456 research outputs found
CTEQ nuclear parton distribution functions
We show for the first time preliminary results of nuclear parton distribution
function analysis of charged lepton DIS and Drell-Yan data within the CTEQ
framework including error PDFs. We compare our error estimates to estimates of
different nPDF groups.Comment: 5 pages, to appear in the proceedings of XXI International Workshop
on Deep-Inelastic Scattering and Related Subjects, Marseilles, Franc
Heavy Quark Production in the ACOT Scheme Beyond NLO
We analyze the properties of the ACOT scheme for heavy quark production and
make use of the MS-Bar massless results at NNLO and N3LO for the structure
functions F2 and FL in neutral current deep-inelastic scattering to estimate
the higher order corrections. The dominant heavy quark mass effects at higher
orders can be taken into account using the massless Wilson coefficients
together with an appropriate slow-rescaling prescription implementing the phase
space constraints. Combining the exact ACOT scheme at NLO with these
expressions should provide a good approximation to the full calculation in the
ACOT scheme at NNLO and N3LO.Comment: 4 pages, 2 figures. Presented at DIS12, March 2012, Bonn, German
A Hybrid Scheme for Heavy Flavors: Merging the FFNS and VFNS
We introduce a Hybrid Variable Flavor Number Scheme for heavy flavors,
denoted H-VFNS, which incorporates the advantages of both the traditional
Variable Flavor Number Scheme (VFNS) as well as the Fixed Flavor Number Scheme
(FFNS). By including an explicit -dependence in both the Parton
Distribution Functions (PDFs) and the strong coupling constant , we
generate coexisting sets of PDFs and for at any
scale , that are related analytically by the
matching conditions. The H-VFNS resums the heavy quark contributions and
provides the freedom to choose the optimal for each particular data set.
Thus, we can fit selected HERA data in a FFNS framework, while retaining the
benefits of the VFNS to analyze LHC data at high scales. We illustrate how such
a fit can be implemented for the case of both HERA and LHC data.Comment: 15 pages, 11 figures, updated to match journa
Update on nCTEQ PDFs: nuclear PDF uncertainties and LHC applications
We present updated nCTEQ nuclear parton distribution functions with errors
including pion production data from RHIC. We compare them with the results of
other groups and present selected LHC applications.Comment: Presented at DIS2014, 28 April - 2 May 2014, Warsaw, Poland.
PoS(DIS2014)04
Strange Quark PDFs and Implications for Drell-Yan Boson Production at the LHC
Global analyses of Parton Distribution Functions (PDFs) have provided
incisive constraints on the up and down quark components of the proton, but
constraining the other flavor degrees of freedom is more challenging.
Higher-order theory predictions and new data sets have contributed to recent
improvements. Despite these efforts, the strange quark PDF has a sizable
uncertainty, particularly in the small x region. We examine the constraints
from experiment and theory, and investigate the impact of this uncertainty on
LHC observables. In particular, we study W/Z production to see how the s-quark
uncertainty propagates to these observables, and examine the extent to which
precise measurements at the LHC can provide additional information on the
proton flavor structure.Comment: 14 pages, 11 figures, added reference
Nuclear corrections in neutrino-nucleus DIS and their compatibility with global NPDF analyses
We perform a global chi^2-analysis of nuclear parton distribution functions
using data from charged current neutrino-nucleus deep-inelastic scattering
(DIS), charged-lepton-nucleus DIS, and the Drell-Yan (DY) process. We show that
the nuclear corrections in nu-A DIS are not compatible with the predictions
derived from l^+A DIS and DY data. We quantify this result using a
hypothesis-testing criterion based on the chi^2 distribution which we apply to
the total chi^2 as well as to the chi^2 of the individual data sets. We find
that it is not possible to accommodate the data from nu-A and l^+A DIS by an
acceptable combined fit. Our result has strong implications for the extraction
of both nuclear and proton parton distribution functions using combined
neutrino and charged-lepton data sets.Comment: 5 page
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