A. Kusina

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.

Inclusion of the QCD next-to-leading order corrections in the quark-gluon Monte Carlo shower

Methodology of including QCD NLO corrections in the quark--gluon Monte Carlo shower is outlined. The work concentrates on two issues: (i) constructing leading order (LO) parton shower Monte Carlo from scratch, such that it rigorously extends collinear factorization into the exclusive (fully unintegrated) one which we call the Monte Carlo factorization scheme; (ii) introducing next-to-leading-order (NLO) corrections to the hard process in this new environment. The presented solution is designed to be extended to the full NLO level Monte Carlo, including NLO corrections not only in the hard process but in the whole shower. The issue of the difference between the factorization scheme implemented in the Monte Carlo (MC) solution and the standard MSbar scheme is addressed. The principal MC implementation is designed for the electroweak boson production process at the LHC, but in order to discuss universality -- process independence, the deep inelastic lepton--hadron scaterring is also brought into the MC framework.

On the intrinsic bottom content of the nucleon and its impact on heavy new physics at the LHC

A bstractHeavy quark parton distribution functions (PDFs) play an important role in several Standard Model and New Physics processes. Most analyses rely on the assumption that the charm and bottom PDFs are generated perturbatively by gluon splitting and do not involve any non-perturbative degrees of freedom. It is clearly necessary to test this hypothesis with suitable QCD processes. Conversely, a non-perturbative, intrinsic heavy quark parton distribution has been predicted in the literature. We demonstrate that to a very good approximation the scale-evolution of the intrinsic heavy quark content of the nucleon is governed by non-singlet evolution equations. This allows us to analyze the intrinsic heavy quark distributions without having to resort to a full-fledged global analysis of parton distribution functions. We exploit this freedom to model intrinsic bottom distributions which are so far missing in the literature in order to estimate the impact of this non-perturbative contribution to the bottom-quark PDF, and on parton-parton luminosities at the LHC. This technique can be applied to the case of intrinsic charm, albeit within the limitations outlined in the following.

Strange quark parton distribution functions 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.

Vector boson production in pPb and PbPb collisions at the LHC and its impact on nCTEQ15 PDFs

We provide a comprehensive comparison of

Hybrid scheme for heavy flavors: Merging the fixed flavor number scheme and variable flavor number scheme

W^pm / Z

Heavy quark production in the Aivazis-Collins-Olness-Tung scheme at next-to-next-to-leading and next-to-next-to-next-to-leading order

W±/Z vector boson production data in pPb and PbPb collisions at the LHC with predictions obtained using the nCTEQ15 PDFs. We identify the measurements which have the largest potential impact on the PDFs, and estimate the effect of including these data using a Bayesian reweighting method. We find this data set can provide information as regards both the nuclear corrections and the heavy flavor (strange quark) PDF components. As for the proton, the parton flavor determination/separation is dependent on nuclear corrections (from heavy target DIS, for example), this information can also help improve the proton PDFs.

Virtual Corrections to the NLO Splitting Functions for Monte Carlo: the non-singlet case

The decade-old technique of combining NLO-corrected hard process with LO-level parton shower Monte Carlo is now mature and used in practice of the QCD calculations in the LHC data analysis. The next step, its extension to an NNLO-corrected hard process combined with the NLO-level parton shower Monte Carlo, will require development of the latter component. It does not exist yet in a complete form. In this note we describe recent progress in developing the NLO parton shower for the initial-state hadron beams. The technique of adding NLO corrections in the fully exclusive form (defined in recent years) is now simplified and tested numerically, albeit for a limited set of NLO diagrams in the evolution kernels.