Ioffe Times in DIS from a Dipole Model Fit

TL;DR

This paper investigates Ioffe times in deep inelastic scattering using a dipole model fit to HERA data, revealing how these times vary with photon virtuality and energy, and discussing implications for the dipole picture's validity.

Contribution

It provides the first detailed analysis of Ioffe-time distributions in DIS from experimental data within a dipole model framework, highlighting their dependence on kinematic variables.

Findings

Ioffe times are broad for transverse photons and narrow for longitudinal photons.

Ioffe times decrease from about 1000 fm to 10 fm as Q^2 increases from 1 to 100 GeV^2.

Results suggest limitations on the applicability of the dipole picture at certain energy and virtuality ranges.

Abstract

We present a study of Ioffe times in deep inelastic electron-proton scattering. We deduce 'experimental' Ioffe-time distributions from the small-x HERA data as described by a particular colour-dipole-model fit. We show distributions for three representative gamma*-proton c.m. energies W and various values of the photon virtuality Q^2. These distributions are rather broad for transversely and very narrow for longitudinally polarised virtual photons. The Ioffe times for W=150 GeV, for example, range from around 1000 fm for Q^2=1 GeV^2 to around 10 fm for Q^2=100 GeV^2. Based on our results we discuss consequences for the limitations of applicability of the dipole picture.