Jpsi Pt Scaling

Motivation

Since the production on the GRID -- LHC12h4 -- corresponds to J/psi flat distribution, one should be careful about the pt dependency of the efficiency. Since we deal with trigger data, the efficiency is quite lower for the lower pt bins. The broad pt bins used in analysis makes this behavior even more intense. In order to correct this feature, one needs to scale the efficiency properly, in order to weight accurately the influence of lower pt bins. The choice was to use the CDF extrapolated pt distribution, in order to scale the pt dependency of J/psi reconstruction efficiency.

1 CDF Extrapolated to 7 TeV ( From AliGenMuon )

CDF Distribution x Pt

Figure 1 (a)

2 Efficiency from LHC11dMC Scaled By CDF Extrapolated cross section

The efficiency from MC Flat J/psi production was divided into 0.1 GeV/c pt bins. Then, two new histograms were by extracting randomly one point from CDF extrapolated cross section ( as in figure 1 a). One of the histograms was filled by this point from figure a, where as the other one was filled according to the efficiency from flat, as in red points from figure 2(a). The division of these two histograms - using the same binning as in real data analysis - gives the new estimation for the efficiency, as one can see by the blue points in figure 2 (b).

3 Final Xsection compared

Figure 3 (a) CDF Scaled	Figure 3 (b) Flat distribution

As one could expect, the final cross section is higher for the scaled case, because the lower pt bin efficiency dominates the final result, since they have lower efficiency due to the trigger selection.