Measurement of heavy-flavour production down to low pT with ALICE Andrea Dainese INFN – Legnaro for the ALICE Collaboration High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Layout Heavy-flavour production at LHC baseline predictions (pQCD) Heavy quarks as probes of the initial state importance of low pT measurements Why ALICE is well-suited for these measurements Strategies and expected performance for: D0  K-p+ B  e + X Summary High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

c and b production in pp at the LHC: testing QCD 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 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

pQCD predictions for the LHC Compare predictions by several different models (HERA-LHC Workshop) 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 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

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. High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

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 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

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 Cartoon charm beauty Window on the rich phenomenology of high-density PDFs gluon saturation / recombination effects breakdown of factorization ? increasing s High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

(A.D., K.Eskola, V.Kolhinen, K.Kutak, H.Jung, K.Peters, R.Vogt) Deviations from pQCD baseline due to small-x effects? maybe already in pp ... “Small-x effects in heavy-quark production in pp” in HERA-LHC workshop proceedings CERN/LHCC 2005-014 hep-ph/0601164 (A.D., K.Eskola, V.Kolhinen, K.Kutak, H.Jung, K.Peters, R.Vogt) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

GLR-MQ non-linear term in DGLAP eq. Eskola, Honkanen, Kolhinen, Qiu, Salgado, NPB660 (2003) 211 R non-linear (quadratic) correction has “–” sign Q2 evolution is slower Refit HERA F2 data, reduces F2 at low x and moderate Q2 xg(x,Q2) at low Q2 (<10 GeV2) and x (<10-3) is larger than in DGLAP High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Non-linear effects in BK equation × Kutak, Kwiecinski, Martin, Stasto Non-linear part has no impact in the kinematical region of HERA H.Jung et al., CASCADE MC with CCFM uPDFs and KKMS nonlinear term High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

GLR-MQ vs BK: gluons R = 5 GeV-1 = 1 fm R = 4 GeV-1 = 0.8 fm Caveat: LO! Linear (dashed) vs non-linear (solid) in BK with R = 4 GeV-1 Linear (blue) vs non-linear (red) in DGLAP Kutak, Kwiecinski, Martin, Stasto Eskola, Honkanen, Kolhinen, Qiu, Salgado, NPB660 (2003) 211 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Charm at s = 14 TeV: x,Q2 range (1) Simple estimate: c High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Charm at s = 14 TeV: x,Q2 range (2) PYTHIA simulation (LO): High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Charm at s = 14 TeV: x,Q2 range (3) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Non-linear effects on charm in pp pp @ 14 TeV R = 0.6 fm R = 0.3 fm |y| < 1 R = 1 fm Charm enhancement due to non-linear effects in GLR-MQ Charm suppression due to non-linear effects in BK Dainese, Bondila, Eskola, Kolhinen, Vogt, JPG30 (2004) 1787 H.Jung et al., CASCADE MC with CCFM uPDFs and KKMS nonlinear term High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Probing nuclear initial state with HQs Shadowing in pA (AA) CGC in pA (AA) Double parton scattering in pA High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Probing nuclear initial state with HQs Shadowing in pA (AA) CGC in pA (AA) Double parton scattering in pA Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Probing nuclear initial state with HQs Shadowing in pA (AA) CGC in pA (AA) Double parton scattering in pA Saturation scale Qs2(x) ~ xg(x)A/RA2 ~ xg(x)A1/3 At LHC for x~10-4, Qs~2-2.5 GeV > mc For mT,c~Qs, charm prod. CGC-dominated: suppression: scales with Npart in pA (not Ncoll) harder pT spectra, since typical kT~Qs~2 GeV, while in standard factorization kT~LQCD~0.2 GeV Kharzeev, Tuchin, NPA 735 (2004) 248 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Probing nuclear initial state with HQs Shadowing in pA (AA) CGC in pA (AA) Double parton scattering in pA probe “many-body” PDFs normal and anomalous: different A dep. signature: events with “tagged” DD (can use D0+e+ or e+e+) and ch. conj. NB: there is a “background” from normal bb events, but it can be estimated from measured single inclusive b cross section predicted rate: cccc/cc ~ 10% (Treleani et al.) Cattaruzza, Del Fabbro, Treleani, PRD 70 (2004) 034022 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

The ALICE Detector |h| < 0.9, B = 0.5 T TPC + silicon tracker g, e, p, K, p identification -4 < h < -2.5 muons High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

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) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

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/y m) e-m correlations talks by M.Gagliardi, D.Stocco central rapidity (this talk) In red, channels studied for the PPR Volume 2 CERN/LHCC 2005-030 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Vertexing: track d0 resolution Resolution mainly provided by the 2 layers of silicon pixels < 60 mm (rf) for pT > 1 GeV/c Primary Vertex B e X d0 rec. track PIXEL CELL z: 425 mm rf: 50 mm Two layers: r = 4 cm r = 7 cm  9.8 M High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

D0 K-p+: Invariant mass analysis Example (extrapolated to expectation for 109 pp events): 0.5-1 GeV/c 3-4 GeV/c 12-14 GeV/c High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

D0 K-p+: Results Down to pT ~ 0 in pp and p-Pb (1 GeV/c in Pb-Pb) inner bars: stat. errors outer bars: stat.  pt-dep. syst. not shown: 9% (Pb-Pb), 5% (pp, p-Pb) normalization errors 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) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

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) Primary Vertex B e X d0 rec. track High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

B  e + X: Results 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 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Comparison to pQCD predictions pp, s = 14 TeV charm (D0  Kp) beauty (B  e+X) 1 year at nominal luminosity (109 pp events) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

How to detect the enhancement due to nonlinear effects? The idea is that the effect (enh. only at very low pt) cannot be mimicked by NLO pQCD In practice: consider ratio “Data/Theory” for all reasonable choices of theory parameters Data: mc = 1.2 GeV, Q2 = 4mT2 and enhancement mc = 1.3 GeV, Q2 = mT2 Dainese, Bondila, Eskola, Kolhinen, Vogt, JPG30 (2004) 1787 High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Sensitivity to D0 RpA at |y|<1 p-Pb pp Example with shadowing R.Grosso, PhD thesis (2004) High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Summary Charm and beauty production study at the LHC: test of QCD in a new energy domain at low pT: access to small-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 sensitivity to small-x QCD Predictions are welcome! High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

EXTRA SLIDES High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

LHC running conditions Pb-PB nominal run pp nominal run Ldt = 5.1026 cm-2 s-1 x 106 s 5.1032 cm-2 PbPb run, 5.5 TeV NPbPb collisions = 2 .109 collisions 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   Muon triggers: ~ 100% efficiency, < 1kHz Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: Bandwidth limitation NPbPb central = 2 .108 collisions Electron triggers: ~ 50% efficiency of TRD L1 20 physics events per event Hadron triggers: Npp minb = 2 .109 collisions Hadron triggers: NPbPb central = 2 .107 collisions   High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Electron ID D and B mesons have 10% B.R. to electrons 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 fraction of misidentified pions High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese

Effect of electron identification residual charm contribution subtracted using D0 measurement  3-5% syst. error High Energy QCD Workshop, ECT* Trento, 13.01.2007 Andrea Dainese