 d2N Ntrig d∆φ

2 < |∆η| < 4

1

|∆φ|

2

3 0

1

|∆φ|

2

3

Figure 3: Long-range (2 < |∆η | < 4) per-trigger-particle associated yields of charged hadrons as a function of |∆φ| under the same conditions as in Fig. 2. The systematic uncertainty of 7.3% for all data points is not shown in the plots. Dashed lines show the fits by the first five terms in the Fourier series, as discussed in Section 3.3. The panels of Figs. 2 and 3 show a modification of the away-side associated yield for |∆φ| > π/2 in central PbPb collisions that is not present in the PYTHIA 8 pp MC simulation. This moditrig fication is most pronounced for lower pT values and is characterized by a similarly broad distribution as seen in lower-energy RHIC measurements, where it was attributed to jet quenching and related phenomena [3, 5]. The near-side associated yield in PbPb data includes the contributions from both the jet-like peak and the ridge structure seen in Fig. 1a. Thus, it is not directly comparable to PYTHIA 8 pp MC events, where the ridge component is absent. A more quantitative comparison of the jet-like component between PbPb data and PYTHIA 8 pp MC events will be discussed below. For azimuthal correlations at large values of ∆η (Fig. 3), a clear maximum at ∆φ ≈ 0 is observed, which corresponds to the ridge structure seen in the 2-D distribution of Fig. 1a. This

3.2

7

Integrated Associated Yield

feature of the long-range azimuthal correlation function is not present in the PYTHIA 8 pp MC trig trig simulation for any pT bin. In PbPb, the height of the ridge structure decreases as pT increases trig (Fig. 3) and has largely vanished for pT ≈ 10–12 GeV/c. The diminishing height of the ridge trig with increasing pT was not evident from previous measurements at RHIC in AuAu collisions presumably because of lack of events at high pT .

3.2

Integrated Associated Yield

The strengths of the jet peak and ridge on the near side, as well as their dependences on ∆η and trig pT , can be quantified by the integrated associated yields. In the presence of multiple sources of correlations, the correlation of interest is commonly estimated using an implementation of the zero-yield-at-minimum (ZYAM) method [17]. However, as mentioned previously, the possible contribution of elliptic flow is not taken into account as it is not the dominant effect for the most central PbPb collisions considered here. The ZYAM method is implemented as follows. A second-order polynomial is fitted to the |∆φ| distributions in the region 0.5 < |∆φ| < 1.5. The location of the minimum of the polynomial in this region is denoted as ∆φZYAM . Using the position of the minimum, the associated yield is then calculated as the integral of the |∆φ| distribution minus its value at ∆φZYAM between |∆φ| = 0 and ∆φZYAM . The uncertainty on the minimum level obtained by the ZYAM procedure, combined with the uncertainty arising from the choice of fit range in |∆φ|, results in an uncertainty on the absolute associated yield that is trig constant with a value of 0.012 over all ∆η and pT bins.

0.4

Associated Yield

CMS

0.3

∫ L dt = 3.1µb

PbPb

-1

sNN = 2.76 TeV, 0-5%

PYTHIA8 pp s = 2.76 TeV

0.2 0.1

trig

4 < pT < 6 GeV/c assoc

2 < pT

< 4 GeV/c

0.0 0

1

2 |∆η|

3

4

trig

Figure 4: Integrated near-side (|∆φ| < ∆φZYAM ) associated yield for 4 < pT < 6 GeV/c and 2 < passoc < 4 GeV/c, above the minimum level found by the ZYAM procedure, as a function of T √ |∆η | for the 0–5% most central PbPb collisions at s NN = 2.76 TeV. The error bars correspond to statistical uncertainties, while the brackets denote the systematic uncertainties. The solid line √ shows the prediction from the PYTHIA 8 simulation of pp collisions at s = 2.76 TeV. The ZYAM procedure enables the direct extraction of integrated yields of the ∆φ-projected distributions in a well-defined manner. Figure 4 shows the resulting near-side associated yield

8

3

assoc

2 < pT

0.3

(a) Jet Region PbPb sNN = 2.76 TeV, 0-5%

0.2

CMS

PYTHIA8 pp s = 2.76 TeV

0.1

Associated Yield

Associated Yield

0.3

< 4 GeV/c

Results

∫ L dt = 3.1µb

-1

(b) Ridge Region

0.2

0.1

0.0

0.0

5

ptrig(GeV/c) T

10

5

10

ptrig(GeV/c) T

Figure 5: Integrated near-side (|∆φ| < ∆φZYAM ) associated yield above the minimum level found by the ZYAM procedure for (a) the short-range jet region (|∆η | < 1) and (b) the longtrig range ridge region (2 < |∆η | < 4), as a function of pT in the 0–5% most central PbPb collisions √ at s NN = 2.76 TeV with 2 < passoc < 4 GeV/c. The error bars correspond to statistical uncertainT ties, while the brackets around the data points denote the systematic uncertainties. The solid √ line shows the prediction from the PYTHIA 8 simulation of pp collisions at s = 2.76 TeV. as a function of |∆η | (in slices of 0.6 units) in both the central PbPb collisions and PYTHIA 8 pp MC. The near-side associated yield for PYTHIA 8 pp shows a strong peak at |∆η | = 0, which corresponds to the expected correlations within jets. This near-side peak diminishes rapidly with increasing |∆η |. The PbPb data also exhibit a jet-like correlation peak in the yield for small |∆η |, but in contrast, the PbPb data clearly show that the ridge extends to the highest |∆η | values measured. Figure 5 presents the integrated associated yield for the jet region (|∆η | < 1) and the ridge trig region (2 < |∆η | < 4) with 2 < passoc < 4 GeV/c, as a function of pT in the 0–5% most T central PbPb collisions. The ridge-region yield is defined as the integral of the near side in long-range ∆φ azimuthal correlation functions (Fig. 3), while the jet-region yield is determined by the difference between the short- and long-range near-side integral, as the ridge is found to be approximately constant in ∆η (Fig. 4). While the jet-region yield shows an increase with trig pT due to the increasing jet transverse energy, the ridge-region yield is most prominent for trig trig 2 < pT < 6 GeV/c and tends to drop to almost zero when pT reaches 10–12 GeV/c. The bars in Fig. 5 correspond to the statistical uncertainties, while the brackets around the data points denote the systematic uncertainties, which are dominated by the tracking performance, as discussed earlier. Results from the PYTHIA 8 pp MC simulation, displayed as solid lines in trig Fig. 5, are consistent with zero for all pT bins in the ridge region and have qualitatively the trig same trend with pT in the jet region as the data. It has been seen from previous studies that the ridge is absent in both minimum bias pp data and PYTHIA 8 MC simulations. However, the PYTHIA 8 program does not fully describe the jet-like correlations observed in pp collisions at

3.3

Fourier Decomposition of ∆φ Distributions

9



s = 7 TeV [27]. A quantitative comparison √ of the correlations in PbPb and pp collisions will therefore be deferred until pp results at s = 2.76 TeV become available.

-0.5 -1.0

Vf2

0.5 0.0 -0.5

PbPb sNN = 2.76 TeV, 0-5% PYTHIA8 pp s = 2.76TeV

5

ptrig (GeV/c) T

-1.0 10

5

ptrig (GeV/c) T

CMS 1.0

Vf3

∫ L dt = 3.1µb

-1

0.5 0.0 -0.5

-1.0 10

5

1.0 0.5 0.0

-0.5

-1.0 10

ptrig (GeV/c) T

Vf4

f -2 Nassoc/NPbPb assoc Vn [10 ]

0.0

2 < passoc < 4 GeV/c T

f -2 Nassoc/NPbPb assoc Vn [10 ]

0.5

1.0

f -2 Nassoc/NPbPb assoc Vn [10 ]

Vf1

f -2 Nassoc/NPbPb assoc Vn [10 ]

f -2 Nassoc/NPbPb assoc Vn [10 ]

2 < |∆η| < 4 1.0

5

ptrig (GeV/c) T

1.0

Vf5

0.5 0.0 -0.5

-1.0 10

5

10

ptrig (GeV/c) T

trig

Figure 6: Fourier coefficients, V1f , V2f , V3f , V4f , and V5f , extracted as functions of pT for 2 < √ passoc < 4 GeV/c for the 0–5% most central PbPb collisions at s NN = 2.76 TeV. The error bars T represent statistical uncertainties √ only. The solid lines show the predictions from the PYTHIA 8 simulation of pp collisions at s = 2.76 TeV.

3.3

Fourier Decomposition of ∆φ Distributions

Motivated by recent theoretical developments in understanding the long-range ridge effect in the context of higher-order hydrodynamic flow induced by initial geometric fluctuations, such as the “triangular flow” effect [26, 38–42], an alternative way of quantifying the observed long-range correlations is investigated in this paper. The 1-D ∆φ-projected distribution for 2 < |∆η | < 4 is decomposed in a Fourier series as ( ) ∞ 1 dN pair Nassoc f = 1 + ∑ 2Vn cos(n∆φ) , (6) Ntrig d∆φ 2π n =1 where Nassoc represents the total number of hadron pairs per trigger particle for a given |∆η | trig range and ( pT , passoc ) bin. The 1-D ∆φ projections displayed in Fig. 3 are fitted by the first T five terms in the Fourier series, the resulting fits being shown as the dashed lines in Fig. 3. The data are well described by the fits. Figure 6 presents the first five Fourier coefficients trig from the fit as functions of pT for 2 < passoc < 4 GeV/c for the 0–5% most central PbPb T collisions and for the PYTHIA 8 pp MC simulation. The PYTHIA 8 results are scaled by the ratio PYTHIA 8 PbPb in order to remove the trivial effect of the multiplicity dependence. The error of Nassoc /Nassoc bars are statistical only, while the systematic uncertainties are found to be negligible because the Fourier coefficients characterize the overall shape of the correlation functions, and thus are not sensitive to the absolute scale. The coefficients from the fit are also found to be largely independent of each other (correlation coefficients typical below 5%). All the Fourier coefficients found from fitting the PbPb data show a similar dependence on trig pT except for the V1f term, which contains an additional negative contribution that grows trig toward higher pT . This negative V1f component is consistent with a contribution from momentum conservation or back-to-back dijets [44]. If the observed correlation is purely driven by the single-particle azimuthal anisotropy arising from the hydrodynamic expansion of the medium [45], the extracted Vnf components would be related to the flow coefficients vn (i.e., trig trig v2 for anisotropic elliptic flow) via Vnf ∼ vn × vassoc , where vn and vassoc are the flow con n efficients for the trigger and associated particles [26]. The flow coefficients, and especially

10

4

Summary

the higher-order terms, are sensitive to the initial conditions and viscosity of the hot, dense medium [38, 46]. This Fourier analysis serves as an alternative way of quantifying the azimuthal correlation functions in heavy-ion collisions and potentially provides new insights in understanding the origin of the ridge effect in these collisions. Analysis of larger data samples trig in terms of pT and passoc , as well as centrality, would allow a more detailed comparison to T theoretical calculations of hydrodynamics, for which the Fourier components provide a concise description of the data.

