Charm and beauty with ALICE at LHC Rosario Turrisi University and INFN, Padova, Italy for the ALICE Collaboration

Contents Why heavy ions at LHC The ALICE detector Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Why heavy ions at LHC The ALICE detector The role of charm and beauty Basic performances Open flavors measurement sensitivity Conclusions and Perspectives Lead not only as shielding…

Why heavy ions at LHC PbPb @ = 5.5 TeV LHC high energy large volume Rosario Turrisi Beach 2004 Saturday, July 03, 2004 LHC PbPb @ = 5.5 TeV high energy & large volume hadronic matter strong interaction plasma of quarks and gluons QGP At SPS (CERN) and RHIC (BNL) already observed deconfinement signals. At LHC: more strictly μB=0 higher energy density DEEP DECONFINEMENT! Tc ~ 170 MeV (μB=0) c ~ 1 GeV/fm3 Lattice QCD with massless flavors Baryon free environment (μB=0) Exploration of the deconfined phase…

ALICE detectors Solenoid magnet B<0.5 T Central tracking system: TPC (the largest ever…): 88 m3 , 510 cm length, 250 cm radius Ar (90%) + CO2 (10%) 88 μs drift time main tracking device, dE/dx Rosario Turrisi Beach 2004 Saturday, July 03, 2004 ALICE detectors 6 Layers, 3 technologies Material budget < 1% of X0 per layer! Silicon Pixels  vertices resolution in xy (0.2 m2, 9.8 Mchannels) Silicon Drift  resolution in z (1.3 m2, 133 kchannels) Double-sided Strip  connection w/TPC (4.9 m2, 2.6 Mchannels) PIXEL CELL z: 425 mm rf: 50 mm Two layers: r = 4 – 7 cm 9.8 Mch Central tracking system: Inner Tracking System Time Projection Chamber 2 * 1.8 units of pseudo-rapidity

ALICE detectors Central tracking system: Transition Radiation Detector 2 * 1.8 units of pseudo-rapidity Rosario Turrisi Beach 2004 Saturday, July 03, 2004 ALICE detectors 6 layers for: electron/pion separation at pt>1 GeV factor 100 rejection at 2 GeV tracking complement, mass resolution 100 MeV/c2 @  high pt trigger (onia studies) Central tracking system: Transition Radiation Detector Time Of Flight Multigap Resistive Plate Chambers 5 years R&D, and  < 100 ps pions, kaons, protons separation (see later) electrons/pions at low pt

{ ALICE detectors Cosmic rays trigger Forward detectors: Photon Mult. Det. Forward Mult. D., T0, V0, Zero Degrees Cal. Rosario Turrisi Beach 2004 Saturday, July 03, 2004 ALICE detectors Specialized detectors: High Momentum PID PHOton Spectrometer { MUON Spectrometer 2.4 <  < 4 +EMCal (under discussion)

Heavy flavors and heavy-ions Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Why measure heavy flavors at LHC ? quarkonium suppression: deconfinement signature B J/ important background open heavy flavors as natural normalization for QQ studies interest in its own right (discovery potential!) probes of the medium: early formation (initial parton-parton), most energetic phase energy loss (medium dependent?) not covered here PbPb @ =5.5 TeV pp reactions, pQCD, nuclear effects (geometry, shadowing) INPUT OUTPUT medium properties

Rosario Turrisi Beach 2004 Saturday, July 03, 2004 pQCD predictions NLO pQCD (Mangano-Nason-Ridolfi), average of MRST e CTEQ5M PDF’s, EKS98 in Pb-Pb for shadowing (shadowing = modification of PDF’s, causes reduction of cross section) Taking into account F,R a factor 4 arises between min. and max. cross section… in central collisions Mesons multiplicities D0/ D0 B(s)+ b pp 0.19 0.0143 PbPb 140 9 In acceptance: ~5 D0  K ~0.85 B  eX

Performance studies Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Detector description with the state-of-the-(ALICE)-art code AliRoot Charm/beauty signal tuned to NLO pQCD pt spectrum (custom tuning of PYTHIA) Background from HIJING, 6000 charged particles per unit rapidity at midrapidity Priorities: the exclusive decay of the D0  K (golden channel): test bench for secondary vertex detection, pid very high background inclusive b  eX decay secondary vertices electron identification “easy” measurement of cross section

Total charged multiplicity Rosario Turrisi Beach 2004 Saturday, July 03, 2004 dNCH/dy (y=0) Current baseline: 6000 Tested up to: 8000 TPC + ITS projection of the full  range (front view) 60 <  < 62 if one does extrapolate from RHIC multiplicity, multiplicity is even less (<3000)

