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 $N_F$-dependence in both the Parton Distribution Functions (PDFs) and the strong coupling constant $\alpha_S$, we generate coexisting sets of PDFs and $\alpha_S$ for $N_F=\{3,4,5,6\}$ at any scale $\mu$, that are related analytically by the $\overline{\text{MS}}$ matching conditions. The H-VFNS resums the heavy quark contributions and provides the freedom to choose the optimal $N_F$ 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

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

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

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

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

nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework

We present the new nCTEQ15 set of nuclear parton distribution functions with uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear dependence using data on nuclei all the way up to 208^Pb. The uncertainties are determined using the Hessian method with an optimal rescaling of the eigenvectors to accurately represent the uncertainties for the chosen tolerance criteria. In addition to the Deep Inelastic Scattering (DIS) and Drell-Yan (DY) processes, we also include inclusive pion production data from RHIC to help constrain the nuclear gluon PDF. Furthermore, we investigate the correlation of the data sets with specific nPDF flavor components, and asses the impact of individual experiments. We also provide comparisons of the nCTEQ15 set with recent fits from other groups.Comment: 35 page

ν(νˉ)\nu(\bar\nu)-208^{208}Pb deep inelastic scattering

Nuclear-medium effects in the weak structure functions $F_2(x,Q^2)$ and $F_3(x,Q^2)$ in the charged current neutrino and antineutrino induced deep inelastic reactions in $^{208}$Pb have been studied. The calculations have been performed in a theoretical model using relativistic nuclear spectral functions which incorporate Fermi motion, binding and nucleon correlations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, the results for the differential cross section have been obtained and compared with the CERN Hybrid Oscillation Research apparatUS (CHORUS) data. The results for the ratios $\frac{2F_{i}^{Pb}}{208F_i^D}$, $\frac{4F_{i}^{Pb}}{208F_i^{He}}$, $\frac{12F_{i}^{Pb}}{208F_i^C}$, $\frac{16F_{i}^{Pb}}{208F_i^O}$, and $\frac{56F_{i}^{Pb}}{208F_i^{Fe}}$ (i=2,3) have also been obtained and a few have been compared with some of the phenomenological fits.Comment: 19Pages, 12 Fig

Compatibility of global NPDF analyses of neutrino DIS and charged-lepton DIS data

The neutrino deep inelastic scattering (DIS) data is very interesting for global analyses of proton and nuclear parton distribution functions (PDFs) since they provide crucial information on the strange quark distribution in the proton and allow for a better flavor decompositon of the PDFs. In order to use neutrino DIS data in a global analysis of proton PDFs nuclear effects need to be understood. We study these effects with the help of nuclear PDFs extracted from global analyses of charged-lepton DIS, Drell-Yan and neutrino DIS data at next-to-leading order in QCD.Comment: Contribution to the XXIst International Europhysics Conference on High Energy Physics, 21-27 July 2011, Grenoble, Franc