The constituent quark model cqm is used to evaluate the pointlike parton distribution functions pdf, the structure functions sf, and the emc ratio of this light nucleus, at the leading. The analysis includes, for the first time, data on the free neutron structure function from jefferson lab and new highprecision charged lepton and wboson asymmetry data from fermilab. Quark and gluon distributions probed in deep inelastic scattering and other high energy processes have provided valuable insights into the workings of qcd in the low energy domain. This thesis is dedicated to the construction and applications of parton distribution functions pdfs, which are precise enough that are suitable for comparison with highprecision collider data from the lhc. Deep inelastic scattering intuitively, it seems obvious that small wavelength. It should be noted that such a bias can in uence other partons since the partons distributions are coupled to each other by the evolution equations, as will be seen in chap.
Structure functions and parton densities bnl conferences. We present a new set of leadingtwist parton distribution functions, referred to as cj15, which take advantage of developments in the theoretical treatment of nuclear corrections as well as new data. Global analyses of nuclear parton distribution functions npdfs. The following steps enter a global analysis see fig. Parton distribution functions pdfs contain a wealth of information on the nonperturbative structure of the nucleon. Nocera university of oxford pdfs for bsm searches october 19, 2015 2 34. Cteq6 parton distribution functions are publicly available as a part of the lhapdf fortran library. Parton distribution functions at the lhc robert thorne february 15th, 20 university college london ippp research associate with contributions from alan martin, james stirling, graeme watt and arnold mathijssen and ben watt ucl february 20. Parton distribution functions at lo, nlo and nnlo with. The properties of generalized parton distributions are described. Wiki ncteq project is an extension of the cteq collaborative effort to determine parton distribution functions inside of a free proton.
The nnpdf collaboration determines the structure of the proton using contemporary methods of artificial intelligence. Pdf new approach to the parton distribution functions. Each parton then carries a momentum fraction xof the protons total longitudinal momentum. Parton distribution functions for beyondstandardmodel. The parton distribution function of the pion in the valence region is extracted in a nexttoleading order analysis from fermilab e615 pionic drellyan data. If pointlike constituents, allow for distribution inside proton formfactors partons, and parton distribution functions roadmap. Pdf new avenue to the parton distribution functions. Experimental information on the parton distribution function pdf in the pion has primarily been inferred from the drellyan reaction in pionnucleon collisions. Parton distribution functions are essential tools in highenergy particle physics emanuele r. Double parton distribution functions shane keane september 4, 20 abstract double parton scattering may constitute a signi cant background to important processes such as higgs boson production.
Parton distribution function how is parton distribution. An introduction to the pdf determination by global analyses of the main pdf. Martinstirlingthornewatt parton distribution functions. Parton distribution functions in the lowenergy limit. Adp1430t889 within the dysonschwinger equation formulation of qcd, a rainbow ladder truncation is used to calculate the pion valencequark. The parton distribution functions pdfs represent the probability densities to nd a speci c parton with a momentum fraction xof the proton. Introduction to parton distribution functions scholarpedia. This will be a reasonable approximation locally if the electric field is uniform over several electron mean free paths. Parton distribution functions for beyondstandardmodel searches. Cross sections for higgs production at the lhc are sensitive to quark, anti quark and gluondistributions in the xrange fromapproximately 0. Flowchart of a global analysis for parton distribution functions. Eps09 a new generation of nlo and lo nuclear parton. Parton, dolly rebecca parton, dolly rebecca parton, dolly rebecca parton, james.