4

Summary

The CMS detector at the LHC has been used to measure angular correlations between charged particles in ∆η and ∆φ up to |∆η | ≈ 4 and over the full range of ∆φ in the 0–5% most central √ PbPb collisions at s NN = 2.76 TeV. This is the first study of long-range azimuthal correlations over a large difference in pseudorapidity in PbPb interactions at the LHC energy. The extracted 2-D associated yield distributions show a variety of characteristic features in heavy-ion collisions that are not present in minimum bias pp interactions. Short- and long-range azimuthal correlations have been studied as a function of the transverse momentum of the trigger particles. The observed long-range ridge-like structure for approximately equal azimuthal angles trig (∆φ ≈ 0) is most evident in the intermediate transverse momentum range, 2 < pT < 6 GeV/c, trig and decreases to almost zero for pT above 10–12 GeV/c. A qualitatively similar dependence of the ridge on transverse momentum has also been observed in high-multiplicity pp events, indicating a potentially similar physical origin of the effect. A Fourier decomposition of the 1-D ∆φ-projected correlation functions in the ridge region (2 < |∆η | < 4) has been presented. This alternative way of quantifying the correlation data provides valuable information to test a wide range of theoretical models, including recent hydrodynamic calculations of higher-order Fourier components. The very broad solid-angle coverage of the CMS detector and the statistical accuracy of the sample analyzed in this paper provide significantly improved observations of short- and long-range particle correlations over previously available measurements.

Acknowledgments We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administrative staff at CERN and other CMS institutes, and acknowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie programme and the European Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Associazione per lo Sviluppo Scientifico e Tecnologico del Piemonte (Italy); the Belgian Federal Science Policy Office; the Fonds pour la For-

11 mation a` la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); and the Council of Science and Industrial Research, India.

References [1] STAR Collaboration, “Disappearance of back-to-back high pT hadron correlations in √ central Au+Au collisions at s NN = 200-GeV”, Phys. Rev. Lett. 90 (2003) 082302, arXiv:nucl-ex/0210033. doi:10.1103/PhysRevLett.90.082302. [2] STAR Collaboration, “Long range rapidity correlations and jet production in high energy nuclear collisions”, Phys. Rev. C80 (2009) 064912, arXiv:0909.0191. doi:10.1103/PhysRevC.80.064912. [3] STAR Collaboration, “Distributions of charged hadrons associated with high transverse √ momentum particles in pp and Au + Au collisions at s NN = 200 GeV”, Phys. Rev. Lett. 95 (2005) 152301, arXiv:nucl-ex/0501016. doi:10.1103/PhysRevLett.95.152301. [4] PHENIX Collaboration, “System size and energy dependence of jet-induced hadron pair √ correlation shapes in Cu + Cu and Au + Au collisions at s NN = 200 GeV and 62.4 GeV”, Phys. Rev. Lett. 98 (2007) 232302, arXiv:nucl-ex/0611019. doi:10.1103/PhysRevLett.98.232302. √ [5] PHENIX Collaboration, “Dihadron azimuthal correlations in Au+Au collisions at s NN = 200 GeV”, Phys. Rev. C78 (2008) 014901, arXiv:0801.4545. doi:10.1103/PhysRevC.78.014901. [6] PHOBOS Collaboration, “High transverse Momentum Triggered Correlations over a √ Large Pseudorapidity Acceptance in Au+Au Collisions at s NN = 200 GeV”, Phys. Rev. Lett. 104 (2010) 062301, arXiv:0903.2811. doi:10.1103/PhysRevLett.104.062301. [7] PHOBOS Collaboration, “System Size Dependence of Cluster Properties from Two√ Particle Angular Correlations in Cu+Cu and Au+Au Collisions at s NN = 200 GeV”, Phys. Rev. C81 (2010) 024904, arXiv:0812.1172. doi:10.1103/PhysRevC.81.024904. [8] STAR Collaboration, “Experimental and Theoretical Challenges in the Search for the Quark Gluon Plasma: The STAR Collaboration’s Critical Assessment of the Evidence from RHIC Collisions”, Nucl. Phys. A757 (2005) 102, arXiv:nucl-ex/0501009. doi:10.1016/j.nuclphysa.2005.03.085. [9] PHENIX Collaboration, “Formation of Dense Partonic Matter in Relativistic Nucleus Nucleus Collisions at RHIC: Experimental Evaluation by the PHENIX Collaboration”, Nucl. Phys. A757 (2005) 184, arXiv:nucl-ex/0410003. doi:10.1016/j.nuclphysa.2005.03.086. [10] PHOBOS Collaboration, “The PHOBOS Perspective on Discoveries at RHIC”, Nucl. Phys. A757 (2005) 28, arXiv:nucl-ex/0410022. doi:10.1016/j.nuclphysa.2005.03.084.

12

4

Summary

[11] BRAHMS Collaboration, “Quark Gluon Plasma an Color Glass Condensate at RHIC? The perspective from the BRAHMS experiment”, Nucl. Phys. A757 (2005) 1, arXiv:nucl-ex/0410020. doi:10.1016/j.nuclphysa.2005.02.130. [12] ALICE Collaboration, “Suppression of Charged Particle Production at Large Transverse √ Momentum in Central Pb–Pb Collisions at s NN = 2.76 TeV”, Phys. Lett. B696 (2011) 30, arXiv:1012.1004. doi:10.1016/j.physletb.2010.12.020. [13] ATLAS Collaboration, “Observation of a Centrality-Dependent Dijet Asymmetry in √ Lead-Lead Collisions at s NN = 2.76 TeV with the ATLAS Detector at the LHC”, Phys. Rev. Lett. 105 (2010) 252303, arXiv:1011.6182. doi:10.1103/PhysRevLett.105.252303. [14] CMS Collaboration, “Observation and studies of jet quenching in PbPb collisions at nucleon-nucleon center-of-mass energy = 2.76 TeV”, arXiv:1102.1957. [15] N. Armesto, C. A. Salgado, and U. A. Wiedemann, “Measuring the collective flow with jets”, Phys. Rev. Lett. 93 (2004) 242301, arXiv:hep-ph/0405301. doi:10.1103/PhysRevLett.93.242301. [16] A. Majumder, B. Muller, and S. A. Bass, “Longitudinal Broadening of Quenched Jets in Turbulent Color Fields”, Phys. Rev. Lett. 99 (2007) 042301, arXiv:hep-ph/0611135. doi:10.1103/PhysRevLett.99.042301. [17] C. B. Chiu and R. C. Hwa, “Pedestal and peak structure in jet correlation”, Phys. Rev. C72 (2005) 034903, arXiv:nucl-th/0505014. doi:10.1103/PhysRevC.72.034903. [18] C.-Y. Wong, “The Momentum Kick Model Description of the Near-Side Ridge and Jet Quenching”, Phys. Rev. C78 (2008) 064905, arXiv:0806.2154. doi:10.1103/PhysRevC.78.064905. [19] S. A. Voloshin, “Transverse radial expansion in nuclear collisions and two particle correlations”, Phys. Lett. B632 (2006) 490, arXiv:nucl-th/0312065. doi:10.1016/j.physletb.2005.11.024. [20] P. Romatschke, “Momentum broadening in an anisotropic plasma”, Phys. Rev. C75 (2007) 014901, arXiv:hep-ph/0607327. doi:10.1103/PhysRevC.75.014901. [21] E. V. Shuryak, “On the Origin of the ’Ridge’ phenomenon induced by Jets in Heavy Ion Collisions”, Phys. Rev. C76 (2007) 047901, arXiv:0706.3531. doi:10.1103/PhysRevC.76.047901. [22] A. Dumitru et al., “Glasma flux tubes and the near side ridge phenomenon at RHIC”, Nucl. Phys. A810 (2008) 91, arXiv:0804.3858. doi:10.1016/j.nuclphysa.2008.06.012. [23] S. Gavin, L. McLerran, and G. Moschelli, “Long Range Correlations and the Soft Ridge in Relativistic Nuclear Collisions”, Phys. Rev. C79 (2009) 051902, arXiv:0806.4718. doi:10.1103/PhysRevC.79.051902. [24] K. Dusling, D. Fernandez-Fraile, and R. Venugopalan, “Three-particle correlation from glasma flux tubes”, Nucl. Phys. A828 (2009) 161, arXiv:0902.4435. doi:10.1016/j.nuclphysa.2009.06.017.

