Measurement of the cross section for electromagnetic dissociation with neutron emission in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV

TL;DR

This paper reports the first measurement of neutron emission cross sections in electromagnetic dissociation of lead nuclei at the LHC, using the ALICE detector's neutron calorimeters, and compares results with theoretical models.

Contribution

It provides the first experimental cross section measurements for electromagnetic dissociation with neutron emission at LHC energies, validating relativistic dissociation models.

Findings

Measured single EMD cross section: 187.4 ± 0.2 (stat.) +13.2/-11.2 (syst.) b

Measured mutual EMD cross section: 5.7 ± 0.1 (stat.) ± 0.4 (syst.) b

Results agree with relativistic electromagnetic dissociation model predictions

Abstract

The first measurement of neutron emission in electromagnetic dissociation of $^{208}$Pb nuclei at the LHC is presented. The measurement is performed using the neutron Zero Degree Calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with neutron emission are $\sigma_{\rm single\ EMD} = 187.4\pm0.2$ (stat.) $^{+13.2} _{-11.2}$ (syst.) b and $\sigma_{\rm mutual\ EMD} = 5.7\pm0.1$ (stat.) $\pm$0.4 (syst.) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.