Heavy-flavor production in pp and Pb-Pb collisions at LHC with ALICE Kai Schweda (for the ALICE Collaboration) Physikalisches Institut University of Heidelberg Hadron 2011, Munich 16 Jun 2011

Outline Introduction LHC and ALICE Heavy-quark production in pp Heavy-quark production in Pb-Pb: D-mesons, e and  Summary 16 Jun 2011 Hadron 2011, Munich

Heavy - flavor: a unique probe mc,b » QCD : new scale mc,b ≈ const., mu,d,s ≠ const. initial conditions: test pQCD, R, F probe gluon distribution early partonic stage: diffusion (), drag () flow, jets, correlations probe thermalization hadronization: chiral symmetry restoration confinement statistical coalescence J/ enhancement / suppression Q2 time X. Zhu, M. Bleicher, S.L. Huang, K.S., H. Stöcker, N. Xu, and P. Zhuang, PLB 647 (2007) 366. 16 Jun 2011 Hadron 2011, Munich

Where does all the charm go ? J/(charmonium) c.f. talk by F. Kramer, 17:30, Quarkonia 5. c D*+ Ds D0 D± Total charm cross section: open-charmed hadrons, e.g. D0, D+, D*+, c, … and c,b  e() + X Quarkonia, e.g. J/ carries 1% of total charm 16 Jun 2011 Hadron 2011, Munich

Heavy-quark detection plot: courtesy of A. Mischke. Open-charm reco. in ALICE D0  K D+  K D*  D0 Under study: Ds  KK D0  K c  pK c   c  K0S e.g., D0  K- +  , c = 123 m displaced decay vertex is signature of heavy-quark decay 16 Jun 2011 Hadron 2011, Munich

Large Hadron Collider LHC at CERN Alice collision system sNN (TeV) #Events analyzed (M) p+p 7 100 - 180 p+p 2.76 65 Pb + Pb 2.76 17

Central barrel (ITS, TPC, TRD, TOF) || < 0.9 Size: 16 x 26 meters Weight: 10,000 tons Detectors: 18 TRD ITS TPC Central barrel (ITS, TPC, TRD, TOF) || < 0.9 Muon spectrometer: -4.0 < y < -2.5 6

First Pb+Pb collisions in ALICE ! ALICE is designed for Highest multiplicities dN/d up to 6000 Excellent tracking & particle identification down to lowest momentum ~ 100 MeV/c

Particle Identification dE/dx: 5% resolution Time-of flight, resolution: 120 ps (Pb-Pb) 160 ps (p-p) TPC dE/dx: separate p from K up to 1.1 GeV Time of flight: separate K from up to ~ 1.5 GeV 16 Jun 2011 Hadron 2011, Munich

Silicon Pixel Alignment 6 silicon layers 2 most inner: pixel layers (at r = 3.9 and 7 cm) Alignment from cosmics and collisions current resolution: 14 m (design 11 m) No deterioration from pp to Pb-Pb multiplicities 16 Jun 2011 Hadron 2011, Munich 9

Open-charm spectra from pp @ 7 TeV FONLL: M. Cacciari et al., priv. commun.; GM-VFNS:: B. Kniehl, priv. commun. 1/4 of total statistics, from 2 up to 12 GeV/c; extend to <2 GeV/c and >20 GeV/c with present data on tape 16 Jun 2011 Hadron 2011, Munich

Open-charm cross section LHC: First collider measurements at TeV scale ATLAS & LHCb agree with ALICE upper band of theory describes experimental data 16 Jun 2011 Hadron 2011, Munich

Heavy-flavor electrons from pp Electron background: cocktail based on measured  spectra + mt scaling + pQCD prompt phot. Hadron contamination < 10% Extract electrons from semi-leptonics decays c,b  e + X FONLL predictions agree with data 16 Jun 2011 Hadron 2011, Munich

Disentangele beauty from charm b-quark has longer lifetime than c-quark Larger displacement from collision vertex Disentangle electrons from semi-leptonics decays c,b  e + X FONLL predictions agree with data 16 Jun 2011 Hadron 2011, Munich

Muons from heavy-flavor in pp Measured d/dp from 2-10 GeV/c, d/d in -4.0 <  < 2.5 FONLL predictions describe data well FONLL indicates dominance of beauty at pt > 6 GeV/c 16 Jun 2011 Hadron 2011, Munich

Fast parton probing the medium J.D. Bjorken, PRD 27 (1983) 140; Graphics: courtesy of T. Ullrich. Leading Hadron quark-gluon plasma quarks and gluons propagate in QCD medium interactions with the medium modify parton momentum characteristic of medium properties mass ordering predicted: E() > E(D) > E(B) Dokshitzer and Kharzeev, PLB 519 (2001) 199. 16 Jun 2011 Hadron 2011, Munich

Nuclear Modification Factor K. Aamodt et al. (ALICE coll.), Phys. Lett. B 696 (2011) 30. define RAA, expect unity in the absence of nuclear effects (for hard processes) <TAA> accounts for the number of binary nucleon-nucleon collisions at RHIC, suppression of factor ~5 at LHC, suppression of factor ~6 strong medium effects ! 16 Jun 2011 Hadron 2011, Munich

Invariant mass spectra in Pb-Pb at highest-multiplicities 16 Jun 2011 Hadron 2011, Munich

pp reference at 2.76 TeV most pp data taken at 7 TeV, Pb-Pb at 2.76 TeV Scaled pp data to 2.76 TeV using FONLL 2.76/7 factor, propagated full theoretical uncertainty Relative scaling uncertainty: 25% (@2 GeV/c) to 10% (@ 10 GeV/c) Checked against short pp 2.76 TeV run (3 days) 16 Jun 2011 Hadron 2011, Munich

QCD-medium modification In Pb-Pb collisions: Charmed hadrons are suppressed by factor ~5 when compared to simple scaling from pp 16 Jun 2011 Hadron 2011, Munich

Comparison to light-quark hadrons Charm suppression as strong (or a bit less ?) than  High-luminosity Pb-Pb run 2011 will give decisive answer 16 Jun 2011 Hadron 2011, Munich

QCD-medium modification Initial state: gluon distribution in p different from Pb, e.g. shadowing, gluon saturation, … ? Observed suppression not an initial state effect; need p-Pb ! 16 Jun 2011 Hadron 2011, Munich

QCD-medium modification Electron background: cocktail based on measured  spectra + mt scaling + pQCD prompt phot. Hadron contamination < 10% Extract electrons from semi-leptonics decays c,b  e + X 16 Jun 2011 Hadron 2011, Munich

QCD-medium modification Electrons from semi-leptonic decays of heavy-quarks suppressed by factor ~ 1.5 - 4 Also  at larger rapidity suppressed by a factor of 3 (FONLL: dominated by b-decays) 16 Jun 2011 Hadron 2011, Munich

Model calculations most predictions are for design energy (5.5 TeV) Radiative E, similar suppr. for D and  Rad. + coll. E, fair description Light-cone wave function approach, somewhat high for D, ok for  Need high-luminosity Pb-Pb data, end of 2011 ! 16 Jun 2011 Hadron 2011, Munich

Summary & Outlook pp @ 2.76 and 7 TeV, heavy-quark production addressed by means of D-mesons, e,  Pb-Pb @ 2.76, heavy quarks are suppressed up to a factor of 5 Not an initial state effect Nov-2011: high-luminosity Pb-Pb data run end 2012: (probably) p-Pb control measurement or early 2013  Characterize QGP by precise heavy-quark production measurements 16 Jun 2011 Hadron 2011, Munich

Charm production and decay 16 Jun 2011 Hadron 2011, Munich