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g +A J/Ψ+A : UPC trigger example
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L1 UltraPeripheral Trigger:
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Veto on coincident BBC (|y| ~3-4):
[avoid periph. nuclear, beam-gas colls.]
Neutron(s) in at least one ZDC (E>30 GeV)
[sensitive to Au* Coulomb dissociation]
Large energy (E > 0.8 GeV) cluster in EMCal:
[e+e- decay from J/]
Definition:
Events collected (~0.4% of MB trigger):
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UPC AuAu: 8.5 M
MB AuAu (BBCLL1): 1122 M (equivalent ∫L = 120 mb-1)