Heavy-flavour production in p-p and Pb-Pb collisions at ALICE André Mischke for the ALICE Collaboration Rencontres de Moriond - QCD and High Energy Interactions La Thuile, Italy – March 2011

Outline Moriond-QCD 20112Andre Mischke (ERC-UU) Motivation ALICE detector setup Trigger and data sample Production cross sections in 7 TeV p-p collisions - D mesons at mid-rapidity - single electrons at mid-rapidity - single muons at forward rapidity First open charm signals in Pb-Pb at √s NN = 2.76 TeV Summary

“Simplest way” to establish the properties of a system - calibrated probe - calibrated interaction - suppression pattern tells about density profile Heavy-ion collision - hard processes serve as calibrated probe (pQCD) - traversing through the medium and interact strongly - suppression provides density measurement - General picture: energy loss via medium induced gluon radiation and collisional energy loss p+p collision Pb-Pb collision Quark-Gluon Plasma after the collision Probing hot and dense QCD matter Quantify medium effects with nuclear modification factor Moriond-QCD 20113Andre Mischke (ERC-UU)

Wicks et al., Nucl. Phys. A784, 426 (2007) Energy loss of heavy quarks Bottom Charm Gluon radiation probability: parton hot and dense medium Higher penetrating power  probe deeper into the medium Dead-cone effect gluon radiation suppressed at small angles (  < m Q /E Q ) Y. Dokshitzer, D. Kharzeev, PLB 519, 199 (2001), hep-ph/ Less energy loss:  E g >  E LQ >  E HQ Moriond-QCD 20114Andre Mischke (ERC-UU)

PID from ~100 MeV/c to above 30 GeV/c Large acceptance in azimuth Mid-rapidity coverage (|  | < 0.9) and -4 <  < -2.5 in forward region Complete ITS, TPC, TOF, HMPID, FMD, T0, V0, ZDC, PMD, EMCAL (approved 2009), Muon arm, Acorde, DAQ, HLT (High Level Trigger) Partial installation 10/18 TRD (approved 2002) 3/5 PHOS (funding) A L arge I on C ollider E xperiment Short status: All systems fully operational L3 magnet B = 0.5 T Size: 16x26 meters Weight: tons Andre Mischke (ERC-UU) 5 Moriond-QCD 2011

SPD V0-C V0-A Trigger and data sample Minimum bias (MB) trigger: coincidences between - SPD or V0 A-side or V0 C-side - at least one charged particle in 8 η units - 95% efficient on  inel single-muon trigger - forward muon in coincidence with MB L ~ cm -2 s -1 rate ~ 100 Hz L int ~ 9 μb -1 YearCollision system Energy (TeV) # of MB events 2009p-p0.93.x p-p2.364.x p-p0.98.x p-p78x Pb- 208 Pb2.76x208~30x10 6 Andre Mischke (ERC-UU) 6 Moriond-QCD 2011 Pb-Pb

Capabilities to measure open charm down to p T =0 in p-p and p-Pb (1 GeV/c in Pb-Pb) High precision tracking, better than 75  m for p T > 1 GeV/c Heavy-flavour measurements Impact parameter resolution SSD SDD SPD Inner Tracking System (ITS) 6 layers of silicon detectors - aligned using cosmics and first p-p data - current resolution for pixels: 14 μm (nominal ≈11 μm) - X/X 0 = 7.18% for radial tracks Andre Mischke (ERC-UU) 7 Moriond-QCD 2011 Radius inner pixel layer: 3.9 cm ≈1 cm from the vacuum 87.2 cm

Reconstruction of D mesons Analysis based on decay topology and invariant mass technique Essential selection cuts - impact parameter - distance of closest approach - pointing angle High precision tracking (ITS+TPC) K and  identification (TPC+TOF)  reducing background at low p T D0  K-+D0  K-+ D 0  K -  + BR: 3.89% D 0  K - 2  +  - BR: 8.09% D* +  D 0 (  K  )  + s BR: 67.7% D +  K -  +  + BR: 9.22% D s +  K + K -  + BR: 5.5%  c +  pK -  + BR: 5.% Andre Mischke (ERC-UU) 8 Moriond-QCD 2011

Open charm signals in 7 TeV p-p Andre Mischke (ERC-UU) 9 Moriond-QCD 2011

D meson cross sections at |η| < 0.5 Moriond-QCD Andre Mischke (ERC-UU) Current p T range: 2-12 GeV/c with 20% of the 2010 statistics B feed-down calculated from theory (10-15%) data driven method will be used with full 2010 statistics Results agree with pQCD calculation (FONLL and GM-VFNS) Ongoing: extension to low and high p T 7 TeV p-p, 1.4 nb -1

Single electrons at mid-rapidity High quality tracks in TPC and ITS - hit in innermost pixel layer to reduce  conversions Electron identification using TPC and TOF - TOF to reject Kaons (<1.5 GeV/c) and protons (<3 GeV/c) - TPC: asymmetric cut around the electron Bethe-Bloch curve - measure contamination by fitting dE/dx with a double Gaussian distributions Andre Mischke (ERC-UU) 11 Moriond-QCD 2011

Inclusive electron spectrum Efficiency correction and corrections for electron Bremsstrahlung Cocktail based on neutral pion cross section measured in PHOS and from double conversion reconstruction in TPC Excess of inclusive/cocktail ratio at high-p T, arising from D and B decay electrons Andre Mischke (ERC-UU) 12 Moriond-QCD 2011

Single electron cross section Andre Mischke (ERC-UU) 13 Moriond-QCD 2011 Total systematic uncertainty is 16-20% p T dependent plus 7% on normalization Single electrons in agreement with expectations from D mesons Results agree with FONLL calculation within errors Extend p T range with EMCal and TRD

