Indications of Suppression of Excited States in Pb-Pb Collisions at
p
ffiffiffiffiffiffiffiffi
s
NN¼ 2:76 TeV
S. Chatrchyan et al.* (CMS Collaboration)
(Received 25 May 2011; published 28 July 2011)
A comparison of the relative yields of resonances in the þ decay channel in Pb-Pb and pp collisions at a center-of-mass energy per nucleon pair of 2.76 TeV is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above4 GeV=c and pseudorapidity below 2.4, the double ratio of theð2SÞ and ð3SÞ excited states to the ð1SÞ ground state in Pb-Pb and pp collisions, ½ð2S þ 3SÞ=ð1SÞPb-Pb=½ð2S þ 3SÞ=ð1SÞpp, is found to be 0:31þ0:190:15ðstatÞ
0:03ðsystÞ. The probability to obtain the measured value, or lower, if the true double ratio is unity, is calculated to be less than 1%.
DOI:10.1103/PhysRevLett.107.052302 PACS numbers: 25.75.Nq, 14.40.Pq
Quantum chromodynamics (QCD) predicts that strongly interacting matter undergoes a phase transition to a decon-fined state, often referred to as the quark-gluon plasma (QGP), in which quarks and gluons are no longer bound within hadrons. Calculations in lattice QCD [1,2] indicate that the transition should occur at a critical temperature Tc ’ 150–175 MeV, corresponding to an energy density "c’ 1 GeV=fm3.
If the QGP is formed in heavy-ion collisions, it is expected to screen the confining potential of heavy quark-antiquark pairs [3], leading to the melting of char-monia (J=c;c0; c. . . ) and bottomonia (ð1SÞ; ð2SÞ; ð3SÞ; b. . .). The melting temperature depends on the binding energy of the quarkonium state. The ground states J=c, andð1SÞ, are expected to dissolve at significantly higher temperatures than the more loosely bound excited states. Quenched lattice QCD calculations [4,5] predict that theðnSÞ states melt at 1.2 Tc (3S), 1.6 Tc (2S), and above 4 Tc (1S), while modern spectral-function ap-proaches with complex potentials [6,7] favor somewhat lower dissolution temperatures. This sequential melting pattern is generally considered a ‘‘smoking-gun’’ signature of the QCD deconfinement transition. However, a large fraction of the observed ð1SÞ yield is due to decays of heavier states (around 50% for theð1SÞ [8]). Therefore the melting of the excited states is expected to result in a significant suppression of the observedð1SÞ yield, even if the medium is not hot enough to directly dissolve it.
Observations of a larger J=c andcð2SÞ suppression in heavy-ion collisions with respect to proton-nucleus colli-sions were reported by the NA38 [9], NA50 [10,11], and NA60 [12] fixed-target experiments at the Super Proton
Synchrotron (SPS), respectively, in sulfur-uranium, lead-lead, and indium-indium collisions, at center-of-mass energies per nucleon pair (pffiffiffiffiffiffiffiffisNN) of about 20 GeV. The PHENIX experiment, at the Relativistic Heavy Ion Collider (RHIC), extended the J=c suppression measure-ments to Au-Au collisions at pffiffiffiffiffiffiffiffisNN¼ 200 GeV [13]. Recent results from ATLAS and CMS show J=c suppression at LHC [14,15]. At RHIC, bottomonia produc-tion becomes measurable [16], though with limited inte-grated luminosities. PHENIX observed that the dimuon yield in the mass region for minimum bias Au-Au collisions is less than 64%, at the 90% confidence level, of the value expected by extrapolating the proton-proton yields [17].
A new era of detailed studies of the bottomonium family in heavy-ion collisions has started at the Large Hadron Collider (LHC). The measurement reported in this Letter is performed with data recorded by the Compact Muon Solenoid (CMS) experiment during the first lead-lead (Pb-Pb) LHC run, at the end of 2010, and during the proton-proton (pp) run of March 2011, both at pffiffiffiffiffiffiffiffisNN¼ 2:76 TeV. The integrated luminosity used in this analysis corresponds to7:28 b1for Pb-Pb and225 nb1for pp collisions, the latter corresponding approximately to the equivalent nucleon-nucleon luminosity of the Pb-Pb run. The momentum resolution of the CMS detector results in well-resolved peaks in the dimuon mass spectrum. The CMS Collaboration has previously studied production in pp data at pffiffiffis¼ 7 TeV [18], using techniques to extract the yields that are very similar to the ones used in the study reported in this Letter.
A detailed description of the CMS detector can be found in [19]. Its central feature is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the field volume are the silicon (Si) pixel and strip tracker, the crystal electromagnetic calorimeter, and the brass or scintillator hadron calorimeter. Muons are measured in gas-ionization detectors embedded in the steel return yoke. In addition, CMS has extensive
*Full author list given at the end of the article.
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PRL 107, 052302 (2011) P H Y S I C A L R E V I E W L E T T E R S 29 JULY 2011week ending
forward calorimetry, in particular, two steel or quartz-fiber Cˇ erenkov hadron forward (HF) calorimeters, which cover the pseudorapidity range2:9 < jj < 5:2.
In this analysis, states are identified through their dimuon decay. The silicon pixel and strip tracker measures charged-particle trajectories in the range jj < 2:5. The tracker consists of 66 M pixel and 10 M strip detector channels, providing a vertex resolution of15 m in the transverse plane. Muons are detected in the jj < 2:4 range, with detection planes based on three technologies: drift tubes, cathode strip chambers, and resistive plate chambers. Because of the strong magnetic field and the fine granularity of the Si tracker, the muon transverse momentum measurement (pT) based on information from the Si tracker alone has a resolution between 1% and 2% for a typical muon in this analysis.
In both the Pb-Pb and pp runs, the events are selected by the CMS two-level trigger. At the first, hardware level, two independent muon candidates are required in the muon detectors. No selection is made on momentum or pseudor-apidity, but in the pp case more stringent quality require-ments are imposed for each muon in order to reduce the higher trigger rate. In both cases, the software-based higher-level trigger accepts the lower-level decision with-out applying further criteria. The single-muon trigger effi-ciencies are measured from reconstructed J=c ! decays, for muons with pT> 4 GeV=c. The values of these efficiencies, ð96:1 1:0Þ% in the Pb-Pb data set andð95:5 0:6Þ% in the pp data set, are consistent.
For the Pb-Pb data, events are preselected offline if they contain a reconstructed primary vertex made of at least two tracks, and a coincidence in both HF calorimeters of energy deposits larger than 3 GeV in at least three towers. These criteria reduce contributions from single-beam interactions (e.g., single-beam-gas and single-beam-halo collisions with the beam pipe), ultraperipheral electromagnetic collisions, and cosmic-ray muons. A small fraction of the most peripheral Pb-Pb collisions is not selected by these requirements, which accept ð97 3Þ% of the hadronic inelastic cross section [20]. For the pp run, a similar event filter is applied, relaxing the HF coincidence to one tower in each HF, with at least 3 GeV deposited. This filter removes only 1% of the pp events satisfying the dimuon trigger.
The muon offline reconstruction is seeded with’ 99% efficiency by tracks in the muon detectors, called stand-alone muons. These tracks are then matched to tracks reconstructed in the Si tracker by means of an algorithm optimized for the heavy-ion environment [21,22]. For muons from decays the Si-tracking efficiency is ’ 85%. This efficiency is lower than in pp, as in Pb-Pb the Si-track reconstruction is seeded by a greater number of pixel hits to reduce the large number of random combina-tions arising from the high multiplicity of each event. Combined fits of the muon and Si-tracker tracks are used
to obtain the results presented in this Letter. The heavy-ion dedicated reconstruction algorithm is applied to the pp data in order to avoid potential biases.
Identical, very-loose selection criteria are applied to the muons in the pp and Pb-Pb data. Their transverse (longi-tudinal) distance of closest approach from the event vertex is required to be less than 3 (15) cm. Tracks are only kept if they have 11 or more hits in the silicon tracker and the 2 per degree of freedom of the combined (tracker) track fit is lower than 20 (4). The two muon trajectories are fit with a common vertex constraint, and events are retained if the fit 2probability is larger than 1%. This removes background arising primarily from the displaced, semileptonic decays of charm and bottom hadrons. As determined from Monte Carlo simulation of the ð1SÞ signal, these selection cri-teria are found to reduce the efficiency by 3.9%, which is consistent with the signal loss observed in both pp and Pb-Pb data. The available event sample limits to20 GeV=c the dimuon transverse momentum range probed in this study.
Only muons with a transverse momentum (pT) higher than4 GeV=c are considered, resulting in a acceptance of approximately 25% for the jyj < 2:4 rapidity range. This requirement optimizes the significance of the ð1SÞ signal in Pb-Pb data and is applied to both data sets. The acceptance of a state depends on its mass, since the excited states give rise to higher-momenta muons. In con-sequence, requiring higher pT increases the acceptance for the excited states relative to the ground state. In the corre-sponding analysis performed with the higher statistics (3:1 pb1) 7 TeV data [18], looser criteria were applied (pT > 3:5 GeV=c and jj < 1:6, or p
T > 2:5 GeV=c and 1:6 < jj < 2:4), where is the muon pseudora-pidity. The stricter (pT > 4 GeV=c) requirements used here enhance the ð2S þ 3SÞ=ð1SÞ yield ratio by ’ 60% in the pp data at 2.76 TeV. It was checked that, applying identical pp reconstruction algorithms and pT requirements, theð2S þ 3SÞ=ð1SÞ yield ratio is consis-tent, within statistical uncertainties, between the 2.76 and 7 TeV pp data sets [15].
