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Register a new userGlobal Analyses of Nuclear PDFs
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V.J. Kolhinen
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A brief overview of the global DGLAP analyses of the nuclear parton distribution functions is given. Although all the current global nPDF sets describe $R_{F_2}^A(x,Q^2)$ well in the large-$x$ region where the data exist, variations between their parton distributions can be substantial.
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In this talk, we shortly report results from our recent global DGLAP analysis of nuclear parton distributions. This is an extension of our former EKS98-analysis improved with an automated $chi^2$ minimization procedure and uncertainty estimates. Although our new analysis show no significant deviation from EKS98, a sign of a significantly stronger gluon shadowing could be seen in the RHIC BRAHMS data.
In this talk, we introduce our recently completed next-to-leading order (NLO) global analysis of the nuclear parton distribution functions (nPDFs) called EPS09 - a higher order successor to the well-known leading-order (LO) analysis EKS98 and also to our previous LO work EPS08. As an extension to similar global analyses carried out by other groups, we complement the data from deep inelastic $l+A$ scattering and Drell-Yan dilepton measurements in p+$A$ collisions by inclusive midrapidity pion production data from d+Au collisions at RHIC, which results in better constrained gluon distributions than before. The most important new ingredient, however, is the detailed error analysis, which employs the Hessian method and which allows us to map out the parameter-space vicinity of the best-fit to a collection of nPDF error sets. These error sets provide the end-user a way to compute how the PDF-uncertainties will propagate into the cross sections of his/her interest. The EPS09 package to be released soon, will contain both the NLO and LO results for the best fits and the uncertainty sets.
Understanding nuclear effects in parton distribution functions (PDF) is an essential component needed to determine the strange and anti-strange quark contributions in the proton. In addition Nuclear Parton Distribution Functions (NPDF) are critically important for any collider experiment with nuclei (e.g. RHIC, ALICE). Here two next-to-leading order chi^2-analyses of NPDF are presented. The first uses neutral current charged-lepton Deeply Inelastic Scattering (DIS) and Drell-Yan data for several nuclear targets and the second uses neutrino-nucleon DIS data. We compare the nuclear corrections factors (F_2^Fe/F_2^D) for the charged-lepton data with other results from the literature. In particular, we compare and contrast fits based upon the charged-lepton DIS data with those using neutrino-nucleon DIS data.
We compare predictions of nCTEQ15 nuclear parton distribution functions with proton-lead vector boson production data from the LHC. We select data sets that are most sensitive to nuclear PDFs and have potential to constrain them. We identify the kinematic regions and flavours where these data can bring new information and will have largest impact on the nuclear PDFs. Finally, we estimate the effect of including these data in a global analysis using a reweighting method.
The strong coupling constant $alpha_s$ and the heavy-quark masses, $m_c$, $m_b$, $m_t$ are extracted simultaneosly with the parton distribution functions (PDFs) in the updated ABM12 fit including recent data from CERN-SPS, HERA, Tevatron, and the LHC. The values of begin{eqnarray} onumber alpha_s(M_Z)&=&0.1147pm0.0008~({rm exp.)}, onumber m_c(m_c)&=&1.252pm 0.018~({rm exp.})~{rm GeV}, onumber m_b(m_b)&=&3.83pm0.12~({rm exp.})~{rm GeV}, onumber m_t(m_t)&=&160.9pm1.1~({rm exp.})~{rm GeV} end{eqnarray} are obtained with the $overline{MS}$ heavy-quark mass definition being employed throughout the analysis.
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