QM09, Knoxville, April 3, 2009 Andrea Dainese Preparation for heavy-flavour measurements with ALICE at the LHC Andrea Dainese INFN – Legnaro for the ALICE Collaboration

QM09, Knoxville, April 3, 2009 Andrea Dainese Contents  Charm and beauty at the LHC: pp and Pb-Pb  Physics motivation for open flavour measurements  ALICE heavy-flavour program  Measurements in preparation  Getting the detector ready for heavy flavours  Examples of expected performance ALICE heavy flavour at QM: Quarkonia, talk by M.Malek D +,D s, poster by R.Bala, S.Senyukov D *+, poster by Y.Wang, C.Ivan ccbar xsection, poster by A.Mischke B  e, poster by H.Yang, R.Bailhache B  J/   ee, poster by C.Di Giglio  c  J/ , poster by A.Marin et al. J/   ee, poster by W.J.Park et al. ALICE heavy flavour at QM: Quarkonia, talk by M.Malek D +,D s, poster by R.Bala, S.Senyukov D *+, poster by Y.Wang, C.Ivan ccbar xsection, poster by A.Mischke B  e, poster by H.Yang, R.Bailhache B  J/   ee, poster by C.Di Giglio  c  J/ , poster by A.Marin et al. J/   ee, poster by W.J.Park et al.

QM09, Knoxville, April 3, 2009 Andrea Dainese LHC: heavy quarks factory!  NLO predictions (ALICE baseline for charm & beauty) system,  s pp, 14 TeVPb-Pb (0-5%), 5.5 TeV 11.2 / / / / 4.6 MNR code (FO NLO): Mangano, Nason, Ridolfi, NPB373 (1992) 295. With EKS98 shadowing. beauty charm factor ~2 uncertainty

QM09, Knoxville, April 3, 2009 Andrea Dainese LHC: heavy quarks factory!  NLO predictions (ALICE baseline for charm & beauty) system,  s pp, 14 TeVPb-Pb (0-5%), 5.5 TeV 11.2 / / / / 4.6 MNR code (FO NLO): Mangano, Nason, Ridolfi, NPB373 (1992) 295. With EKS98 shadowing. factor ~2 uncertainty LHC startup at  s = 10 TeV (after few days at 0.9 TeV?)  yields lower by  25%

QM09, Knoxville, April 3, 2009 Andrea Dainese c and b in pp at the LHC: testing pQCD at  s = TeV  Important test of pQCD in a new energy domain (5- 7  s TEVATRON )  Tevatron: 15 years to get to a good understanding of b production …  …and c production on the upper edge of prediction   RHIC (pp, 200 GeV): HF electrons underpredicted? o PHENIX/STAR discrepancy CDF, PRL91 (2003) FONLL: Cacciari, Nason FONLL, Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033

QM09, Knoxville, April 3, 2009 Andrea Dainese Heavy quarks as medium probes: Energy Loss Parton Energy Loss by  medium-induced gluon radiation  collisions with medium gluons pred: q: colour triplet QCD medium u,d,s: m~0, C R =4/3 (difficult to tag at LHC) g: m=0, C R =3 > E loss, dominant at LHC c: m~1.5 GeV, C R =4/3 small m, tagged by D’s b: m~5 GeV, C R =4/3 large mass  dead cone  < E loss Q: colour triplet g: colour octet Dokshitzer and Kharzeev, PLB 519 (2001) 199. Armesto, Salgado, Wiedemann, PRD 69 (2004) Djordjevic, Gyulassy, Horowitz, Wicks, NPA 783 (2007) 493 A puzzle at RHIC

QM09, Knoxville, April 3, 2009 Andrea Dainese HQ Energy loss at LHC Armesto, Cacciari, Dainese, Salgado, Wiedemann, “Last Call for LHC Predictions” workshop massive heavy-to-light ratio Wicks, Gyulassy, “Last Call for LHC Predictions” workshop New at LHC  Factor 5 suppression for D mesons  Significantly smaller suppression for B  Enhanched “Heavy-to-light” double ratio

QM09, Knoxville, April 3, 2009 Andrea Dainese Medium-blind, Control Real photon: colourless Virtual photon/W: colourless QCD medium Parton Energy Loss by  medium-induced gluon radiation  collisions with medium gluons pred: u,d,s: m~0, C R =4/3 (difficult to tag at LHC) g: m=0, C R =3 > E loss, dominant at LHC c: m~1.5 GeV, C R =4/3 small m, tagged by D’s b: m~5 GeV, C R =4/3 large mass, < E loss Q: colour triplet g: colour octet q: colour triplet Heavy quarks as medium probes: Energy Loss