The dimuon invariant-mass spectra with the selection criteria applied are shown in Fig. 1for the pp and Pb-Pb data sets. Within the 7–14 GeV=c2 mass range, there are 561 (628) opposite-sign muon pairs in the pp (Pb-Pb) data set. The three Y peaks are clearly observed in the pp case, but the ð2SÞ and ð3SÞ are not visible over the residual background in Pb-Pb collisions.
An extended unbinned maximum likelihood fit to the two invariant-mass distributions of Fig.1is performed to extract the yields, following the method described in [18]. The measured mass line shape of each state is parame-trized by a ‘‘crystal ball’’ (CB) function, i.e., a Gaussian resolution function with the lowside tail replaced by a power law describing final-state radiation (FSR). Since the three resonances partially overlap in the measured dimuon mass, they are fit simultaneously. Therefore, the
probability distribution function (PDF) describing the signal consists of three CB functions. In addition to the threeðnSÞ yields, the ð1SÞ mass is the only parameter left free, to accommodate a possible bias in the momentum scale calibration. The mass ratios between the states are fixed to their world average values [23] and the mass resolution is forced to scale with the resonance mass. The ð1SÞ resolution is fixed to the value estimated in the simulation,92 MeV=c2, which is compatible with the resolution obtained from both the Pb-Pb and pp data. The lowside tail parameters are also fixed to the values obtained via simulation. Finally, a second-order polynomial is chosen to describe the background in the 7–14 GeV=c2 mass-fit range.
The quality of the unbinned fit is checked a posteriori by comparing the obtained line shapes to the binned data of Fig.1. The 2probabilities are 74% and 77%, respectively, for pp and Pb-Pb.
The ratios of the observed (uncorrected) yields of the ð2SÞ and ð3SÞ excited states to the ð1SÞ ground state in the pp and Pb-Pb data are
ð2S þ 3SÞ=ð1SÞjpp¼ 0:78þ0:160:14 0:02; (1) ð2S þ 3SÞ=ð1SÞjPb-Pb¼ 0:24þ0:130:12 0:02; (2) where the first uncertainty is statistical and the second is systematic.
The systematic uncertainties are computed by varying the line shape in the following ways: (1) the CB-tail parameters are varied randomly according to their covari-ance matrix and within conservative values covering im-perfect knowledge of the amount of detector material and FSR in the underlying process; (2) the resolution is varied by 5 MeV=c2, which is a conservative variation given the current understanding of the detector performance and reasonable changes that can be anticipated in the -resonance kinematics between pp and Pb-Pb data; (3) the background shape is changed from quadratic to linear while the mass range of the fit is varied from 6–15 to 8–12 GeV=c2; the observed root-mean-square of the results is taken as the systematic uncertainty. The quadratic sum of these three systematic uncertainties gives a relative uncertainty on the ratio of 10% (3%) for the Pb-Pb (pp) data.
The ratio of theð2S þ 3SÞ=ð1SÞ ratios in Pb-Pb and pp benefits from an almost complete cancellation of pos-sible acceptance and/or efficiency differences among the reconstructed resonances. A simultaneous fit to the pp and Pb-Pb mass spectra gives the double ratio
ð2S þ 3SÞ=ð1SÞjPb-Pb
ð2S þ 3SÞ=ð1SÞjpp ¼ 0:31 þ0:19
0:15ðstatÞ 0:03ðsystÞ; (3) where the systematic uncertainty (9%) arises from varying the line shape as described above in the simultaneous fit, thus taking into account partial cancellations of systematic effects.
The single-muon lower momentum requirement is a posteriori varied from 3 to 5 GeV=c in steps of 500 MeV=c, and it is found that pT requirements other than 4 GeV=c produce lower values of the double ratio. Fitting the pp and Pb-Pb spectra with free and independent mass resolution parameters leads to an increase of the double ratio by 15%.
To evaluate possible imperfect cancellations of accep-tance and efficiency effects in the double ratio, a full [24] detector simulation is performed. The effect of the higher Pb-Pb underlying event activity is accounted for by em-bedding, at the level of detector signals,ð1SÞ and ð2SÞ decays simulated by PYTHIA 6.424 [25] in Pb-Pb events simulated with HYDJET [26]. Track characteristics, such as the number of hits and the 2 of the track fit, have similar distributions in data and simulation. As mentioned above, the trigger efficiency is evaluated with data, by using single-muon-triggered data events, and reconstruc-ting J=c signal with and without the dimuon trigger ]
2 invariant mass [GeV/c µ µ 7 8 9 10 11 12 13 14 ) 2 Events / ( 0.14 GeV/c 0 10 20 30 40 50 60 70 80
requirement. The same exercise is carried out with the simulation and it agrees with the efficiency measured in data at the 2% level. The track efficiency in the silicon detector is measured with standalone muons, applying all selection criteria. The efficiencies in data and simulation agree within the 4% statistical uncertainty of the efficiency determined from data.
The difference in reconstruction and selection efficien-cies between the states is less than 5% and the relative variation with charged-particle multiplicity is about 10% from pp to central Pb-Pb collisions, producing a maximum change of 0.5% on the double ratio. The good agreement between single-muon trigger efficiencies extracted from data for the pp and Pb-Pb trigger requirements, applied to the ð1SÞ and ð2SÞ trigger efficiencies derived from simulation, leads to a negligible effect on the double ratio. The single-muon trigger efficiencies extracted from data agree within 1.5% for the pp and Pb-Pb trigger require-ments, and theð1SÞ and ð2SÞ trigger efficiencies agree within 3%, according to simulation: the potential trigger bias on the double ratio is negligible. Even doubling the size of these variations, to take the ð3SÞ into account, leads to a negligible change in the double ratio. The magnitudes of the statistical and systematic uncertainties on the double ratio, respectively, 55% and 9%, are signifi-cantly larger than the systematic uncertainties associated with possible imperfect cancellation of acceptance and efficiency effects. Therefore no additional uncertainty from these sources is applied.
Finally, using an ensemble of 1 106 pseudoexperi-ments, generated with the signal line shape obtained from the pp data [Fig. 1(a)], the background line shapes from both data sets, and a double ratio [Eq. (3)] equal to unity within statistical and systematic uncertainties, the probability of finding the measured value of 0.31 or below is estimated to be 0.9%. In other words, in the absence of a suppression due to physics mechanisms, the probability of a downward departure of the ratio from unity of this significance or greater is 0.9%, i.e., that corresponding to 2.4 sigma in a one-tailed integral of a Gaussian distribution.
Other studies from the CMS experiment show that the ð1SÞ is suppressed by about 40% [15] in minimum bias Pb-Pb collisions atpffiffiffiffiffiffiffiffisNN¼ 2:76 TeV. Since a large frac-tion of the ð1SÞ yield arises from decays of heavier bottomonium states [8], thisð1SÞ suppression could be indirectly caused by the suppression of the excited states reported in this Letter.
Production yields of quarkonium states can also be modified, from pp to Pb-Pb collisions, in the absence of QGP formation, by cold nuclear matter effects [27]. However, such effects should have a small impact on the double ratio reported here. The nuclear modifications of the parton distribution functions (shadowing) should have an equivalent effect on the three states, because their
production involves very similar partons, canceling in the ratio, at least to first order. The same should happen to any other initial-state nuclear effect. In principle, the larger and more loosely bound excited quarkonium states are more likely to be broken up by final-state interactions while traversing the nuclear matter, something extensively studied in the context of charmonium suppression at lower energies [28]. This ‘‘nuclear absorption’’ becomes weaker with increasing energy, and should be negligible at the LHC. At RHIC energies, the STAR experiment [29] has reported a ð1S þ 2S þ 3SÞ yield in d-Au collisions of 0:78 0:28 0:20 times the yield expected by scaling pp collisions, compatible with the absence of absorption. Furthermore, the double ratio presented here would only be sensitive to a difference between the nuclear dependen-cies of the three states and already at much lower energies the Fermilab E772 experiment observed [30], in proton-nucleus collisions, no such difference, within uncertainties, between theð1SÞ and the sum ð2S þ 3SÞ.
Future high-statistics heavy-ion and proton-nucleus runs at the LHC will provide further quarkonia measurements, which should help disentangle nuclear from medium effects and aid the interpretation of the result reported in this Letter.
In summary, a comparison of the relative yields of resonances has been performed in Pb-Pb and pp collisions at the same center-of-mass energy per nucleon pair of 2.76 TeV. The double ratio of theð2SÞ and ð3SÞ excited states to theð1SÞ ground state in Pb-Pb and pp collisions, ½ð2Sþ3SÞ=ð1SÞPb-Pb=½ð2Sþ3SÞ=ð1SÞpp, is found to be 0:31þ0:190:15ðstatÞ 0:03ðsystÞ, for muons of pT> 4 GeV=c and jj < 2:4. The probability to obtain the measured value, or lower, if the true double ratio is unity, has been calculated to be less than 1%.
We wish to congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC machine. We thank the technical and administra-tive staff at CERN and other CMS institutes, and acknowl-edge 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, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA an 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); 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 (U.S.). 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 Formation a` la Recherche dans l’industrie et dans l’Agriculture (FRIA-Belgium); and the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium).
