Charm Production and QCD Analysis at HERA and LHC

TL;DR

This review discusses charm production measurements at HERA and LHC, highlighting how combined data refine gluon distribution models and enable precise determination of the charm quark mass within perturbative QCD.

Contribution

It integrates HERA and LHCb charm data to improve gluon distribution functions and accurately determine the charm quark mass, advancing QCD analysis.

Findings

Agreement between data and NLO QCD predictions

Enhanced gluon distribution shape down to x ~ 10^{-6}

Precise determination of the charm quark mass

Abstract

This review is devoted to the study of charm production in ep and pp collisions. The total set of measurements obtained by the two collaborations H1 and ZEUS from HERA and their combination is outlined, as well as complementary data obtained by the LHCb collaboration at the LHC. After fitting the parton distribution functions the charm production cross sections are predicted within perturbative QCD at next-to-leading order using the fixed-flavour-number scheme. Agreement with the data is found. The combined HERA charm data are sensitive to the $c$-quark mass and enabled its accurate determination. The predictions crucially depend upon the knowledge of the gluon distribution function. It is shown that the shape of the gluon distribution based on the HERA data is considerably improved by adding the measurements from LHCb and applicable down to values x of about 10^{-6}, where x is the proton momentum fraction carried by a parton.