Measurements of open heavy-flavour production in pp and p-Pb collisions with ALICE Sarah LaPointe INFN Torino For the ALICE collaboration The 7th international workshop on charm physics May 18-22, 2015
Why study open heavy flavour? Heavy quarks (charm and beauty) are produced via JHEP 1207 (2012) 191 ‣ b) initial high-Q 2 parton scattering processes µ ALICE (total unc.) ( ALICE extr. unc. 4 10 c ATLAS Preliminary (total unc.) c ATLAS extr. unc. σ LHCb Preliminary (total unc.) PHENIX Abundant production of heavy quarks STAR ‣ HERA-B (pA) 3 10 E653 (pA) E743 (pA) Increase in σ QQ from RHIC to the LHC: NA27 (pA) NA16 (pA) E769 (pA) ~ 10* σ cc (RHIC) NLO (MNR) 2 10 ~ 50* σ bb (RHIC) 10 pp collisions 2 3 4 10 10 10 10 s (GeV) ALI − PUB − 15089 Phys.Lett. B738 (2014) 97 Tests of perturbative QCD (pQCD) ‣ b) µ ALICE, pp = 2.76 TeV, |y|<0.8 s /dy ( 2 10 ALICE, pp = 7 TeV, |y|<0.9 s b CDF, p p = 1.96 TeV, |y|<0.6 s b σ Multi-parton interactions (MPI) influence heavy- ‣ UA1, p p = 0.63 TeV, |y|<1.5 d s PHENIX, pp = 0.2 TeV, |y|<0.35 s flavour (HF) production at the LHC FONLL 10 Reference system for p-Pb and Pb-Pb collisions ‣ 1 Study jet structure and fragmentation ‣ ALICE extr. unc. ALICE extr. unc. 3 2 4 10 10 10 (GeV) s ALI-PUB-82157 S. LaPointe S. LaPointe Charm 2015: The 7th International Workshop on Charm Physics Charm: The 7th international conference on charm physics 2 2
Why study open heavy flavour? p-Pb collisions JHEP 0904(2009) 65 Study cold nuclear matter effects, to better evaluate hot matter effects in ‣ Pb-Pb collisions Modification of parton distributions in nuclei ‣ shadowing / gluon saturation at low Bjorken x ‣ k T -broadening from multiple soft scatterings ‣ Study partonic energy loss from initial- and final-state radiation ‣ Investigate potential final-state effects ‣ Results from Pb-Pb collisions C. Bianchin (this session) Experimental overview ➜ A. Dainese (this morning) S. LaPointe Charm 2015: The 7th International Workshop on Charm Physics 3
A Large Ion Collider Experiment EMCal - Trigger, TPC - Tracking energy measurement and PID w/ dE/dx Central barrel | η |<0.9 Muon arm -4 < η <-2.5 Muon spectrometer - Trigger, tracking, and PID VZERO - trigger, event topology TOF - PID w/ ZDC - trigger, event Time Of Flight topology ITS - Trigger, event topology, tracking, PID S.LaPointe Charm 2015: The 7th International Workshop on Charm Physics 4
Open heavy-flavour program 6000 2 Entries/11 MeV/c - Mid-rapidity + + + D K and charge conjugate, 2<p <24GeV/c → π π T min. bias p-Pb, s = 5.02 TeV, 102 M events NN 5000 D mesons (D 0 , D + , D * , D s ) via hadronic decays 4000 • Select displaced vertex topologies using TPC and ITS Significance (3 ) 59.7 ± 0.8 σ 6/07/2013 S (3 ) 7166 ± 133 σ • Particle ID using TPC and TOF 3000 S/B (3 ) 0.9926 σ 2 = 1.869 0.0003 GeV/c µ ± • Invariant mass analysis 2 = 0.010 0.0003 GeV/c ± σ 2000 • FONLL-pQCD based correction for beauty feed-down 1000 JHEP, 1210 (2012) 137 1.7 1.75 1.8 1.85 1.9 1.95 2 2 Invariant Mass (K ) (GeV/c ) π π ALI − PERF − 52390 Single electrons from semi-leptonic HF-hadron decays 2 E/p 1.8 • Electron ID using TPC, TOF, and EMCal (high p T ) 1.6 1.4 • Background estimation: 15/05/2012 1.2 • MC cocktail pp s =2.76 TeV e 10 1 EMCal Trigger Events π K+p Track 3.5<p <4.5 GeV/c 0.8 • e + e - invariant-mass method T e | η | < 0.7 0.6 • Beauty-decay electrons using ITS - exploiting displacement from 0.4 0.2 primary vertex 1 0 -10 -8 -6 -4 -2 0 2 4 6 8 10 dE/dx - 〈 dE/dx 〉 e σ ALI − PERF − 14772 dE/dx Forward rapidity Single muons from semi-leptonic HF-hadron decays • Muon spectrometer • Estimation of background sources • For pp collisions a MC simulation is used • For p-Pb collisions, data-tuned MC cocktail ALI-PUB-13314 S.LaPointe Charm 2015: The 7th International Workshop on Charm Physics 5
Heavy-flavour production cross sections pp collisions at √ s = 7 TeV HF-decay electrons D mesons -1 10 HF-decay muons ) 3 10 2 b/GeV/c) dy) (mb/(GeV/c) pp, s = 7 TeV ALICE -2 10 + -1 D , pp s = 7 TeV, L = 5 nb 2 int 10 -3 10 JHEP 1201 (2012) 128, µ ( -4 10 D s in PLB 178 (2012) 279 t /(dp 10 |y|<0.5 σ -5 2 10 ) d PLB 708 (2012) 265 t p | π -6 1 1/(2 t 10 / dp -7 stat. unc. 10 σ ALICE c, b e -1 → syst. unc. 10 d -8 ATLAS c, b e FONLL 10 → GM-VFNS FONLL c, b e, |y| < 0.5 → 3.5% lumi, 2.1% BR norm. unc. (not shown) ± ± -9 -2 10 10 FONLL c, b e, |y| < 2 excl. 1.37 < |y| < 1.52 → 3.5 0 5 10 15 20 25 Data/FONLL 3 4.5 FONLL p GeV/c 2.5 Data 4 ALICE: PRD 86 (2012) 11200 t 2 1.5 3.5 ATLAS: PLB 707 (2012) 438 1 3 0.5 0 0 5 10 15 20 25 GM-VFNS 3.5 2.5 p (GeV/c) t 3 2.5 2 Data 2 1.5 1.5 1 1 0.5 0 0 5 10 15 20 25 0.5 p (GeV/c) 0 t ALI − PUB − 12507 -1 4 10 2 3 4 5 6 7 8 910 20 30 1 × p (GeV/c) ALI − PUB − 16461 t • pQCD predictions describe the data within uncertainties FONLL: JHEP 1210 (2012) 37, GM-VFNS: EPJ C72 (2012) 2082, k T- factorization: PRD 87 (2013) 094022 • Measurements of HF-decay electrons complementary to the high- p T ATLAS result • Similar situation for pp collisions at √ s = 2.76 TeV S. LaPointe S. LaPointe Charm 2015: The 7th International Workshop on Charm Physics Charm: The 7th international conference on charm physics 2 6
Electrons from beauty-hadron decays pp collisions at √ s = 7 TeV Beauty-hadron decays • relatively long lifetime ( c τ ~500 μ m) ➜ broad impact parameter distribution • decay kinematics ➜ ∆ φ between electron-hadron wider than for other sources ) ALICE pp, = 2.76 TeV -2 s 2 10 ) Impact-parameter electron-hadron c dy) (mb/(GeV/ b ( c) e -3 → → 10 data -4 analysis azimuthal correlation 10 FONLL k factorization -5 10 T T p GM-VFNS (a) /(d 4 ALICE pp, = 2.76 TeV PYTHIA s -6 ) (a) MB