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S. Liang,15X. Meng,15J. Tao,15J. Wang,15J. Wang,15X. Wang,15Z. Wang,15H. Xiao,15M. Xu,15J. Zang,15 Z. Zhang,15Y. Ban,16S. Guo,16Y. Guo,16W. Li,16Y. Mao,16S. J. Qian,16H. Teng,16B. Zhu,16W. Zou,16 A. Cabrera,17B. Gomez Moreno,17A. A. Ocampo Rios,17A. F. Osorio Oliveros,17J. C. Sanabria,17N. Godinovic,18
D. Lelas,18K. Lelas,18R. Plestina,18,dD. Polic,18I. Puljak,18Z. Antunovic,19M. Dzelalija,19V. Brigljevic,20 S. Duric,20K. Kadija,20S. Morovic,20A. Attikis,21M. Galanti,21J. Mousa,21C. Nicolaou,21F. Ptochos,21 P. A. Razis,21M. Finger,22M. Finger, Jr.,22Y. Assran,23,eA. Ellithi Kamel,23S. Khalil,23,fM. A. Mahmoud,23,g A. Hektor,24M. Kadastik,24M. Mu¨ntel,24M. Raidal,24L. Rebane,24A. Tiko,24V. Azzolini,25P. Eerola,25G. Fedi,25
S. Czellar,26J. Ha¨rko¨nen,26A. Heikkinen,26V. Karima¨ki,26R. Kinnunen,26M. J. Kortelainen,26T. Lampe´n,26 K. Lassila-Perini,26S. Lehti,26T. Linde´n,26P. Luukka,26T. Ma¨enpa¨a¨,26E. Tuominen,26J. Tuominiemi,26 E. Tuovinen,26D. Ungaro,26L. Wendland,26K. Banzuzi,27A. Karjalainen,27A. Korpela,27T. Tuuva,27D. Sillou,28
M. Besancon,29S. Choudhury,29M. Dejardin,29D. Denegri,29B. Fabbro,29J. L. Faure,29F. Ferri,29S. Ganjour,29 F. X. Gentit,29A. Givernaud,29P. Gras,29G. Hamel de Monchenault,29P. Jarry,29E. Locci,29J. Malcles,29
M. Marionneau,29L. Millischer,29J. Rander,29A. Rosowsky,29I. Shreyber,29M. Titov,29P. Verrecchia,29 S. Baffioni,30F. Beaudette,30L. Benhabib,30L. Bianchini,30M. Bluj,30,hC. Broutin,30P. Busson,30C. Charlot,30 T. Dahms,30L. Dobrzynski,30S. Elgammal,30R. Granier de Cassagnac,30M. Haguenauer,30P. Mine´,30C. Mironov,30
C. Ochando,30P. Paganini,30D. Sabes,30R. Salerno,30Y. Sirois,30C. Thiebaux,30B. Wyslouch,30,iA. Zabi,30 J.-L. Agram,31,jJ. Andrea,31D. Bloch,31D. Bodin,31J.-M. Brom,31M. Cardaci,31E. C. Chabert,31C. Collard,31
E. Conte,31,jF. Drouhin,31,jC. Ferro,31J.-C. Fontaine,31,jD. Gele´,31U. Goerlach,31S. Greder,31P. Juillot,31 M. Karim,31,jA.-C. Le Bihan,31Y. Mikami,31P. Van Hove,31F. Fassi,32D. Mercier,32C. Baty,33S. Beauceron,33
N. Beaupere,33M. Bedjidian,33O. Bondu,33G. Boudoul,33D. Boumediene,33H. Brun,33J. Chasserat,33 R. Chierici,33D. Contardo,33P. Depasse,33H. El Mamouni,33J. Fay,33S. Gascon,33B. Ille,33T. Kurca,33 T. Le Grand,33M. Lethuillier,33L. Mirabito,33S. Perries,33V. Sordini,33S. Tosi,33Y. Tschudi,33P. Verdier,33
D. Lomidze,34G. Anagnostou,35S. Beranek,35M. Edelhoff,35L. Feld,35N. Heracleous,35O. Hindrichs,35 R. Jussen,35K. Klein,35J. Merz,35N. Mohr,35A. Ostapchuk,35A. Perieanu,35F. Raupach,35J. Sammet,35S. Schael,35 D. Sprenger,35H. Weber,35M. Weber,35B. Wittmer,35M. Ata,36E. Dietz-Laursonn,36M. Erdmann,36T. Hebbeker,36 C. Heidemann,36A. Hinzmann,36K. Hoepfner,36T. Klimkovich,36D. Klingebiel,36P. Kreuzer,36D. Lanske,36,a J. Lingemann,36C. Magass,36M. Merschmeyer,36A. Meyer,36P. Papacz,36H. Pieta,36H. Reithler,36S. A. Schmitz,36
L. Sonnenschein,36J. Steggemann,36D. Teyssier,36M. Bontenackels,37M. Davids,37M. Duda,37G. Flu¨gge,37 H. Geenen,37M. Giffels,37W. Haj Ahmad,37D. Heydhausen,37F. Hoehle,37B. Kargoll,37T. Kress,37Y. Kuessel,37
A. Linn,37A. Nowack,37L. Perchalla,37O. Pooth,37J. Rennefeld,37P. Sauerland,37A. Stahl,37M. Thomas,37 D. Tornier,37M. H. Zoeller,37M. Aldaya Martin,38W. Behrenhoff,38U. Behrens,38M. Bergholz,38,kA. Bethani,38 K. Borras,38A. Cakir,38A. Campbell,38E. Castro,38D. Dammann,38G. Eckerlin,38D. Eckstein,38A. Flossdorf,38
G. Flucke,38A. Geiser,38J. Hauk,38H. Jung,38,bM. Kasemann,38I. Katkov,38,lP. Katsas,38C. Kleinwort,38 H. Kluge,38A. Knutsson,38M. Kra¨mer,38D. Kru¨cker,38E. Kuznetsova,38W. Lange,38W. Lohmann,38,kR. Mankel,38 M. Marienfeld,38I.-A. Melzer-Pellmann,38A. B. Meyer,38J. Mnich,38A. Mussgiller,38J. Olzem,38A. Petrukhin,38
D. Pitzl,38A. Raspereza,38A. Raval,38M. Rosin,38R. Schmidt,38,kT. Schoerner-Sadenius,38N. Sen,38 A. Spiridonov,38M. Stein,38J. Tomaszewska,38R. Walsh,38C. Wissing,38C. Autermann,39V. Blobel,39 S. Bobrovskyi,39J. Draeger,39H. Enderle,39U. Gebbert,39M. Go¨rner,39T. Hermanns,39K. Kaschube,39 G. Kaussen,39H. Kirschenmann,39R. Klanner,39J. Lange,39B. Mura,39S. Naumann-Emme,39F. Nowak,39 N. Pietsch,39C. Sander,39H. Schettler,39P. Schleper,39E. Schlieckau,39M. Schro¨der,39T. Schum,39H. Stadie,39
G. Steinbru¨ck,39J. Thomsen,39C. Barth,40J. Bauer,40J. Berger,40V. Buege,40T. Chwalek,40W. De Boer,40 A. Dierlamm,40G. Dirkes,40M. Feindt,40J. Gruschke,40C. Hackstein,40F. Hartmann,40M. Heinrich,40H. Held,40 K. H. Hoffmann,40S. Honc,40J. R. Komaragiri,40T. Kuhr,40D. Martschei,40S. Mueller,40Th. Mu¨ller,40M. Niegel,40 O. Oberst,40A. Oehler,40J. Ott,40T. Peiffer,40G. Quast,40K. Rabbertz,40F. Ratnikov,40N. Ratnikova,40M. Renz,40
C. Saout,40A. Scheurer,40P. Schieferdecker,40F.-P. Schilling,40G. Schott,40H. J. Simonis,40F. M. Stober,40 D. Troendle,40J. Wagner-Kuhr,40T. Weiler,40M. Zeise,40V. Zhukov,40,lE. B. Ziebarth,40G. Daskalakis,41
T. Geralis,41S. Kesisoglou,41A. Kyriakis,41D. Loukas,41I. Manolakos,41A. Markou,41C. Markou,41 C. Mavrommatis,41E. Ntomari,41E. Petrakou,41L. Gouskos,42T. J. Mertzimekis,42A. Panagiotou,42E. Stiliaris,42 I. Evangelou,43C. Foudas,43P. Kokkas,43N. Manthos,43I. Papadopoulos,43V. Patras,43F. A. Triantis,43A. Aranyi,44
G. Bencze,44L. Boldizsar,44C. Hajdu,44,bP. Hidas,44D. Horvath,44,mA. Kapusi,44K. Krajczar,44,nF. Sikler,44,b G. I. Veres,44,nG. Vesztergombi,44,nN. Beni,45J. Molnar,45J. Palinkas,45Z. Szillasi,45V. Veszpremi,45P. Raics,46
Z. L. Trocsanyi,46B. Ujvari,46S. B. Beri,47V. Bhatnagar,47N. Dhingra,47R. Gupta,47M. Jindal,47M. Kaur,47 J. M. Kohli,47M. Z. Mehta,47N. Nishu,47L. K. Saini,47A. Sharma,47A. P. Singh,47J. Singh,47S. P. Singh,47 S. Ahuja,48B. C. Choudhary,48P. Gupta,48S. Jain,48A. Kumar,48A. Kumar,48M. Naimuddin,48K. Ranjan,48 R. K. Shivpuri,48S. Banerjee,49S. Bhattacharya,49S. Dutta,49B. Gomber,49S. Jain,49R. Khurana,49S. Sarkar,49 R. K. Choudhury,50D. Dutta,50S. Kailas,50V. Kumar,50P. Mehta,50A. K. Mohanty,50,bL. M. Pant,50P. Shukla,50
T. Aziz,51M. Guchait,51,oA. Gurtu,51M. Maity,51,pD. Majumder,51G. Majumder,51K. Mazumdar,51 G. B. Mohanty,51A. Saha,51K. Sudhakar,51N. Wickramage,51S. Banerjee,52S. Dugad,52N. K. Mondal,52 H. Arfaei,53H. Bakhshiansohi,53,qS. M. Etesami,53A. Fahim,53,qM. Hashemi,53H. Hesari,53A. Jafari,53,q M. Khakzad,53A. Mohammadi,53,rM. Mohammadi Najafabadi,53S. Paktinat Mehdiabadi,53B. Safarzadeh,53
M. Zeinali,53,sM. Abbrescia,54a,54bL. Barbone,54a,54bC. Calabria,54a,54bA. Colaleo,54aD. Creanza,54a,54c N. De Filippis,54a,54c,bM. De Palma,54a,54bL. Fiore,54aG. Iaselli,54a,54cL. Lusito,54a,54bG. Maggi,54a,54c M. Maggi,54aN. Manna,54a,54bB. Marangelli,54a,54bS. My,54a,54cS. Nuzzo,54a,54bN. Pacifico,54a,54bG. A. Pierro,54a
A. Pompili,54a,54bG. Pugliese,54a,54cF. Romano,54a,54cG. Roselli,54a,54bG. Selvaggi,54a,54bL. Silvestris,54a R. Trentadue,54aS. Tupputi,54a,54bG. Zito,54aG. Abbiendi,55aA. C. Benvenuti,55aD. Bonacorsi,55a S. Braibant-Giacomelli,55a,55bL. Brigliadori,55aP. Capiluppi,55a,55bA. Castro,55a,55bF. R. Cavallo,55a M. Cuffiani,55a,55bG. M. Dallavalle,55aF. Fabbri,55aA. Fanfani,55a,55bD. Fasanella,55aP. Giacomelli,55a
