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Misura della produzione di heavy flavour nel barrel di ALICE

Misura della produzione di heavy flavour nel barrel di ALICE. Andrea Dainese INFN – LNL per la Collaborazione ALICE. Layout. Motivation for heavy-flavour measurements in pp at LHC & theoretical predictions for c and b production Why ALICE is well-suited for these measurements

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Misura della produzione di heavy flavour nel barrel di ALICE

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  1. Misura della produzione di heavy flavour nel barrel di ALICE Andrea Dainese INFN – LNL per la Collaborazione ALICE MCWS, Frascati, 24.10.2006 Andrea Dainese

  2. Layout • Motivation for heavy-flavour measurements in pp at LHC & theoretical predictions for c and b production • Why ALICE is well-suited for these measurements • Strategies and expected performance for: • D0 K-p+ • B  e + X • Summary MCWS, Frascati, 24.10.2006 Andrea Dainese

  3. c and b production at the LHC:testing pQCD at s = 14 TeV • Important test of pQCD in a new energy domain (7sTEVATRON) • remember the “15-years saga of b production at the Tevatron”*… • …and D production not yet fully reconciled  Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033 CDF, PRL91 (2003) 241804 FONLL: Cacciari, Nason * M.Mangano MCWS, Frascati, 24.10.2006 Andrea Dainese

  4. pQCD predictions for the LHC Compare predictions by several different models (HERA-LHC Worksohp) CERN/LHCC 2005-014 hep-ph/0601164 charm beauty Good agreement between collinear fact.-based calculations: FO NLO (Mangano, Nason, Risolfi) and FONLL (Cacciari, Nason) kt fact. CASCADE (Jung) higher at large pt MCWS, Frascati, 24.10.2006 Andrea Dainese

  5. Theoretical Uncertainties Evaluation of theoretical uncertainties (HERA-LHC Workshop) CERN/LHCC 2005-014 hep-ph/0601164 charm beauty MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. MCWS, Frascati, 24.10.2006 Andrea Dainese

  6. ALICE baseline yields • Cross sections: NLO (MNR code) • mc=1.2 GeV, mF=mR=2mc; mb=4.75 GeV, mF=mR=mb • Yields: assuming sppinel = 70 mb at 14 TeV MCWS, Frascati, 24.10.2006 Andrea Dainese

  7. increasing s charm beauty Cartoon c and b production at the LHC:a probe of small-x gluons • Probe unexplored small-x region with HQs at low pt and/or forward y • down to x~10-4 with charm already at y=0 • Window on the rich phenomenology of high-density PDFs • gluon saturation / recombination effects • breakdown of factorization ? • Charm at low pt predicted to be sensitive: • DGLAP (coll. fact.) + GLRMQ (nonlinear terms): enhancement • BK approach (kt fact): suppression Eskola, Kolhinen, Vogt, PLB582 (2004) 157 Gotsmann, Levin, Maor, Naftali, hep-ph/0504040 MCWS, Frascati, 24.10.2006 Andrea Dainese

  8. The ALICE Detector • M.Monteno • D.Stocco |h| < 0.9, B = 0.5 T TPC + silicon tracker g,e, p, K, p identification -4 < h < -2.5 muons MCWS, Frascati, 24.10.2006 Andrea Dainese

  9. ALICE heavy-flavour potential HERA-LHC Workshop CERN/LHCC 2005-014 hep-ph/0601164 • ALICE combines electronic (|h|<0.9), muonic (-4<h<-2.5), hadronic (|h|<0.9) channels • ALICE covers low-pt region • ALICE covers central and forward regions • Precise vertexing in the central region to identify D (ct ~ 100-300 mm) and B (ct ~ 500 mm) decays A.Dainese (ALICE) M.Smizanska (ATLAS) C.Weiser (CMS) U.Uwer (LHCb) MCWS, Frascati, 24.10.2006 Andrea Dainese

  10. Heavy-flavour analyses • Hadronic decays: • D0K-p+, D*+D0p+, D+K-p+p+, Ds+K+K0*/fp+… • Leptonic decays: • B e/m + X • Invariant mass analysis of lepton pairs: BB, DD, BDsame, J/y, y’,  family, B J/Y + X • BB m m m (J/ym) • e-m correlations In red, channels studied in the PPR Volume 2 CERN/LHCC 2005-030 MCWS, Frascati, 24.10.2006 Andrea Dainese

  11. rf: 50 mm rec. track e z: 425 mm Primary Vertex PIXEL CELL B < 60 mm (rf) for pt > 1 GeV/c d0 X Two layers: r = 4 cm r = 7 cm INFN Padova/Legnaro Vertexing: track d0 resolution Resolution mainly provided by the 2 layers of silicon pixels  9.8 M MCWS, Frascati, 24.10.2006 Andrea Dainese

  12. Effect of primary vertex uncertainty • Vertex position reconstructed event-by-event using tracks • More precise vertex pos. in (x,y) from mean over many events • Beam spread at ALICE I.P. may be as large as 50-100 mm (ALICE LMAX ~ 1030 cm-2 s-1) effect on d0 resolution vertex resolution MCWS, Frascati, 24.10.2006 Andrea Dainese

