Hadron contamination study by using E/p

Studied hadron contamination at high pT. The contamination estimated with Gaussian + exponent fitting doesn't work at high pT. In the current analysis, it is around 20-30 % at pT > 5 GeV/c. Here we checked whether the contamination is high at high pT. The method of the study is following

• first fit the E/p and find the mean and sigma of the distribution
• Calculate yields
  • Up = Integral(m,nXsigma), Dw = Integral(-nXsigma,m), All = Intergal(-nXsigma, nXsigma)
  • here n goes from 1 to 3, m is mean of the distribution
• Calculate Up/All and Dw/All
• if the contamination is high Dw/All >> 0.5

The E/p distribution with the fitting curve

• Fig. E/p distribution in pT bins. The distributions are fit with Gaussian + Exponent. Mean and SIgma were extracted from the fitting. The red line indicated 2 sigma (mean+- 2 sigma) position and the blue line indicates 3 sigma position.

Mean position of the distribution as a function of pT

• Fig. E/p mean position as a function of pT.

Sigma of the distribution as a function of pT

• Fig. E/p sigma position as a function of pT.

Yields for 1 sigma, 2sigma and 3 sigma cuts of E/p.

• Fig. Raw electron yields with 3 different n Sigma cuts (+-1, +-2 and +-3).

The relative ratios of integrals in the upward vs downward vs total integrals of the signal within the E/p peak

Summary

• for 1sigma: 10% effect for all pT's
  • for 2 and 3 sigma: from 1-few% effect at low-pT to 10% max at high-pT (max deviation ~20% at 5.5 GeV but suffering from the stat uncertainty) - average: ~4%
  • important note: the actual signal for the analysis is well within 3sigma and the systematic uncertainty for the related to these effects is driven by the 3sigma selection