Trigger Sample ALICE pp, s = 2.76 TeV -1 10 σ b ( c) e (rad 2 Data → → Normalized counts (a.u.) 3.5 e ) d 1.5 < p < 2.5 GeV/ c 3 PLB 738 (2014) 97-108 10 c e Conversions (V0) T → T -7 10 p h > 0.3 GeV/ c p Conversions (V0) 3 e-h π T 1/(2 Dalitz decays ) 1.9% normalization uncertainty not shown | η | < 0.9 ϕ -8 10 2.5 ∆ 2 /d 2 /NDF = 19/18 10 χ 3 Data/Theory (a) FONLL 2 N 2.5 (b) (d 2 1.5 e 1.5 N 1 10 1/ 1 0.5 8 3 (b) EMCal Trigger Sample k -factorization Data: c,b e Data/Theory → 2.5 T e (c) 7 4.5 < p < 6.0 GeV/ c 2 MC fit T 1 h 1.5 6 p > 0.3 GeV/ c MC: c e → T 1 | | < 0.7 η MC: b (c ) e 3 5 → → 0.5 Conversions (V0) (b) Data/MC 2.5 2 χ /NDF = 8.5 / 9 4 3 Data/Theory GM-VFNS 2 2.5 (d) 1.5 3 2 1 1.5 2 0.5 1 0.5 0 1 -600 -400 -200 0 200 400 600 -3 -2 -1 0 1 2 3 0 2 4 6 8 10 d ( m) µ (rad) ∆ ϕ 0 (GeV/ ) ALI-PUB-82084 ALI-PUB-82098 p c T ALI-PUB-82148 • p T -differential production cross section of electrons from beauty-hadron decays • Compatibility with FONLL, GM-VFNS and k T -factorization calculations FONLL: JHEP 1210 (2012) 37, GM-VFNS: EPJ C72 (2012) 2082, k T -factorization: PRD 87 (2013) 094022 S. LaPointe S. LaPointe Charm 2015: The 7th International Workshop on Charm Physics Charm: The 7th international conference on charm physics 2 7
D meson-hadron azimuthal correlations Measure the associated hadron yield on the near ( ∆ φ around 0) and away side ( ∆ φ around π ) • Sensitive to quark fragmentation pp collisions at √ s = 7 TeV • Insight into cc production mechanisms 5 < p TD < 8 GeV/ c 8 < p TD < 16 GeV/ c p TAssoc. > 0.5 GeV/ c p TAssoc. > 1 GeV/ c ) ) -1 -1 D meson - charged particle correlation D meson - charged particle correlation - baseline (rad - baseline (rad 3.5 3.5 0 + *+ 0 + *+ Average D ,D ,D Average D ,D ,D D assoc D assoc 5 < p < 8 GeV/ c , p > 0.5 GeV/ c , | ∆ η | < 1.0 8 < p < 16 GeV/ c , p > 1.0 GeV/ c , | ∆ η | < 1.0 T T T T PYTHIA8 3 3 pp s =7 TeV Data ALICE Preliminary pp s =7 TeV Data ALICE Preliminary Simulations, pp s =7 TeV Simulations, pp s =7 TeV Perugia 2010 Pythia8 baseline uncertainty Pythia8 baseline uncertainty 2.5 2.5 assoc assoc Pythia6, Perugia2010 Pythia6, Perugia2010 ϕ ϕ +13% +13% scale uncertainty scale uncertainty Pythia6, Perugia2011 Pythia6, Perugia2011 ∆ ∆ Perugia 2011 -10% -10% N d N d 2 2 d d D D 1 1 N N 1.5 1.5 1 1 0.5 0.5 0 0 -0.5 -0.5 -1 0 1 2 3 4 5 -1 0 1 2 3 4 5 (rad) (rad) ∆ ϕ ∆ ϕ ALI − PREL − 78598 ALI − PREL − 78716 • Baseline subtracted azimuthal correlation of D mesons and charged hadrons • Different PYTHIA tunes consistent with the measurement • Data from Run-II at the LHC will provide more precision ➜ constrain models S. LaPointe S. LaPointe Charm 2015: The 7th International Workshop on Charm Physics Charm: The 7th international conference on charm physics 2 8
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