In this page the pid selection is described. The selection is done using HMPID detector and is done on track-by-track basis using the detector response. Correction is being determined using MC productions:

• LHC11h(2c+3c)
  • runs: 117112(LHC10b anchor), 119161-120671(LHC10c anchor)
  • 7 million events
• LHC11h(2a+3a)
  • runs: 117112(LHC10b anchor), 119161-120671(LHC10c anchor)
  • 9.5 million events

PID selection

• using n(sigmas, excl) and n(sigmas, incl)

Pion selection

• HMPID pion identification capability: 3sigma separation up to pT = 3 GeV/c
• possibility to extend the identification by a pT dependent cut and/or using 2D cut using information from TPC to improve purity of the selection in pT > 3 GeV/c
• n(sigmas, excl)
  • this cut requires the track to be a certain number of sigmas away from a theoretical value of Theta(chkov, Kaon) and Theta(chkov, proton)
  • the separation of p/K changes with momentum, that is why we decided to use a pT dependent exclusion cut for Theta(chkov, Kaon)
  • pT in (1.5;3.0)
    • n(sigmas, excl, Kaon) > 1.
    • n(sigmas, excl, proton) > 1.
  • pT in (3.0;4.1)
    • n(sigmas, excl, Kaon) > 1.2
    • n(sigmas, excl, proton) > 1.
  • pT in (4.1;5)
    • n(sigmas, excl, Kaon) > 2.
    • n(sigmas, excl, proton) > 1.
• n(sigmas, incl)
  • this cut requires the track to be within a certain number of sigmas close to the theoretical value of Theta(chkov, pion)
  • pT in (1.5;4.1): |n(sigmas, incl, pion)| < 2
  • pT in (4.1;5.): |n(sigmas, incl, pion)| < 1

Proton selection

• HMPID proton identification capability: 3sigma separation up to pT = 5 GeV/c
• n(sigmas, excl)
  • this cut requires the track to be a certain number of sigmas away from a theoretical value of Theta(chkov, Kaon) and Theta(chkov, pion)
  • pT in (1.5;4.1)
    • n(sigmas, excl, Kaon) < -2.
    • n(sigmas, excl, pion) < -2.
  • pT in (4.1;5)
    • n(sigmas, excl, Kaon) < -1.
    • n(sigmas, excl, pion) < -1.
• n(sigmas, incl)
  • this cut requires the track to be within a certain number of sigmas close to the theoretical value of Theta(chkov, proton)
  • pT in (4.1;5.): |n(sigmas, incl, proton)| < 2

PID correction factor

Correction factor is determined as purity(PID)/efficiency(PID)

• hmpidTrack
  • hmpidSignal > 0
  • dist(mip-track) < 5 cm
• purity := n(hmpidTrack, PID selection, MC Truth) / n(hmpidTrack, PID selection)
• efficiency := n(hmpidTrack, PID selection, MC Truth) / n(hmpidTrack, MC Truth)

Pion

• Purity, efficiency and a correction factor for Pion PID selection:
  

Proton

• Purity, efficiency and a correction factor for Proton PID selection:
  

• Comparison of PID selection to pp@7TeV spectra:
  

-- SonaPochybova - 28 Feb 2014