13 [25] Y. Hama et al., “Trying to understand the ridge effect in hydrodynamic model”, Nonlin. Phenom. Complex Syst. 12 (2009) 466, arXiv:0911.0811. [26] B. Alver and G. Roland, “Collision geometry fluctuations and triangular flow in heavy-ion collisions”, Phys. Rev. C81 (2010) 054905, arXiv:1003.0194. doi:10.1103/PhysRevC.81.054905. [27] CMS Collaboration, “Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC”, JHEP 09 (2010) 091, arXiv:1009.4122. doi:10.1007/JHEP09(2010)091. [28] CMS Collaboration, “The CMS Experiment at the CERN LHC”, JINST 03 (2008) S08004. doi:10.1088/1748-0221/3/08/S08004. [29] O. Djuvsland and J. Nystrand, “Single and Double Photonuclear Excitations in Pb+Pb Collisions at the LHC”, arXiv:1011.4908. [30] CMS Collaboration, “Measurement of CMS Luminosity”, CMS Physics Analysis Summary CMS-PAS-EWK-10-004 (2010). [31] CMS Collaboration, “Absolute luminosity normalization”, CMS Detector Performance Summary CMS-DP-2011-002 (2011). [32] CMS Collaboration, “CMS physics technical design report: Addendum on high density QCD with heavy ions”, J. Phys. G34 (2007) 2307. doi:10.1088/0954-3899/34/11/008. [33] I. P. Lokhtin and A. M. Snigirev, “A model of jet quenching in ultrarelativistic heavy ion collisions and high-pT hadron spectra at RHIC”, Eur. Phys. J. C45 (2006) 211, arXiv:hep-ph/0506189. doi:10.1140/epjc/s2005-02426-3. [34] STAR Collaboration, “Azimuthal di-hadron correlations in d+Au and Au+Au collisions √ at s NN = 200 GeV from STAR”, Phys. Rev. C82 (2010) 024912, arXiv:1004.2377. doi:10.1103/PhysRevC.82.024912. [35] V. Chetluru and O. Barannikova, “Jet Studies for 5.5 TeV Pb+Pb Collisions via Di-Hadron Correlations”, Indian Journal of Physics 84 (2011) 1807. doi:10.1007/s12648-010-0177-x. ¨ [36] T. Sjostrand, S. Mrenna, and P. Z. Skands, “A Brief Introduction to PYTHIA 8.1”, Comput. Phys. Commun. 178 (2008) 852, arXiv:0710.3820. doi:10.1016/j.cpc.2008.01.036. [37] PHOBOS Collaboration, “System Size, Energy, Pseudorapidity, and Centrality Dependence of Elliptic Flow”, Phys. Rev. Lett. 98 (2007) 242302, arXiv:nucl-ex/0610037. doi:10.1103/PhysRevLett.98.242302. [38] B. H. Alver et al., “Triangular flow in hydrodynamics and transport theory”, Phys. Rev. C82 (2010) 034913, arXiv:1007.5469. doi:10.1103/PhysRevC.82.034913. [39] B. Schenke, S. Jeon, and C. Gale, “Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics”, Phys. Rev. Lett. 106 (2011) 042301, arXiv:1009.3244. doi:10.1103/PhysRevLett.106.042301.

14

4

Summary

[40] H. Petersen et al., “Triangular flow in event-by-event ideal hydrodynamics in Au+Au √ collisions at sNN = 200A GeV”, Phys. Rev. C82 (2010) 041901, arXiv:1008.0625. doi:10.1103/PhysRevC.82.041901. [41] J. Xu and C. M. Ko, “The effect of triangular flow on di-hadron azimuthal correlations in relativistic heavy ion collisions”, Phys. Rev. C83 (2011) 021903, arXiv:1011.3750. doi:10.1103/PhysRevC.83.021903. [42] D. Teaney and L. Yan, “Triangularity and Dipole Asymmetry in Heavy Ion Collisions”, arXiv:1010.1876. [43] ALICE Collaboration, “Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV”, Phys. Rev. Lett. 105 (2010) 252302, arXiv:1011.3914. doi:10.1103/PhysRevLett.105.252302. [44] M. Luzum and J.-Y. Ollitrault, “Directed flow at midrapidity in heavy-ion collisions”, Phys. Rev. Lett. 106 (2011) 102301, arXiv:1011.6361. doi:10.1103/PhysRevLett.106.102301. [45] S. Voloshin and Y. Zhang, “Flow study in relativistic nuclear collisions by Fourier expansion of Azimuthal particle distributions”, Z. Phys. C70 (1996) 665, arXiv:hep-ph/9407282. doi:10.1007/s002880050141. [46] P. Staig and E. Shuryak, “The Fate of the Initial State Fluctuations in Heavy Ion Collisions. II The Fluctuations and Sounds”, arXiv:1008.3139.

15

A

The CMS Collaboration

Yerevan Physics Institute, Yerevan, Armenia S. Chatrchyan, V. Khachatryan, A.M. Sirunyan, A. Tumasyan Institut fur ¨ Hochenergiephysik der OeAW, Wien, Austria ¨ C. Fabjan, M. Friedl, R. Fruhwirth, ¨ W. Adam, T. Bergauer, M. Dragicevic, J. Ero, V.M. Ghete, ¨ J. Hammer1 , S. H¨ansel, M. Hoch, N. Hormann, J. Hrubec, M. Jeitler, W. Kiesenhofer, ¨ M. Krammer, D. Liko, I. Mikulec, M. Pernicka, H. Rohringer, R. Schofbeck, J. Strauss, A. Taurok, F. Teischinger, P. Wagner, W. Waltenberger, G. Walzel, E. Widl, C.-E. Wulz National Centre for Particle and High Energy Physics, Minsk, Belarus V. Mossolov, N. Shumeiko, J. Suarez Gonzalez Universiteit Antwerpen, Antwerpen, Belgium S. Bansal, L. Benucci, E.A. De Wolf, X. Janssen, J. Maes, T. Maes, L. Mucibello, S. Ochesanu, B. Roland, R. Rougny, M. Selvaggi, H. Van Haevermaet, P. Van Mechelen, N. Van Remortel Vrije Universiteit Brussel, Brussel, Belgium F. Blekman, S. Blyweert, J. D’Hondt, O. Devroede, R. Gonzalez Suarez, A. Kalogeropoulos, M. Maes, W. Van Doninck, P. Van Mulders, G.P. Van Onsem, I. Villella Universit´e Libre de Bruxelles, Bruxelles, Belgium O. Charaf, B. Clerbaux, G. De Lentdecker, V. Dero, A.P.R. Gay, G.H. Hammad, T. Hreus, P.E. Marage, L. Thomas, C. Vander Velde, P. Vanlaer Ghent University, Ghent, Belgium V. Adler, A. Cimmino, S. Costantini, M. Grunewald, B. Klein, J. Lellouch, A. Marinov, J. Mccartin, D. Ryckbosch, F. Thyssen, M. Tytgat, L. Vanelderen, P. Verwilligen, S. Walsh, N. Zaganidis Universit´e Catholique de Louvain, Louvain-la-Neuve, Belgium S. Basegmez, G. Bruno, J. Caudron, L. Ceard, E. Cortina Gil, J. De Favereau De Jeneret, C. Delaere1 , D. Favart, A. Giammanco, G. Gr´egoire, J. Hollar, V. Lemaitre, J. Liao, O. Militaru, S. Ovyn, D. Pagano, A. Pin, K. Piotrzkowski, N. Schul Universit´e de Mons, Mons, Belgium N. Beliy, T. Caebergs, E. Daubie Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil G.A. Alves, D. De Jesus Damiao, M.E. Pol, M.H.G. Souza Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil W. Carvalho, E.M. Da Costa, C. De Oliveira Martins, S. Fonseca De Souza, L. Mundim, H. Nogima, V. Oguri, W.L. Prado Da Silva, A. Santoro, S.M. Silva Do Amaral, A. Sznajder Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil C.A. Bernardes2 , F.A. Dias, T.R. Fernandez Perez Tomei, E. M. Gregores2 , C. Lagana, F. Marinho, P.G. Mercadante2 , S.F. Novaes, Sandra S. Padula Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria N. Darmenov1 , L. Dimitrov, V. Genchev1 , P. Iaydjiev1 , S. Piperov, M. Rodozov, S. Stoykova, G. Sultanov, V. Tcholakov, R. Trayanov, I. Vankov

16

A

The CMS Collaboration

University of Sofia, Sofia, Bulgaria A. Dimitrov, R. Hadjiiska, A. Karadzhinova, V. Kozhuharov, L. Litov, M. Mateev, B. Pavlov, P. Petkov Institute of High Energy Physics, Beijing, China J.G. Bian, G.M. Chen, H.S. Chen, C.H. Jiang, D. Liang, S. Liang, X. Meng, J. Tao, J. Wang, J. Wang, X. Wang, Z. Wang, H. Xiao, M. Xu, J. Zang, Z. Zhang State Key Lab. of Nucl. Phys. and Tech., Peking University, Beijing, China Y. Ban, S. Guo, Y. Guo, W. Li, Y. Mao, S.J. Qian, H. Teng, L. Zhang, B. Zhu, W. Zou Universidad de Los Andes, Bogota, Colombia A. Cabrera, B. Gomez Moreno, A.A. Ocampo Rios, A.F. Osorio Oliveros, J.C. Sanabria Technical University of Split, Split, Croatia N. Godinovic, D. Lelas, K. Lelas, R. Plestina3 , D. Polic, I. Puljak University of Split, Split, Croatia Z. Antunovic, M. Dzelalija Institute Rudjer Boskovic, Zagreb, Croatia V. Brigljevic, S. Duric, K. Kadija, S. Morovic University of Cyprus, Nicosia, Cyprus A. Attikis, M. Galanti, J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis Charles University, Prague, Czech Republic M. Finger, M. Finger Jr. Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt Y. Assran4 , S. Khalil5 , M.A. Mahmoud6 National Institute of Chemical Physics and Biophysics, Tallinn, Estonia ¨ A. Hektor, M. Kadastik, M. Muntel, M. Raidal, L. Rebane Department of Physics, University of Helsinki, Helsinki, Finland V. Azzolini, P. Eerola, G. Fedi Helsinki Institute of Physics, Helsinki, Finland ¨ S. Czellar, J. H¨arkonen, A. Heikkinen, V. Karim¨aki, R. Kinnunen, M.J. Kortelainen, T. Lamp´en, K. Lassila-Perini, S. Lehti, T. Lind´en, P. Luukka, T. M¨aenp¨aa¨ , E. Tuominen, J. Tuominiemi, E. Tuovinen, D. Ungaro, L. Wendland Lappeenranta University of Technology, Lappeenranta, Finland K. Banzuzi, A. Korpela, T. Tuuva Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France D. Sillou DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France M. Besancon, S. Choudhury, M. Dejardin, D. Denegri, B. Fabbro, J.L. Faure, F. Ferri, S. Ganjour, F.X. Gentit, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, E. Locci, J. Malcles, M. Marionneau, L. Millischer, J. Rander, A. Rosowsky, I. Shreyber, M. Titov, P. Verrecchia