M. Giunta,55aC. Grandi,55aS. Marcellini,55aG. Masetti,55bM. Meneghelli,55a,55bA. Montanari,55a F. L. Navarria,55a,55bF. Odorici,55aA. Perrotta,55aF. Primavera,55aA. M. Rossi,55a,55bT. Rovelli,55a,55b G. Siroli,55a,55bR. Travaglini,55a,55bS. Albergo,56a,56bG. Cappello,56a,56bM. Chiorboli,56a,56b,bS. Costa,56a,56b
A. Tricomi,56a,56bC. Tuve,56a,56bG. Barbagli,57aV. Ciulli,57a,57bC. Civinini,57aR. D’Alessandro,57a,57b E. Focardi,57a,57bS. Frosali,57a,57bE. Gallo,57aS. Gonzi,57a,57bP. Lenzi,57a,57bM. Meschini,57aS. Paoletti,57a G. Sguazzoni,57aA. Tropiano,57a,bL. Benussi,58S. Bianco,58S. Colafranceschi,58,tF. Fabbri,58D. Piccolo,58 P. Fabbricatore,59R. Musenich,59A. Benaglia,60a,60bF. De Guio,60a,60b,bL. Di Matteo,60a,60bS. Gennai,60a,b
A. Ghezzi,60a,60bS. Malvezzi,60aA. Martelli,60a,60bA. Massironi,60a,60bD. Menasce,60aL. Moroni,60a M. Paganoni,60a,60bD. Pedrini,60aS. Ragazzi,60a,60bN. Redaelli,60aS. Sala,60aT. Tabarelli de Fatis,60a,60b S. Buontempo,61aC. A. Carrillo Montoya,61a,bN. Cavallo,61a,uA. De Cosa,61a,61bF. Fabozzi,61a,uA. O. M. Iorio,61a,b
L. Lista,61aM. Merola,61a,61bP. Paolucci,61aP. Azzi,62aN. Bacchetta,62aP. Bellan,62a,62bD. Bisello,62a,62b A. Branca,62aR. Carlin,62a,62bP. Checchia,62aT. Dorigo,62aU. Dosselli,62aF. Fanzago,62aF. Gasparini,62a,62b U. Gasparini,62a,62bA. Gozzelino,62aS. Lacaprara,62aI. Lazzizzera,62a,62cM. Margoni,62a,62bM. Mazzucato,62a A. T. Meneguzzo,62a,62bM. Nespolo,62a,bL. Perrozzi,62a,bN. Pozzobon,62a,62bP. Ronchese,62a,62bF. Simonetto,62a,62b
E. Torassa,62aM. Tosi,62a,62bS. Vanini,62a,62bP. Zotto,62a,62bG. Zumerle,62a,62bP. Baesso,63a,63bU. Berzano,63a S. P. Ratti,63a,63bC. Riccardi,63a,63bP. Torre,63a,63bP. Vitulo,63a,63bC. Viviani,63a,63bM. Biasini,64a,64bG. M. Bilei,64a
B. Caponeri,64a,64bL. Fano`,64a,64bP. Lariccia,64a,64bA. Lucaroni,64a,64b,bG. Mantovani,64a,64bM. Menichelli,64a A. Nappi,64a,64bF. Romeo,64a,64bA. Santocchia,64a,64bS. Taroni,64a,64b,bM. Valdata,64a,64bP. Azzurri,65a,65c G. Bagliesi,65aJ. Bernardini,65a,65bT. Boccali,65a,bG. Broccolo,65a,65cR. Castaldi,65aR. T. D’Agnolo,65a,65c R. Dell’Orso,65aF. Fiori,65a,65bL. Foa`,65a,65cA. Giassi,65aA. Kraan,65aF. Ligabue,65a,65cT. Lomtadze,65a L. Martini,65a,vA. Messineo,65a,65bF. Palla,65aG. Segneri,65aA. T. Serban,65aP. Spagnolo,65aR. Tenchini,65a
G. Tonelli,65a,65b,bA. Venturi,65a,bP. G. Verdini,65aL. Barone,66a,66bF. Cavallari,66aD. Del Re,66a,66b E. Di Marco,66a,66bM. Diemoz,66aD. Franci,66a,66bM. Grassi,66a,bE. Longo,66a,66bP. Meridiani,66a S. Nourbakhsh,66aG. Organtini,66a,66bF. Pandolfi,66a,66b,bR. Paramatti,66aS. Rahatlou,66a,66bC. Rovelli,66a,b
N. Amapane,67a,67bR. Arcidiacono,67a,67cS. Argiro,67a,67bM. Arneodo,67a,67cC. Biino,67aC. Botta,67a,67b,b N. Cartiglia,67aR. Castello,67a,67bM. Costa,67a,67bN. Demaria,67aA. Graziano,67a,67b,bC. Mariotti,67a M. Marone,67a,67bS. Maselli,67aE. Migliore,67a,67bG. Mila,67a,67bV. Monaco,67a,67bM. Musich,67a,67b M. M. Obertino,67a,67cN. Pastrone,67aM. Pelliccioni,67a,67bA. Potenza,67a,67bA. Romero,67a,67bM. Ruspa,67a,67c R. Sacchi,67a,67bV. Sola,67a,67bA. Solano,67a,67bA. Staiano,67aA. Vilela Pereira,67aS. Belforte,68aF. Cossutti,68a
G. Della Ricca,68a,68bB. Gobbo,68aD. Montanino,68a,68bA. Penzo,68aS. G. Heo,69S. K. Nam,69S. Chang,70 J. Chung,70D. H. Kim,70G. N. Kim,70J. E. Kim,70D. J. Kong,70H. Park,70S. R. Ro,70D. C. Son,70T. Son,70 Zero Kim,71J. Y. Kim,71S. Song,71S. Choi,72B. Hong,72M. Jo,72H. Kim,72J. H. Kim,72T. J. Kim,72K. S. Lee,72 D. H. Moon,72S. K. Park,72K. S. Sim,72M. Choi,73S. Kang,73H. Kim,73C. Park,73I. C. Park,73S. Park,73G. Ryu,73 PRL 107, 052302 (2011) P H Y S I C A L R E V I E W L E T T E R S 29 JULY 2011week ending
Y. Choi,74Y. K. Choi,74J. Goh,74M. S. Kim,74J. Lee,74S. Lee,74H. Seo,74I. Yu,74M. J. Bilinskas,75I. Grigelionis,75 M. Janulis,75D. Martisiute,75P. Petrov,75T. Sabonis,75H. Castilla-Valdez,76E. De La Cruz-Burelo,76
I. Heredia-de La Cruz,76R. Lopez-Fernandez,76R. Magan˜a Villalba,76A. Sa´nchez-Herna´ndez,76 L. M. Villasenor-Cendejas,76S. Carrillo Moreno,77F. Vazquez Valencia,77H. A. Salazar Ibarguen,78 E. Casimiro Linares,79A. Morelos Pineda,79M. A. Reyes-Santos,79D. Krofcheck,80J. Tam,80P. H. Butler,81
R. Doesburg,81H. Silverwood,81M. Ahmad,82I. Ahmed,82M. I. Asghar,82H. R. Hoorani,82W. A. Khan,82 T. Khurshid,82S. Qazi,82G. Brona,83M. Cwiok,83W. Dominik,83K. Doroba,83A. Kalinowski,83M. Konecki,83
J. Krolikowski,83T. Frueboes,84R. Gokieli,84M. Go´rski,84M. Kazana,84K. Nawrocki,84
K. Romanowska-Rybinska,84M. Szleper,84G. Wrochna,84P. Zalewski,84N. Almeida,85P. Bargassa,85A. David,85 P. Faccioli,85P. G. Ferreira Parracho,85M. Gallinaro,85,bP. Musella,85A. Nayak,85J. Pela,85,bP. Q. Ribeiro,85 J. Seixas,85J. Varela,85S. Afanasiev,86I. Belotelov,86P. Bunin,86I. Golutvin,86A. Kamenev,86V. Karjavin,86 G. Kozlov,86A. Lanev,86P. Moisenz,86V. Palichik,86V. Perelygin,86S. Shmatov,86V. Smirnov,86A. Volodko,86
A. Zarubin,86V. Golovtsov,87Y. Ivanov,87V. Kim,87P. Levchenko,87V. Murzin,87V. Oreshkin,87I. Smirnov,87 V. Sulimov,87L. Uvarov,87S. Vavilov,87A. Vorobyev,87An. Vorobyev,87Yu. Andreev,88A. Dermenev,88 S. Gninenko,88N. Golubev,88M. Kirsanov,88N. Krasnikov,88V. Matveev,88A. Pashenkov,88A. Toropin,88 S. Troitsky,88V. Epshteyn,89V. Gavrilov,89V. Kaftanov,89,aM. Kossov,89,bA. Krokhotin,89N. Lychkovskaya,89
V. Popov,89G. Safronov,89S. Semenov,89V. Stolin,89E. Vlasov,89A. Zhokin,89E. Boos,90A. Ershov,90 A. Gribushin,90O. Kodolova,90V. Korotkikh,90I. Lokhtin,90A. Markina,90S. Obraztsov,90M. Perfilov,90 S. Petrushanko,90L. Sarycheva,90V. Savrin,90A. Snigirev,90I. Vardanyan,90V. Andreev,91M. Azarkin,91 I. Dremin,91M. Kirakosyan,91A. Leonidov,91S. V. Rusakov,91A. Vinogradov,91I. Azhgirey,92I. Bayshev,92 S. Bitioukov,92V. Grishin,92,bV. Kachanov,92D. Konstantinov,92A. Korablev,92V. Krychkine,92V. Petrov,92 R. Ryutin,92A. Sobol,92L. Tourtchanovitch,92S. Troshin,92N. Tyurin,92A. Uzunian,92A. Volkov,92P. Adzic,93,w M. Djordjevic,93D. Krpic,93,wJ. Milosevic,93M. Aguilar-Benitez,94J. Alcaraz Maestre,94P. Arce,94C. Battilana,94 E. Calvo,94M. Cepeda,94M. Cerrada,94M. Chamizo Llatas,94N. Colino,94B. De La Cruz,94A. Delgado Peris,94
C. Diez Pardos,94D. Domı´nguez Va´zquez,94C. Fernandez Bedoya,94J. P. Ferna´ndez Ramos,94A. Ferrando,94 J. Flix,94M. C. Fouz,94P. Garcia-Abia,94O. Gonzalez Lopez,94S. Goy Lopez,94J. M. Hernandez,94M. I. Josa,94
G. Merino,94J. Puerta Pelayo,94I. Redondo,94L. Romero,94J. Santaolalla,94M. S. Soares,94C. Willmott,94 C. Albajar,95G. Codispoti,95J. F. de Troco´niz,95J. Cuevas,96J. Fernandez Menendez,96S. Folgueras,96 I. Gonzalez Caballero,96L. Lloret Iglesias,96J. M. Vizan Garcia,96J. A. Brochero Cifuentes,97I. J. Cabrillo,97
A. Calderon,97S. H. Chuang,97J. Duarte Campderros,97M. Felcini,97,xM. Fernandez,97G. Gomez,97 J. Gonzalez Sanchez,97C. Jorda,97P. Lobelle Pardo,97A. Lopez Virto,97J. Marco,97R. Marco,97
