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

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.


Phys. Rev. Lett. 131 (2023) 041901
HEP Data
e-Print: arXiv:2204.10166 | PDF | inSPIRE
Figure group

Figure 1

Second order to first order cumulant ratio of the \dbar multiplicity distribution as a function of collision centrality in Pb--Pb collisions at \snn$ = $5.02 TeV. Statistical and systematic uncertainties are shown by the bars and boxes, respectively. Measured cumulant ratios are compared with estimations from the CE version of the SHM, from a simple coalescence model and from a MUSIC+UrQMD+Coalescence simulation. The width of the SHM model and MUSIC+UrQMD+Coalescence bands corresponds to the statistical uncertainty of the model estimation, whereas the width of the bands for the coalescence model corresponds to the uncertainty coming from the variation of the coalescence parameters.

Figure 2

Pearson correlation between the measured \pbar and \dbar as a function of collision centrality in Pb--Pb collisions at \snn$ = $5.02 TeV. Bars and boxes represent statistical and systematic uncertainties, respectively. Measured correlations are compared with estimations from the CE version of the SHM for two different baryon number conservation volumes, from coalescence model and from MUSIC+UrQMD+COAL.

Figure 3

Dependence of \pbar--\dbar correlation on pseudorapidity acceptance of \pbar and \dbar selection in Pb--Pb collisions at \snn$ = $5.02 TeV for three different centrality classes. Measurements are compared with calculations from the CE version of the SHM, coalescence model and MUSIC+UrQMD+COAL.