Abstract
The ALICE Zero Degree Calorimeter system (ZDC) is composed of two identical sets of calorimeters, placed at opposite sides with respect to the interaction point, 114 meters away from it, complemented by two small forward electromagnetic calorimeters (ZEM). Each set of detectors consists of a neutron (ZN) and a proton (ZP) ZDC. They are placed at zero degrees with respect to the LHC axis and allow to detect particles emitted close to beam direction, in particular neutrons and protons emerging from hadronic heavy-ion collisions (spectator nucleons) and those emitted from electromagnetic processes. For neutrons emitted by these two processes, the ZN calorimeters have nearly 100% acceptance.
Highlights
Theoretical models [6] predict that the electromagnetic dissociation of colliding 208Pb nuclei occurs mainly through the excitation and subsequent decay of the Giant Dipole Resonance (GDR) (∼60% of EMD events at the Large Hadron Collider (LHC)) and via emission of one or two neutrons
This can be exploited to measure the luminosity at heavy-ion colliders by detecting forward neutrons [7] using the Zero Degree Calorimeters (ZDCs) as is done in the ALICE experiment [8] at the Large Hadron Collider (LHC)
We achieved a good immunity from the photomultiplier noise exploiting the redundancy in the sampling that is present in the calorimeter design
Summary
Theoretical models [6] predict that the electromagnetic dissociation of colliding 208Pb nuclei occurs mainly through the excitation and subsequent decay of the Giant Dipole Resonance (GDR) (∼60% of EMD events at the LHC) and via emission of one or two neutrons This can be exploited to measure the luminosity at heavy-ion colliders by detecting forward neutrons [7] using the Zero Degree Calorimeters (ZDCs) as is done in the ALICE experiment [8] at the Large Hadron Collider (LHC). RELDIS accurately reproduces this experimental observation and predicts further increase of the mean number of neutrons and of the width of their multiplicity distribution as photon energy increases [10] Calculations based on this model provide a good description of neutron emission in electromagnetic dissociation of Pb ions at the CERN SPS [11] and of Au ions at the Relativistic Heavy Ion Collider (RHIC) [12]
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