17 Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France S. Baffioni, F. Beaudette, L. Benhabib, L. Bianchini, M. Bluj7 , C. Broutin, P. Busson, C. Charlot, T. Dahms, L. Dobrzynski, S. Elgammal, R. Granier de Cassagnac, M. Haguenauer, P. Min´e, C. Mironov, C. Ochando, P. Paganini, D. Sabes, R. Salerno, Y. Sirois, C. Thiebaux, B. Wyslouch8 , A. Zabi Institut Pluridisciplinaire Hubert Curien, Universit´e de Strasbourg, Universit´e de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France J.-L. Agram9 , J. Andrea, D. Bloch, D. Bodin, J.-M. Brom, M. Cardaci, E.C. Chabert, C. Collard, E. Conte9 , F. Drouhin9 , C. Ferro, J.-C. Fontaine9 , D. Gel´e, U. Goerlach, S. Greder, P. Juillot, M. Karim9 , A.-C. Le Bihan, Y. Mikami, P. Van Hove Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules (IN2P3), Villeurbanne, France F. Fassi, D. Mercier Universit´e de Lyon, Universit´e Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucl´eaire de Lyon, Villeurbanne, France C. Baty, S. Beauceron, N. Beaupere, M. Bedjidian, O. Bondu, G. Boudoul, D. Boumediene, H. Brun, J. Chasserat, R. Chierici, D. Contardo, P. Depasse, H. El Mamouni, J. Fay, S. Gascon, B. Ille, T. Kurca, T. Le Grand, M. Lethuillier, L. Mirabito, S. Perries, V. Sordini, S. Tosi, Y. Tschudi, P. Verdier Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi, Georgia D. Lomidze RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany G. Anagnostou, M. Edelhoff, L. Feld, N. Heracleous, O. Hindrichs, R. Jussen, K. Klein, J. Merz, N. Mohr, A. Ostapchuk, A. Perieanu, F. Raupach, J. Sammet, S. Schael, D. Sprenger, H. Weber, M. Weber, B. Wittmer RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany M. Ata, W. Bender, E. Dietz-Laursonn, M. Erdmann, J. Frangenheim, T. Hebbeker, A. Hinzmann, K. Hoepfner, T. Klimkovich, D. Klingebiel, P. Kreuzer, D. Lanske† , C. Magass, M. Merschmeyer, A. Meyer, P. Papacz, H. Pieta, H. Reithler, S.A. Schmitz, L. Sonnenschein, J. Steggemann, D. Teyssier RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany ¨ M. Bontenackels, M. Davids, M. Duda, G. Flugge, H. Geenen, M. Giffels, W. Haj Ahmad, D. Heydhausen, T. Kress, Y. Kuessel, A. Linn, A. Nowack, L. Perchalla, O. Pooth, J. Rennefeld, P. Sauerland, A. Stahl, M. Thomas, D. Tornier, M.H. Zoeller Deutsches Elektronen-Synchrotron, Hamburg, Germany M. Aldaya Martin, W. Behrenhoff, U. Behrens, M. Bergholz10 , A. Bethani, K. Borras, A. Cakir, A. Campbell, E. Castro, D. Dammann, G. Eckerlin, D. Eckstein, A. Flossdorf, G. Flucke, A. Geiser, J. Hauk, H. Jung1 , M. Kasemann, I. Katkov11 , P. Katsas, C. Kleinwort, H. Kluge, ¨ A. Knutsson, M. Kr¨amer, D. Krucker, E. Kuznetsova, W. Lange, W. Lohmann10 , R. Mankel, M. Marienfeld, I.-A. Melzer-Pellmann, A.B. Meyer, J. Mnich, A. Mussgiller, J. Olzem, D. Pitzl, A. Raspereza, A. Raval, M. Rosin, R. Schmidt10 , T. Schoerner-Sadenius, N. Sen, A. Spiridonov, M. Stein, J. Tomaszewska, R. Walsh, C. Wissing University of Hamburg, Hamburg, Germany C. Autermann, V. Blobel, S. Bobrovskyi, J. Draeger, H. Enderle, U. Gebbert, K. Kaschube,

18

A

The CMS Collaboration

G. Kaussen, R. Klanner, J. Lange, B. Mura, S. Naumann-Emme, F. Nowak, N. Pietsch, C. Sander, ¨ ¨ H. Schettler, P. Schleper, M. Schroder, T. Schum, J. Schwandt, H. Stadie, G. Steinbruck, J. Thomsen Institut fur ¨ Experimentelle Kernphysik, Karlsruhe, Germany C. Barth, J. Bauer, J. Berger, V. Buege, T. Chwalek, W. De Boer, A. Dierlamm, G. Dirkes, M. Feindt, J. Gruschke, C. Hackstein, F. Hartmann, M. Heinrich, H. Held, K.H. Hoffmann, ¨ S. Honc, J.R. Komaragiri, T. Kuhr, D. Martschei, S. Mueller, Th. Muller, M. Niegel, O. Oberst, A. Oehler, J. Ott, T. Peiffer, G. Quast, K. Rabbertz, F. Ratnikov, N. Ratnikova, M. Renz, C. Saout, A. Scheurer, P. Schieferdecker, F.-P. Schilling, G. Schott, H.J. Simonis, F.M. Stober, D. Troendle, J. Wagner-Kuhr, T. Weiler, M. Zeise, V. Zhukov11 , E.B. Ziebarth Institute of Nuclear Physics ”Demokritos”, Aghia Paraskevi, Greece G. Daskalakis, T. Geralis, S. Kesisoglou, A. Kyriakis, D. Loukas, I. Manolakos, A. Markou, C. Markou, C. Mavrommatis, E. Ntomari, E. Petrakou University of Athens, Athens, Greece L. Gouskos, T.J. Mertzimekis, A. Panagiotou, E. Stiliaris University of Io´annina, Io´annina, Greece I. Evangelou, C. Foudas, P. Kokkas, N. Manthos, I. Papadopoulos, V. Patras, F.A. Triantis KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary A. Aranyi, G. Bencze, L. Boldizsar, C. Hajdu1 , P. Hidas, D. Horvath12 , A. Kapusi, K. Krajczar13 , F. Sikler1 , G.I. Veres13 , G. Vesztergombi13 Institute of Nuclear Research ATOMKI, Debrecen, Hungary N. Beni, J. Molnar, J. Palinkas, Z. Szillasi, V. Veszpremi University of Debrecen, Debrecen, Hungary P. Raics, Z.L. Trocsanyi, B. Ujvari Panjab University, Chandigarh, India S.B. Beri, V. Bhatnagar, N. Dhingra, R. Gupta, M. Jindal, M. Kaur, J.M. Kohli, M.Z. Mehta, N. Nishu, L.K. Saini, A. Sharma, A.P. Singh, J.B. Singh, S.P. Singh University of Delhi, Delhi, India S. Ahuja, S. Bhattacharya, B.C. Choudhary, B. Gomber, P. Gupta, S. Jain, S. Jain, R. Khurana, A. Kumar, M. Naimuddin, K. Ranjan, R.K. Shivpuri Bhabha Atomic Research Centre, Mumbai, India R.K. Choudhury, D. Dutta, S. Kailas, V. Kumar, P. Mehta, A.K. Mohanty1 , L.M. Pant, P. Shukla Tata Institute of Fundamental Research - EHEP, Mumbai, India T. Aziz, M. Guchait14 , A. Gurtu, M. Maity15 , D. Majumder, G. Majumder, K. Mazumdar, G.B. Mohanty, A. Saha, K. Sudhakar, N. Wickramage Tata Institute of Fundamental Research - HECR, Mumbai, India S. Banerjee, S. Dugad, N.K. Mondal Institute for Research and Fundamental Sciences (IPM), Tehran, Iran H. Arfaei, H. Bakhshiansohi16 , S.M. Etesami, A. Fahim16 , M. Hashemi, A. Jafari16 , M. Khakzad, A. Mohammadi17 , M. Mohammadi Najafabadi, S. Paktinat Mehdiabadi, B. Safarzadeh, M. Zeinali18

