Nuclear PDFs at NLO – status report and review of the EPS09 results

Abstract

We review the current status of the global DGLAP analysis of nuclear parton distribution functions, nPDFs, focusing on the recent EPS09 analysis [1], whose output, EPS09NLO, is the best-constrained NLO nPDF set on the market. Collinear factorization is found to work very well in the kinematical region studied. With the error sets released in the EPS09 package one can compute how the nPDF-related uncertainties propagate into factorizable nuclear hard-process cross sections. A comparison with the other existing NLO nPDF sets is shown, and the BRAHMS forward-η hadron data from d+Au collisions are discussed in the light of the EPS09 nPDFs and their error sets.

Evolution ofπ0Suppression inAu+AuCollisions fromsNN=39Adare1, Afanasiev2, Aidala3 et al. 2012Phys. Rev. Lett.6014701View full textAdd to dashboardCite

“…4 GeV and compared to earlier measurements at 200 GeV in transverse-momentum range of 1 < pT < 10 GeV/c. The high-pT tail is well described by a power law in all cases and the powers decrease significantly with decreasing center-of-mass energy.…”

“…Above pT = 7 Gev/c, RAA is similar for √ s NN = 62. 4 and 200 GeV at all centralities. Perturbative-quantumchromodynamics calculations that describe RAA well at 200 GeV fail to describe the 39 GeV data, raising the possibility that for the same pT region, the relative importance of initial-state effects and soft processes increases at lower energies.…”

“…This was first observed in p+A and this enhancement is generally attributed to multiple soft scattering ("Cronin effect" [3]), and is presumed to occur in ion-ion collisions as well. Initial parton-distribution functions in nuclei (nPDF) are different from those in protons [4].…”

Polarization of prompt J/ψ and ϒ(1S) production in the color evapo

“…We compare our results to the results from the E866/NuSea Collaboration for the polarization of J/ψ [25,26] and Υ(1S) [27] in p+Cu collisions at √ s N N = 38.8 GeV as well as J/ψ in π+W at √ s = 22 GeV by the CIP Collaboration [28]. We multiply the CTEQ6L1 PDFs by the central EPS09 [29] nuclear modification to obtain the PDFs for Cu and W. We employ the GRS99 [30] pion PDFs. The polarizations measured by the E866/Nusea Collaboration are made in Collins-Soper frame and the polarization measured by the CIP Collaboration is measured in Gottfried-Jackson frame.…”

Global analysis of nuclear PDFs – latest developments

“…From[16]. Right: Q 2 evolution of the EPS09 nuclear effects at fixed values of x. From[29]. (Color on-line) The EPS09 fit to some of the l+A…”