Neutron emission in electromagnetic dissociation of ultrarelativistic Pb ions

New data on forward neutron emission in fragmentation of 30A-GeV /sup 208/Pb ions on Al, Cu, Sn, and Pb nuclei are presented. The measurements were performed at the CERN SPS in the framework of the ALICE-LUMI experiment. The measured cross sections are compared with predictions of the RELDIS model for electromagnetic interactions and with results of the abrasion-ablation model for hadronic interactions. The electromagnetic excitation of a Pb projectile followed by single- and double-neutron emission is found to be the dominant process in full agreement with theoretical estimations. The measured 1nX cross sections are generally well described. The measured 2nX data, which are 4-5 times lower than the 1nX data, are slightly underestimated by theory. Nevertheless, the sum of 1nX and 2nX cross sections is in good agreement with theory. This confirms the predictive power of the RELDIS model, which can be used to calculate the sum of 1nX and 2nX emission rates for the purpose of calibration of luminosity measurements in PbPb collisions at the Large Hadron Collider at CERN