Status of hadron identification in semi-inclusive analysis

1
Status of hadron identification in semi-inclusive
analysis

• Rafal Gazda
• SINS, Warsaw

Analysis Meeting, CERN, 5 September 2006
2
Motivation
Goal polarized strange sea quarks
distributions. One needs asymmetries of K and
K-.
Hadron identification for longitudinal data
Tuning LH cuts
RICH stability (badspills)
3
RICH code for identification

• Two RICH methods are available
• Chi2 and LH
• Two codes for LH are available for different
  data(corespond to 04All-LH and 05All-LH)
• The best results come from LH5 method, but part
  of data has only LH4
• Only data with available LH5 was used
• (part of 2004 and 2002 data)
• For LH5 six likelihood values are available
• background
• Pion
• Kaon
• Proton
• Electron
• Muon

4
hadron identification
Standard cuts for SIDIS with Q2gt1GeV2

• Hadrons
• neither µB nor µ
• Zlast lt 33m
• zh(p)lt1

• pions
• LHmaxLH(p)
• Plt50 GeV
• LH(p)/...

• kaons
• LHmaxLH(K)
• Plt50 GeV
• LH(K)/...

5
Particle Identification

• Main problem is to distinguish pions from kaons
• Three cuts are tested on each kind of particle
• K
  p
• LH(K)/LH(p)
  LH(p)/LH(K)
• LH(K)/LH(bg)
  LH(p)/LH(bg)
• LH(K)/LH(2ndmax)
  LH(p)/LH(2ndmax)
• Cuts using LH of muon and electron were tried but
  without any improvement (these particles are
  partly removed with hadron cuts)
• Use LH of proton brings no improvement either.

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LH distributions
p
K
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Tuning LH cuts...

• Tuning cuts on these parameters was done looking
  at ?-gtpp- and F -gt KK- distributions.
• Only events with three particles from primary
  vertex were chosen µ and two oposite charged
  hadrons (identified as p or K).
• Ratio S/(SB) is calculated for each set of cuts
  (each cut was changed from 1 to 1.3 with step
  0.01)

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Results of tuning
Example 2004, W40
very preliminary LH(p)/LH(K) gt
1 LH(p)/LH(bg) gt 1.08 LH(p)/LH(2ndmax)
gt 1
very preliminary LH(K)/LH(p) gt 1.09
LH(K)/LH(bg) gt
1.18 LH(K)/LH(2ndmax) gt 1.01
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Conclusions

• Cuts on LH to identify p and K have been
  optimized using sample of ? and F mesons.
• Cuts are not finalized yet, work is in progress
• Also
• RICH stability check for longitudinal data has
  been started

No conclusions yet...