Femtoscopy and energy-momentum conservation effects in proton-proton collisions at 900 GeV in ALICE

TL;DR

This paper investigates two-particle correlations in 900 GeV proton-proton collisions at CERN, revealing Bose-Einstein effects and long-range correlations due to energy-momentum conservation, using a novel quantification technique.

Contribution

It introduces a new method, adapted from STAR, to quantify long-range correlations caused by energy-momentum conservation in small collision systems.

Findings

Baseline of correlation functions explained by energy-momentum conservation

Observation of Bose-Einstein correlations in identical particles

Long-range correlations affect the correlation function baseline

Abstract

Two particle correlations are used to extract information about the characteristic size of the system for proton-proton collisions at 900 GeV measured by the ALICE (A Large Ion Collider experiment) detector at CERN. The correlation functions obtained show the expected Bose-Einstein effect for identical particles, but there are also long range correlations present that shift the baseline from the expected flat behavior. A possible source of these correlations is the conservation of energy and momentum, especially for small systems, where the energy available for particle production is limited. A new technique, first introduced by the STAR collaboration, of quantifying these long range correlations using energy-momentum conservation considerations is presented here. It is shown that the baseline of the two particle correlation function can be described using this technique.