When determining the yield of J/ψ events, it is necessary to correct the raw count to account for both the detector’s acceptance and the muon reconstruction efficiency. The acceptance is governed by geometrical and kinematic constraints and is estimated through simulation. Meanwhile, the efficiency is primarily influenced by the detector’s operational characteristics and can be directly measured using data.
The acceptance for the decay J/ψ→μ+μ− is defined as the fraction of events that can be detected, expressed as a function of the dimuon transverse momentum pT and rapidity y:
where N_det is the number of events passing the detector’s criteria in a given (p_T, y) bin, and N_gen is the total number of generated J/ψ events (from simulation) in the same bin. The parameter λθ shows the fact that the acceptance has been computed for various polarization scenarios. The large amount of simulated events available allows here the use of a much smaller bin size with respect to what is used for the cross-section determination in data.
Reference: https://inspirehep.net/literature/925282
Plots:
PRELIMINARY (Not Final!): MC generated JPsi 10k events:
