Phenomenology of diffractive DIS in the framework of fracture functions and determination of diffractive parton distribution functions

Hamzeh Khanpour

doi:10.1103/physrevd.99.054007

Abstract

The goal of this study is to determine a set of diffractive parton distribution function (diffractive PDFs) from a QCD analysis of all available and up-to-date diffractive deep inelastic scattering (diffractive DIS) data sets from HERA $ep$ collider, including the most recent H1 and ZUES combined inclusive diffractive cross section measurements. This extraction of diffractive PDFs, referred to as {\tt HK19-DPDF}, is performed at next-to-leading (NLO) and next-to-next-to-leading (NNLO) in perturbative QCD. This new determination of diffractive PDFs is based on the fracture functions methodology, a QCD framework designed to provide a statistically sound representation of diffractive DIS processes. Heavy quark contributions to the diffractive DIS are considered within the framework of the FONLL general mass variable flavor number scheme (GM-VFNS) and the "Hessian approach" is used to determine the uncertainties of diffractive PDFs. We discuss the novel aspects of the approach used in the present analysis, namely an optimized and flexible parametrization of the diffractive PDFs as well as a strategy based on the fully factorization theorem for diffractive hard processes. We then present the diffractive PDFs, and discuss the fit quality and the stability upon variations of the kinematic cuts and the fitted data sets. We find that the systematic inclusion of higher-order QCD corrections could improves the description of the data. We compare the extracted sets of diffractive PDFs based on the fracture functions approach to other recent sets of diffractive PDFs, finding in general very good agreements.

Highlights

In the past decades, there has been an increasing interest in attempting to understand the structure of the hadron [1,2]
We will return to this issue that due to the lack of enough diffractive deep-inelastic scattering (DIS) datasets, one needs to fixed some of these variables at their best fit values, and there are potentially less free parameters in the diffractive parton distribution functions (PDFs) fit rather than what we presented in Eq (10)
In order to show the effects arising from the use of the different diffractive DIS datasets, in Tables II–VI, we present the χ2 for each bin of xP for our next-to-leading order (NLO) quantum chromodynamics (QCD) analysis

Summary

Introduction

There has been an increasing interest in attempting to understand the structure of the hadron [1,2]. The high energy processes of interest which contains information on the hadron structure in quantum chromodynamics (QCD) mostly include the hadron production in lepton-nucleon (lp) deep-inelastic scattering (DIS) and in proton-proton (pp) collisions. Information from hadron collisions, especially at the large hadron collider (LHC) at CERN, is useful in order to achieve a precise understanding of nonperturbative QCD dynamics.

Objectives

Methods

Results