In depth analysis of the combined HERA data in the dipole models with and without saturation

TL;DR

This paper updates and compares saturation and non-saturation dipole models fitted to HERA data, analyzing saturation effects, quark masses, and the role of large dipoles, with implications for future experiments.

Contribution

It introduces an updated impact parameter dependent saturation model and compares it with a linearized version, assessing saturation effects using combined HERA data.

Findings

Both models describe data well with confinement scale dynamics.

Light and charm quark masses are consistently determined.

Large dipoles significantly impact the structure function F2.

Abstract

We present an updated impact parameter dependent saturation model (IPsat) determined trough a fit to the combined HERA I and I+II reduced cross section data. The same HERA data are used to fit the linearized (IPnonsat) version of the applied dipole amplitude, which makes it possible to estimate the magnitude of the saturation effects in various experiments. We find that both parametrizations provide comparable descriptions of the considered data when an effective confinement scale dynamics is incorporated with quark masses. Moreover, it is possible to consistently determine the light and charm quark masses. The role of potentially non-perturbatively large dipoles is examined in detail, with the result that, especially in case of the structure function $F_2$, their contribution is numerically significant. Potential to discriminate between the two models in future $e+p$ and $e+A$ experiments is also illustrated.