19 INFN Sezione di Bari a , Universit`a di Bari b , Politecnico di Bari c , Bari, Italy M. Abbresciaa,b , L. Barbonea,b , C. Calabriaa,b , A. Colaleoa , D. Creanzaa,c , N. De Filippisa,c,1 , M. De Palmaa,b , L. Fiorea , G. Iasellia,c , L. Lusitoa,b , G. Maggia,c , M. Maggia , N. Mannaa,b , B. Marangellia,b , S. Mya,c , S. Nuzzoa,b , N. Pacificoa,b , G.A. Pierroa , A. Pompilia,b , G. Pugliesea,c , F. Romanoa,c , G. Rosellia,b , G. Selvaggia,b , L. Silvestrisa , R. Trentaduea , S. Tupputia,b , G. Zitoa INFN Sezione di Bologna a , Universit`a di Bologna b , Bologna, Italy G. Abbiendia , A.C. Benvenutia , D. Bonacorsia , S. Braibant-Giacomellia,b , L. Brigliadoria , P. Capiluppia,b , A. Castroa,b , F.R. Cavalloa , M. Cuffiania,b , G.M. Dallavallea , F. Fabbria , A. Fanfania,b , D. Fasanellaa , P. Giacomellia , M. Giuntaa , C. Grandia , S. Marcellinia , G. Masettib , M. Meneghellia,b , A. Montanaria , F.L. Navarriaa,b , F. Odoricia , A. Perrottaa , F. Primaveraa , A.M. Rossia,b , T. Rovellia,b , G. Sirolia,b , R. Travaglinia,b INFN Sezione di Catania a , Universit`a di Catania b , Catania, Italy S. Albergoa,b , G. Cappelloa,b , M. Chiorbolia,b,1 , S. Costaa,b , A. Tricomia,b , C. Tuvea INFN Sezione di Firenze a , Universit`a di Firenze b , Firenze, Italy G. Barbaglia , V. Ciullia,b , C. Civininia , R. D’Alessandroa,b , E. Focardia,b , S. Frosalia,b , E. Galloa , S. Gonzia,b , P. Lenzia,b , M. Meschinia , S. Paolettia , G. Sguazzonia , A. Tropianoa,1 INFN Laboratori Nazionali di Frascati, Frascati, Italy L. Benussi, S. Bianco, S. Colafranceschi19 , F. Fabbri, D. Piccolo INFN Sezione di Genova, Genova, Italy P. Fabbricatore, R. Musenich INFN Sezione di Milano-Biccoca a , Universit`a di Milano-Bicocca b , Milano, Italy A. Benagliaa,b , F. De Guioa,b,1 , L. Di Matteoa,b , S. Gennai1 , A. Ghezzia,b , S. Malvezzia , A. Martellia,b , A. Massironia,b , D. Menascea , L. Moronia , M. Paganonia,b , D. Pedrinia , S. Ragazzia,b , N. Redaellia , S. Salaa , T. Tabarelli de Fatisa,b INFN Sezione di Napoli a , Universit`a di Napoli ”Federico II” b , Napoli, Italy S. Buontempoa , C.A. Carrillo Montoyaa,1 , N. Cavalloa,20 , A. De Cosaa,b , F. Fabozzia,20 , A.O.M. Iorioa,1 , L. Listaa , M. Merolaa,b , P. Paoluccia INFN Sezione di Padova a , Universit`a di Padova b , Universit`a di Trento (Trento) c , Padova, Italy P. Azzia , N. Bacchettaa , P. Bellana,b , M. Bellatoa , M. Biasottoa,21 , D. Biselloa,b , A. Brancaa , P. Checchiaa , M. De Mattiaa,b , T. Dorigoa , F. Gasparinia,b , F. Gonellaa , A. Gozzelino, M. Gulminia,21 , S. Lacapraraa,21 , I. Lazzizzeraa,c , M. Margonia,b , G. Marona,21 , A.T. Meneguzzoa,b , M. Nespoloa,1 , M. Passaseoa , L. Perrozzia,1 , N. Pozzobona,b , P. Ronchesea,b , F. Simonettoa,b , E. Torassaa , M. Tosia,b , A. Triossia , S. Vaninia,b INFN Sezione di Pavia a , Universit`a di Pavia b , Pavia, Italy P. Baessoa,b , U. Berzanoa , S.P. Rattia,b , C. Riccardia,b , P. Torrea,b , P. Vituloa,b , C. Viviania,b INFN Sezione di Perugia a , Universit`a di Perugia b , Perugia, Italy M. Biasinia,b , G.M. Bileia , B. Caponeria,b , L. Fano` a,b , P. Laricciaa,b , A. Lucaronia,b,1 , G. Mantovania,b , M. Menichellia , A. Nappia,b , F. Romeoa,b , A. Santocchiaa,b , S. Taronia,b,1 , M. Valdataa,b INFN Sezione di Pisa a , Universit`a di Pisa b , Scuola Normale Superiore di Pisa c , Pisa, Italy P. Azzurria,c , G. Bagliesia , J. Bernardinia,b , T. Boccalia,1 , G. Broccoloa,c , R. Castaldia , R.T. D’Agnoloa,c , R. Dell’Orsoa , F. Fioria,b , L. Fo`aa,c , A. Giassia , A. Kraana , F. Ligabuea,c ,

20

A

The CMS Collaboration

T. Lomtadzea , L. Martinia,22 , A. Messineoa,b , F. Pallaa , G. Segneria , A.T. Serbana , P. Spagnoloa , R. Tenchinia , G. Tonellia,b,1 , A. Venturia,1 , P.G. Verdinia INFN Sezione di Roma a , Universit`a di Roma ”La Sapienza” b , Roma, Italy L. Baronea,b , F. Cavallaria , D. Del Rea,b , E. Di Marcoa,b , M. Diemoza , D. Francia,b , M. Grassia,1 , E. Longoa,b , S. Nourbakhsha , G. Organtinia,b , F. Pandolfia,b,1 , R. Paramattia , S. Rahatloua,b , C. Rovelli1 INFN Sezione di Torino a , Universit`a di Torino b , Universit`a del Piemonte Orientale (Novara) c , Torino, Italy N. Amapanea,b , R. Arcidiaconoa,c , S. Argiroa,b , M. Arneodoa,c , C. Biinoa , C. Bottaa,b,1 , N. Cartigliaa , R. Castelloa,b , M. Costaa,b , N. Demariaa , A. Grazianoa,b,1 , C. Mariottia , M. Maronea,b , S. Masellia , E. Migliorea,b , G. Milaa,b , V. Monacoa,b , M. Musicha,b , M.M. Obertinoa,c , N. Pastronea , M. Pelliccionia,b , A. Romeroa,b , M. Ruspaa,c , R. Sacchia,b , V. Solaa,b , A. Solanoa,b , A. Staianoa , A. Vilela Pereiraa INFN Sezione di Trieste a , Universit`a di Trieste b , Trieste, Italy S. Belfortea , F. Cossuttia , G. Della Riccaa,b , B. Gobboa , D. Montaninoa,b , A. Penzoa Kangwon National University, Chunchon, Korea S.G. Heo, S.K. Nam Kyungpook National University, Daegu, Korea S. Chang, J. Chung, D.H. Kim, G.N. Kim, J.E. Kim, D.J. Kong, H. Park, S.R. Ro, D. Son, D.C. Son, T. Son Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea Zero Kim, J.Y. Kim, S. Song Korea University, Seoul, Korea S. Choi, B. Hong, M.S. Jeong, M. Jo, H. Kim, J.H. Kim, T.J. Kim, K.S. Lee, D.H. Moon, S.K. Park, H.B. Rhee, E. Seo, S. Shin, K.S. Sim University of Seoul, Seoul, Korea M. Choi, S. Kang, H. Kim, C. Park, I.C. Park, S. Park, G. Ryu Sungkyunkwan University, Suwon, Korea Y. Choi, Y.K. Choi, J. Goh, M.S. Kim, E. Kwon, J. Lee, S. Lee, H. Seo, I. Yu Vilnius University, Vilnius, Lithuania M.J. Bilinskas, I. Grigelionis, M. Janulis, D. Martisiute, P. Petrov, T. Sabonis Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico H. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-de La Cruz, R. Lopez-Fernandez, ˜ Villalba, A. S´anchez-Hern´andez, L.M. Villasenor-Cendejas R. Magana Universidad Iberoamericana, Mexico City, Mexico S. Carrillo Moreno, F. Vazquez Valencia Benemerita Universidad Autonoma de Puebla, Puebla, Mexico H.A. Salazar Ibarguen Universidad Autonoma ´ de San Luis Potos´ı, San Luis Potos´ı, Mexico E. Casimiro Linares, A. Morelos Pineda, M.A. Reyes-Santos

21 University of Auckland, Auckland, New Zealand D. Krofcheck, J. Tam University of Canterbury, Christchurch, New Zealand P.H. Butler, R. Doesburg, H. Silverwood National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan M. Ahmad, I. Ahmed, M.I. Asghar, H.R. Hoorani, W.A. Khan, T. Khurshid, S. Qazi Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland G. Brona, M. Cwiok, W. Dominik, K. Doroba, A. Kalinowski, M. Konecki, J. Krolikowski Soltan Institute for Nuclear Studies, Warsaw, Poland ´ T. Frueboes, R. Gokieli, M. Gorski, M. Kazana, K. Nawrocki, K. Romanowska-Rybinska, M. Szleper, G. Wrochna, P. Zalewski Laboratorio ´ de Instrumenta¸ca˜ o e F´ısica Experimental de Part´ıculas, Lisboa, Portugal N. Almeida, P. Bargassa, A. David, P. Faccioli, P.G. Ferreira Parracho, M. Gallinaro, P. Musella, A. Nayak, P.Q. Ribeiro, J. Seixas, J. Varela Joint Institute for Nuclear Research, Dubna, Russia S. Afanasiev, I. Belotelov, P. Bunin, I. Golutvin, A. Kamenev, V. Karjavin, G. Kozlov, A. Lanev, P. Moisenz, V. Palichik, V. Perelygin, S. Shmatov, V. Smirnov, A. Volodko, A. Zarubin Petersburg Nuclear Physics Institute, Gatchina (St Petersburg), Russia V. Golovtsov, Y. Ivanov, V. Kim, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev, A. Vorobyev Institute for Nuclear Research, Moscow, Russia Yu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov, N. Krasnikov, V. Matveev, A. Pashenkov, A. Toropin, S. Troitsky Institute for Theoretical and Experimental Physics, Moscow, Russia V. Epshteyn, V. Gavrilov, V. Kaftanov† , M. Kossov1 , A. Krokhotin, N. Lychkovskaya, V. Popov, G. Safronov, S. Semenov, V. Stolin, E. Vlasov, A. Zhokin Moscow State University, Moscow, Russia E. Boos, A. Ershov, A. Gribushin, O. Kodolova, V. Korotkikh, I. Lokhtin, A. Markina, S. Obraztsov, M. Perfilov, S. Petrushanko, L. Sarycheva, V. Savrin, A. Snigirev, I. Vardanyan P.N. Lebedev Physical Institute, Moscow, Russia V. Andreev, M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, S.V. Rusakov, A. Vinogradov State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia I. Azhgirey, S. Bitioukov, V. Grishin1 , V. Kachanov, D. Konstantinov, A. Korablev, V. Krychkine, V. Petrov, R. Ryutin, S. Slabospitsky, A. Sobol, L. Tourtchanovitch, S. Troshin, N. Tyurin, A. Uzunian, A. Volkov University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia P. Adzic23 , M. Djordjevic, D. Krpic23 , J. Milosevic Centro de Investigaciones Energ´eticas Medioambientales y Tecnologicas ´ (CIEMAT), Madrid, Spain M. Aguilar-Benitez, J. Alcaraz Maestre, P. Arce, C. Battilana, E. Calvo, M. Cepeda, M. Cerrada,

