1 / 33

Heavy- flavour production in p-p and Pb-Pb collisions at ALICE

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 – 20-27 March 2011. Outline. Motivation ALICE detector setup Trigger and data sample

portia
Download Presentation

Heavy- flavour production in p-p and Pb-Pb collisions at ALICE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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 – 20-27 March 2011

  2. Outline • Motivation • ALICE detector setup • Trigger and data sample • Production cross sections in 7 TeVp-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 √sNN = 2.76 TeV • Summary Andre Mischke (ERC-UU)

  3. Probing hot and dense QCD matter Quark-Gluon Plasma p+p collision Pb-Pbcollision after the collision • “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 Quantify medium effects with nuclear modification factor Andre Mischke (ERC-UU) Moriond-QCD 2011 3

  4. Energy loss of heavy quarks hot and dense medium parton • Higher penetrating power probe deeper into the medium • Dead-cone effectgluon radiation suppressed at small angles (q < mQ/EQ)Y. Dokshitzer, D. Kharzeev, PLB 519, 199 (2001), hep-ph/0106202 • Less energy loss: Eg > ELQ > EHQ Wicks et al., Nucl. Phys. A784, 426 (2007) Bottom Charm Gluon radiation probability: Andre Mischke (ERC-UU) • Moriond-QCD 2011 4

  5. ALarge Ion Collider Experiment Size: 16x26 meters Weight: 10.000 tons L3 magnetB = 0.5 T Complete • ITS, TPC, TOF,HMPID,FMD, T0, V0, ZDC, PMD,EMCAL (approved 2009),Muonarm, Acorde, DAQ,HLT (High Level Trigger) Partial installation 10/18 TRD(approved 2002) 3/5 PHOS(funding) Short status: All systems fully operational • 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 5 • Moriond-QCD 2011 Andre Mischke (ERC-UU)

  6. 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 sinel • single-muon trigger • - forward muon in coincidence with MB SPD V0-A V0-C L ~ 1025 cm-2s-1 rate ~ 100 Hz Lint ~ 9 μb-1 Pb-Pb 6 • Moriond-QCD 2011 Andre Mischke (ERC-UU)

  7. Heavy-flavourmeasurements Impact parameter resolution SSD SDD SPD 87.2 cm • Radius inner pixel layer: 3.9 cm • ≈1 cm from the vacuum 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/X0 = 7.18% for radial tracks • Capabilities to measure open charm down to pT=0 in p-p and p-Pb (1 GeV/c in Pb-Pb) • High precision tracking, better than 75 mm for pT > 1 GeV/c 7 Moriond-QCD 2011 Andre Mischke (ERC-UU)

  8. Reconstruction of D mesons • D0K-+ BR: 3.89% • D0K-2+-BR: 8.09% • D*+D0(K)+s BR: 67.7% • D+K-++ BR: 9.22% • Ds+K+K-+ BR: 5.5% • Lc+pK-+ BR: 5.% D0K-+ • 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 p identification (TPC+TOF)  reducing background at low pT 8 • Moriond-QCD 2011 Andre Mischke (ERC-UU)

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

  10. D meson cross sections at |η| < 0.5 7 TeVp-p, 1.4 nb-1 • Current pT 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 pT Andre Mischke (ERC-UU)

  11. Single electrons at mid-rapidity • High quality tracks in TPC and ITS • - hit in innermost pixel layer to reduce γ 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 11 Moriond-QCD 2011 Andre Mischke (ERC-UU)

  12. 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-pT, arising from D and B decay electrons 12 Moriond-QCD 2011 Andre Mischke (ERC-UU)

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

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

  15. Single muon cross section 1.3 108 events • 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 RAA 15 Moriond-QCD 2011 Andre Mischke (ERC-UU)

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

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

  18. Open charm in Pb-Pb: Perspectives D0Kp MC simulations:1 year at nominal luminosity 107 central Pb-Pb and 109 p-p events Curves: Armesto et al, 2005 B  e+X mb = 4.8 GeV • Initial energy density (from meas. dNch/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 18 Andre Mischke (ERC-UU)

  19. Explore energy loss mechanisms in more detail MC simulations Colour charge dependence Mass dependence (dead cone effect) CR is 4/3 for quarksand 3 for gluons RcAA/RbAA ratio different for pQCD and AdS/CFT 19 Andre Mischke (ERC-UU)

  20. Summary • 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 TeVp-p collisions • cross-section of single muons, electrons and D mesons measured up to pT = 6.5, 4 and 12 GeV/c, respectively • data described by pQCD predictions • Many more to come 20 Andre Mischke (ERC-UU)

  21. Thank you Andre Mischke (ERC-UU)

  22. Backup Andre Mischke (ERC-UU)

  23. Charm production cross section in p-p pp@ 1.96 TeV 5.8 pb-1 ¯ CDF, PRL, 91, 241804 (2003) NLO pQCD, CTEQ6M parton densities R. Vogt, private communication, 2009 – FONLL LHC: 7-14 TeV • 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 pT capabilities of ALICE) 23 Andre Mischke (ERC-UU)

  24. PID using ITS Vertex detector pT(min) < 100 MeV/c Andre Mischke (ERC-UU)

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

  26. D0 signal in different pT bins Andre Mischke (ERC-UU)

  27. D+ signal in different pT bins Andre Mischke (ERC-UU)

  28. D*± signal in different pT bins Andre Mischke (ERC-UU)

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

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

  31. Feed-down 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 Andre Mischke (ERC-UU)

  32. Systematic uncertainties • Total systematic is 20-40% pT dependent + 10% on normalization (Van der Meer-scans) • Main systematic error: B feed-down from FONLL+MCto be reduced using data-driven method with full 2010 statistics Andre Mischke (ERC-UU)

  33. Comparison with world data D0/D+ and D0/D* ratios in line with previous measurements at lower energies Andre Mischke (ERC-UU)

More Related