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 coalescence calculations, which fail to describe the measurement, in particular if a correlated production of protons and neutrons is assumed. Thermal-statistical model calculations describe the data 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.

 

Submitted to: PRL
e-Print: arXiv:2204.10166 | PDF | inSPIRE
CERN-EP-2022-040
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 for two different baryon number conservation volumes and from a simple coalescence model. The width of the SHM model bands corresponds to the statistical uncertainty of the model estimation, whereas the width of the band for 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 and from a simple coalescence model.

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 and coalescence model.