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B hadron cross-section via single muons in pp collisions at 14 TeV with ALICE @ LHC

B hadron cross-section via single muons in pp collisions at 14 TeV with ALICE @ LHC. Heavy ion collisions Heavy flavours: QGP probes ALICE detector overview Method/Results Summary/Outlooks. L. Manceau (LPC Clermont-Ferrand). Heavy ion collisions. Central Pb-Pb (Au-Au).

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B hadron cross-section via single muons in pp collisions at 14 TeV with ALICE @ LHC

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  1. B hadron cross-section via single muonsin pp collisions at 14 TeVwith ALICE @ LHC • Heavy ion collisions • Heavy flavours: QGP probes • ALICE detector overview • Method/Results • Summary/Outlooks L. Manceau (LPC Clermont-Ferrand) manceau@clermont.in2p3.fr

  2. Heavy ion collisions Central Pb-Pb (Au-Au) • Super Proton Synchroton CERN (1986-2003): • 1986-1994: early work on heavy ions • 1994-2003: 7 experiments → NA44, NA45, NA49, NA50/60, NA52, WA97/NA57, WA98 • Relativistic Heavy Ion Collider Brookhaven National Laboratory (2000): • 4 experiments: STAR, BRAHMS, PHOBOS, PHENIX σc(LHC)= σc(RHIC) × 10 σb(LHC)= σb(RHIC) × 100 LHC: unprecedented conditions to study hot QCD matter manceau@clermont.in2p3.fr

  3. Open flavours: Quarkonia: • Heavy mass→ quarks are produced very early in the collision • Interaction with deconfined medium Heavy-flavours as probes of QGP (I) c hard processes approach vacuum • Quarkonia suppression as a signature of deconfinement: • Color screening of static potential between heavy quark pair → J/Ψ suppressionMatsui and Satz, Phys. Lett. B 178 (1986) 416 • Tsup. determined by lattice QCD • Screening competes with recombination of uncorrelated pairs of heavy quarks? QGP Sensitivity to temperature manceau@clermont.in2p3.fr

  4. Hadron gas QGP Heavy-flavours as probes of QGP (II) • Heavy quark Energy loss: • collisions • gluonstralhung: • αs: strong interaction coupling const. • CR: color couplling factor (q(g)→4/3(3)) • : medium transport coefficient • L: path length Q Q Sensitivity to energy density g + Dead cone effect → gluon radiation suppressed at θ < mQ/EQ θ Q • Key observable (J/Ψ, E loss…): nuclear modification factor → • If no hot effects: • RAA<1 low pt (shadowing) • RAA=1 high pt • hot effects → suppression: • - RAA<1 even at high pt No hot effects hard physics domain Average number of NN collisions in a AA collision soft physics domain manceau@clermont.in2p3.fr

  5. SPS & RHIC results on heavy flavours • SPS: J/Ψ suppression in Pb-Pb • Debye screening not a unique scenario (statistical hadronisation, comovers…) • Models cannot reproduce data in In-In • RHIC: J/Ψ suppression in Au-Au • Large uncertainties on cold nuclear effects • Larger suppression at forward angles? • RHIC: charm quenching ~ light hadron quenching • Non photonic vs. hadron RAA • A challenge for models (recombination…) • Experiments disagree on charm cross-section (p-p) Phys. Lett. B477 (2000) 28 Phys. Rev. C77 (2008)024912 Phys. Rev. Lett. 98 (2007) 192301 manceau@clermont.in2p3.fr

  6. B[D] hadron cross-section in p-p @ LHC: motivations (I) • Testing NLO pQCD with heavy flavours Charm Beauty D.L. Vititoe, PhD, Arizona Univ. (1996) (D0 exp.) hep-ph/0601164 • Unravel NLO processes • Large theoretical uncertainties on cross-sections • σ(B) [σ(D)] in p-p is the most natural normalisation for: • σ(Υ) [σ(J/Ψ)] in p-p, p-A & A-A: production, absorption, suppression, recombination (?) • σ(J/ψ) in p-p (→ p-A & A-A): N(B→J/Ψ)/N(direct J/Ψ) ~ 20% in 4π → Informations on the thermodynamical state of QCD medium : Ec, Tc manceau@clermont.in2p3.fr