Tracking performance < 50 μm   < 150 μm z pt resolution: Rosario Turrisi Beach 2004 Saturday, July 03, 2004 impact parameter resolution:  σ= @ pt=1.3 GeV pt resolution: σ= 1(2)% @ 1(10) GeV 9% @ 100 GeV < 50 μm   < 150 μm z EFFICIENCY pions kaons

PID: e,, K, p PbPb events dN/dy=6000 test beam: p id. as e = 1 % Rosario Turrisi Beach 2004 Saturday, July 03, 2004 PbPb events dN/dy=6000 test beam: p id. as e = 1 % Combined π/e ~ 10-4 @ pt~1-2 GeV electrons TPC TRD p (Gev/c) TOF hadrons

Selection cuts impact parameters product D0  K Rosario Turrisi Beach 2004 Saturday, July 03, 2004 D0  K decay topology impact parameter of tracks (in bending plane, d0~100 μm) momenta identification ~ 0.5 D0 with |y|<1 but also 12000 charged /K in PbPb collisions sottolineare correlazione d*d/costh impact parameters product

Performance: D0K K, MINV integrated over pt Rosario Turrisi Beach 2004 Saturday, July 03, 2004 S/B initial (M3s) S/evt final (M1s) Significance S/S+B 5  10-6 1.3  10-3 11 % 37 (for 107 evts, ~1 month) K, MINV integrated over pt 107 PbPb events (one-month run) dN/dy(y=0) = 6000 (charged) measurement of pt distribution Significance

Quark energy loss: basics Rosario Turrisi Beach 2004 Saturday, July 03, 2004 path length L c g Origin: parton energy loss due to gluon radiation Average energy loss (BDMPS model): CR Casimir factor = 3 for gluons 4/3 for quarks q = medium transport coefficient  gluon density and momenta Study to get the medium effect h spiegare meglio figura RAA =1 means AA is superposition of independent pp collisions RAA measured at RHIC with pions: clear quenching effect Quark Matter Conference ’04 R.Baier, Yu.L.Dokshitzer, A.H.Mueller, S.Peigne' and D.Schiff, Nucl. Phys. B483 (1997) 291. C.A.Salgado and U.A.Wiedemann, Phys. Rev. D68 (2003) 014008 [arXiv:hep-ph/0302184].

Energy loss with charm? Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Effect present in light mesons, what about other particles? D meson originate from c quark Cr = 4/3, whereas light flavors originate mainly from gluons (C=3) Dead cone effect*: due to destructive interference, gluons radiation is suppressed at angles  < mQ/EQ *Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/0106202]. bars= statistical error shadow= syst. err. (MC+centrality+theory extr.) q = 4 GeV2/fm at LHC requiring same hadron suppression as at RHIC nuclear shadowing effect (shadowing = modification of PDF’s, causes reduction of cross section)

Energy loss vs. dead cone Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Quantitative difference heavy/light mesons measurement? E gluons/quarks energy loss ~ 2 E gluons/quarks fragmentation ~ 1/2 D/h ratio: RD/h = RAAD / RAAh q = 4 GeV2/fm at LHC requiring same hadron suppression as at RHIC eliminare???? dead cone makes the difference! RD/h ~ 2 in hot QGP sensitive to medium density

b e+X: strategy Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Task: tag ~ 0.8 e /event from b decays among ~ 103 electrons from other sources Main backgrounds: pions misidentified as electrons Dalitz decays charm semi-electronic decays photon conversions in the detector materials strange decays Strategy: high impact parameter: c ~ 500 μm for beauty high momenta: beauty harder than lighter flavors electron/pion separation critical

Pt and d0 comparison beauty electrons charm electrons charged pions Rosario Turrisi Beach 2004 Saturday, July 03, 2004 beauty electrons charm electrons charged pions

b e+X: purity and statistics Rosario Turrisi Beach 2004 Saturday, July 03, 2004 pT> 1 GeV pT> 2 GeV pT> 3 GeV background cure charm electrons pt thr. light mesons electrons d0 thr. charged pions identification pT>2 GeV, 180  d0  400mm 90% purity 50,000 B's (including TRD efficiency)

Conclusions & perspectives Rosario Turrisi Beach 2004 Saturday, July 03, 2004 ALICE has a good potential to measure heavy flavors in different channels Charm: production cross section pt distribution study of charm energy loss Beauty: Production cross section Coming up b’s pt distribution additional D, D* channels semi-electronic b/c deconvolution exclusive b decays 11% S/B, significance=37 pT> 1 GeV pT> 2 GeV pT> 3 GeV