Abstract
The transverse momentum spectra of charged particles have been measured in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV by the CMS experiment at the LHC. In the transverse momentum range pt = 5-10 GeV/c, the charged particle yield in the most central PbPb collisions is suppressed by up to a factor of 5 compared to the pp yield scaled by the number of incoherent nucleon-nucleon collisions. At higher pt, this suppression is significantly reduced, approaching roughly a factor of 2 for particles with pt in the range pt=40-100 GeV/c.
Highlights
The charged particle spectrum at large transverse momentum, dominated by hadrons originating from parton fragmentation, is an important observable for studying the properties of the hot, dense medium produced in highenergy heavy-ion collisions
Using data collected by the Compact Muon Solenoid (CMS) experiment at the LHC, this paper presents measurements of charged particle yields as a function of pT
The results for the PbPb collisions have been compared to the measured pp pT spectrum scaled by the corresponding number of incoherent nucleon–nucleon collisions
Summary
The charged particle spectrum at large transverse momentum (pT), dominated by hadrons originating from parton fragmentation, is an important observable for studying the properties of the hot, dense medium produced in highenergy heavy-ion collisions. The measurements are motivated by lower-energy results [6,7,8,9] from the Relativistic Heavy Ion Collider (RHIC), where high-pT particle production was found to be strongly suppressed relative to expectations from an independent superposition of nucleon–nucleon collisions This observation is typically expressed in terms of the nuclear modification factor, RAA(pT) =. In order to compare the yield of high-pT charged particles produced in PbPb and pp collisions, a scaling factor, the nuclear overlap function TAA, is needed to provide a proper normalization at a given PbPb centrality This factor is computed as the ratio between the number of binary nucleon–nucleon collisions Ncoll, calculated from the Glauber model of the nuclear collision geometry [10], and nucleon (NN) cross section σiNneNl =. The CMS measurement presented in this paper confirms these results with improved experimental uncertainties and extends the measured transverse momentum range to 100 GeV/c
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
