The almost hermetic coverage of CMS is used to measure the distribution of transverse energy as a function of pseudo-rapidity for pPb collisions at $sqrt{s_{NN}} = 5.02$ TeV. For minimum bias collisions $(1/N)~dE_T/deta$ reaches 23 GeV which implies an $E_T$ per participant pair comparable to that of peripheral PbPb collisions at $sqrt{s_{NN}} = 2.76$ TeV. The centrality dependence of transverse energy production has been studied using centrality measures defined in three different angular regions. There is a strong auto-correlation between $(1/N)~dE_T/deta$ and the $eta$ range used to define centrality %both for data and the EPOS-LHC and HIJING event generators. The centrality dependence of the data is much stronger for $eta$ values on the lead side than the proton side and shows significant differences from that predicted by either event generator.
Dijet production has been measured in pPb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. A data sample corresponding to an integrated luminosity of 35 inverse nanobarns was collected using the Compact Muon Solenoid detector at the Large Hadron Collider. The dijet transverse momentum balance, azimuthal angle correlations, and pseudorapidity distributions are studied as a function of the transverse energy in the forward calorimeters (ETHFfour). For pPb collisions, the dijet transverse momentum ratio and the width of the distribution of dijet azimuthal angle difference are comparable to the same quantities obtained from a simulated pp reference and insensitive to ETHFfour. In contrast, the mean value of the dijet pseudorapidity is found to change monotonically with increasing ETHFfour, indicating a correlation between the energy emitted at large pseudorapidity and the longitudinal motion of the dijet frame. The pseudorapidity distribution of the dijet system in minimum bias pPb collisions is compared with next-to-leading-order perturbative QCD predictions obtained from both nucleon and nuclear parton distribution functions, and the data more closely match the latter.
The study of charm production in heavy-ion collisions is considered an excellent probe for the properties of the hot and dense medium created in heavy-ion collisions. Measurements of D-meson nuclear modification can provide strong constraints into the mechanisms of in-medium energy loss and charm flow in the medium. The measurement of $D^0$ elliptic flow in pPb collisions helps us understand the strength of charm quarks coupling to significantly reduced systems which demonstrate hydrodynamic properties. In this paper, the measurements of the $D^0$ nuclear modification factor in PbPb collisions at 5.02 TeV together with the new measurement of $D^0$ elliptic flow in high multiplicity pPb collisions at 5.02 TeV using the two-particle correlation method will be presented.
This paper presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system.
Based on a kinetic description of J/psi dissociation and production in an expanding quark-gluon plasma that is described by a 2+1 dimensional ideal hydrodynamics, we have studied the double ratio R_{p Pb}(psi)/R_{p Pb}(J/psi) of charmonia in p+Pb collisions at sqrt(s_NN)=5.02 TeV by including not only the cold nuclear matter effects but also the hot nuclear matter effects. We find that the double ratio of prompt charmonia is significantly suppressed in the most central collisions as a result of the hot nuclear matter effects.
One of the most striking results is the large elliptic flow ($v_2$) at RHIC. Detailed mass and transverse momentum dependence of elliptic flow are well described by ideal hydrodynamic calculations for $p_{mathrm{T}} < $ 1 GeV/c, and by parton coalescence/recombination picture for $p_{mathrm{T}} = 2 - 6$ GeV/c. The systematic error on $v_2$ is dominated by so-called non-flow effects, which is the correlation not originated from reaction plane. It is crucial to understand and reduce the systematic error from non-flow effects in order to understand the underlying collision dynamics. In this paper, we present the centrality dependence of $v_2$ with respect to the first harmonic event plane at ZDC-SMD ($v_2${ZDC-SMD}) in Au + Au collisions at $sqrt{s_{NN}}$ = 200 GeV. Large rapidity gap ($|Deltaeta| > 6$) between midrapidity and the ZDC could enable us to minimize possible non-flow contributions. We compare the results of $v_2${ZDC-SMD} with $v_2${BBC}, which is measured by event plane determined at $|eta| = 3.1 - 3.9$. Possible non-flow contributions in those results will be discussed.
Christopher Bruner
,Michael Murray
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(2015)
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"Centrality and pseudorapidity dependence of the transverse energy flow in pPb collisions at sqrt(s_NN) = 5.02 TeV"
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Michael Murray
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