QM09, Knoxville, April 3, 2009 Andrea Dainese Beauty energy loss: use W-decay muons as a reference First observation of b energy loss at LHC? single  R CP (p t ) beauty W Conesa del Valle, Dainese, et al, PLB663 (2008) 202 New at LHC

beauty W QM09, Knoxville, April 3, 2009 Andrea Dainese Beauty energy loss: use W-decay muons as a reference First observation of b energy loss at LHC? single  R CP (p t ) medium-sensitive and medium-blind probe in same measurement Conesa del Valle, Dainese, et al, PLB663 (2008) 202 New at LHC

Heavy quarks as medium probes: azimuthal asymmetry  Elliptic flow (v 2 ) vs p t for heavy quarks probes:  <5 Ge V/c: degree of thermalization of heavy c and b in the medium  >5 GeV/c: path length dependence of E loss QM09, Knoxville, April 3, 2009 Andrea Dainese QCD medium pressure gradient Q Q

QM09, Knoxville, April 3, 2009 Andrea Dainese Measurements in preparation

QM09, Knoxville, April 3, 2009 Andrea Dainese TPC (tracking) TOF (K/  id) ITS (tracking & vertexing) K  D 0  K  D +  K  D s  KK  D*  D 0  D 0  K   c   Kp under study Measurements in preparation

QM09, Knoxville, April 3, 2009 Andrea Dainese D 0  K  D +  K  D s  KK  D*  D 0  D 0  K   c   Kp under study B  e+X B   5 pr. B  J/  ee tagged b-jets under study ITS (tracking & vertexing) TPC (tracking e/  id) TRD (e/  id) e Measurements in preparation

QM09, Knoxville, April 3, 2009 Andrea Dainese MUON (tracking,id)  B   +X D   +X D 0  K  D +  K  D s  KK  D*  D 0  D 0  K   c   Kp under study B  e+X B   5 pr. B  J/  ee tagged b-jets under study under study Measurements in preparation

QM09, Knoxville, April 3, 2009 Andrea Dainese Primary Vertex B e X d0d0 rec. track Vertexing: track d 0 resolution 16 Beam pipe Outer layer Inner layer Resolution mainly provided by the 2 layers of silicon pixels M cells 50 (r  ) x 425 (z)  m 2 -- at 4 and 7 cm from the beam line  F.Prino, talk

QM09, Knoxville, April 3, 2009 Andrea Dainese Primary Vertex B e X d0d0 rec. track Vertexing: track d 0 resolution < 60  m (r  ) for p T > 1 GeV/c Beam pipe Outer layer Inner layer Resolution mainly provided by the 2 layers of silicon pixels M cells 50 (r  ) x 425 (z)  m 2 -- at 4 and 7 cm from the beam line  F.Prino, talk

Cosmic in Muon Spectrometer QM09, Knoxville, April 3, 2009 Andrea Dainese ALICE commissioning with cosmics and first beams Inner Tracking System Time Projection Chamber LHC stray particles in Inner Tracking System  alignment and calibration

QM09, Knoxville, April 3, 2009 Andrea Dainese Preparing ALICE for HF measurements: alignment of the Inner Tracking System  Alignment is crucial to reach the design resolution  ~13,000 parameters with a precision of ~10  m  Track-based alignment using cosmics and collisions (Millepede) realigned (Millepede) 2008 cosmic data, B=0  ~ 30  m track-to-track transverse distance at y=0 [cm] /√2 ~ 21  m promising! already close to target ideal geometry target of alignment ALICE Preliminary  F.Prino, talk  A.Rossi, poster

 Main selection: displaced-vertex topology  Example: D 0  K -  +  good pointing of reconstructed D momentum to the primary vertex  pair of opposite-charge tracks with large impact parameters QM09, Knoxville, April 3, 2009 Andrea Dainese Charm reconstruction: strategy and results in one slide pp, Pb-Pb: 1 year at nominal luminosity (10 9 pp events, 10 7 central Pb-Pb events) p-Pb: 1 month (10 8 events)

