Eur. Phys. J. C (2017) 77: 288
https://doi.org/10.1140/epjc/s10052-017-4847-0

Regular Article - Theoretical Physics

Correlated stopping, proton clusters and higher order proton cumulants

¹ Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059, Kraków, Poland
² Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
³ RIKEN/BNL, Brookhaven National Laboratory, Upton, NY, 11973, USA

^* e-mail: bzdak@fis.agh.edu.pl

Received: 1 February 2017
Accepted: 20 April 2017
Published online: 5 May 2017

Abstract

We investigate possible effects of correlations between stopped nucleons on higher order proton cumulants at low energy heavy-ion collisions. We find that fluctuations of the number of wounded nucleons lead to rather nontrivial dependence of the correlations on the centrality; however, this effect is too small to explain the large and positive four-proton correlations found in the preliminary data collected by the STAR collaboration at GeV. We further demonstrate that, by taking into account additional proton clustering, we are able to qualitatively reproduce the preliminary experimental data. We speculate that this clustering may originate either from collective/multi-collision stopping which is expected to be effective at lower energies or from a possible first-order phase transition, or from (attractive) final state interactions. To test these ideas we propose to measure a mixed multi-particle correlation between stopped protons and a produced particle (e.g. pion, antiproton).