  7. B[D] hadron cross-section in p-p @ LHC: motivations (II) • Measurement of σ(B) [σ(D)] in p-p is mandatory for understanding: • σ(B) [σ(D)] in p-A: shadowing & anti-shadowing → gluonspdf in nucleus • σ(B) [σ(D)] in A-A: energy loss → initial density of gluon, dissipative properties (transport coefficient) • New ratio to understand energy loss →mass, color charge Stronger coupling of gluons with the medium Dead cone effect Light quarks (→ light hadrons) mainly created by gluons fusion • R(D)/h color charge dependence • R(B)/h mass dependence • RB/D isolate mass dep. N. Armesto et al., Phys. Rev. D 71 (2005) 054027 J. Phys. G 35 (2008) 054001 manceau@clermont.in2p3.fr

  8. Heavy ions @ LHC CMS ATLAS ALICE manceau@clermont.in2p3.fr

  9. ALICE @ LHC Muon Spectrometer (-4 ≤ η≤ -2.5) • Central barrel (-0.9 ≤ η≤ 0.9): (di-)electrons, photons, hadrons • Muon spectrometer (-4 ≤ η≤ -2.5): (di-)muons • Backward, forward small acceptance detectors: multiplicity, centrality, luminosity manceau@clermont.in2p3.fr

  10. ALICE muon spectrometer dipole magnet muon filter absorber beam shield - 4 ≤ η ≤ -2.5 tracking chambers • Tracking: measurement of µ pt • Position resolution < 100 μm (bending plane) • →ΔM < 100 MeV/c² @ 10 GeV/c² • 1.1 M read-out channels • Trigger: select high pt muons ( ~1GeV, ~2GeV) • Time resolution < 2 ns • Rate < 1kHz • Decision in < 800 ns • 21000 read-out channels trigger chambers manceau@clermont.in2p3.fr

  11. B hadron cross-section via single muons: method 1. Extract N(  B) from “data” • π/K subtraction • Combined Fit 2. Correct for integrated luminosity, detection efficiency, acceptance & decay kinematics 3. Get differential inclusive B hadron cross-section manceau@clermont.in2p3.fr

  12. Method widely used and well documented 1. 1.UA1: collisions @ , single muons & dimuons C. Albajar et al., PLB 213 (1988) 405 2.CDF: collisions @ , single electrons F. Abe et al., PRL 71 (1993) 4 3.D0: collisions @ , single muons & dimuons B. Abbott et al., PLB 487 (2000) 264-272 2. 3. ALICE : 4. collisions @ , single electrons F. Antinori et al., ALICE-INT-2006-015 5. collisions @ , single electrons • F. Antinori et al., ALICE-INT-2005-33 6. collisions @ , single muons & dimuons • R. Guernane et al., ALICE-INT-2005-018 4. 5. 6. manceau@clermont.in2p3.fr

  13. Simulation input & statistic estimates • Physics Data Chalenge 2006 • Full simulation on grid generation → reconstruction • 1·106 single muonevents • Efficiency correction for muon detection in the acceptance • Hypothesis: μ←π,K perfectly subtracted • PDC06: • Extrapolated to 20 GeV • Scaled → 3 scenarii: 1. L=1030 cm-2 s-1 , T=1 month 2. L=3.1030 cm-2 s-1,T=1 month 3. L=3.1030 cm-2 s-1 ,T=1 year (Nominal) • Large yield over a broad pt range → Statistical error negligible manceau@clermont.in2p3.fr

  14. Extraction of N(µ←B) Combined fit: (T-B) (fc+R·fb) • T: total number of muons • B: number of muons from B → free parameter • fc (fb) model dependent shape distribution of muons from D(B) decay • R: number of muons from B over number of muons from D → free parameter fixed within 30% Chi2/ddl=0.07 µ←B off by 0.5% manceau@clermont.in2p3.fr

  15. Systematic uncertainties Charm Beauty Beauty Charm µ←B off by 1% 1.Hadrons 2.Muons 1.Theoretical predictions for D & B: 2.MC simulation: Get μ dN/dpt & Fit μ dN/dpt → biased shapes fc & fb 3. Investigate systematics hep-ph/0601164 µ←B off by 19% • Systematic uncertainties: 20% µ←B off by 36% 3.Fits manceau@clermont.in2p3.fr