QM09, Knoxville, April 3, 2009 Andrea Dainese Charm candidates “production” (vertexing) Raw signal extraction Corrections (efficiencies, acceptance, feed-down from B) Charm reconstruction: analysis scheme, or “how to get there”

 Secondary vertex reconstruction  Candidates for D 0  K , D *+  D 0 , D + /D s /  c  3prong, D 0  K  in one go, written to the Analysis Object Data (AOD)  Runs on the ALICE Grid: >50 centres, ~10k simulataneous jobs  already tested on simulated data QM09, Knoxville, April 3, 2009 Andrea Dainese Charm candidates “production” (vertexing) Raw signal extraction Corrections (efficiencies, acceptance, feed-down from B) Charm reconstruction: analysis scheme, or “how to get there”

 Selection cuts to separate signal and background  Example on D +  K  : correlation of pointing angle and vertex displacement QM09, Knoxville, April 3, 2009 Andrea Dainese Charm candidates “production” (vertexing) Raw signal extraction Corrections (efficiencies, acceptance, feed-down from B) Charm reconstruction: analysis scheme, or “how to get there”  R.Bala et al., poster

 Selection cuts to separate signal and background  semi-automatic significance maximization  Invariant mass analysis to extract the raw signal yield  subtract combinatorial background, if needed (probably not in pp) o like-sign candidates o event mixing o sub-event rotating  invariant mass fit QM09, Knoxville, April 3, 2009 Andrea Dainese Charm candidates “production” (vertexing) Raw signal extraction Corrections (efficiencies, acceptance, feed-down from B) Charm reconstruction: analysis scheme, or “how to get there” “one day” pp 14 TeV, D 0  K 

 Feed-down from B  D >15% at LHC  need to correct  direct measurement of prompt charm fraction, based on D displacement from primary vertex (à la CDF)  Corrections for efficiency/acceptance  estimate systematic errors due to detector response, residual misalignment,... QM09, Knoxville, April 3, 2009 Andrea Dainese Charm candidates “production” (vertexing) Raw signal extraction Corrections (efficiencies, acceptance, feed-down from B) Charm reconstruction: analysis scheme, or “how to get there” dN/dp T D0KD0K input MC reco, corrected

QM09, Knoxville, April 3, 2009 Andrea Dainese Beauty in the barrel: B  e + X 1)Electron PID (TPC+TRD): 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  H.Yang, R.Bailhache, poster

QM09, Knoxville, April 3, 2009 Andrea Dainese Beauty in the barrel: B  e + X 1)Electron PID (TPC+TRD): 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

QM09, Knoxville, April 3, 2009 Andrea Dainese Beauty in the barrel: B  e + X 1)Electron PID (TPC+TRD): 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

QM09, Knoxville, April 3, 2009 Andrea Dainese Beauty in the barrel: B  e + X 1)Electron PID (TPC+TRD): 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 electron 1 year at nominal luminosity (3  cm -2 s -1 pp, 5  cm -2 s -1 Pb-Pb) (10 9 pp events, 10 7 central Pb-Pb events)

QM09, Knoxville, April 3, 2009 Andrea Dainese pp,  s = 14 TeV Comparison to pQCD predictions charm (D 0  K  )beauty (B  e+X) 1 year at nominal luminosity (3  cm -2 s -1 ) (10 9 pp events)

QM09, Knoxville, April 3, 2009 Andrea Dainese c and b Energy Loss in Pb-Pb: R AA & “heavy-to-light” ratio m b = 4.8 GeV D 0  K  B  e 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events) probes mass dep. of QCD energy loss E loss calc.: Armesto, Dainese, Salgado, Wiedemann

v 2 of c and b QM09, Knoxville, April 3, 2009 Andrea Dainese  Expected uncertainties on D + (  K  ) and electrons from B  Best sensitivity at intermediate p t : 3 – 7 GeV/c  charm and beauty thermalization in the medium (recombination models 2  10 7 min.bias Pb-Pb events D+ v 2 calc. from Ko et al. b ele v 2 from van Hees et al. + Armesto et al. D +  K  B  e

More beauty in the barrel: displaced J/  ee & b-tagged jets Displaced di-electrons (TPC,TRD) from J/  from B decays tagged by and impact parameter cut (ITS). Standard method for B cross section measurement at Tevatron First approach to b-tagging: Reconstructed jets (TPC, EMCAL) with ≥3 tracks displaced from the primary vertex (ITS) QM09, Knoxville, April 3, 2009 Andrea Dainese total background all J/  J/  from B Pseudoproper decay time (p t >0) under study Single-track impact parameter significance d 0 /  d0  C.Di Giglio, poster

