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Light Nuclei Spectra in STAR Run5 62GeV Cu+Cu Experiments

Light Nuclei Spectra in STAR Run5 62GeV Cu+Cu Experiments. Jianhang Zhou Rice University. Motivation. Light nuclei spectra are important for calculating coalescence parameter.

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Light Nuclei Spectra in STAR Run5 62GeV Cu+Cu Experiments

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  1. Light Nuclei Spectra in STAR Run5 62GeV Cu+Cu Experiments Jianhang Zhou Rice University

  2. Motivation Light nuclei spectra are important for calculating coalescence parameter. D/Dbar, He3, and alpha spectra, B2 parameters, P/Pi ratios, are important to learn the physical features in the QGP freeze-out stage. 2) The spectra based on 200GeV Au+Au collisions have already been studied (by Haidong Liu). 3) This is an atempt to analyze the spectra based on 62GeV Cu+Cu collisions.

  3. Data Used: RHIC STAR Run-5 data 62GeV Cu+Cu from : 1) Calibrated Time of Flight (TOF) data 2) TPC MuDst data

  4. STAR PID Capable Detectors: TPC and TOF TPC(Time Projection Chamber) PID method: Ionization Energy Loss dE/dx PID method: measure TOF=T(stop)-T(start), along with p from TPC, => calculate Mass TOF (Time of Flight) Structure: pVPD and TOF tray

  5. TOF PID: M^2 Distribution Cuts: |nσ_D|<2, refmult>4, 2.5<m^2<-4.5, -0.1<eta< -0.9. M^2 of Deuteron: fitted by a Gaussian, and then integral M^2 of Anti-D: Too few events, No fitting, just use number counts

  6. TOF Spectra: P, Pbar, D, Dbar, Pi+, Pi- Match efficiency is fixed at 0.5%.

  7. TPC PID: N-sigma Distribution Cut: |q|=1, refmult>=18, nHitsFit>=25,nHitsDedx>=15,dca<=1 N-sigma of Proton, For 0.2GeV<Pt<0.4GeV, Close to Gaussian Distribution N-sigma of Proton, For 0.7GeV<Pt<1.0GeV, Fit by Gaussian(particle) + Exponential(background)

  8. N-Sigma of Proton for different Pt ranges: histogram is fit by: Exponential +Gaussian N-Sigma of Deuteron for different Pt ranges:

  9. TPC Spectra: P, Pbar, D, Dbar, Pi+, Pi-

  10. Comparison of spectra from TPC and TOF

  11. Summary Attempts were made to study the spectra of P/Pbar, D/Dbar, Pion+/- of STAR run5 62GeV Cu+Cu data. The spectra of nuclei were plotted for based on TOF and TPC PID respectively. Two results are combined and compared. Further studies are in the plan: Re-calculate match efficiency for TOF. Low Pt absorption correction will be applied. Coalescence parameter B2 will be calculated. TPC data of different centrality will be studied separately. Helium3 and alpha will also be studied. All will be compared to 200GeV Au+Au results.

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