Femtoscopy of stopped protons

TL;DR

This paper proposes a femtoscopic method to analyze stopped protons in heavy ion collisions, revealing oscillations in correlation functions that can help measure baryon density and verify Lorentz contraction effects.

Contribution

It introduces a novel femtoscopy approach to study stopped protons and demonstrates the potential to experimentally observe characteristic oscillations in correlation functions.

Findings

Oscillations in proton-proton correlation functions are detectable.

The method can estimate baryon density in the collision center.

It provides a way to verify Lorentz contraction of nuclei.

Abstract

The longitudinal proton-proton femtoscopy (HBT) correlation function, based on the idea that in a heavy ion collision at $\sqrt{s} \lesssim 20$ GeV stopped protons are likely to be separated in configuration space, is evaluated. It shows a characteristic oscillation which appears sufficiently pronounced to be accessible in experiment. The proposed measurement is essential for estimating the baryon density in the central rapidity region, and can be also viewed as an (almost) direct verification of the Lorentz contraction of the fast-moving nucleus.