QM09, Knoxville, April 3, 2009 Andrea Dainese ALICE’s forward muons  Muons “identified” in the spectrometer (-4 <  < -2.5) W  (medium-blind reference) dominates for p t > 25 GeV/c ALICE muon spectrometer acc.: -4 1 GeV, p > 4 GeV b dominates for 3 < p t < 25 GeV/c Pb-Pb 0-5% 5.5 TeV: single muon statistics for 1 month at nominal lumi (4 x 10 8 events) c dominates for 1 < p t < 3 GeV/c

QM09, Knoxville, April 3, 2009 Andrea Dainese Beauty via muons in pp and Pb-Pb  MC-based deconvolution procedure d   /dp t  d  B /dp t min  Large p t reach: ~80% of the total beauty cross-section is reconstructed  (Very) small statistical error, systematics ~10-15%  Works in pp & AA collisions (  R AA ) inner bars: stat. errors outer bars: syst. errors Pb-Pb: 1 month at nominal luminosity (4 x 10 8 central Pb-Pb events) pp: 1 month at reduced luminosity (10 30 cm -2 s -1, 7 x pp events) bars: stat. errors boxes: syst. errors Pb-Pb (0-5%)pp single-   single-  

QM09, Knoxville, April 3, 2009 Andrea Dainese Muons from charm at forward rapidity: without dca cut  Unfold single muon p t and dimuon invariant mass spectra  No dca cuts  use large statistics to constrain the fits 1 month at reduced luminosity (10 30 cm -2 s -1, 7 x pp events) pp, single muon p t pp, di-muon invariant mass pp GeV/c  x ~ 10 -5

QM09, Knoxville, April 3, 2009 Andrea Dainese Muons from charm at forward rapidity: with dca cut Decay probability for primary muons  1-exp(-D/c  ); D=distance of IP from absorber, which varies with IP position. Secondaries can be reduced through cut on DCA under study

QM09, Knoxville, April 3, 2009 Andrea Dainese Summary  LHC: heavy quarks factory  Heavy quarks as probes of QCD in extreme conditions  test pQCD in a new energy domain o breakdown of factorisation at small-x (high energy, low p t ) ?  test our understanding of parton-medium interaction o is the mass dependence of E loss understood ? o do heavy quarks thermalize in the medium  ALICE in excellent position:  dedicated detectors (ITS, TPC, TRD, EMCAL, MUON) o commissioning with cosmics steadily progressing  all analysis tools being sharpened

QM09, Knoxville, April 3, 2009 Andrea Dainese EXTRA SLIDES

QM09, Knoxville, April 3, 2009 Andrea Dainese 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 

QM09, Knoxville, April 3, 2009 Andrea Dainese The ALICE Detector |  | < 0.9, B = 0.5 T TPC + silicon tracker (ITS) ,  e, , K, p identification -4 <  < -2.5 muons ALICE Collaboration: >1000 people, 31 countries, 109 Institutes

QM09, Knoxville, April 3, 2009 Andrea Dainese  Probe unexplored small-x region with HQs at low p t and/or forward y  Charm measurements at low-p t  Window on high-density PDFs phenomenology: gluon saturation / shadowing effects / CGC The charm of small-x gluons Cartoon charm beauty D mesons p t  0, y=0c R pA with shadowing x~10 -4 pPb/pp  s=8.8 TeV  s=14 TeV

 Main criterion: displaced-vertex selection  pair of opposite-charge tracks with large impact parameters  good pointing of reconstructed D momentum to the primary vertex  large distance (d PS ) between primary and secondary vertex  good pointing of reconstructed D momentum to the primary vertex QM09, Knoxville, April 3, 2009 Andrea Dainese Charm reconstruction: D 0  K -  + & D +  K -  +  + D0D0 D+D+ 1 year at nominal luminosity (10 9 pp events, 10 7 central Pb-Pb events) D+D+ D0D0

QM09, Knoxville, April 3, 2009 Andrea Dainese c and b Energy Loss in Pb-Pb: R AA & “heavy-to-light” ratio m b = 4.8 GeV D 0  K  B  e 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events) E loss calc.: Armesto, Dainese, Salgado, Wiedemann