Motivation

Previously, Track-matched (T.M.) clusters were used for the evaluation of trigger rejection factors. However, T.M. clusters also contain contamination of pions, which tends to reduce the rejection factor. The motivation of this study is to check whether the selection of electrons improves the rejection factor calculation.

0--95

All the clusters

Using all the clusters -- this is the proposed for this analysis -- we are dominated by gamma clusters, which should have similar efficiency for triggering as electrons.

Figure 1 -- Trigger Ratio with all the clusters

Clusters + M20 > 0.006 and M20 < 0.4

For this selection a shower shape cut is applied, which reduces the charged pions contamination

Figure 2 -- Trigger Ratio with M20 selection

Clusters + T.M.

Figure 3 --Trigger Ratio Clusters + T.M.

Clusters + Electron -1 < NsigmaTPC < 3 cut

Electron candidate selection. Notice that this is not very pure (there are many pions in the high momentum region). It is impossible to apply M20 + E/P, due to lack of statistics in the MB sample.

Figure 4 -- Trigger Ratio Clusters + -1 < sigmaTPCe < 3

0--20

All the clusters

For this selection a shower shape cut is applied, which reduces the charged pions contamination

Figure 5 -- Trigger Ratio with all the clusters

Clusters + M20

For this selection a shower shape cut is applied, which reduces the charged pions contamination

Figure 6 -- Trigger Ratio with M20 selection

Clusters + T.M.

Figure 7 --Trigger Ratio Clusters + T.M.

Clusters + -1 < Electron NsigmaTPC < 3 cut

Electron candidate selection. Notice that this is not very pure (there are many pions in the high momentum region). It is impossible to apply M20 + E/P, due to lack of statistics in the MB sample.

Figure 8 -- Trigger Ratio Clusters + -1 < sigmaTPCe < 3

Summary of results

0-95%

0-20%

Conclusions

As expected, the trigger ratios using T.M. clusters have smaller values, due to charged pion contamination. Using a selection of Electrons using TPC improves the trigger factor, being closer to the ones using all the clusters. However it is not possible to have a clean high-pt electron cluster without E/P + M20 cut. So, one expects that there is still a bit of pion even in this study. Note: To be more precise, one would need to apply E/P + M20 + NsigmaTPC cut for the sample studied. However, MB lacks statistics in high momentum.

-- MarcelFigueredo - 2016-08-05