C. Martinez Rivero,97F. Matorras,97F. J. Munoz Sanchez,97J. Piedra Gomez,97,yT. Rodrigo,97 A. Y. Rodrı´guez-Marrero,97A. Ruiz-Jimeno,97L. Scodellaro,97M. Sobron Sanudo,97I. Vila,97 R. Vilar Cortabitarte,97D. Abbaneo,98E. Auffray,98G. Auzinger,98P. Baillon,98A. H. Ball,98D. Barney,98 A. J. Bell,98,zD. Benedetti,98C. Bernet,98,dW. Bialas,98P. Bloch,98A. Bocci,98S. Bolognesi,98M. Bona,98 H. Breuker,98K. Bunkowski,98T. Camporesi,98G. Cerminara,98J. A. Coarasa Perez,98B. Cure´,98D. D’Enterria,98
A. De Roeck,98S. Di Guida,98N. Dupont-Sagorin,98A. Elliott-Peisert,98B. Frisch,98W. Funk,98A. Gaddi,98 G. Georgiou,98H. Gerwig,98D. Gigi,98K. Gill,98D. Giordano,98F. Glege,98R. Gomez-Reino Garrido,98 M. Gouzevitch,98P. Govoni,98S. Gowdy,98L. Guiducci,98M. Hansen,98C. Hartl,98J. Harvey,98J. Hegeman,98 B. Hegner,98H. F. Hoffmann,98A. Honma,98V. Innocente,98P. Janot,98K. Kaadze,98E. Karavakis,98P. Lecoq,98 C. Lourenc¸o,98T. Ma¨ki,98M. Malberti,98L. Malgeri,98M. Mannelli,98L. Masetti,98A. Maurisset,98F. Meijers,98 S. Mersi,98E. Meschi,98R. Moser,98M. U. Mozer,98M. Mulders,98E. Nesvold,98,bM. Nguyen,98T. Orimoto,98 L. Orsini,98E. Palencia Cortezon,98E. Perez,98A. Petrilli,98A. Pfeiffer,98M. Pierini,98M. Pimia¨,98D. Piparo,98 G. Polese,98A. Racz,98W. Reece,98J. Rodrigues Antunes,98G. Rolandi,98,aaT. Rommerskirchen,98M. Rovere,98
H. Sakulin,98C. Scha¨fer,98C. Schwick,98I. Segoni,98A. Sharma,98P. Siegrist,98M. Simon,98P. Sphicas,98,bb M. Spiropulu,98,ccM. Stoye,98P. Tropea,98A. Tsirou,98P. Vichoudis,98M. Voutilainen,98W. D. Zeuner,98W. Bertl,99
K. Deiters,99W. Erdmann,99K. Gabathuler,99R. Horisberger,99Q. Ingram,99H. C. Kaestli,99S. Ko¨nig,99 D. Kotlinski,99U. Langenegger,99F. Meier,99D. Renker,99T. Rohe,99J. Sibille,99,ddA. Starodumov,99,eeL. Ba¨ni,100
P. Bortignon,100L. Caminada,100,ffB. Casal,100N. Chanon,100Z. Chen,100S. Cittolin,100G. Dissertori,100 M. Dittmar,100J. Eugster,100K. Freudenreich,100C. Grab,100W. Hintz,100P. Lecomte,100W. Lustermann,100 C. Marchica,100,ffP. Martinez Ruiz del Arbol,100P. Milenovic,100,ggF. Moortgat,100C. Na¨geli,100,ffP. Nef,100
F. Nessi-Tedaldi,100L. Pape,100F. Pauss,100T. Punz,100A. Rizzi,100F. J. Ronga,100M. Rossini,100L. Sala,100 A. K. Sanchez,100M.-C. Sawley,100B. Stieger,100L. Tauscher,100,aA. Thea,100K. Theofilatos,100D. Treille,100 C. Urscheler,100R. Wallny,100M. Weber,100L. Wehrli,100J. Weng,100E. Aguilo,101C. Amsler,101V. Chiochia,101
S. De Visscher,101C. Favaro,101M. Ivova Rikova,101B. Millan Mejias,101P. Otiougova,101P. Robmann,101 A. Schmidt,101H. Snoek,101Y. H. Chang,102K. H. Chen,102C. M. Kuo,102S. W. Li,102W. Lin,102Z. K. Liu,102 Y. J. Lu,102D. Mekterovic,102R. Volpe,102J. H. Wu,102S. S. Yu,102P. Bartalini,103P. Chang,103Y. H. Chang,103
Y. W. Chang,103Y. Chao,103K. F. Chen,103W.-S. Hou,103Y. Hsiung,103K. Y. Kao,103Y. J. Lei,103R.-S. Lu,103 J. G. Shiu,103Y. M. Tzeng,103M. Wang,103A. Adiguzel,104M. N. Bakirci,104,hhS. Cerci,104,iiC. Dozen,104 I. Dumanoglu,104E. Eskut,104S. Girgis,104G. Gokbulut,104I. Hos,104E. E. Kangal,104A. Kayis Topaksu,104 G. Onengut,104K. Ozdemir,104S. Ozturk,104,jjA. Polatoz,104K. Sogut,104,kkD. Sunar Cerci,104,iiB. Tali,104,ii H. Topakli,104,hhD. Uzun,104L. N. Vergili,104M. Vergili,104I. V. Akin,105T. Aliev,105B. Bilin,105S. Bilmis,105
M. Deniz,105H. Gamsizkan,105A. M. Guler,105K. Ocalan,105A. Ozpineci,105M. Serin,105R. Sever,105 U. E. Surat,105E. Yildirim,105M. Zeyrek,105M. Deliomeroglu,106D. Demir,106,llE. Gu¨lmez,106B. Isildak,106 M. Kaya,106,mmO. Kaya,106,mmM. O¨ zbek,106S. Ozkorucuklu,106,nnN. Sonmez,106,ooL. Levchuk,107F. Bostock,108
J. J. Brooke,108T. L. Cheng,108E. Clement,108D. Cussans,108R. Frazier,108J. Goldstein,108M. Grimes,108 D. Hartley,108G. P. Heath,108H. F. Heath,108L. Kreczko,108S. Metson,108D. M. Newbold,108,ppK. Nirunpong,108 A. Poll,108S. Senkin,108V. J. Smith,108L. Basso,109,qqA. Belyaev,109,qqC. Brew,109R. M. Brown,109B. Camanzi,109 D. J. A. Cockerill,109J. A. Coughlan,109K. Harder,109S. Harper,109J. Jackson,109B. W. Kennedy,109E. Olaiya,109
D. Petyt,109B. C. Radburn-Smith,109C. H. Shepherd-Themistocleous,109I. R. Tomalin,109W. J. Womersley,109 S. D. Worm,109R. Bainbridge,110G. Ball,110J. Ballin,110R. Beuselinck,110O. Buchmuller,110D. Colling,110
N. Cripps,110M. Cutajar,110G. Davies,110M. Della Negra,110W. Ferguson,110J. Fulcher,110D. Futyan,110 A. Gilbert,110A. Guneratne Bryer,110G. Hall,110Z. Hatherell,110J. Hays,110G. Iles,110M. Jarvis,110 G. Karapostoli,110L. Lyons,110B. C. MacEvoy,110A.-M. Magnan,110J. Marrouche,110B. Mathias,110R. Nandi,110 J. Nash,110A. Nikitenko,110,eeA. Papageorgiou,110M. Pesaresi,110K. Petridis,110M. Pioppi,110,rrD. M. Raymond,110 S. Rogerson,110N. Rompotis,110A. Rose,110M. J. Ryan,110C. Seez,110P. Sharp,110A. Sparrow,110A. Tapper,110 S. Tourneur,110M. Vazquez Acosta,110T. Virdee,110S. Wakefield,110N. Wardle,110D. Wardrope,110T. Whyntie,110 M. Barrett,111M. Chadwick,111J. E. Cole,111P. R. Hobson,111A. Khan,111P. Kyberd,111D. Leslie,111W. Martin,111 I. D. Reid,111L. Teodorescu,111K. Hatakeyama,112H. Liu,112C. Henderson,113T. Bose,114E. Carrera Jarrin,114
C. Fantasia,114A. Heister,114J. St. John,114P. Lawson,114D. Lazic,114J. Rohlf,114D. Sperka,114L. Sulak,114 A. Avetisyan,115S. Bhattacharya,115J. P. Chou,115D. Cutts,115A. Ferapontov,115U. Heintz,115S. Jabeen,115 G. Kukartsev,115G. Landsberg,115M. Luk,115M. Narain,115D. Nguyen,115M. Segala,115T. Sinthuprasith,115 T. Speer,115K. V. Tsang,115R. Breedon,116G. Breto,116M. Calderon De La Barca Sanchez,116S. Chauhan,116
M. Chertok,116J. Conway,116P. T. Cox,116J. Dolen,116R. Erbacher,116E. Friis,116W. Ko,116A. Kopecky,116 R. Lander,116H. Liu,116S. Maruyama,116T. Miceli,116M. Nikolic,116D. Pellett,116J. Robles,116S. Salur,116 T. Schwarz,116M. Searle,116J. Smith,116M. Squires,116M. Tripathi,116R. Vasquez Sierra,116C. Veelken,116 V. Andreev,117K. Arisaka,117D. Cline,117R. Cousins,117A. Deisher,117J. Duris,117S. Erhan,117C. Farrell,117 J. Hauser,117M. Ignatenko,117C. Jarvis,117C. Plager,117G. Rakness,117P. Schlein,117,aJ. Tucker,117V. Valuev,117
J. Babb,118A. Chandra,118R. Clare,118J. Ellison,118J. W. Gary,118F. Giordano,118G. Hanson,118G. Y. Jeng,118 S. C. Kao,118F. Liu,118H. Liu,118O. R. Long,118A. Luthra,118H. Nguyen,118B. C. Shen,118,aR. Stringer,118 J. Sturdy,118
K. Stenson,123K. A. Ulmer,123S. R. Wagner,123S. L. Zang,123L. Agostino,124J. Alexander,124D. Cassel,124 A. Chatterjee,124N. Eggert,124L. K. Gibbons,124B. Heltsley,124K. Henriksson,124W. Hopkins,124
A. Khukhunaishvili,124B. Kreis,124G. Nicolas Kaufman,124J. R. Patterson,124D. Puigh,124A. Ryd,124M. Saelim,124 E. Salvati,124X. Shi,124W. Sun,124W. D. Teo,124J. Thom,124J. Thompson,124J. Vaughan,124Y. Weng,124 L. Winstrom,124P. Wittich,124A. Biselli,125G. Cirino,125D. Winn,125S. Abdullin,126M. Albrow,126J. Anderson,126
G. Apollinari,126M. Atac,126J. A. Bakken,126L. A. T. Bauerdick,126A. Beretvas,126J. Berryhill,126P. C. Bhat,126 I. Bloch,126F. Borcherding,126K. Burkett,126J. N. Butler,126V. Chetluru,126H. W. K. Cheung,126F. Chlebana,126