  13. Hadron ID: Time-of-flight TOF Pb-Pb, dNch/dy=6000 Optimization for hadronic charm decays was studied: minimize probability to tag K as p K id. required for D0pt < 2 GeV/c MCWS, Frascati, 24.10.2006 Andrea Dainese

  14. fraction of misidentified pions Electron ID • Combined info from TRD (trans. rad.) and TPC (dE/dx) • TRD rejects 99% of the p and ALL heavier hadrons (pt > 1 GeV/c) • TPC further rejects residual pions (up to 99% at low p) • About 20% of electrons rejected MCWS, Frascati, 24.10.2006 Andrea Dainese

  15. increase S/B by factor ~103! D0 K-p+ reconstruction • Main selection: displaced-vertex selection • pair of opposite-charge tracks with large impact parameters • good pointing of reconstructed D0 momentum to the primary vertex MCWS, Frascati, 24.10.2006 Andrea Dainese

  16. Invariant mass analysis • Example (extrapolated to expectation for 109 pp events): 0.5-1 GeV/c 3-4 GeV/c 12-14 GeV/c MCWS, Frascati, 24.10.2006 Andrea Dainese

  17. inner bars: stat. errors outer bars: stat.  pt-dep. syst. not shown: 9% (Pb-Pb), 5% (pp, p-Pb) normalization errors D0 K-p+: Results 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) + 1 year with 1month of p-Pb running (108 p-Pb events) Down to pt ~ 0 in pp and p-Pb (1 GeV/c in Pb-Pb) MCWS, Frascati, 24.10.2006 Andrea Dainese

  18. rec. track e Primary Vertex B d0 X B  e + X: Detection strategy • Electron PID: reject most of the hadrons • d0 cut: reduce charm and bkg electrons (Dalitz, g conv.) • Subtract (small) residual background (ALICE data + MC) MCWS, Frascati, 24.10.2006 Andrea Dainese

  19. Effect of electron identification residual charm contribution subtracted using D0 measurement  3-5% syst. error MCWS, Frascati, 24.10.2006 Andrea Dainese

  20. inner bars: stat. errors outer bars: stat.  pt-dep. syst. errors not shown: 5% normalization error Using electrons in 2 < pt < 20 GeV/c obtain B meson 2 < ptmin < 30 GeV/c MC-based procedure à la UA1 B  e + X: Results 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) MCWS, Frascati, 24.10.2006 Andrea Dainese

  21. Comparison to pQCD predictions pp, s = 14 TeV charm (D0  Kp) beauty (B  e+X) 1 year at nominal luminosity (109 pp events) MCWS, Frascati, 24.10.2006 Andrea Dainese

  22. 1 year at nominal luminosity ~1 month Perspectives for the “1st month at 14 TeV” • Expected statistical errors for a low-stats sample: • Scaling of statistical errors according to Nevts • No dedicated cuts study yet D0 Kp B  e + X Detector configuration: ITS + TPC + TOF Detector configuration: ITS + TPC + TRD MCWS, Frascati, 24.10.2006 Andrea Dainese

  23. Summary • Charm and beauty production study at the LHC: • test of QCD in a new energy domain • at low pt: access to low-x gluon dynamics; saturation? • ALICE is well-equiped for heavy-flavour studies • using several different channels / strategies • acceptance down low pt at central and forward rapidity • small extrapolation for total cross section • With 109 events (nominal year): • ~5% statistical error on total cross sections (c and b) • statistical error < 20% up ~ 20-25 GeV/c MCWS, Frascati, 24.10.2006 Andrea Dainese

  24. EXTRA SLIDES MCWS, Frascati, 24.10.2006 Andrea Dainese

  25. LHC running conditions pp nominal run Pb-PB nominal run Ldt dt = 3.1030 cm-2 s-1 x 107 s 5.1037 cm-2 for pp run, 14 TeV Npp collisions = 2 .1012 collisions Ldt = 5.1026 cm-2 s-1 x 106 s 5.1032 cm-2 PbPb run, 5.5 TeV NPbPb collisions = 2 .109 collisions   Muon triggers: ~ 100% efficiency, < 1kHz Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: ~ 50% efficiency of TRD L1 20 physics events per event Electron triggers: Bandwidth limitation NPbPb central = 2 .108 collisions Hadron triggers: Npp minb = 2 .109 collisions Hadron triggers: NPbPb central = 2 .107 collisions   MCWS, Frascati, 24.10.2006 Andrea Dainese

  26. bb bb dy ~ 1  both muons in the acceptance Beauty via single and di- muons in central Pb-Pb collisions • Muons “identified” in the forward spectrometer (-4<  <-2.5) • 15 interaction lengths, but.. • muon pt threshold as low as 1-1.5 GeV/c  single muons in the spectrometer: beauty dominates for pt > 2-3 GeV/c MCWS, Frascati, 24.10.2006 Andrea Dainese

  27. Di-muons invariant mass • Single muon cut: pt > 2 GeV/c • Di-muon combinatorial bkgd subtracted with evt-mixing MCWS, Frascati, 24.10.2006 Andrea Dainese

  28. Open Beauty with Muons: Results • Combined fit of low-mass, high-mass dimuons and single muons with shapes from MC to extract muons from B • Use MC to exctract down to ~1 GeV/c! systematic error analysis in progress 1 year at nominal luminosity (107 central Pb-Pb events) MCWS, Frascati, 24.10.2006 Andrea Dainese

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