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Unpolarized $pi^+pi^-$ Cross Section Preliminary Result

Updated on Fri, 2023-09-22 10:16. Originally created by pokhrel on 2023-02-28 18:19.
Measurement of Unpolarized π+π-   Cross Section Using Run 12 Proton-Proton Collision Data at √s = 200 GeV at STAR  
(Preliminary Result)

Please refer to the analysis note for the analysis details in the attachment: Analysis Note

Dataset
MuDst -> picoDst Production
Run year: 2012
Dataset: pp200_production_2012
Production: P12id
Library: SL21d
BFC Chain:  
DbV20220301,picoDst,PicoVtxMode:PicoVtxVpdOrDefault,TpcVpdVzDiffCut:6,PicoCovMtxMode:PicoCovMtxWrite,PicoBEmcSmdMode:PicoBEmcSmdWrite

Event And Tracks Selecion Cuts

Event Cuts:                  

  • |Vz | < 60 cm
  • Vz,rank > 1e6
  • Triggers: JP0, JP1, JP2
Track QA Cuts At Detector Level  
  • 0.5 < pT < 15 GeV/c   
  • pT dependence dca cut
  • |eta|<1
  • nFitPts > 15
  • nFitPts/nFitPtsPoss  > 0.51
  • -1 < nSigmaPion < 2 (default pion selection cut)

π+π- Pair Selection Cuts

  • 0.02< cone < 0.7 ( π+π- opening angle in eta-phi space)
  • 1< pT < 15 GeV/c
  • 0.27 < Minv< 4 GeV/c2
  • |etapair|<1

Selection Cuts at the Particle Level

  • 0.5 < pT < 15 GeV/c   
  • |eta|<1
  • GEANT Pion IDs : 8 (π+), 9 (π-)
  • PYTHIA Pion IDs : 211 (π+), -211 (π-)
  • All the pair cuts are retained at the particle level as well.

Luminosity Per Trigger 

  • L (JP0) = 0.16 pb-1
  • L (JP1) = 7.68 pb-1
  • L (JP2) = 18.8 pb-1

Cross-sections per trigger
     
 
Figure 1 : Top Panel :: Final cross-section for individual trigger, and  the final  cross-section, which is the weighted average of the all three cross-sections.  Bottom Panel :: Relative difference between the triggered cross-sections to the final cross-section. 

Preliminary Result (Money Plot)


dipion cross section
Figure 2 : Money Plot : : Top panel: the measured and PYTHIA  cross-sections.  Bottom panel: total relative systematic error (green band), statistical error (red band), shown on the left axis , and  relative difference between the PYTHIA and measured cross-section  (Ratio) is shown in the right axis.   

Figure 3: Updated money plot including theory prediction from JAM collaboration. This png format is not displaying all the information correctly. So the pdf version is recommended for reuse of the result. 

Contact:
Babu Pokhrel, Temple University
babu.pokhrel@temple.edu

Bernd Surrow (PI), Temple University
surrow@temple.edu 
 
for the STAR Collaboration

03/07/2023
  


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