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

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Presentation on theme: "Charm and beauty with ALICE at LHC Rosario Turrisi University and INFN, Padova, Italy for the ALICE Collaboration."— Presentation transcript:

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

2 Rosario Turrisi Beach 2004 Saturday, July 03, Contents Why heavy ions at LHC Why heavy ions at LHC The ALICE detector The ALICE detector The role of charm and beauty The role of charm and beauty Basic performances Basic performances Open flavors measurement sensitivity Open flavors measurement sensitivity Conclusions and Perspectives Conclusions and Perspectives

3 Rosario Turrisi Beach 2004 Saturday, July 03, Why heavy ions at LHC strong interaction LHC = 5.5 TeV hadronic matter plasma of quarks and gluons QGP high energy & large volume Exploration of the deconfined phase… T c ~ 170 MeV (μ B =0) c ~ 1 GeV/fm 3 Lattice QCD with massless flavors Baryon free environment (μ B =0) At SPS (CERN) and RHIC (BNL) already observed deconfinement signals. At LHC: more strictly μ B =0 higher energy density DEEP DECONFINEMENT!

4 Rosario Turrisi Beach 2004 Saturday, July 03, ALICE detectors Solenoid magnet B<0.5 T TPC (the largest ever…): 88 m 3, 510 cm length, 250 cm radius Ar (90%) + CO 2 (10%) 88 μs drift time main tracking device, dE/dx 2 * 1.8 units of pseudo-rapidity 6 Layers, 3 technologies Material budget < 1% of X 0 per layer! Silicon Pixels vertices resolution in xy (0.2 m 2, 9.8 Mchannels) Silicon Drift resolution in z (1.3 m 2, 133 kchannels) Double-sided Strip connection w/TPC (4.9 m 2, 2.6 Mchannels) PIXEL CELL z: 425 m r : 50 m Two layers: r = 4 – 7 cm 9.8 Mch Central tracking system: Inner Tracking System Time Projection Chamber

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

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

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

8 Rosario Turrisi Beach 2004 Saturday, July 03, pQCD predictions NLO pQCD (Mangano-Nason-Ridolfi), average of MRST e CTEQ5M PDFs, EKS98 in Pb-Pb for shadowing NLO pQCD (Mangano-Nason-Ridolfi), average of MRST e CTEQ5M PDFs, EKS98 in Pb-Pb for shadowing (shadowing = modification of PDFs, causes reduction of cross section) (shadowing = modification of PDFs, causes reduction of cross section) Taking into account F, R a factor 4 arises between min. and max. cross section… In acceptance: D 0 / D 0 B (s) + b pp PbPb1409 ~5 D 0 K ~0.85 B eX Mesons multiplicities in central collisions

9 Rosario Turrisi Beach 2004 Saturday, July 03, Performance studies Detector description with the state-of-the-(ALICE)-art code AliRoot Detector description with the state-of-the-(ALICE)-art code AliRoot Charm/beauty signal tuned to NLO pQCD p t spectrum Charm/beauty signal tuned to NLO pQCD p t spectrum (custom tuning of PYTHIA) (custom tuning of PYTHIA) Background from HIJING, 6000 charged particles per unit rapidity at midrapidity Background from HIJING, 6000 charged particles per unit rapidity at midrapidity Priorities: the exclusive decay of the D 0 K (golden channel): the exclusive decay of the D 0 K (golden channel): –test bench for secondary vertex detection, pid –very high background inclusive b eX decay inclusive b eX decay –secondary vertices –electron identification –easy measurement of cross section

10 Rosario Turrisi Beach 2004 Saturday, July 03, < < 62 Total charged multiplicity TPC + ITS projection of the full range (front view) dN CH /dy (y=0) Current baseline: 6000 Tested up to: 8000

11 Rosario Turrisi Beach 2004 Saturday, July 03, Tracking performance impact parameter resolution: p t =1.3 GeV p t =1.3 GeV < 50 μm < 150 μm z p t resolution: σ= 1(10) GeV 100 GeV 100 GeV EFFICIENCY pions kaons

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

13 Rosario Turrisi Beach 2004 Saturday, July 03, Selection cuts D 0 K D 0 K –decay topology –impact parameter of tracks (in bending plane, d 0 ~100 μm) –momenta –identification D 0 with |y|<1 ~ 0.5 D 0 with |y|<1 but also charged /K in PbPb collisions impact parameters product

14 Rosario Turrisi Beach 2004 Saturday, July 03, Performance: D 0 K Performance: D 0 K K, M INV integrated over p t K, M INV integrated over p t 10 7 PbPb events (one-month run) 10 7 PbPb events (one-month run) dN/dy(y=0) = 6000 (charged) dN/dy(y=0) = 6000 (charged)S/Binitial (M 3 ) S/evtfinal (M 1 ) S/Bfinal Significance S/ S+B (M 1 ) % (for 10 7 evts, ~1 month) measurement of p t distribution Significance

15 Rosario Turrisi Beach 2004 Saturday, July 03, Quark energy loss: basics Origin: parton energy loss due to gluon radiation Origin: parton energy loss due to gluon radiation –Average energy loss (BDMPS model): C R Casimir factor = 3 for gluons 4/3 for quarks q = medium transport coefficient q = medium transport coefficient gluon density and momenta path length L c g 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) [arXiv:hep-ph/ ]. Study to get the medium effect R AA measured at RHIC with pions: clear quenching effect h R AA =1 means AA is superposition of independent pp collisions Quark Matter Conference 04

16 Rosario Turrisi Beach 2004 Saturday, July 03, Energy loss with charm? Effect present in light mesons, what about other particles? Effect present in light mesons, what about other particles? –D meson originate from c quark = 4/3, whereas light flavors –D meson originate from c quark C r = 4/3, whereas light flavors originate mainly from gluons (C=3) originate mainly from gluons (C=3) –Dead cone effect * : due to destructive interference, –Dead cone effect * : due to destructive interference, gluons radiation is suppressed at angles < m Q /E Q nuclear shadowing effect bars= statistical error shadow= syst. err. (MC+centrality+theory extr.) q = 4 GeV 2 /fm at LHC requiring same hadron suppression as at RHIC (shadowing = modification of PDFs, causes reduction of cross section) * Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/ ].

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

18 Rosario Turrisi Beach 2004 Saturday, July 03, Task: Task: tag ~ 0.8 e /event from b decays among ~ 10 3 electrons tag ~ 0.8 e /event from b decays among ~ 10 3 electrons from other sources from other sources Main backgrounds: Main backgrounds: – –pions misidentified as electrons – –Dalitz decays – –charm semi-electronic decays – –photon conversions in the detector materials – –strange decays Strategy: Strategy: –high impact parameter: c ~ 500 μm for beauty –high momenta: beauty harder than lighter flavors –electron/pion separation critical b e+X: strategy

19 Rosario Turrisi Beach 2004 Saturday, July 03, P t and d 0 comparison beauty electrons charm electrons charged pions

20 Rosario Turrisi Beach 2004 Saturday, July 03, b e+X: purity and statistics background cure charm electrons p t thr. light mesons electrons d 0 thr. charged pions identification p T > 1 GeV p T > 2 GeV p T > 3 GeV p T >2 GeV, 180 d 0 400mm 90% purity 50,000 B's (including TRD efficiency)

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


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