S. Cihangir,126W. Cooper,126D. P. Eartly,126V. D. Elvira,126S. Esen,126I. Fisk,126J. Freeman,126Y. Gao,126 E. Gottschalk,126D. Green,126K. Gunthoti,126O. Gutsche,126J. Hanlon,126R. M. Harris,126J. Hirschauer,126 B. Hooberman,126H. Jensen,126M. Johnson,126U. Joshi,126R. Khatiwada,126B. Klima,126K. Kousouris,126
S. Kunori,126S. Kwan,126C. Leonidopoulos,126P. Limon,126D. Lincoln,126R. Lipton,126J. Lykken,126 K. Maeshima,126J. M. Marraffino,126D. Mason,126P. McBride,126T. Miao,126K. Mishra,126S. Mrenna,126
Y. Musienko,126,ttC. Newman-Holmes,126V. O’Dell,126R. Pordes,126O. Prokofyev,126N. Saoulidou,126 E. Sexton-Kennedy,126S. Sharma,126W. J. Spalding,126L. Spiegel,126P. Tan,126L. Taylor,126S. Tkaczyk,126
L. Uplegger,126E. W. Vaandering,126R. Vidal,126J. Whitmore,126W. Wu,126F. Yang,126F. Yumiceva,126 J. C. Yun,126D. Acosta,127P. Avery,127D. Bourilkov,127M. Chen,127S. Das,127M. De Gruttola,127 G. P. Di Giovanni,127D. Dobur,127A. Drozdetskiy,127R. D. Field,127M. Fisher,127Y. Fu,127I. K. Furic,127 J. Gartner,127J. Hugon,127B. Kim,127J. Konigsberg,127A. Korytov,127A. Kropivnitskaya,127T. Kypreos,127 J. F. Low,127K. Matchev,127G. Mitselmakher,127L. Muniz,127C. Prescott,127R. Remington,127A. Rinkevicius,127
M. Schmitt,127B. Scurlock,127P. Sellers,127N. Skhirtladze,127M. Snowball,127D. Wang,127J. Yelton,127 M. Zakaria,127V. Gaultney,128L. M. Lebolo,128S. Linn,128P. Markowitz,128G. Martinez,128J. L. Rodriguez,128 T. Adams,129A. Askew,129J. Bochenek,129J. Chen,129B. Diamond,129S. V. Gleyzer,129J. Haas,129S. Hagopian,129
V. Hagopian,129M. Jenkins,129K. F. Johnson,129H. Prosper,129L. Quertenmont,129S. Sekmen,129 V. Veeraraghavan,129M. M. Baarmand,130B. Dorney,130S. Guragain,130M. Hohlmann,130H. Kalakhety,130 R. Ralich,130I. Vodopiyanov,130M. R. Adams,131I. M. Anghel,131L. Apanasevich,131Y. Bai,131V. E. Bazterra,131
R. R. Betts,131J. Callner,131R. Cavanaugh,131C. Dragoiu,131L. Gauthier,131C. E. Gerber,131D. J. Hofman,131 S. Khalatyan,131G. J. Kunde,131,vvF. Lacroix,131M. Malek,131C. O’Brien,131C. Silkworth,131C. Silvestre,131 A. Smoron,131D. Strom,131N. Varelas,131U. Akgun,132E. A. Albayrak,132B. Bilki,132W. Clarida,132F. Duru,132
C. K. Lae,132E. McCliment,132J.-P. Merlo,132H. Mermerkaya,132,uuA. Mestvirishvili,132A. Moeller,132 J. Nachtman,132C. R. Newsom,132E. Norbeck,132J. Olson,132Y. Onel,132F. Ozok,132S. Sen,132J. Wetzel,132 T. Yetkin,132K. Yi,132B. A. Barnett,133B. Blumenfeld,133A. Bonato,133C. Eskew,133D. Fehling,133G. Giurgiu,133
A. V. Gritsan,133Z. J. Guo,133G. Hu,133P. Maksimovic,133S. Rappoccio,133M. Swartz,133N. V. Tran,133 A. Whitbeck,133P. Baringer,134A. Bean,134G. Benelli,134O. Grachov,134R. P. Kenny Iii,134M. Murray,134 D. Noonan,134S. Sanders,134J. S. Wood,134V. Zhukova,134A. F. Barfuss,135T. Bolton,135I. Chakaberia,135
A. Ivanov,135S. Khalil,135M. Makouski,135Y. Maravin,135S. Shrestha,135I. Svintradze,135Z. Wan,135 J. Gronberg,136D. Lange,136D. Wright,136A. Baden,137M. Boutemeur,137S. C. Eno,137D. Ferencek,137 J. A. Gomez,137N. J. Hadley,137R. G. Kellogg,137M. Kirn,137Y. Lu,137A. C. Mignerey,137K. Rossato,137 P. Rumerio,137F. Santanastasio,137A. Skuja,137J. Temple,137M. B. Tonjes,137S. C. Tonwar,137E. Twedt,137
B. Alver,138G. Bauer,138J. Bendavid,138W. Busza,138E. Butz,138I. A. Cali,138M. Chan,138V. Dutta,138 P. Everaerts,138G. Gomez Ceballos,138M. Goncharov,138K. A. Hahn,138P. Harris,138Y. Kim,138M. Klute,138 Y.-J. Lee,138W. Li,138C. Loizides,138P. D. Luckey,138T. Ma,138S. Nahn,138C. Paus,138D. Ralph,138C. Roland,138
G. Roland,138M. Rudolph,138G. S. F. Stephans,138F. Sto¨ckli,138K. Sumorok,138K. Sung,138D. Velicanu,138 E. A. Wenger,138S. Xie,138M. Yang,138Y. Yilmaz,138A. S. Yoon,138M. Zanetti,138S. I. Cooper,139P. Cushman,139
B. Dahmes,139A. De Benedetti,139P. R. Dudero,139G. Franzoni,139A. Gude,139J. Haupt,139K. Klapoetke,139 Y. Kubota,139J. Mans,139N. Pastika,139V. Rekovic,139R. Rusack,139M. Sasseville,139A. Singovsky,139 N. Tambe,139L. M. Cremaldi,140R. Godang,140R. Kroeger,140L. Perera,140R. Rahmat,140D. A. Sanders,140 D. Summers,140K. Bloom,141S. Bose,141J. Butt,141D. R. Claes,141A. Dominguez,141M. Eads,141J. Keller,141
T. Kelly,141I. Kravchenko,141J. Lazo-Flores,141H. Malbouisson,141S. Malik,141G. R. Snow,141U. Baur,142 A. Godshalk,142I. Iashvili,142S. Jain,142A. Kharchilava,142A. Kumar,142S. P. Shipkowski,142K. Smith,142 J. Zennamo,142G. Alverson,143E. Barberis,143D. Baumgartel,143O. Boeriu,143M. Chasco,143S. Reucroft,143
R. A. Ofierzynski,144B. Pollack,144A. Pozdnyakov,144M. Schmitt,144S. Stoynev,144M. Velasco,144S. Won,144 L. Antonelli,145D. Berry,145A. Brinkerhoff,145M. Hildreth,145C. Jessop,145D. J. Karmgard,145J. Kolb,145 T. Kolberg,145K. Lannon,145W. Luo,145S. Lynch,145N. Marinelli,145D. M. Morse,145T. Pearson,145R. Ruchti,145
J. Slaunwhite,145N. Valls,145M. Wayne,145J. Ziegler,145B. Bylsma,146L. S. Durkin,146J. Gu,146C. Hill,146 P. Killewald,146K. Kotov,146T. Y. Ling,146M. Rodenburg,146G. Williams,146N. Adam,147E. Berry,147P. Elmer,147
D. Gerbaudo,147V. Halyo,147P. Hebda,147A. Hunt,147J. Jones,147E. Laird,147D. Lopes Pegna,147D. Marlow,147 T. Medvedeva,147M. Mooney,147J. Olsen,147P. Piroue´,147X. Quan,147B. Safdi,147H. Saka,147D. Stickland,147
C. Tully,147J. S. Werner,147A. Zuranski,147J. G. Acosta,148X. T. Huang,148A. Lopez,148H. Mendez,148 S. Oliveros,148J. E. Ramirez Vargas,148A. Zatserklyaniy,148E. Alagoz,149V. E. Barnes,149G. Bolla,149 L. Borrello,149D. Bortoletto,149M. De Mattia,149A. Everett,149A. F. Garfinkel,149L. Gutay,149Z. Hu,149
M. Jones,149O. Koybasi,149M. Kress,149A. T. Laasanen,149N. Leonardo,149C. Liu,149V. Maroussov,149 P. Merkel,149D. H. Miller,149N. Neumeister,149I. Shipsey,149D. Silvers,149A. Svyatkovskiy,149H. D. Yoo,149 J. Zablocki,149Y. Zheng,149P. Jindal,150N. Parashar,150C. Boulahouache,151K. M. Ecklund,151F. J. M. Geurts,151 B. P. Padley,151R. Redjimi,151J. Roberts,151J. Zabel,151B. Betchart,152A. Bodek,152Y. S. Chung,152R. Covarelli,152 P. de Barbaro,152R. Demina,152Y. Eshaq,152H. Flacher,152A. Garcia-Bellido,152P. Goldenzweig,152Y. Gotra,152
J. Han,152A. Harel,152D. C. Miner,152D. Orbaker,152G. Petrillo,152W. Sakumoto,152D. Vishnevskiy,152 M. Zielinski,152A. Bhatti,153R. Ciesielski,153L. Demortier,153K. Goulianos,153G. Lungu,153S. Malik,153 C. Mesropian,153O. Atramentov,154A. Barker,154D. Duggan,154Y. Gershtein,154R. Gray,154E. Halkiadakis,154
D. Hidas,154D. Hits,154A. Lath,154S. Panwalkar,154R. Patel,154K. Rose,154S. Schnetzer,154S. Somalwar,154 R. Stone,154S. Thomas,154G. Cerizza,155M. Hollingsworth,155S. Spanier,155Z. C. Yang,155A. York,155 R. Eusebi,156W. Flanagan,156J. Gilmore,156A. Gurrola,156T. Kamon,156V. Khotilovich,156R. Montalvo,156 I. Osipenkov,156Y. Pakhotin,156J. Pivarski,156A. Safonov,156S. Sengupta,156A. Tatarinov,156D. Toback,156 M. Weinberger,156N. Akchurin,157C. Bardak,157J. Damgov,157C. Jeong,157K. Kovitanggoon,157S. W. Lee,157
