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Feasibility study of V 0 analysis with first data ( p+p @ √s = 900 GeV )

Feasibility study of V 0 analysis with first data ( p+p @ √s = 900 GeV ). Alberica T oia. Besides A+A. Strangeness enhancement At RHIC 200 GeV comparable to 17 GeV Canonical suppression in p+p data reduced at higher energy N part scaling not applicable to strangeness ?

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Feasibility study of V 0 analysis with first data ( p+p @ √s = 900 GeV )

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  1. Feasibility study of V0 analysis with first data (p+p @ √s = 900 GeV) AlbericaToia

  2. Besides A+A... • Strangeness enhancement • At RHIC 200 GeV comparable to 17 GeV • Canonical suppression in p+p data reduced at higher energy • Npart scaling not applicable to strangeness ? • Intermediate pT • Particle ratios, flow, indicative of coalescence mechanisms. • Energy dependence • smooth excitation function between SPS and top energy RHIC data • Constituent quark scaling still present

  3. pT-spectra for strange particles • PYTHIA Version 6.326 used • Incorporates parameter tunes from CDF (tune A) • New multiple scattering and shower algorithms • Tune: • MSEL=1 (inelastic collisions) • K-Factor = 3 (higher order corrections) • First NLO calculations K0s and Lambda at 200 GeV were obtained privately from W.Vogelsang (BNL) • In 2005 calculations at NLO by Albino, Kniehl & Kramer (AKK) for K0s and Lambda produced better agreement by constraining gluon FF.

  4. Baryon-meson “anomalies” PYTHIA cannot describe Baryon/Meson ratio at intermediate pTeven with tuned K-factors. In addition di-quark probabilities need to be tuned. PYTHIA also underpredicts the Baryon/meson ratio for higher energies at UA1, √s= 630 GeV Gluon Jets will produce a larger Baryon/Meson ratio than quark-jets in the region of interest

  5. Existing data • < 62 GeV: SPS • 62-200 GeVp+p: STAR • 630 GeVp+p: UA1 and CDF (decent uncertainties) • 900 GeVp+p : UA5 (very poor statistics) • 1800 GeVp+p: CDF has results

  6. V0 Analysis with ALICE • Detectors needed: • TPC: tracking + dE/dx • ITS: secondary vertex, improve pT resolution, reconstruct low pT particles lost in TPC • Reconstruction: Invariant mass method

  7. V0 Analysis with ALICE II • Reconstruction: • Selection of secondary tracks depending on their dca to primary vertex; • Association of two opposite charged secondary tracks + topological cuts. • (PID  improve L) • V0 finders: • "on-the-fly“: identifies V0 during track reconstruction ( more efficient) • "offline“: combines secondary tracks after the track reconstruction ( slightly less efficient but less background)The difference should be more pronounced with a higher multiplicity (EPOS ?)

  8. Data Used • LHC09b8(10,12,14) _0.9TeV_0.5T, i.e.: • PYTHIA 900 GeV 0.5T • Phojet 900 GeV 0.5T • PYTHIA 7000 GeV 0.5T • Phojet 7000 GeV 0.5T

  9. Pythia0.9GeV *** bug in storing like sign V0s.https://savannah.cern.ch/bugs/?func=detailitem&item_id=47412

  10. Phojet 0.9GeV *** bug in storing like sign V0s.https://savannah.cern.ch/bugs/?func=detailitem&item_id=47412

  11. Pythia 7TeV *** bug in storing like sign V0s.https://savannah.cern.ch/bugs/?func=detailitem&item_id=47412

  12. Phojet 7TeV *** bug in storing like sign V0s.https://savannah.cern.ch/bugs/?func=detailitem&item_id=47412

  13. Feasibility studies with 900 GeV data • LHC09b10 production • Phojetevent generator • √s = 0.9TeV • field = 0.5T • N. of events on CAF = 217,800

  14. Peak Extraction Method • Fit all mass range with gauss + pol2 – determine mean and sigma • Fit mass range (excluding signal region) with pol2 (~background) – prolong the background below the signal • Extract yield – from the gauss fit – bin counting:signal = (m0 - 5s , m0 + 5s)background = 0.5 * ( (m0 - 20s , m0 - 10s) + (m0 + 10s , m0 + 20s)) – bin counting:signal = (m0 - 5s , m0 + 5s)background = pol2 in (m0 - 5s, m0 + 5s)

  15. L Inv. Mass Spectra pol2+gauss pol2 (excluding signal) extrapolate pol2 integration window signal integration window bkg M(Kp) (GeV/c2)

  16. L Inv. Mass Spectra pol2+gauss pol2 (excluding signal) extrapolate pol2 integration window signal integration window bkg M(Kp) (GeV/c2)

  17. K0s Inv. Mass Spectra pol2+gauss pol2 (excluding signal) extrapolate pol2 integration window signal integration window bkg M(pp) (GeV/c2)

  18. Peak Position AntilambdaLambda K0s pT (GeV/c)

  19. Width AntilambdaLambda K0s pT (GeV/c)

  20. pT Spectra AntilambdaLambda K0s pT (GeV/c) full points: from gauss fit open coloured points: from bin counting open black points: signal from bin counting, bkg from fit

  21. ratio AntilambdaLambda K0s pT (GeV/c) all from bin counting / signal from bin counting, bkg from fit  Systematic uncertainty of peak extraction

  22. L/L ratio Spectra not corrected  just an idea of the statistics pT (GeV/c)

  23. L/K0s ratio Spectra not corrected  just an idea of the statistics pT (GeV/c)

  24. Summary & Outlook • Cut investigation • Peak extraction  improve for L’s  study background sources(shift in peak position: material dependent?) • Use new production • “offline” vs “on-the-fly” • Efficiency correction / systematic uncertainties (can be partly done already with MC) • Use different generators • Analysis of first data at 900 GeV

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