22

A

The CMS Collaboration

M. Chamizo Llatas, N. Colino, B. De La Cruz, A. Delgado Peris, C. Diez Pardos, D. Dom´ınguez V´azquez, C. Fernandez Bedoya, J.P. Fern´andez Ramos, A. Ferrando, J. Flix, M.C. Fouz, P. Garcia-Abia, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa, G. Merino, J. Puerta Pelayo, I. Redondo, L. Romero, J. Santaolalla, M.S. Soares, C. Willmott Universidad Autonoma ´ de Madrid, Madrid, Spain ´ C. Albajar, G. Codispoti, J.F. de Troconiz Universidad de Oviedo, Oviedo, Spain J. Cuevas, J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero, L. Lloret Iglesias, J.M. Vizan Garcia Instituto de F´ısica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain J.A. Brochero Cifuentes, I.J. Cabrillo, A. Calderon, S.H. Chuang, J. Duarte Campderros, M. Felcini24 , M. Fernandez, G. Gomez, J. Gonzalez Sanchez, C. Jorda, P. Lobelle Pardo, A. Lopez Virto, J. Marco, R. Marco, C. Martinez Rivero, F. Matorras, F.J. Munoz Sanchez, J. Piedra Gomez25 , T. Rodrigo, A.Y. Rodr´ıguez-Marrero, A. Ruiz-Jimeno, L. Scodellaro, M. Sobron Sanudo, I. Vila, R. Vilar Cortabitarte CERN, European Organization for Nuclear Research, Geneva, Switzerland D. Abbaneo, E. Auffray, G. Auzinger, P. Baillon, A.H. Ball, D. Barney, A.J. Bell26 , D. Benedetti, C. Bernet3 , W. Bialas, P. Bloch, A. Bocci, S. Bolognesi, M. Bona, H. Breuker, K. Bunkowski, T. Camporesi, G. Cerminara, J.A. Coarasa Perez, B. Cur´e, D. D’Enterria, A. De Roeck, S. Di Guida, N. Dupont-Sagorin, A. Elliott-Peisert, B. Frisch, W. Funk, A. Gaddi, G. Georgiou, H. Gerwig, D. Gigi, K. Gill, D. Giordano, F. Glege, R. Gomez-Reino Garrido, M. Gouzevitch, P. Govoni, S. Gowdy, L. Guiducci, M. Hansen, C. Hartl, J. Harvey, J. Hegeman, B. Hegner, H.F. Hoffmann, A. Honma, V. Innocente, P. Janot, K. Kaadze, E. Karavakis, P. Lecoq, C. Lourenc¸o, T. M¨aki, M. Malberti, L. Malgeri, M. Mannelli, L. Masetti, A. Maurisset, F. Meijers, S. Mersi, E. Meschi, R. Moser, M.U. Mozer, M. Mulders, E. Nesvold1 , M. Nguyen, T. Orimoto, L. Orsini, E. Perez, A. Petrilli, A. Pfeiffer, M. Pierini, M. Pimi¨a, D. Piparo, G. Polese, A. Racz, J. Rodrigues Antunes, G. Rolandi27 , T. Rommerskirchen, M. Rovere, H. Sakulin, C. Sch¨afer, C. Schwick, I. Segoni, A. Sharma, P. Siegrist, M. Simon, P. Sphicas28 , M. Spiropulu29 , M. Stoye, M. Tadel, P. Tropea, A. Tsirou, P. Vichoudis, M. Voutilainen, W.D. Zeuner Paul Scherrer Institut, Villigen, Switzerland W. Bertl, K. Deiters, W. Erdmann, K. Gabathuler, R. Horisberger, Q. Ingram, H.C. Kaestli, ¨ S. Konig, D. Kotlinski, U. Langenegger, F. Meier, D. Renker, T. Rohe, J. Sibille30 , A. Starodumov31 Institute for Particle Physics, ETH Zurich, Zurich, Switzerland P. Bortignon, L. Caminada32 , N. Chanon, Z. Chen, S. Cittolin, G. Dissertori, M. Dittmar, J. Eugster, K. Freudenreich, C. Grab, W. Hintz, P. Lecomte, W. Lustermann, C. Marchica32 , P. Martinez Ruiz del Arbol, P. Meridiani, P. Milenovic33 , F. Moortgat, C. N¨ageli32 , P. Nef, F. Nessi-Tedaldi, L. Pape, F. Pauss, T. Punz, A. Rizzi, F.J. Ronga, M. Rossini, L. Sala, A.K. Sanchez, M.-C. Sawley, B. Stieger, L. Tauscher† , A. Thea, K. Theofilatos, D. Treille, C. Urscheler, R. Wallny, M. Weber, L. Wehrli, J. Weng Universit¨at Zurich, ¨ Zurich, Switzerland ´ C. Amsler, V. Chiochia, S. De Visscher, C. Favaro, M. Ivova Rikova, B. Millan Mejias, E. Aguilo, P. Otiougova, C. Regenfus, P. Robmann, A. Schmidt, H. Snoek National Central University, Chung-Li, Taiwan

23 Y.H. Chang, K.H. Chen, S. Dutta, C.M. Kuo, S.W. Li, W. Lin, Z.K. Liu, Y.J. Lu, D. Mekterovic, R. Volpe, J.H. Wu, S.S. Yu National Taiwan University (NTU), Taipei, Taiwan P. Bartalini, P. Chang, Y.H. Chang, Y.W. Chang, Y. Chao, K.F. Chen, W.-S. Hou, Y. Hsiung, K.Y. Kao, Y.J. Lei, R.-S. Lu, J.G. Shiu, Y.M. Tzeng, M. Wang Cukurova University, Adana, Turkey A. Adiguzel, M.N. Bakirci34 , S. Cerci35 , C. Dozen, I. Dumanoglu, A. Ekenel, E. Eskut, S. Girgis, G. Gokbulut, I. Hos, E.E. Kangal, A. Kayis Topaksu, G. Onengut, K. Ozdemir, S. Ozturk, A. Polatoz, K. Sogut36 , D. Sunar Cerci35 , B. Tali35 , H. Topakli34 , D. Uzun, L.N. Vergili, M. Vergili, S. Yilmaz Middle East Technical University, Physics Department, Ankara, Turkey I.V. Akin, T. Aliev, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler, K. Ocalan, A. Ozpineci, M. Serin, R. Sever, U.E. Surat, E. Yildirim, M. Zeyrek Bogazici University, Istanbul, Turkey ¨ M. Deliomeroglu, D. Demir37 , E. Gulmez, B. Isildak, M. Kaya38 , O. Kaya38 , S. Ozkorucuklu39 , N. Sonmez40 National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine L. Levchuk University of Bristol, Bristol, United Kingdom F. Bostock, J.J. Brooke, T.L. Cheng, E. Clement, D. Cussans, R. Frazier, J. Goldstein, M. Grimes, M. Hansen, D. Hartley, G.P. Heath, H.F. Heath, L. Kreczko, S. Metson, D.M. Newbold41 , K. Nirunpong, A. Poll, S. Senkin, V.J. Smith, S. Ward Rutherford Appleton Laboratory, Didcot, United Kingdom L. Basso42 , A. Belyaev42 , C. Brew, R.M. Brown, B. Camanzi, D.J.A. Cockerill, J.A. Coughlan, K. Harder, S. Harper, J. Jackson, B.W. Kennedy, E. Olaiya, D. Petyt, B.C. Radburn-Smith, C.H. Shepherd-Themistocleous, I.R. Tomalin, W.J. Womersley, S.D. Worm Imperial College, London, United Kingdom R. Bainbridge, G. Ball, J. Ballin, R. Beuselinck, O. Buchmuller, D. Colling, N. Cripps, M. Cutajar, G. Davies, M. Della Negra, W. Ferguson, J. Fulcher, D. Futyan, A. Gilbert, A. Guneratne Bryer, G. Hall, Z. Hatherell, J. Hays, G. Iles, M. Jarvis, G. Karapostoli, L. Lyons, B.C. MacEvoy, A.M. Magnan, J. Marrouche, B. Mathias, R. Nandi, J. Nash, A. Nikitenko31 , A. Papageorgiou, M. Pesaresi, K. Petridis, M. Pioppi43 , D.M. Raymond, S. Rogerson, N. Rompotis, A. Rose, M.J. Ryan, C. Seez, P. Sharp, A. Sparrow, A. Tapper, S. Tourneur, M. Vazquez Acosta, T. Virdee, S. Wakefield, N. Wardle, D. Wardrope, T. Whyntie Brunel University, Uxbridge, United Kingdom M. Barrett, M. Chadwick, J.E. Cole, P.R. Hobson, A. Khan, P. Kyberd, D. Leslie, W. Martin, I.D. Reid, L. Teodorescu Baylor University, Waco, USA K. Hatakeyama, H. Liu Boston University, Boston, USA T. Bose, E. Carrera Jarrin, C. Fantasia, A. Heister, J. St. John, P. Lawson, D. Lazic, J. Rohlf, D. Sperka, L. Sulak

