1,077 research outputs found
Constraints for nuclear gluon shadowing from DIS data
The dependence of the ratios of the cross sections of deep inelastic
lepton--nucleus scattering is studied in the framework of leading twist, lowest
order perturbative QCD. The slope of the ratio is computed by using the DGLAP evolution equations, and shown
to be sensitive to the nuclear gluon distribution functions. Four different
parametrizations for the nuclear effects of parton distributions are studied.
We show that the NMC data on the dependence of
rule out the case where nuclear shadowing (suppression) of gluons at is much larger than the shadowing observed in the ratio . We also show that the possible nonlinear correction terms due to gluon
fusion in the evolution equations do not change this conclusion. Some
consequences for computation of RHIC multiplicities, which probe the region
x\gsim0.01, are also discussed.Comment: 11 pages, 3 eps figure
Global DGLAP fit analyses of the nPDF: EKS98 and HKM
The DGLAP analyses of the nuclear parton distribution functions (nPDF) based
on the global fits to the data are reviewed, and the results from EKS98 and HKM
are compared. The usefulness of measuring hard probes in collisions, at
the LHC in particular, is demonstrated.Comment: 10 pages, 3 figures. Contribution to CERN Yellow Report on Hard
Probes in Heavy Ion Collisions at the LH
Constraints for nuclear gluon densities from DIS data
The dependence of the ratios of nuclear structure functions is
studied by performing QCD evolution of nuclear parton distribution functions.
The log slope of these ratios is very sensitive to the nuclear gluon
distribution function. Taking different parametrizations, we show that the NMC
data on the dependence of rule out the case
where nuclear shadowing (suppression) of gluons at is much larger
than the shadowing observed in the ratio . We also take into
account modifications to the DGLAP evolution by including gluon fusion terms
and see that the effect is small at present energies, and, in any case, a
strong gluon shadowing is not favored. The region studied () is
the most relevant for RHIC multiplicities.Comment: 4 pages, 3 postscript figures. Contributed to 37th Rencontres de
Moriond on QCD and Hadronic Interactions, Les Arcs, France, 16-23 Mar 200
Modeling the Impact Parameter Dependence of the nPDFs With EKS98 and EPS09 Global Fits
So far the nuclear PDFs (nPDFs) in the global DGLAP fits have been taken to
be spatially independent. In this work, using the -dependence of the
globally fitted sets EPS09 and EKS98, we have determined the spatial dependence
of the nPDFs in terms of powers of the nuclear thickness functions. New
spatially dependent nPDF sets EPS09s (NLO, LO, error sets) and EKS98s (LO) are
released. As an application, we consider the nuclear modification factor
at midrapidity for neutral pion production in deuteron-gold
collisions at RHIC in NLO. Comparison with the PHENIX data in different
centrality classes is also shown. In addition, predictions for the
corresponding nuclear modification factor in proton-lead
collisions at the LHC are discussed.Comment: 4 pages, 4 figures, Talk given at Hard Probes 2012, 27 May - 1 June,
2012, Cagliari (Sardinia, Italy). V2: Added one commen
EPS09s and EKS98s: Impact parameter dependent nPDF sets
In our recent study we have determined two new spatially dependent nuclear
PDF (nPDF) sets, EPS09s and EKS98s. With these, the hard-process cross-sections
can be calculated in different centrality classes consistently with the
globally analyzed nPDFs for the first time. The sets were determined by
exploiting the -systematics of the globally fitted nPDF sets, EPS09 and
EKS98. For the spatial dependence of the nPDFs we used a power series ansatz in
the nuclear thickness function . In this flash talk we introduce the
framework, and present our NLO EPS09s-based predictions for the nuclear
modification factor in four centrality classes for inclusive neutral pion
production in p+Pb collisions at the LHC and for inclusive prompt photon
production in d+Au collisions at RHIC at midrapidity.Comment: 4 pages, 4 figures, Contribution to the proceedings of the Quark
Matter 2012, Washington D.C., August 12-18, 201
Nuclear parton distributions in the DGLAP approach
Determination of the nuclear parton distributions within the framework of
perturbative QCD, the DGLAP equations in particular, is discussed. Scale and
flavour dependent nuclear effects in the parton distributions are compared with
the scale and flavour independent parametrizations of HIJING and of the Hard
Probe Collaboration. A comparison with the data from deep inelastic
lepton-nucleus scattering and the Drell-Yan process in proton-nucleus
collisions is shown.Comment: 19 pages, 6 eps-figures, to appear in the Proceedings of the Hard
Probe Collaboratio
Hadron multiplicities, pT-spectra and net-baryon number in central Pb+Pb collisions at the LHC
We compute the initial energy density and net baryon number density in 5%
most central Pb+Pb collisions at TeV from pQCD + (final state)
saturation, and describe the evolution of the produced system with
boost-invariant transversely expanding hydrodynamics. In addition to the total
multiplicity at midrapidity, we give predictions for the multiplicity of
charged hadrons, pions, kaons and (anti)protons, for the total transverse
energy and net-baryon number, as well as for the -spectrum of charged
hadrons, pions and kaons. We also predict the region of applicability of
hydrodynamics by comparing these results with high- hadron spectra
computed from pQCD and energy losses.Comment: 2 pages, 2 figures, to be presented at the workshop "Heavy Ion
Collisions at the LHC: Last Call for Predictions" at CERN 29 May - 2 Jun
- …