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K* 0 analysis in Pb-Pb collision at √s NN = 2.76 TeV

K* 0 analysis in Pb-Pb collision at √s NN = 2.76 TeV. Subhash Singha NISER, Bhubaneswar. India-ALICE Collaboration Meeting 27-28 April 2013. Outline: --- Motivation --- Data Sets and analysis detail --- Mass/Width as a function of p T --- Systematic error extraction

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K* 0 analysis in Pb-Pb collision at √s NN = 2.76 TeV

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  1. K*0 analysis in Pb-Pb collision at √sNN = 2.76 TeV Subhash Singha NISER, Bhubaneswar India-ALICE Collaboration Meeting 27-28 April 2013

  2. Outline: --- Motivation --- Data Sets and analysis detail --- Mass/Width as a function of pT --- Systematic error extraction --- Corrected pT spectra --- Particle ratio: K*0/K- --- Summary

  3. Motivation • Lifetime of resonances are comparable to the lifetime of fireball  sensitive to • the properties of the medium. Re-scattering and re-generation: Kinetic freeze out Re-generation Qualitative plot Re-scattering time K*0/K Centrality • (K*0/K)AA and (K*0/K)pp  re-scattering / re-generation effects.

  4. Data Set Data Sets: Pb-Pb/AOD049 90 Good Runs with No V-drift problems 00 to 20 ===> 3.05627e+06 20 to 40 ===> 3.04396e+06 40 to 60 ===> 3.04714e+06 60 to 80 ===> 3.06153e+06 00 to 80 ===> 1.22089e+07

  5. Event, Track and PID selection Event Selection: Physics Selections, |vZ| < 10 cm Centrality Selection: using V0M Track Selection: --- pT > 0.15 GeV/c. --- |η| < 0.8 --- |(DCA)r (pT)| < 0.018 + 0.035pT-1.01 --- |(DCA)z|< 2 cm --- ITS and TPC refits. --- min cluster in TPC: 70 --- max Chi-square in TPC: 4 --- Kπ pair rapidity |y|< 0.5 Decay Channel: K*0  K+ π- , K- π+ (BR: 66%) PID Selection: |Nσ| < 2.0 (using TPC only) Standard 2010 track quality cuts with filterbit 32

  6. K*0 Signal extraction: Event Mixing (EM) and Like Sign (LS) distributions Event mixing: Number of mixed events = 5 10 bins in Z vertex (-10, 10) 10 bins in centrality (0,100) 12 bins in event plane angle (0,2π) R Normalization factor • Kπ invariant mass distribution • Background estimated using: • Event mixing technique • Like Sign technique Like Sign:

  7. Example of K*0 Signal extraction The combinatorial background is normalized in the invariant mass region (1.1, 1.3) GeV/c2 0.8 < pT < 1.2 GeV/c2 0.8 < pT < 1.2 GeV/c2

  8. Example of K*0 Signal extraction After combinatorial background subtraction, signal is fitted with a p-wave relativistic Breit Wigner function 0.8 < pT < 1.2 GeV/c2 0.8 < pT < 1.2 GeV/c2 BW Mass(M0) and width(Γ0) extracted from fit parameters Where

  9. Mass of K*0 as a function of pT Mass consistent with PDG value

  10. Width of K*0 as a function of pT Width consistent to PDG value

  11. Would like to request for preliminary approval Mass and Width of K*0: comparison with MC K* signal in MC HIJING 0-20% Mass and width consistent with MC HIJING simulations

  12. Sources of systematic uncertainty • List of Systematic checks: • Varying fitting ranges • Varying normalization regions • Varying residual backgrounds (poly2 vs. poly3) • Keeping free width vs. fixed PDG width • Varying Non Rel. BW and Rel. BW • Track Selections (10% constant as a function of pT) • PID : N sigma cuts • Material Budget. (1% constant as a function of pT) • Centrality Selection • Like Sign Method (consistency check)

  13. Sources of systematic uncertainty in K*0 yield

  14. Sources of uncorrelated systematic uncertainty in K*0 yield

  15. pT Spectra of K*0: Tsallis Levy Fit dN/dy and <pT> calculated using data in the measured region and fit in the extrapolation region.