  16. Decay kinematics corrections F(μ←B) • F(µ←B): Pythia simulation • 90% of B → μ in the acceptance have a transverse momentum larger than ptmin • ptmin: minimisation of the correction dependence on shape distributions used in Pythia Muons pt 4-6 GeV/c Ptmin = 6.4 GeV/c F(μ←B) = 48.31 90% Ptmin manceau@clermont.in2p3.fr

  17. Inclusive differential B hadron cross-section • Input distribution well reconstructed • 82% of the total cross-section is reconstructed • Statistical errors negligible (even in scenario 1 !) • Statistical errors from F(μ←B): from 0.1% to 6% at high ptmin • Systematic errors from F(μ←B) negligible • Systematic errors from fit 20% • Error from normalisation ~5% (not included) • Results in agreement with σ(B) via dimuons (dimuons by X. Zhang) manceau@clermont.in2p3.fr

  18. Summary/Outlooks • Heavy flavours and QGP @ LHC: • Probes: quarkonia + energy loss • Key observable: RAA • B cross-section extraction: • Extraction of B cross-section for 3 ≤ ptmin ≤ 26GeV/c, statistical errors are negligible, systematic errors are: 20% • Outlooks: • Realistic π/K subtraction → another source of error on muon yield (especially at low pt ) • Does this allows to extract σ(D) simultaneously ? (work in progress) Realistic distributions including background Different distances between IP and muon decay allow to discriminate signal (b/c) from background (π/K) Interaction Point (IP) µ spectrometer manceau@clermont.in2p3.fr

  19. Back up manceau@clermont.in2p3.fr

  20. Transverse Plane Inclusive differential B hadron cross-section via single electrons TRD TPC ITS • Strategy: • Electron identification: dE/dx TPC, TRD • Impact parameter cut d0: ITS • cτof B ~ 500µm → displaced vertex for electrons ~100 µm. • (π0 background reduction → loss of statistics) • Different method → different stat. & different syst. → cross-check C. Bombonati et al., PWG3, March 07 ALICE-INT-2006-015 manceau@clermont.in2p3.fr

  21. Electrons in central barrel C. Bombonati et al., PWG3, March 07 ALICE-INT-2006-015 manceau@clermont.in2p3.fr

  22. Efficiency correction Global efficiency for μ detection in the acceptance (trigger & tracking): framework developed by Z. Conesa del Valle (ALICE-Physics Week, Munster) • Need some smoothing • New framework in progress: N. Le Bris manceau@clermont.in2p3.fr

  23. PDC06 Realistic input • L=1030 cm-2 s-1 , T=106 s • L=3.1030 cm-2 s-1, T=106 s μ←πΚ perfectly subtracted • Charm cross-section corrected • Extrapolation to pt 20 GeV/c • 3 statistical scenarii • L=3.1030 cm-2 s-1 , T=107 s • (Nominal) • Realistic input: • 3 statistical scenarii • Fit PDC06: extrapolation 2 GeV/c ≤ pt ≤ 20 GeV/c • NLO calculation: • M.L. Mangano, P. Nason and G. Ridolfi, • Nucl. Phys. B 373 (1992) 295→ • PDC06: • 106 single muon events • 2 GeV/c ≤ pt ≤ 10 GeV/c • Charm underestimated: → manceau@clermont.in2p3.fr

  24. Statistics estimates Scenarii: 1. L=1030 cm-2 s-1 , T=106 s 2. L=3.1030 cm-2 s-1,T=106 s 3. L=3.1030 cm-2 s-1 ,T=107 s (Nominal) • Large yield over a broad pt range (even in scenario 1 !) → Statistical errors negligible manceau@clermont.in2p3.fr

  25. Systematic uncertainties (I) D hadron B hadron D hadron B hadron Hera LHC • Pythia is tuned to reproduce « Hera LHC » predictions on D and B hadron production cross-section:hep-ph/0601164 manceau@clermont.in2p3.fr

  26. Systematic uncertainties (II) 1 Hadrons 2 Muons 3 Fit • Get μ dN/dpt from D & B • Fit μ dN/dpt • Investigate systematics manceau@clermont.in2p3.fr

