Definition

In general, the probability that an event is accepted depends on the characteristics of the measured event, and not on the process that produced it. The measured probability density $\bar{P}(x,\alpha)$ can be related to the produced probability density $P(x,\alpha)$: $\bar{P}(x,\alpha)=Acc(x) P(x,\alpha)$ where $ Acc(x)$ is the detector acceptance, which depends only on $ x $

In the computation of the likelihood of the MatrixElement, this acceptance term induce the following term: $\int Acc(x) P(x,\alpha)dx$

This could be estimated easily, by MC, as the number of accepted events on the number of generated events. $\frac{N_{accepted}}{N_{generated}}$

How to compute Acceptance term with pythia/PGS.

WARNING: This module is in devellopment. This module is (not yet) on any official distribution.

1. In order to have the computation of the acceptance term in MW you have to put in the MadWeight_card.dat the following option

   Block MW_Run
        4.         T            # normalizes weight  (1/sigma prefactor)
        acceptance_run T       # computes the acceptance term
   

-- Main.OlivierMattelaer - 22 May 2009