  16. pT Spectra of K*0: Boltzmann Gibbs Blast Wave Fit

  17. <pT> of K*0

  18. <pT> of ϕ, K*0 with π, K, p-bar Increasing mass <pT>ϕ~ <pT>K*0 ~ <pT>pbar

  19. Particle ratio: K*0/K- vs Npart Log scale on Y-axis K*0/K- ratio vs Npart hadronic rescattering for central collisions(?)

  20. Particle ratio: K*0/K- vs √sNN (K*0/K-)AA < (K*/K-)pp  hadronic recattering (?)

  21. Particle ratio: K*0/K- vs (dN/dη) 1/3 K*0/K- vs (dN/dη)1/3  effect of size of the fireball (?)

  22. Summary: -- Mass and width of K*0 consistent with PDG value. -- <pT>ϕ~ <pT>K*0 ~ <pT>pbar -- K*0/K- ratio vs Npart hadronic rescattering for central collisions(?) -- (K*0/K-)AA < (K*/K-)pp  hadronic recattering in AA collision. -- K*0/K- vs (dN/dη)1/3  effect of size of the fireball(?).

  23. Back Up Slides

  24. Correlated and uncorrelated errors Eratio= Echeck/Ydef Eratio= √(E2check- E2def)/Ydef

  25. Sources of uncorrelated systematic uncertainty in K*0 yield

  26. pT Spectra of K*0: Blast Wave predictions (0-20%) Integral of BW function = 19.88 Integral of K* = 15.22 Blast wave parameters: ========================================================= beta_max = 0.878514 <beta> = 0.644618 +- 0.002296 (e+ = 0.002262, e- = -0.002292) T = 0.096984 +- 0.002141 (e+ = 0.002103, e- = -0.002047) n = 0.725690 +- 0.011371 (e+ = 0.011362, e- = -0.011364) chi2 = 57.718817 ndf = 124.000000 ========================================================= 04/18/13 26

  27. K*0 /K as a function of pT Kaon

  28. K*0 and K spectra Since the pT binning of Kaon and K*0 spectra are different, I have taken the Kaon yields using the fit function Boltzmann Gibbs Blast Wave.

  29. K*0 (pT)/K(pT) Linear scale Log scale

  30. K*0 (p*T)/K(pT) Log scale Linear scale After mass correction for radial flow p*T = pT (MK/MK*)

  31. K*0 and K spectra: With BGBW model K*0 BGBW model with parameters taking from Kaon

  32. Comparison with preliminary analysis

  33. Comparison: K*0 Spectra

  34. K*0 : Mass/Width : Material Budget productions Mat. Budg. Productions: LHC10h9 Pb-Pb Hijing (137366), 25 K events, +7% material LHC10h10 Pb-Pb Hijing (137366), 25 K events, -7% material

  35. K*0 Signals

  36. K*0 signals : BW Fits (TPC analysis) 0-20%

  37. K*0 signals : BW Fits (TPC analysis) 20-40%

  38. K*0 signals : BW Fits (TPC analysis) 40-60%

  39. K*0 signals : BW Fits (TPC analysis) 60-80%

  40. Efficiency x Acceptance

  41. Efficiency x Acceptance Production: LHC10a11a_bis/ESDs

  42. Efficiency of K* with different event and track selections

  43. Efficiency of K* with different pT combinations (0.3-5.0) in 0.4 GeV step (0.3-5.0) in 0.5 GeV step

  44. Efficiency of K* and anti-K*

  45. Looking at K* and anti-K* separately An example: Comparison K+ π- and K- π+ distributions 0-20% 0-20% 0-20% Difference ~ 2%

  46. K*/anti-K* signals : 0-80% K* Anti-K*

  47. Other plots

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