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Prelimenary results for measurement of transverse polarization of lambda in pp collision at 200GeV

Updated on Fri, 2023-09-15 08:54. Originally created by gty on 2023-08-24 02:12.

Measurement of Transverse Polarization of Lambda in pp Collision at 200GeV at STAR

Previous presentation:

Dataset

Run year: 2015
Dataset:
pp200long2_2015
pp200trans_2015
Production: P16id
Liberary: SL18h

Event and Tracks Selection Cut

Event Cuts:

  • |PvZ|<90 cm
  • Vrank > 0
  • Triggers: JP1(6.0), JP2(8.4)

Track QA Cuts At Detector Level  
  • pT > 0.15 GeV/c   
  • DCA < 30 cm
  • nHitsFit> 15
  • nHitsFit/nHitsPoss  > 0.51
  • |nSigmaPion|<3 or |nSigmaProton|<3

Lambda Topological Cuts 
  • nSigmacuts for proton from Lambda:
    • |nSigmaProton|<= nSigmaProtection(showed in table) or |nSigmaProton| <= |nSigmaPion|
  • nSigmacuts for pion from Kshort:
    • |nSigmaPionpos|<= nSigmaProtection(showed in table) or |nSigmaPionpos|<=|nSigmaProtonpos|
    • |nSigmaPionneg|<= nSigmaProtection(showed in table) or |nSigmaPionneg|<=|nSigmaProtonneg|
       
  • pT dependent topological cuts
 
V0 Jet Reconstruction
  • Input Lambda to jet particle list
  • Correction of anti-proton annihilation effects
  • DeltaR < 0.6
  • Anti-kT algorithm
  • Jet pt > 5 GeV
  • Standard

MC sample

  • Pythia6+GEANT3
  • pTHard>5GeV/c
  • Lambda filter
    • Every event includes lambda(anti-lambda)
    • lambda pT>0.5 GeV
    • lambda |eta| < 1.5
  • JP1 trigger filter

Preliminary Results
Figure1: The transverse polarization of Lambda/Anti-Lambda versus z for JP1 trigger.


Figure2: The transverse polarization of Lambda/Anti-Lambda versus jT for JP1 trigger.


Figure3: The transverse polarization of Lambda/Anti-Lambda versus jet pT for JP1 trigger.

Conclusion:

  • No siginificant dependence for polarization
  • Lambda polarization: consistent with 0 within 1 sigma
  • Anti-LAmbda polarization: more than 2 sigma


Contact:
Taoya Gao, Shandong University
gao.ty@outlook.com

for the STAR Collaboration

08/26/2023


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