Abstract
The cross sections of forward emission of one, two and three neutrons by 158A GeV 115In nuclei in collisions with Al, Cu, Sn and Pb targets are reported. The measurements were performed in the framework of the ALICE–LUMI experiment at the SPS facility at CERN. Various corrections accounting for the absorption of beam nuclei and produced neutrons in target material and surrounding air were introduced. The corrected cross section data are compared with the predictions of the RELDIS model for electromagnetic fragmentation of 115In in ultraperipheral collisions, as well as with the results of the abrasion–ablation model for neutron emission in hadronic interactions. The measured neutron emission cross sections well agree with the RELDIS results, with the exception of In–Al collisions where the measured cross sections are larger compared to RELDIS. This is attributed to a relatively large contribution of hadronic fragmentation of In on Al target with respect to electromagnetic fragmentation, in contrast to similar measurements performed earlier with 30A GeV 208Pb colliding with Al.
Highlights
The researches studying nucleus–nucleus collisions at the Super Proton Synchrotron (SPS) and at the Large Hadron Collider (LHC) at CERN are mostly focused on the studies of hot and dense nuclear matter, which is created in collisions of ultrarelativistic nuclei
The collected data are compared with the cross sections of neutron emission in electromagnetic dissociation of 115In calculated with the RELDIS model
The measured cross sections agree with the cross sections calculated by RELDIS for ultraperipheral collisions with Cu, Sn and Pb targets within estimated uncertainties of the measurements
Summary
The researches studying nucleus–nucleus collisions at the Super Proton Synchrotron (SPS) and at the Large Hadron Collider (LHC) at CERN are mostly focused on the studies of hot and dense nuclear matter, which is created in collisions of ultrarelativistic nuclei. As demonstrated by recent measurements [4,5], the total cross section of neutron emission from at least one of the colliding lead nuclei approaches 187 b at 1.38A TeV + 1.38A TeV collision energy In this case the nucleus which impacts another nucleus via the action of its electromagnetic field is characterized by a large Lorentz factor γ ∼ 4.3 × 106 which defines the scale of contraction. The single and mutual EMD cross sections of neutron emission were measured at the LHC for Pb–Pb collisions at 1.38A TeV + 1.38A TeV [4,5], and a very good agreement with the RELDIS results was demonstrated. In this sense our data complement the data collected in Ref. [15] and provide specific information on electromagnetic interactions of ultrarelativistic 115In nuclei
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