First measurement of antideuteron number fluctuations at energies available at the Large Hadron Collider

TL;DR

This paper reports the first measurement of event-by-event antideuteron fluctuations in high-energy Pb-Pb collisions at the LHC, revealing a negative correlation with antiprotons and testing theoretical models of particle production.

Contribution

It provides the first experimental data on antideuteron number fluctuations at LHC energies and compares these results with coalescence and thermal-statistical models.

Findings

Significant negative correlation between antiprotons and antideuterons observed.

Coalescence model describes cumulant ratios but not the correlation magnitude.

Thermal-statistical models fit observables only with adjusted correlation volumes.

Abstract

The first measurement of event-by-event antideuteron number fluctuations in high energy heavy-ion collisions is presented. The measurements are carried out at midrapidity ($|\eta| < 0.8$) as a function of collision centrality in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV using the ALICE detector. A significant negative correlation between the produced antiprotons and antideuterons is observed in all collision centralities. The results are compared with a state-of-the-art coalescence calculation. While it describes the ratio of higher order cumulants of the antideuteron multiplicity distribution, it fails to describe quantitatively the magnitude of the correlation between antiproton and antideuteron production. On the other hand, thermal-statistical model calculations describe all the measured observables within uncertainties only for correlation volumes that are different with respect to those describing proton yields and a similar measurement of net-proton number fluctuations.