Inclusive jet and charged hadron nuclear modification factors in PbPb collisions at 2.76 TeV with CMS

AbstractMeasurements are reported for charged hadron and inclusive jet transverse momentum (pT) spectra in pp and PbPb collisions at a nucleon–nucleon center-of-mass energy of 2.76 TeV with the CMS detector. These measurements make use of the high-statistics jet-triggered data recorded in 2011, including the total available PbPb luminosity of 150μb−1. Charged particles are reconstructed using an iterative algorithm and spurious high-pT tracks are suppressed by requiring appropriate energy deposits in the calorimeter system. Jets are reconstructed with the anti-kT algorithm, using combined information from tracking and calorimetry. The charged particle pT distributions are measured in the pseudorapidity range of |η|<1, and pT up to 100 GeV/c. The jet pT distributions are measured in the pseudorapidity range of |η|<2, and pT from 100 to 300 GeV/c. The nuclear modification factors, RAA, for charged hadrons and jets are presented as a function of pT and collision centrality. In the range pT=5–10 GeV/c the charged hadron production in PbPb collisions is suppressed by up to a factor of seven, compared to the pp yield scaled by the number of incoherent nucleon–nucleon collisions. The charged hadron RAA increases at higher pT and approaches a value of approximately 0.5 in the range pT=40–100 GeV/c for the most central collisions

System size, energy and pseudorapidity dependence of directed and elliptic flow at RHIC

PHOBOS measurements of elliptic flow are presented as a function of pseudorapidity, centrality, transverse momentum, energy and nuclear species. The elliptic flow in Cu-Cu is surprisingly large, particularly for the most central events. After scaling out the geometry through the use of an alternative form of eccentricity, called the participant eccentricity, which accounts for nucleon position fluctuations in the colliding nuclei, the relative magnitude of the elliptic flow in the Cu-Cu system is qualitatively similar to that measured in the Au-Au system.Comment: Presented at the 18th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions in Budapest, Hungary, Aug. 4-9, 200

The Landscape of Particle Production: Results from PHOBOS

Recent results from the PHOBOS experiment at RHIC are presented, both from Au+Au collisions from the 2001 run and p+p and d+Au collisions from 2003. The centrality dependence of the total charged particle multiplicity in p+p and d+Au show features, such as Npart-scaling and limiting fragmentation, similar to p+A collisions at lower energies. Multiparticle physics in Au+Au is found to be local in (pseudo)rapidity, both when observed by HBT correlations and by forward-backward pseudorapidity correlations. The shape of elliptic flow in Au+Au, measured over the full range of pseudorapidity, appears to have a very weak centrality dependence. Identified particle ratios in d+Au reactions show little difference between the shape of proton and anti-proton spectra, while the absolute yields show an approximate m_T scaling.Comment: 8 Pages, 11 Figures, Plenary talk at Quark Matter 2004, Oakland, CA, January 11-18, 200

Nuclear modification of jet and hadron spectra with CMS

The Compact Muon Solenoid (CMS) experiment measures various stages of nuclear collisions utilizing the different types of beams from the Large Hadron Collider (LHC). PbPb collisions can provide remarkable insight into the final state effects, such as jet quenching. However, recent studies of pPb collisions shed light on initial state effects and complement a chronological picture of the nuclear interaction. CMS results of jet and hadron measurements in such collisions are presented

EXPECTED TRIGGER RATES OF HIGH PT JETS AND DIRECT PHOTONS IN THE STAR EMC.

The STAR experiment at RHIC is a large acceptance detector. The electromagnetic calorimeter (EMC) will provide a sensitive trigger to study high p{sub t} jets and hard photons in AuAu, pp, and pAu collisions. The capability for the EMC to trigger on jets and direct photons was studied for trigger level 0. Trigger efficiencies and expected process rates were obtained for pp reactions. Results from pp interactions will be essential to the interpretation of AuAu results as well as for the spin physics program. These studies were performed with the standard STAR software chain which includes GEANT and EMC simulations. The HIJING event generator was used to provide input for the simulations

Tests of CMS Hadron Forward Calorimeter Upgrade Readout Box Prototype

A readout box prototype for CMS Hadron Forward calorimeter upgrade is built and tested in CERN H2 beamline. The prototype is designed to enable simultaneous tests of different readout options for the four anode upgrade PMTs, new front-end electronics design and new cabling. The response of the PMTs with different readout options is uniform and the background response is minimal. Multi-channel readout options further enhance the background elimination. Passing all the electronics, mechanical and physics tests, the readout box proves to be capable of providing the forward hadron calorimeter operations requirements in the upgrade era