  27. Systematic uncertainties (IV) Hera LHC • Systematic errors: • ~ Pt independent • Charm ~ 15% • Beauty ~ 20% • Allow to constrain models manceau@clermont.in2p3.fr

  28. Systematic error on decay kinematics & acceptance correction 90% 60% 20% 90% 60% 20% Systematic error is negligible manceau@clermont.in2p3.fr

  29. Sources of systematic uncertainties manceau@clermont.in2p3.fr

  30. π/K subtraction: simulation input • Physics Data Chalenge 2008 • Full simulation on grid generation → reconstruction • 2·105 single muon events • Efficiency correction for muon detection in the acceptance • Realistic π/K background Interaction Point (IP) absorber Primary π/K fly longer than heavy flavours µ spectrometer manceau@clermont.in2p3.fr

  31. π/K subtraction: simulation input • Physics Data Chalenge 2008 • Full simulation on grid generation → reconstruction • 2·105 single muon events • Efficiency correction for muon detection in the acceptance • Realistic π/K background µ Heavy Flavours b/c absorber IP Primary π/K π/K µ absorber IP Primary pi/K fly longer than heavy flavours π/K Secondary π/K π/K µ absorber manceau@clermont.in2p3.fr IP

  32. Point where π/K is absorbed IP Origin absorber z d = 90 cm a ~ 40 cm zvertex z = 0 zabsorption Primary π/K subtraction method • IP displacement: • Gaussian smearing of theµvertex distribution • π/K prim. fly different distances event by event: • IP closer to absorber → lessproba. to decay before absorption → lessµ produced • IP further to absorber → moreproba. to decay before absorption → moreµ produced µ counts decrease ~ linearly with IP to absorber distance Fit dN/dz slice for each pt pt = 1GeV α = 39+-13 β = 6672+-172 dN/dz Fit fonction : d²N/dptdz • N : normalisation → • σ = 5.3 cm • α, β: free parameters: • π/K prim. → dN/dpt = (a+d)α(pt) • b+c+ π/K sec. → = dN/dpt = β(pt) dN/dz slice (pt = 1GeV) manceau@clermont.in2p3.fr

  33. Secondary π/K subtraction (I) • Cut µ tracks wich don’t match with a trigger signal: • Low energy µ (mainly µ ←π/K) → don’t pass through the iron filter • High energy µ (mainly µ ← b,c) → deliver a trigger signal Subtraction method doesn’t allows to substract secondary π/K Matching with trigger • Rejection rate: • b →15% • c → 23% • π/K prim. → 69% • π/K sec. → 74% No cut manceau@clermont.in2p3.fr

  34. Secondary π/K subtraction (I) • Cut µ tracks wich don’t match with a trigger signal: • Low energy µ (mainly µ ←π/K) → don’t pass through the iron filter • High energy µ (mainly µ ← b,c) → deliver a trigger signal Subtraction method doesn’t allows to substract secondary π/K Matching with trigger • Rejection rate: • b →15% • c → 23% • π/K prim. → 69% • π/K sec. → 74% No cut manceau@clermont.in2p3.fr

  35. DCA π/K prim. µ←π/K prim. π/K prim. π/K sec. DCA π/K sec. DCA b/c µ←π/K sec. µ←b/c Secondary π/K subtraction (II) • Distance of Closest Approach : distance between the extrapolated track and the interaction vertex, measured in the plane orhogonal to the beam pipe and containing the vertex itself • Cut on DCA: → b/c DCA< < π/K prim. DCA < π/K sec. DCA Rejection rate π/K sec. π/K prim. charm beauty Cut rejecting a maximum of π/K Cut rejecting a maximum of π/K Matching trigger cut is already applied manceau@clermont.in2p3.fr

  36. Subtraction results Trigger Matching No Cut DCA cut chosen to reject: ~ 5% b & c (saving statisic) ~ 10% primary π/K ~ 40% secondary π/K TriggerMatching + DCA cut • Fit method → Primary π/K subtracted until 0.5 GeV (below no effeciency correction) • Matching Trigger + Cut DCA → Secondary π/K subtracted until 1 GeV manceau@clermont.in2p3.fr

  37. D hadron cross-section manceau@clermont.in2p3.fr

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