24

A

The CMS Collaboration

Brown University, Providence, USA A. Avetisyan, S. Bhattacharya, J.P. Chou, D. Cutts, A. Ferapontov, U. Heintz, S. Jabeen, G. Kukartsev, G. Landsberg, M. Luk, M. Narain, D. Nguyen, M. Segala, T. Sinthuprasith, T. Speer, K.V. Tsang University of California, Davis, Davis, USA R. Breedon, M. Calderon De La Barca Sanchez, S. Chauhan, M. Chertok, J. Conway, P.T. Cox, J. Dolen, R. Erbacher, E. Friis, W. Ko, A. Kopecky, R. Lander, H. Liu, S. Maruyama, T. Miceli, M. Nikolic, D. Pellett, J. Robles, S. Salur, T. Schwarz, M. Searle, J. Smith, M. Squires, M. Tripathi, R. Vasquez Sierra, C. Veelken University of California, Los Angeles, Los Angeles, USA V. Andreev, K. Arisaka, D. Cline, R. Cousins, A. Deisher, J. Duris, S. Erhan, C. Farrell, J. Hauser, M. Ignatenko, C. Jarvis, C. Plager, G. Rakness, P. Schlein† , J. Tucker, V. Valuev University of California, Riverside, Riverside, USA J. Babb, A. Chandra, R. Clare, J. Ellison, J.W. Gary, F. Giordano, G. Hanson, G.Y. Jeng, S.C. Kao, F. Liu, H. Liu, O.R. Long, A. Luthra, H. Nguyen, B.C. Shen† , R. Stringer, J. Sturdy, S. Sumowidagdo, R. Wilken, S. Wimpenny University of California, San Diego, La Jolla, USA W. Andrews, J.G. Branson, G.B. Cerati, D. Evans, F. Golf, A. Holzner, R. Kelley, M. Lebourgeois, J. Letts, B. Mangano, S. Padhi, C. Palmer, G. Petrucciani, H. Pi, M. Pieri, R. Ranieri, M. Sani, ¨ V. Sharma, S. Simon, E. Sudano, Y. Tu, A. Vartak, S. Wasserbaech44 , F. Wurthwein, A. Yagil, J. Yoo University of California, Santa Barbara, Santa Barbara, USA D. Barge, R. Bellan, C. Campagnari, M. D’Alfonso, T. Danielson, K. Flowers, P. Geffert, J. Incandela, C. Justus, P. Kalavase, S.A. Koay, D. Kovalskyi, V. Krutelyov, S. Lowette, N. Mccoll, V. Pavlunin, F. Rebassoo, J. Ribnik, J. Richman, R. Rossin, D. Stuart, W. To, J.R. Vlimant California Institute of Technology, Pasadena, USA A. Apresyan, A. Bornheim, J. Bunn, Y. Chen, M. Gataullin, Y. Ma, A. Mott, H.B. Newman, C. Rogan, K. Shin, V. Timciuc, P. Traczyk, J. Veverka, R. Wilkinson, Y. Yang, R.Y. Zhu Carnegie Mellon University, Pittsburgh, USA B. Akgun, R. Carroll, T. Ferguson, Y. Iiyama, D.W. Jang, S.Y. Jun, Y.F. Liu, M. Paulini, J. Russ, H. Vogel, I. Vorobiev University of Colorado at Boulder, Boulder, USA J.P. Cumalat, M.E. Dinardo, B.R. Drell, C.J. Edelmaier, W.T. Ford, A. Gaz, B. Heyburn, E. Luiggi Lopez, U. Nauenberg, J.G. Smith, K. Stenson, K.A. Ulmer, S.R. Wagner, S.L. Zang Cornell University, Ithaca, USA L. Agostino, J. Alexander, D. Cassel, A. Chatterjee, S. Das, N. Eggert, L.K. Gibbons, B. Heltsley, W. Hopkins, A. Khukhunaishvili, B. Kreis, G. Nicolas Kaufman, J.R. Patterson, D. Puigh, A. Ryd, E. Salvati, X. Shi, W. Sun, W.D. Teo, J. Thom, J. Thompson, J. Vaughan, Y. Weng, L. Winstrom, P. Wittich Fairfield University, Fairfield, USA A. Biselli, G. Cirino, D. Winn Fermi National Accelerator Laboratory, Batavia, USA S. Abdullin, M. Albrow, J. Anderson, G. Apollinari, M. Atac, J.A. Bakken, S. Banerjee, L.A.T. Bauerdick, A. Beretvas, J. Berryhill, P.C. Bhat, I. Bloch, F. Borcherding, K. Burkett,

25 J.N. Butler, V. Chetluru, H.W.K. Cheung, F. Chlebana, S. Cihangir, W. Cooper, D.P. Eartly, V.D. Elvira, S. Esen, I. Fisk, J. Freeman, Y. Gao, E. Gottschalk, D. Green, K. Gunthoti, O. Gutsche, J. Hanlon, R.M. Harris, J. Hirschauer, B. Hooberman, H. Jensen, M. Johnson, U. Joshi, R. Khatiwada, B. Klima, K. Kousouris, S. Kunori, S. Kwan, C. Leonidopoulos, P. Limon, D. Lincoln, R. Lipton, J. Lykken, K. Maeshima, J.M. Marraffino, D. Mason, P. McBride, T. Miao, K. Mishra, S. Mrenna, Y. Musienko45 , C. Newman-Holmes, V. O’Dell, R. Pordes, O. Prokofyev, N. Saoulidou, E. Sexton-Kennedy, S. Sharma, W.J. Spalding, L. Spiegel, P. Tan, L. Taylor, S. Tkaczyk, L. Uplegger, E.W. Vaandering, R. Vidal, J. Whitmore, W. Wu, F. Yang, F. Yumiceva, J.C. Yun University of Florida, Gainesville, USA D. Acosta, P. Avery, D. Bourilkov, M. Chen, M. De Gruttola, G.P. Di Giovanni, D. Dobur, A. Drozdetskiy, R.D. Field, M. Fisher, Y. Fu, I.K. Furic, J. Gartner, B. Kim, J. Konigsberg, A. Korytov, A. Kropivnitskaya, T. Kypreos, K. Matchev, G. Mitselmakher, L. Muniz, C. Prescott, R. Remington, M. Schmitt, B. Scurlock, P. Sellers, N. Skhirtladze, M. Snowball, D. Wang, J. Yelton, M. Zakaria Florida International University, Miami, USA C. Ceron, V. Gaultney, L. Kramer, L.M. Lebolo, S. Linn, P. Markowitz, G. Martinez, D. Mesa, J.L. Rodriguez Florida State University, Tallahassee, USA T. Adams, A. Askew, J. Bochenek, J. Chen, B. Diamond, S.V. Gleyzer, J. Haas, S. Hagopian, V. Hagopian, M. Jenkins, K.F. Johnson, H. Prosper, L. Quertenmont, S. Sekmen, V. Veeraraghavan Florida Institute of Technology, Melbourne, USA M.M. Baarmand, B. Dorney, S. Guragain, M. Hohlmann, H. Kalakhety, R. Ralich, I. Vodopiyanov University of Illinois at Chicago (UIC), Chicago, USA M.R. Adams, I.M. Anghel, L. Apanasevich, Y. Bai, V.E. Bazterra, R.R. Betts, J. Callner, R. Cavanaugh, C. Dragoiu, L. Gauthier, C.E. Gerber, S. Hamdan, D.J. Hofman, S. Khalatyan, G.J. Kunde46 , F. Lacroix, M. Malek, C. O’Brien, C. Silvestre, A. Smoron, D. Strom, N. Varelas The University of Iowa, Iowa City, USA U. Akgun, E.A. Albayrak, B. Bilki, W. Clarida, F. Duru, C.K. Lae, E. McCliment, J.-P. Merlo, H. Mermerkaya47 , A. Mestvirishvili, A. Moeller, J. Nachtman, C.R. Newsom, E. Norbeck, J. Olson, Y. Onel, F. Ozok, S. Sen, J. Wetzel, T. Yetkin, K. Yi Johns Hopkins University, Baltimore, USA B.A. Barnett, B. Blumenfeld, A. Bonato, C. Eskew, D. Fehling, G. Giurgiu, A.V. Gritsan, Z.J. Guo, G. Hu, P. Maksimovic, S. Rappoccio, M. Swartz, N.V. Tran, A. Whitbeck The University of Kansas, Lawrence, USA P. Baringer, A. Bean, G. Benelli, O. Grachov, R.P. Kenny Iii, M. Murray, D. Noonan, S. Sanders, J.S. Wood, V. Zhukova Kansas State University, Manhattan, USA A.f. Barfuss, T. Bolton, I. Chakaberia, A. Ivanov, S. Khalil, M. Makouski, Y. Maravin, S. Shrestha, I. Svintradze, Z. Wan Lawrence Livermore National Laboratory, Livermore, USA J. Gronberg, D. Lange, D. Wright