Remove hadrons and low-p T muons (secondary , K) by requiring muon tracking-trigger Remove decay muons (primary , K) by subtracting MC dN/dp T normalized to data at low p T (< 2 GeV/c) Remaining contribution are muons from charm and bottom Corrections on acceptance x efficiency (~80% for p T > 2 GeV/c) charm, bottom , K primaries , K secondaries punch-through Muon sources from Pythia Single muons at -4<  <-2.5: analysis strategy Moriond-QCD Andre Mischke (ERC-UU)

Good agreement with FONLL within (large) errors 20-25% systematic uncertainties Will be extended to 15 GeV/c with more statistics and improved spectrometer alignment Reference for single muon R AA Single muon cross section events Andre Mischke (ERC-UU) 15 Moriond-QCD 2011

Jump in collision energy by a factor of ~15 compared to RHIC Pb-Pb collision at 0.57 PeV Andre Mischke (ERC-UU) 16 Moriond-QCD 2011

D meson signals in 0.57 PeV Pb-Pb Andre Mischke (ERC-UU) 17 Moriond-QCD 2011 First open charm signals in heavy-ion collisions Next - R AA (energy rescaling for p-p reference,…) - elliptic flow (event plane definition,…)

m b = 4.8 GeV D 0  K  B  e+X MC simulations: 1 year at nominal luminosity 10 7 central Pb-Pb and 10 9 p-p events Andre Mischke (ERC-UU) Open charm in Pb-Pb: Perspectives 18 Initial energy density (from meas. dN ch /dy): at least 3x higher than at RHIC Relatively long-lived QGP phase; thermal equilibrium reached much faster(?) Most of the in-medium effects should be enhanced Bottom energy loss expected to be lower due to dead-cone effect Elliptic flow of charmed particles sensitive to thermalisation in the medium Moriond-QCD 2011 Curves: Armesto et al, 2005

Mass dependence (dead cone effect) Colour charge dependence R c AA /R b AA ratio different for pQCD and AdS/CFT Andre Mischke (ERC-UU) 19 Explore energy loss mechanisms in more detail Moriond-QCD 2011 MC simulations C R is 4/3 for quarks and 3 for gluons

Heavy quarks (charm and bottom) - particularly good probes to study the properties of hot quark matter (especially the transport properties) - abundantly produced at LHC energies Open charm in heavy-ion collisions - detailed understanding of energy loss mechanisms - flow: thermalisation and hydrodynamic expansion in QGP Charm production in 7 TeV p-p collisions - cross-section of single muons, electrons and D mesons measured up to p T = 6.5, 4 and 12 GeV/c, respectively - data described by pQCD predictions Many more to come Heavy quarks (charm and bottom) - particularly good probes to study the properties of hot quark matter (especially the transport properties) - abundantly produced at LHC energies Open charm in heavy-ion collisions - detailed understanding of energy loss mechanisms - flow: thermalisation and hydrodynamic expansion in QGP Charm production in 7 TeV p-p collisions - cross-section of single muons, electrons and D mesons measured up to p T = 6.5, 4 and 12 GeV/c, respectively - data described by pQCD predictions Many more to come Summary Andre Mischke (ERC-UU) 20 Moriond-QCD 2011

21Andre Mischke (ERC-UU) Thank you

Backup Moriond-QCD Andre Mischke (ERC-UU)

LHC: 7-14 TeV NLO pQCD, CTEQ6M parton densities R. Vogt, private communication, 2009 Andre Mischke (ERC-UU) 23 Charm production cross section in p-p – FONLL CDF, PRL, 91, (2003) Test pQCD (theoretically not fully understood?) Baseline for Quarkonia measurements in Pb-Pb Parton spectra from pQCD input for energy loss models  prompt charm production cross section from D spectra in p- p (advantage: low p T capabilities of ALICE) Moriond-QCD 2011 p 1.96 TeV 5.8 pb -1 ¯

Vertex detector p T (min) < 100 MeV/c PID using ITS Moriond-QCD Andre Mischke (ERC-UU)

Particle Identification TOF (150k channels)  ≈ 90 ps Specific ionisation energy loss; PID based on comparison with Bethe-Bloch curves PID based on comparison of time of flight with particle mass hypothesis TPC  dE/dx /dEdx ≈ 5-6%  p/p = 5% at 100 GeV/c Andre Mischke (ERC-UU) 25 Moriond-QCD 2011

D 0 signal in different p T bins Moriond-QCD Andre Mischke (ERC-UU)

D + signal in different p T bins Moriond-QCD Andre Mischke (ERC-UU)

D* ± signal in different p T bins Moriond-QCD Andre Mischke (ERC-UU)

Data – Monte-Carlo comparison Moriond-QCD Andre Mischke (ERC-UU) Detector response well described in Monte-Carlo

Efficiencies for D mesons Moriond-QCD Andre Mischke (ERC-UU) PID strategy developed to retain almost 100% of the signal for p T > 2 GeV/c 1-10% efficiency from low to high p T Factor 2 larger for D mesons from B decays

FONLL calculations used for B feed-down: contribution about 10-15% Final results will be corrected based on data with full 2010 statistics; displaced-D meson analysis Feed-down from B decays Moriond-QCD Andre Mischke (ERC-UU)

Systematic uncertainties Moriond-QCD Andre Mischke (ERC-UU) Total systematic is 20-40% p T dependent + 10% on normalization (Van der Meer-scans) Main systematic error: B feed- down from FONLL+MC to be reduced using data-driven method with full 2010 statistics

Comparison with world data D 0 /D + and D 0 /D* ratios in line with previous measurements at lower energies Moriond-QCD Andre Mischke (ERC-UU)