T. Libeiro,157P. Mane,157Y. Roh,157A. Sill,157I. Volobouev,157R. Wigmans,157E. Yazgan,157E. Appelt,158 E. Brownson,158D. Engh,158C. Florez,158W. Gabella,158M. Issah,158W. Johns,158P. Kurt,158C. Maguire,158 A. Melo,158P. Sheldon,158B. Snook,158S. Tuo,158J. Velkovska,158M. W. Arenton,159M. Balazs,159S. Boutle,159
B. Cox,159B. Francis,159J. Goodell,159R. Hirosky,159A. Ledovskoy,159C. Lin,159C. Neu,159R. Yohay,159 S. Gollapinni,160R. Harr,160P. E. Karchin,160P. Lamichhane,160M. Mattson,160C. Milste`ne,160A. Sakharov,160
M. Anderson,161M. Bachtis,161J. N. Bellinger,161D. Carlsmith,161S. Dasu,161J. Efron,161L. Gray,161 K. S. Grogg,161M. Grothe,161R. Hall-Wilton,161M. Herndon,161A. Herve´,161P. Klabbers,161J. Klukas,161 A. Lanaro,161C. Lazaridis,161J. Leonard,161R. Loveless,161A. Mohapatra,161F. Palmonari,161D. Reeder,161
I. Ross,161A. Savin,161W. H. Smith,161J. Swanson,161and M. Weinberg161 (CMS Collaboration)
1Yerevan Physics Institute, Yerevan, Armenia 2Institut fu¨r Hochenergiephysik der OeAW, Wien, Austria 3National Centre for Particle and High Energy Physics, Minsk, Belarus
4Universiteit Antwerpen, Antwerpen, Belgium 5Vrije Universiteit Brussel, Brussel, Belgium 6Universite´ Libre de Bruxelles, Bruxelles, Belgium
7Ghent University, Ghent, Belgium 8
Universite´ Catholique de Louvain, Louvain-la-Neuve, Belgium
9Universite´ de Mons, Mons, Belgium
10Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil 11Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil 12Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil
13Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria 14University of Sofia, Sofia, Bulgaria
15Institute of High Energy Physics, Beijing, China
16State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China 17
Universidad de Los Andes, Bogota, Colombia
18Technical University of Split, Split, Croatia 19University of Split, Split, Croatia
PRL 107, 052302 (2011) P H Y S I C A L R E V I E W L E T T E R S 29 JULY 2011week ending
20Institute Rudjer Boskovic, Zagreb, Croatia 21University of Cyprus, Nicosia, Cyprus 22Charles University, Prague, Czech Republic
23Academy of Scientific Research and Technology of the Arab Republic of Egypt,
Egyptian Network of High Energy Physics, Cairo, Egypt
24National Institute of Chemical Physics and Biophysics, Tallinn, Estonia 25Department of Physics, University of Helsinki, Helsinki, Finland
26Helsinki Institute of Physics, Helsinki, Finland 27
Lappeenranta University of Technology, Lappeenranta, Finland
28Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France 29DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France
30Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
31Institut Pluridisciplinaire Hubert Curien, Universite´ de Strasbourg, Universite´ de Haute Alsace Mulhouse,
CNRS/IN2P3, Strasbourg, France
32Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules (IN2P3), Villeurbanne, France 33Universite´ de Lyon, Universite´ Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucle´aire de Lyon, Villeurbanne, France
34Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi, Georgia 35RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany
36RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany 37RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany
38Deutsches Elektronen-Synchrotron, Hamburg, Germany 39University of Hamburg, Hamburg, Germany 40Institut fu¨r Experimentelle Kernphysik, Karlsruhe, Germany 41Institute of Nuclear Physics ‘‘Demokritos,’’ Aghia Paraskevi, Greece
42
University of Athens, Athens, Greece
43University of Ioa´nnina, Ioa´nnina, Greece
44KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary 45Institute of Nuclear Research ATOMKI, Debrecen, Hungary
46University of Debrecen, Debrecen, Hungary 47Panjab University, Chandigarh, India
48University of Delhi, Delhi, India 49Saha Institute of Nuclear Physics, Kolkata, India
50Bhabha Atomic Research Centre, Mumbai, India 51Tata Institute of Fundamental Research-EHEP, Mumbai, India 52Tata Institute of Fundamental Research-HECR, Mumbai, India 53Institute for Research and Fundamental Sciences (IPM), Tehran, Iran
54aINFN Sezione di Bari, Bari, Italy 54bUniversita` di Bari, Bari, Italy 54cPolitecnico di Bari, Bari, Italy 55aINFN Sezione di Bologna, Bologna, Italy
55bUniversita` di Bologna, Bologna, Italy 56aINFN Sezione di Catania, Catania, Italy
56bUniversita` di Catania, Catania, Italy 57aINFN Sezione di Firenze, Firenze, Italy
57bUniversita` di Firenze, Firenze, Italy
58INFN Laboratori Nazionali di Frascati, Frascati, Italy 59INFN Sezione di Genova, Genova, Italy 60a
INFN Sezione di Milano-Bicocca, Milano, Italy
60bUniversita` di Milano-Bicocca, Milano, Italy 61aINFN Sezione di Napoli, Napoli, Italy 61bUniversita` di Napoli ‘‘Federico II,’’ Napoli, Italy
62aINFN Sezione di Padova, Padova, Italy 62bUniversita` di Padova, Padova, Italy 62cUniversita` di Trento (Trento), Padova, Italy
63aINFN Sezione di Pavia, Pavia, Italy 63bUniversita` di Pavia, Pavia, Italy 64a
INFN Sezione di Perugia, Perugia, Italy
64bUniversita` di Perugia, Perugia, Italy 65aINFN Sezione di Pisa, Pisa, Italy
65bUniversita` di Pisa, Pisa, Italy 65cScuola Normale Superiore di Pisa, Pisa, Italy
66aINFN Sezione di Roma, Roma, Italy 66bUniversita` di Roma ‘‘La Sapienza,’’ Roma, Italy
67aINFN Sezione di Torino, Torino, Italy 67bUniversita` di Torino, Torino, Italy
67cUniversita` del Piemonte Orientale (Novara), Torino, Italy 68aINFN Sezione di Trieste, Trieste, Italy
68bUniversita` di Trieste, Trieste, Italy 69Kangwon National University, Chunchon, Korea
70
Kyungpook National University, Daegu, Korea
71Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea 72Korea University, Seoul, Korea
73University of Seoul, Seoul, Korea 74Sungkyunkwan University, Suwon, Korea
75Vilnius University, Vilnius, Lithuania
76Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico 77Universidad Iberoamericana, Mexico City, Mexico
78Benemerita Universidad Autonoma de Puebla, Puebla, Mexico 79Universidad Auto´noma de San Luis Potosı´, San Luis Potosı´, Mexico
80University of Auckland, Auckland, New Zealand 81University of Canterbury, Christchurch, New Zealand
82National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan 83Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
84Soltan Institute for Nuclear Studies, Warsaw, Poland
85Laborato´rio de Instrumentac¸a˜o e Fı´sica Experimental de Partı´culas, Lisboa, Portugal 86
Joint Institute for Nuclear Research, Dubna, Russia
87Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia 88Institute for Nuclear Research, Moscow, Russia
89Institute for Theoretical and Experimental Physics, Moscow, Russia 90Moscow State University, Moscow, Russia
91P. N. Lebedev Physical Institute, Moscow, Russia
92State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia 93University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia
