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

MCWS, Frascati, 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: D 0  K    B  e  + X Summary

MCWS, Frascati, 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  s TEVATRON ) remember the “15-years saga of b production at the Tevatron” *… …and D production not yet fully reconciled  * M.Mangano CDF, PRL91 (2003) FONLL: Cacciari, Nason Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033

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

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

MCWS, Frascati, Andrea Dainese 6 ALICE baseline yields Cross sections: NLO (MNR code) m c =1.2 GeV,  F =  R =2m c ; m b =4.75 GeV,  F =  R =m b Yields: assuming  pp inel = 70 mb at 14 TeV

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

MCWS, Frascati, Andrea Dainese 8 The ALICE Detector |  | < 0.9, B = 0.5 T TPC + silicon tracker ,  e, , K, p identification -4 <  < -2.5 muons  M.Monteno  D.Stocco

MCWS, Frascati, Andrea Dainese 9 ALICE heavy-flavour potential ALICE combines electronic (|  |<0.9), muonic (-4<  <-2.5), hadronic (|  |<0.9) channels ALICE covers low-p t region ALICE covers central and forward regions Precise vertexing in the central region to identify D (c  ~  m) and B (c  ~ 500  m) decays HERA-LHC Workshop CERN/LHCC hep-ph/ A.Dainese (ALICE) M.Smizanska (ATLAS) C.Weiser (CMS) U.Uwer (LHCb)

MCWS, Frascati, Andrea Dainese 10 Heavy-flavour analyses Hadronic decays: D 0  K -  +, D *+  D 0  +, D +  K -  +  +, D s +  K + K 0* /  + … Leptonic decays: B  e/  + X Invariant mass analysis of lepton pairs: BB, DD, BD same, J/ ,  ’,  family, B  J/  + X BB  (J/   ) e-  correlations In red, channels studied in the PPR Volume 2 CERN/LHCC

MCWS, Frascati, Andrea Dainese 11 Primary Vertex B e X d0d0 rec. track Vertexing: track d 0 resolution < 60  m (r  ) for p t > 1 GeV/c Resolution mainly provided by the 2 layers of silicon pixels PIXEL CELL z: 425  m r  : 50  m Two layers: r = 4 cm r = 7 cm  9.8 M INFN Padova/Legnaro

MCWS, Frascati, 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  m (ALICE L MAX ~ cm -2 s -1 ) vertex resolution effect on d 0 resolution

MCWS, Frascati, Andrea Dainese 13 Hadron ID: Time-of-flight TOF Pb-Pb, dN ch /dy=6000 Optimization for hadronic charm decays was studied: minimize probability to tag K as  K id. required for D 0 p t < 2 GeV/c

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

MCWS, Frascati, Andrea Dainese 15 D 0  K -  + reconstruction Main selection: displaced-vertex selection pair of opposite-charge tracks with large impact parameters good pointing of reconstructed D 0 momentum to the primary vertex increase S/B by factor ~10 3 !

MCWS, Frascati, Andrea Dainese 16 Invariant mass analysis Example (extrapolated to expectation for 10 9 pp events): GeV/c 3-4 GeV/c GeV/c

MCWS, Frascati, Andrea Dainese 17 D 0  K -  + : Results inner bars: stat. errors outer bars: stat.  p t -dep. syst. not shown: 9% (Pb-Pb), 5% (pp, p-Pb) normalization errors Down to p t ~ 0 in pp and p-Pb (1 GeV/c in Pb-Pb) 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events) + 1 year with 1month of p-Pb running (10 8 p-Pb events)

MCWS, Frascati, Andrea Dainese 18 B  e + X: Detection strategy 1)Electron PID: reject most of the hadrons 2)d 0 cut: reduce charm and bkg electrons (Dalitz,  conv.) 3)Subtract (small) residual background (ALICE data + MC) Primary Vertex B e X d0d0 rec. track

MCWS, Frascati, Andrea Dainese 19 Effect of electron identification residual charm contribution subtracted using D 0 measurement  3-5% syst. error

MCWS, Frascati, Andrea Dainese 20 B  e + X: Results Using electrons in 2 < p t < 20 GeV/c obtain B meson 2 < p t min < 30 GeV/c MC-based procedure à la UA1 inner bars: stat. errors outer bars: stat.  p t -dep. syst. errors not shown: 5% normalization error 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events)

MCWS, Frascati, Andrea Dainese 21 pp,  s = 14 TeV Comparison to pQCD predictions charm (D 0  K  )beauty (B  e+X) 1 year at nominal luminosity (10 9 pp events)

MCWS, Frascati, Andrea Dainese 22 Perspectives for the “1 st month at 14 TeV” Detector configuration: ITS + TPC + TOF Expected statistical errors for a low-stats sample: Scaling of statistical errors according to  N evts No dedicated cuts study yet D 0  K  Detector configuration: ITS + TPC + TRD B  e + X ~1 month 1 year at nominal luminosity

MCWS, Frascati, Andrea Dainese 23 Summary Charm and beauty production study at the LHC: test of QCD in a new energy domain at low p t : access to low-x gluon dynamics; saturation? ALICE is well-equiped for heavy-flavour studies using several different channels / strategies acceptance down low p t at central and forward rapidity  small extrapolation for total cross section With 10 9 events (nominal year): ~5% statistical error on total cross sections (c and b) statistical error < 20% up ~ GeV/c

MCWS, Frascati, Andrea Dainese 24 EXTRA SLIDES

MCWS, Frascati, Andrea Dainese 25 LHC running conditions  Ldt = cm -2 s -1 x 10 6 s cm -2 PbPb run, 5.5 TeV N PbPb collisions = collisions  Ldt dt = cm -2 s -1 x 10 7 s cm -2 for pp run, 14 TeV N pp collisions = collisions Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: Bandwidth limitation N PbPb central = collisions  Muon triggers: ~ 100% efficiency, < 1kHz Pb-PB nominal run pp nominal run Electron triggers: ~ 50% efficiency of TRD L1 20 physics events per event Hadron triggers: N PbPb central = collisions Hadron triggers: N pp minb = collisions 

MCWS, Frascati, Andrea Dainese 26 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 p t threshold as low as GeV/c bb  single muons in the spectrometer: beauty dominates for p t > 2-3 GeV/c bb  y ~ 1  both muons in the acceptance

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

MCWS, Frascati, 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 (10 7 central Pb-Pb events)