26

A

The CMS Collaboration

University of Maryland, College Park, USA A. Baden, M. Boutemeur, S.C. Eno, D. Ferencek, J.A. Gomez, N.J. Hadley, R.G. Kellogg, M. Kirn, Y. Lu, A.C. Mignerey, K. Rossato, P. Rumerio, F. Santanastasio, A. Skuja, J. Temple, M.B. Tonjes, S.C. Tonwar, E. Twedt Massachusetts Institute of Technology, Cambridge, USA B. Alver, G. Bauer, J. Bendavid, W. Busza, E. Butz, I.A. Cali, M. Chan, V. Dutta, P. Everaerts, G. Gomez Ceballos, M. Goncharov, K.A. Hahn, P. Harris, Y. Kim, M. Klute, Y.-J. Lee, W. Li, C. Loizides, P.D. Luckey, T. Ma, S. Nahn, C. Paus, D. Ralph, C. Roland, G. Roland, M. Rudolph, ¨ G.S.F. Stephans, F. Stockli, K. Sumorok, K. Sung, E.A. Wenger, S. Xie, M. Yang, Y. Yilmaz, A.S. Yoon, M. Zanetti University of Minnesota, Minneapolis, USA S.I. Cooper, P. Cushman, B. Dahmes, A. De Benedetti, P.R. Dudero, G. Franzoni, J. Haupt, K. Klapoetke, Y. Kubota, J. Mans, V. Rekovic, R. Rusack, M. Sasseville, A. Singovsky University of Mississippi, University, USA L.M. Cremaldi, R. Godang, R. Kroeger, L. Perera, R. Rahmat, D.A. Sanders, D. Summers University of Nebraska-Lincoln, Lincoln, USA K. Bloom, S. Bose, J. Butt, D.R. Claes, A. Dominguez, M. Eads, J. Keller, T. Kelly, I. Kravchenko, J. Lazo-Flores, H. Malbouisson, S. Malik, G.R. Snow State University of New York at Buffalo, Buffalo, USA U. Baur, A. Godshalk, I. Iashvili, S. Jain, A. Kharchilava, A. Kumar, S.P. Shipkowski, K. Smith Northeastern University, Boston, USA G. Alverson, E. Barberis, D. Baumgartel, O. Boeriu, M. Chasco, S. Reucroft, J. Swain, D. Trocino, D. Wood, J. Zhang Northwestern University, Evanston, USA A. Anastassov, A. Kubik, N. Odell, R.A. Ofierzynski, B. Pollack, A. Pozdnyakov, M. Schmitt, S. Stoynev, M. Velasco, S. Won University of Notre Dame, Notre Dame, USA L. Antonelli, D. Berry, M. Hildreth, C. Jessop, D.J. Karmgard, J. Kolb, T. Kolberg, K. Lannon, W. Luo, S. Lynch, N. Marinelli, D.M. Morse, T. Pearson, R. Ruchti, J. Slaunwhite, N. Valls, M. Wayne, J. Ziegler The Ohio State University, Columbus, USA B. Bylsma, L.S. Durkin, J. Gu, C. Hill, P. Killewald, K. Kotov, T.Y. Ling, M. Rodenburg, G. Williams Princeton University, Princeton, USA N. Adam, E. Berry, P. Elmer, D. Gerbaudo, V. Halyo, P. Hebda, A. Hunt, J. Jones, E. Laird, D. Lopes Pegna, D. Marlow, T. Medvedeva, M. Mooney, J. Olsen, P. Pirou´e, X. Quan, H. Saka, D. Stickland, C. Tully, J.S. Werner, A. Zuranski University of Puerto Rico, Mayaguez, USA J.G. Acosta, X.T. Huang, A. Lopez, H. Mendez, S. Oliveros, J.E. Ramirez Vargas, A. Zatserklyaniy Purdue University, West Lafayette, USA E. Alagoz, V.E. Barnes, G. Bolla, L. Borrello, D. Bortoletto, A. Everett, A.F. Garfinkel, L. Gutay, Z. Hu, M. Jones, O. Koybasi, M. Kress, A.T. Laasanen, N. Leonardo, C. Liu, V. Maroussov,

27 P. Merkel, D.H. Miller, N. Neumeister, I. Shipsey, D. Silvers, A. Svyatkovskiy, H.D. Yoo, J. Zablocki, Y. Zheng Purdue University Calumet, Hammond, USA P. Jindal, N. Parashar Rice University, Houston, USA C. Boulahouache, V. Cuplov, K.M. Ecklund, F.J.M. Geurts, B.P. Padley, R. Redjimi, J. Roberts, J. Zabel University of Rochester, Rochester, USA B. Betchart, A. Bodek, Y.S. Chung, R. Covarelli, P. de Barbaro, R. Demina, Y. Eshaq, H. Flacher, A. Garcia-Bellido, P. Goldenzweig, Y. Gotra, J. Han, A. Harel, D.C. Miner, D. Orbaker, G. Petrillo, D. Vishnevskiy, M. Zielinski The Rockefeller University, New York, USA A. Bhatti, R. Ciesielski, L. Demortier, K. Goulianos, G. Lungu, S. Malik, C. Mesropian, M. Yan Rutgers, the State University of New Jersey, Piscataway, USA O. Atramentov, A. Barker, D. Duggan, Y. Gershtein, R. Gray, E. Halkiadakis, D. Hidas, D. Hits, A. Lath, S. Panwalkar, R. Patel, A. Richards, K. Rose, S. Schnetzer, S. Somalwar, R. Stone, S. Thomas University of Tennessee, Knoxville, USA G. Cerizza, M. Hollingsworth, S. Spanier, Z.C. Yang, A. York Texas A&M University, College Station, USA R. Eusebi, J. Gilmore, A. Gurrola, T. Kamon, V. Khotilovich, R. Montalvo, I. Osipenkov, Y. Pakhotin, J. Pivarski, A. Safonov, S. Sengupta, A. Tatarinov, D. Toback, M. Weinberger Texas Tech University, Lubbock, USA N. Akchurin, C. Bardak, J. Damgov, C. Jeong, K. Kovitanggoon, S.W. Lee, P. Mane, Y. Roh, A. Sill, I. Volobouev, R. Wigmans, E. Yazgan Vanderbilt University, Nashville, USA E. Appelt, E. Brownson, D. Engh, C. Florez, W. Gabella, M. Issah, W. Johns, P. Kurt, C. Maguire, A. Melo, P. Sheldon, B. Snook, S. Tuo, J. Velkovska University of Virginia, Charlottesville, USA M.W. Arenton, M. Balazs, S. Boutle, B. Cox, B. Francis, R. Hirosky, A. Ledovskoy, C. Lin, C. Neu, R. Yohay Wayne State University, Detroit, USA S. Gollapinni, R. Harr, P.E. Karchin, P. Lamichhane, M. Mattson, C. Milst`ene, A. Sakharov University of Wisconsin, Madison, USA M. Anderson, M. Bachtis, J.N. Bellinger, D. Carlsmith, S. Dasu, J. Efron, K. Flood, L. Gray, K.S. Grogg, M. Grothe, R. Hall-Wilton, M. Herndon, A. Herv´e, P. Klabbers, J. Klukas, A. Lanaro, C. Lazaridis, J. Leonard, R. Loveless, A. Mohapatra, F. Palmonari, D. Reeder, I. Ross, A. Savin, W.H. Smith, J. Swanson, M. Weinberg †: Deceased 1: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland 2: Also at Universidade Federal do ABC, Santo Andre, Brazil 3: Also at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France 4: Also at Suez Canal University, Suez, Egypt

28

A

The CMS Collaboration

5: Also at British University, Cairo, Egypt 6: Also at Fayoum University, El-Fayoum, Egypt 7: Also at Soltan Institute for Nuclear Studies, Warsaw, Poland 8: Also at Massachusetts Institute of Technology, Cambridge, USA 9: Also at Universit´e de Haute-Alsace, Mulhouse, France 10: Also at Brandenburg University of Technology, Cottbus, Germany 11: Also at Moscow State University, Moscow, Russia 12: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary ¨ os ¨ Lor´and University, Budapest, Hungary 13: Also at Eotv 14: Also at Tata Institute of Fundamental Research - HECR, Mumbai, India 15: Also at University of Visva-Bharati, Santiniketan, India 16: Also at Sharif University of Technology, Tehran, Iran 17: Also at Shiraz University, Shiraz, Iran 18: Also at Isfahan University of Technology, Isfahan, Iran 19: Also at Facolt`a Ingegneria Universit`a di Roma ”La Sapienza”, Roma, Italy 20: Also at Universit`a della Basilicata, Potenza, Italy 21: Also at Laboratori Nazionali di Legnaro dell’ INFN, Legnaro, Italy 22: Also at Universit`a degli studi di Siena, Siena, Italy 23: Also at Faculty of Physics of University of Belgrade, Belgrade, Serbia 24: Also at University of California, Los Angeles, Los Angeles, USA 25: Also at University of Florida, Gainesville, USA 26: Also at Universit´e de Gen`eve, Geneva, Switzerland 27: Also at Scuola Normale e Sezione dell’ INFN, Pisa, Italy 28: Also at University of Athens, Athens, Greece 29: Also at California Institute of Technology, Pasadena, USA 30: Also at The University of Kansas, Lawrence, USA 31: Also at Institute for Theoretical and Experimental Physics, Moscow, Russia 32: Also at Paul Scherrer Institut, Villigen, Switzerland 33: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia 34: Also at Gaziosmanpasa University, Tokat, Turkey 35: Also at Adiyaman University, Adiyaman, Turkey 36: Also at Mersin University, Mersin, Turkey 37: Also at Izmir Institute of Technology, Izmir, Turkey 38: Also at Kafkas University, Kars, Turkey 39: Also at Suleyman Demirel University, Isparta, Turkey 40: Also at Ege University, Izmir, Turkey 41: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom 42: Also at School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom 43: Also at INFN Sezione di Perugia; Universit`a di Perugia, Perugia, Italy 44: Also at Utah Valley University, Orem, USA 45: Also at Institute for Nuclear Research, Moscow, Russia 46: Also at Los Alamos National Laboratory, Los Alamos, USA 47: Also at Erzincan University, Erzincan, Turkey

Lihat lebih banyak...

Komentar

Copyright © 2017 KULSLIDE Inc.