135 research outputs found
EPS09 - Nuclear PDFs and Their Uncertainties at NLO
In this talk, we present our recent next-to-leading order (NLO) nuclear
parton distribution functions (nPDFs), which we call EPS09. As an extension to
earlier NLO analyses, we supplement the deep inelastic scattering and Drell-Yan
dilepton data by inclusive midrapidity pion measurements from RHIC in order to
reduce the otherwize large freedom in the nuclear gluon densities. Our
Hessian-type error analysis leading to a collection of nPDF error sets, is the
first of its kind among the nPDF analyses.Comment: 4 pages, 4 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
Energy loss in a fluctuating hydrodynamical background
Recently it has become apparent that event-by-event fluctuations in the
initial state of hydrodynamical modelling of ultrarelativistic heavy-ion
collisions are crucial in order to understand the full centrality dependence of
the elliptic flow coefficient v_2. In particular, in central collisions the
density fluctuations play a major role in generating the spatial eccentricity
in the initial state. This raises the question to what degree high P_T physics,
in particular leading-parton energy loss, which takes place in the background
of an evolving medium, is sensitive to the presence of the event-by-event
density fluctuations in the background. In this work, we report results for the
effects of fluctuations on the nuclear modification factor R_AA in both central
and noncentral sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC. Two different
types of energy-loss models, a radiative and an elastic, are considered. In
particular, we study the dependence of the results on the assumed spatial size
of the density fluctuations, and discuss the angular modulation of R_AA with
respect to the event plane.Comment: 9 pages, 9 figure
LHC data challenges the contemporary parton-to-hadron fragmentation functions
We discuss the inclusive high-pT charged-particle production in proton-proton
collisions at the LHC. The experimental data are compared to the NLO
perturbative QCD calculations employing various sets of parton-to-hadron
fragmentation functions. Most of the theoretical predictions are found to
disastrously overpredict the measured cross sections, even if the scale
variations and PDF errors are accounted for. The problem appears to arise from
the presently too hard gluon-to-hadron fragmentation functions.Comment: Transcription of the talk given in DIS2014 conferenc
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