Data Analysis - Particle ID Efficiencies: Determining Good Electron Cuts

Electron Detection Efficiency

The electron detection efficiency can be described as the quantitative ability of a particular detector to distinguish the electrons from pions. To calculate the electron detection efficiency, first a clean electron sample (Ns) is chosen with the help of the detector other than the one in question. Then, it is investigated how many of those electrons are detected (Nd) in the detector for which we would like to calculate the electron detection efficiency. The electron detection efficiency can be defined quantitatively as the ratio of Nd to Ns.

Calorimeter Electron Detection Efficiency

To calculate the electron efficiency of the calorimeter, the Cherenkov is used to select the electron sample (Ns) by applying a relatively strict cut to the main peak of the Cherenkov number of photoelectron(npe) distribution. Then, this selected electron sample is projected on the calorimeter and the number of electrons (Nd) deposited more than certain threshold energy i.e. electrons with total E/p > Cj where Cj is the threshold cut position of the calorimeter total E/p distribution, is estimated. The ratio gives the electron efficiency for the calorimeter.

Cherenkov Electron Detection Efficiency

The electron detection efficiency for the Cherenkov is estimated in a similar fashion as for the calorimeter. Since electrons and pions deposit distinct amount of energy on the pre-shower and shower parts of the calorimeter, one can use the calorimeter energy deposition plots to select electrons or pions. The electron sample chosen with the calorimeter is projected on the Cherenkov distribution and the electrons that fired the Cherenkov i.e. electrons with npe > Ci where Ci is the threshold cut value on the npe distribution, is counted. The ratio is the electron efficiency for the Cherenkov detector.

Pion Rejection Factor

Pion rejection factor (PRF) can be used as another measurement to study the ability of the detectors to separate pions from the electrons. Similar to the electron detection efficiency but this time a clean pion sample (Ns) is chosen with the help of the other detector that isn't under investigation. Then it was counted how many of those fired the detector that is in question (Nd). PRF can be described as the ratio of Ns to Nd.