Electromagnetic dissociation of heavy nuclei in ultra-peripheral interactions at high energies can be used to monitor the beam luminosity at colliders. In ALICE neutrons emitted by the excited nuclei close to beam rapidity are detected by the Zero Degree Calorimeters (ZDCs), providing a precise measurement of the event rate. During the 2010 Pb run, a dedicated data taking was performed triggering on electromagnetic processes with the ZDCs. These data, combined with the results from a Van der Meer scan, allowed to measure the electromagnetic dissociation cross-section of Pb nuclei at $sqrt{s_{rm NN}}$~=~2.76~TeV. Experimental results on various cross-sections are presented together with a comparison to the available predictions.
Download