94Centro de Investigaciones Energe´ticas Medioambientales y Tecnolo´gicas (CIEMAT), Madrid, Spain 95Universidad Auto´noma de Madrid, Madrid, Spain
96Universidad de Oviedo, Oviedo, Spain
97Instituto de Fı´sica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain 98CERN, European Organization for Nuclear Research, Geneva, Switzerland
99Paul Scherrer Institut, Villigen, Switzerland
100Institute for Particle Physics, ETH Zurich, Zurich, Switzerland 101Universita¨t Zu¨rich, Zurich, Switzerland
102National Central University, Chung-Li, Taiwan 103National Taiwan University (NTU), Taipei, Taiwan
104Cukurova University, Adana, Turkey
105Middle East Technical University, Physics Department, Ankara, Turkey 106Bogazici University, Istanbul, Turkey
107National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine 108University of Bristol, Bristol, United Kingdom
109
Rutherford Appleton Laboratory, Didcot, United Kingdom
110Imperial College, London, United Kingdom 111Brunel University, Uxbridge, United Kingdom
112Baylor University, Waco, Texas 76706, USA
113The University of Alabama, Tuscaloosa, Alabama 35487, USA 114Boston University, Boston, Massachusetts 02215, USA 115Brown University, Providence, Rhode Island 02912, USA 116University of California, Davis, Davis, California 95616, USA 117University of California, Los Angeles, Los Angeles, California 90095, USA
118
University of California, Riverside, Riverside, California 92521, USA
119University of California, San Diego, La Jolla, California 92093, USA 120University of California, Santa Barbara, Santa Barbara, California 93106, USA
121California Institute of Technology, Pasadena, California 91125, USA 122Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
PRL 107, 052302 (2011) P H Y S I C A L R E V I E W L E T T E R S 29 JULY 2011week ending
123University of Colorado at Boulder, Boulder, Colorado 80309, USA 124Cornell University, Ithaca, New York 14853, USA 125Fairfield University, Fairfield, Connecticut 06824, USA 126Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
127University of Florida, Gainesville, Florida 32611, USA 128Florida International University, Miami, Florida 33199, USA
129Florida State University, Tallahassee, Florida 32306, USA 130Florida Institute of Technology, Melbourne, Florida 32901, USA 131
University of Illinois at Chicago (UIC), Chicago, Illinois 60607, USA
132The University of Iowa, Iowa City, Iowa 52242, USA 133Johns Hopkins University, Baltimore, Maryland 21218, USA
134The University of Kansas, Lawrence, Kansas 66045, USA 135Kansas State University, Manhattan, Kansas 66506, USA
136Lawrence Livermore National Laboratory, Livermore, California 94720, USA 137University of Maryland, College Park, Maryland 20742, USA 138Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
139University of Minnesota, Minneapolis, Minnesota 55455, USA 140University of Mississippi, University, Mississippi 38677, USA 141University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA 142State University of New York at Buffalo, Buffalo, New York 14260, USA
143Northeastern University, Boston, Massachusetts 02115, USA 144Northwestern University, Evanston, Illinois 60208, USA 145University of Notre Dame, Notre Dame, Indiana 46556, USA
146The Ohio State University, Columbus, Ohio 43210, USA 147
Princeton University, Princeton, New Jersey 08544, USA
148University of Puerto Rico, Mayaguez, Puerto Rico 00680 149Purdue University, West Lafayette, Indiana 47907, USA 150Purdue University Calumet, Hammond, Indiana 46323, USA
151Rice University, Houston, Texas 77251, USA 152University of Rochester, Rochester, New York 14627, USA 153The Rockefeller University, New York, New York 10021, USA
154Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA 155University of Tennessee, Knoxville, Tennessee 37996, USA
156Texas A&M University, College Station, Texas 77843, USA 157Texas Tech University, Lubbock, Texas 79409, USA 158Vanderbilt University, Nashville, Tennessee 37235, USA 159University of Virginia, Charlottesville, Virginia 22901, USA
160Wayne State University, Detroit, Michigan 48202, USA 161University of Wisconsin, Madison, Wisconsin 53706, USA
a
Deceased.
bAlso at CERN, European Organization for Nuclear Research, Geneva, Switzerland. cAlso at Universidade Federal do ABC, Santo Andre, Brazil.
dAlso at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France. eAlso at Suez Canal University, Suez, Egypt.
fAlso at British University, Cairo, Egypt. gAlso at Fayoum University, El-Fayoum, Egypt.
hAlso at Soltan Institute for Nuclear Studies, Warsaw, Poland.
iAlso at Massachusetts Institute of Technology, Cambridge, MA, USA. jAlso at Universite´ de Haute-Alsace, Mulhouse, France.
kAlso at Brandenburg University of Technology, Cottbus, Germany. lAlso at Moscow State University, Moscow, Russia.
mAlso at Institute of Nuclear Research ATOMKI, Debrecen, Hungary. nAlso at Eo¨tvo¨s Lora´nd University, Budapest, Hungary.
oAlso at Tata Institute of Fundamental Research-HECR, Mumbai, India. p
Also at University of Visva-Bharati, Santiniketan, India.
qAlso at Sharif University of Technology, Tehran, Iran. rAlso at Shiraz University, Shiraz, Iran.
tAlso at Facolta` Ingegneria Universita` di Roma ‘‘La Sapienza,’’ Roma, Italy. uAlso at Universita` della Basilicata, Potenza, Italy.
vAlso at Universita` degli studi di Siena, Siena, Italy.
wAlso at Faculty of Physics of University of Belgrade, Belgrade, Serbia. xAlso at University of California, Los Angeles, Los Angeles, CA, USA. yAlso at University of Florida, Gainesville, FL, USA.
zAlso at Universite´ de Gene`ve, Geneva, Switzerland. aaAlso at Scuola Normale e Sezione dell’ INFN, Pisa, Italy. bbAlso at University of Athens, Athens, Greece.
ccAlso at California Institute of Technology, Pasadena, CA, USA. ddAlso at The University of Kansas, Lawrence, KS, USA.
eeAlso at Institute for Theoretical and Experimental Physics, Moscow, Russia. ffAlso at Paul Scherrer Institut, Villigen, Switzerland.
ggAlso at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia. hh
Also at Gaziosmanpasa University, Tokat, Turkey.
iiAlso at Adiyaman University, Adiyaman, Turkey. jjAlso at The University of Iowa, Iowa City, IA, USA. kkAlso at Mersin University, Mersin, Turkey.
llAlso at Izmir Institute of Technology, Izmir, Turkey. mmAlso at Kafkas University, Kars, Turkey.
nnAlso at Suleyman Demirel University, Isparta, Turkey. ooAlso at Ege University, Izmir, Turkey.
ppAlso at Rutherford Appleton Laboratory, Didcot, U.K.
qqAlso at School of Physics and Astronomy, University of Southampton, Southampton, U.K. rrAlso at INFN Sezione di Perugia, Universita` di Perugia, Perugia, Italy.
ssAlso at Utah Valley University, Orem, UT, USA. ttAlso at Institute for Nuclear Research, Moscow, Russia. uuAlso at Erzincan University, Erzincan, Turkey.
vvAlso at Los Alamos National Laboratory, Los Alamos, NM, USA.
PRL 107, 052302 (2011) P H Y S I C A L R E V I E W L E T T E R S 29 JULY 2011week ending