The parton distribution functions are determined with the herafitter program using the data from the hera experiments and preserving correlations between uncertainties for the lo, nlo and nnlo pdf sets. Thomas acssm, school of chemistry and physics university of adelaide, adelaide sa 5005, australia abstract preprint no. Parton distribution functions gavin salam lpthe, cnrs and upmc univ. The electron mean free path in air is approximately m. The dynamical approach to parton distributions the longitudinal structure function the dynamical determination of strange parton distributions the treatment of heavy quarks. These pdfs are released by individual groups as discrete grids as a function of the bjorkenx and energy scale q. The study of the pion structure function is of great interest as a fundamental test of our understanding of nonperturbative qcd. A precise knowledge of the socalled parton distribution functions pdfs of the proton, which describe their structure in terms of their quark and gluon constituents, is a crucial ingredient of the physics program of the large hadron collider of cern. This paper examines certain features of double parton distribution functions, which are required to fully calculate the crosssections for double. We find that the resulting negative nonlinear corrections can improve the perturbative stability of the qcd. Parametrize pdf at parametrize pdf at q 0, evolve to q. Paris 6 at the 2009 european school of highenergy physics june 2009, bautzen, germany. The sets are used to study crosssection ratios and their uncertainties when calculated at different orders in qcd. We present a determination of the parton distribution functions of the proton in which nlo and nnlo fixedorder calculations are supplemented by nllx smallx resummation.
Nuclear cteq parton distribution functions hepforge ncteq project is an extension of the cteq collaborative effort to determine parton distribution functions inside of a free proton. Continuous distributions are to discrete distributions as type realis to type intin ml. Axial and vector structure functions for electron and neutrino nucleon scattering using effective leading order parton distribution functions arie bodek rochester pdf txt. Parton distribution functions with percent level precision. The nonlinear dokshitzergribovlipatovaltarelliparisi dglap evolution equations with parton recombination corrections are used to dynamically evaluate the protons parton distribution functions starting from a low scale. Including lhc measurements into a qcd analysis for pdf. That is, the electron distribution function will be assumed to be independent of x. A parton distribution function pdf within so called.
Factorisation theorems and parton density functions 5. Soms are visualization algorithms based on competitive learning among spatiallyordered. Nuclear cteq parton distribution functions hepforge. Pion valencequark parton distribution function lei chang a, anthony w. We propose a parton distribution function pdf fitting technique which is based on an interactive neural network algorithm using selforganizing maps soms. It starts with the physics of form factors and parton distributions. Deep inelastic scattering and structure functions 2. This is the usual way to plot parton distribution functions, since otherwise, the gluon pdf rises too rapidly towards zero.
In the advent of the lhc becoming online, the knowledge of free and bound nucleon parton distribution functions pdfs together with their uncertainties, is perhaps more topical than ever. Parton sets must be extracted from data, and are then used to compute theoretical predic. We construct a set of parton distribution functions pdfs in which fixedorder nlo and nnlo calculations are supplemented with softgluon threshold resummation up to nll and nnll accuracy respectively, suitable for use in conjunction with any qcd calculation in which threshold resummation is included at the level of partonic cross sections. Dynamical parton distribution functions the dynamical approach to parton distributions the longitudinal structure function the dynamical determination of strange parton distributions the treatment of heavy quarks. Towards parton distribution functions with smallx resummation. A parton distribution function pdf within so called collinear factorization is defined as the probability density for finding a particle with a certain longitudinal momentum fraction x at resolution scale q 2. Q where i labels the parton species depends on two variables. Such a pdf for the valence up quarks is shown in fig. Here you can download a standalone fortran interface and demonstration program, as well as the tables with interpolated pdf values for the latest generalpurpose set cteq6. Pdf pion parton distribution function in the valence region. Ct18 parton distribution functions this page provides numerical table files for the. Because of the inherent nonperturbative nature of partons which cannot be observed as free particles, parton densities cannot be calculated using perturbative qcd. It generalizes the freeproton pdf framework to determine densities of partons in bound protons hence ncteq which stands for nuclear cteq.
The cteq6 family of pdfs is superseded by newer, more complete, ct10 pdf sets. This page provides numerical table files for the computation of ct18 nexttoleading order nlo and nexttonexttoleading order nnlo parton distribution functions. Parton distribution functions pdfs are essential nonperturbative inputs for calculation of any observable with hadronic initial states. Here we provide the standalone interface code and grids for the mstw 2008 lo, nlo, nnlo pdfs described in arxiv.
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