Dipole amplitude with uncertainty estimate from HERA data and applications in Color Glass Condensate phenomenology

TL;DR

This paper derives the initial dipole amplitude from HERA data with uncertainty estimates, enabling improved predictions in Color Glass Condensate phenomenology for particle production in high-energy collisions.

Contribution

It introduces a new parametrization for the dipole amplitude that ensures positivity and incorporates uncertainty estimates, advancing the modeling of small-x evolution in QCD.

Findings

The initial dipole amplitude is extracted with uncertainty from HERA data.

The approach predicts the nuclear modification factor approaches unity at high transverse momentum.

Consistent use of proton transverse area and inelastic cross section affects the R_{pA} predictions.

Abstract

We determine the initial condition for the small-$x$ evolution equation (BK) from the HERA deep inelastic scattering data using a new parametrization that also keeps the unintegrated gluon distribution positive. The obtained dipole amplitude and its uncertainty estimate can be used to compute single inclusive particle production in proton-proton and proton-nucleus collisions. We argue that one has to use consistently the proton transverse area measured in DIS and the total inelastic cross section when calculating the single inclusive cross section. This leads to a midrapidity nuclear modification factor $R_{pA}$ that approaches unity at large transverse momentum, independently of the center-of-mass energy.