Recent results from the ALICE experiment on open heavy flavours Sarah Porteboeuf-Houssais for the ALICE collaboration 52th International Winter Meeting on Nuclear Physics January 2014, Bormio, Italy  The ALICE LHC  Open heavy flavours (HF): physics motivations

2 Open heavy flavours (HF): physics motivations HF in pp collisions -Test of pQCD-based calculations (production cross sections) -Investigation of charm production mechanisms -Reference measurement for p-Pb and Pb-Pb HF in p-Pb collisions - Control experiment for Pb-Pb measurement via understanding of cold nuclear matter (CNM) effects HF in Pb-Pb collisions Heavy quarks produced in initial hard scatterings. HF sensitive to hot medium effects. Energy loss ( Δ E) Collectivity in the QGP Colour-charge dependence: α C R Quark mass dependence: Δ E uds > Δ E c > Δ E b Δ E g > Δ E uds > Δ E c > Δ E b R AA ( π ) < R AA (D) < R AA (B) JPG 17 (1991) 1602;, PLB 519 (2001) 199; PRD 71 (2005) ; NPA 783 (2007) 493 ? C R (g)= 3, C R (q)= 4/3 Initial spatial anisotropy momentum anisotropy of particles If heavy quarks participate in the expansion of QGP : v 2 (c,b) > 0 => v 2 (D, HF-e, HF- μ ) > 0 The anisotropy is quantified via a Fourier expansion in azimuthal angle φ with respect to the reaction plane Ψ RP The second coefficient is v 2 (elliptic flow) R AA and v 2 are the experimental observables.

The Alice LHC D mesons D 0 -> K - π + D + ->K - π + π + D *+ -> D 0 π + D s + -> φ π + ->K - K + π + | ƞ | < 0.9 ITS: tracking, vertexing TPC: tracking PID TOF: PID HF decay electrons D, B, Λ c, … -> e + X | ƞ | < 0.9 ITS : tracking, vertexing TPC : tracking PID TOF, EMCAL, TRD : e-ID HF decay muons D, B, Λ c, … -> μ + X -4 < ƞ < -2.5 Muon Spectrometer : trigger and μ -ID VZERO: Trigger, centrality determination 3

Data Samples SystemEnergyLHC Run D mesonsHF electronsHF muons pp2.76 TeV nb -1 (MB trigger) JHEP 1207 (2012) cross sections 0.5 (11.9) nb -1 MB (EMCAL) triggers Cross sections 19 nb -1 ( μ trigger) PRL 109 (2012) cross sections pp7 TeV nb -1 (MB trigger) JHEP 01 (2012) cross sections D-h correlation D vs. mult PLB 718 (2012) nb -1 (MB trigger) PRD 86 (2012) nb -1 PLB 721 (2013) 13 - cross sections 16.5 nb -1 ( μ trigger) PLB 708 (2012) cross sections p-Pb5.02 TeV μ b -1 (MB trigger) R pPb 48.6 μ b -1 (MB trigger) R pPb e-h correlation Work in progress Pb-Pb2.76 TeV μ b -1 (0-80%) JHEP 09 (2012) R AA 2.0 μ b -1 (0-80%)2.7 μ b -1 (MB trigger) PRL 109 (2012) R AA Pb-Pb2.76 TeV μ b -1 in 0-10% 6.2 μ b -1 in 10-50% PRL 111 (2013) v 2 R AA 22(37) μ b -1 in 0-10% 6(34) μ b -1 in 20-40% MB(EMCAL)trig. R AA, v μ b -1 in 0-10% 3.5 μ b -1 in 10-40% v 2 Green: recent published results discussed in this talk Purple: recent preliminary results discussed in this talk Black: ALICE published results for HF observables Large amount of data collected by ALICE for HF observables Several analyses, results, plots In this talk: a selection 4

pp: the baseline for heavy ion study, reference measurement, test of pQCD D mesonsHeavy-flavour decay muons JHEP 1201 (2012) 128 Phys. Lett. B 718 (2012) 279 Phys. Rev. D 86 (2012) for HF decay electrons Phys. Lett. B 721 (2013) 13 Phys. Lett. B 708 (2012) 265 pQCD-based calculations compatible with data FONLL: JHEP 1210 (2012) 137; GM-VFNS: Eur. Phys. J. C 72 (2012) Heavy-flavour decay electrons

D mesons Heavy-flavour decay electronsHeavy-flavour decay muons JHEP 1207 (2012) 191Phys. Rev. Lett. 109 (2012) pQCD-based calculations compatible with data FONLL: JHEP 1210 (2012) 137; GM-VFNS: Eur. Phys. J. C 72 (2012) 2082 HF muon data used as reference for Pb-Pb at the same energy For other channels, a scaling based on pQCD calculations is used arXiv: pp: the baseline for heavy ion study, reference measurement, test of pQCD 6

pp: looking at more exclusive observables to better understand production mechanisms D-hadron correlation Correlation measurements well described by PYTHIA6.4 within statistical and systematic uncertainties Precise measurement expected from LHC Run2 7 Reference for Pb-Pb studies of charm jet modification due to hot medium effects Insight into charm production mechanisms in pp by measuring the associated hadron yields in the near and away side region

8 pp: looking at more exclusive observables to better understand production mechanisms D and non-prompt J/ Ψ vs. multiplicity Approximately linear increase with charged particle multiplicity within statistical and systematic uncertainties Observable related to the underlying event accompanying heavy-flavour production Connected with Multi Parton Interaction (MPI) and possible contributions from hadronic activity associated with heavy-flavour production and gluon splitting (g->cc)

D mesons Heavy-flavour decay electrons HF e R pPb measurement is compatible with unity within uncertainties Consistent with predictions from FONLL +EPS09 Similar results for the four D-meson species (and for the D s, not shown here) D R pPb measurement is compatible with unity within uncertainties Consistent with predictions from: MNR (HF production) + EPS09 (Shadowing) Nucl. Phys. B 373 (1992) JHEP 0904 (2009) 065 CGC arXiv: Two analyses based on different PID strategies TPC + TOF at low p T TPC + EMCAL at high p T Phys. Rev. Lett. 109 (2012)

Correlation between trigger particles (electron from HF hadron decay) and associated particles (charged hadrons) Analysis performed in 3 multiplicity classes defined with signal multiplicity in the region 2.8 < ƞ < 5.1 in the Pb hemisphere A double-ridge structure observed also for HF e-h correlations as in h-h correlations when subtracting low mult to high mult. For h-h, possible interpretation: hydrodynamical evolution of the system or CGC Phys. Lett. B 719 (2013) 29 In the highest multiplicity event class (0- 20%), stronger correlation than the one observed in pp minimum bias 10

% for electrons and 40-80% for muons Central Collisions (0-10%)Semi-peripheral collisions Clear suppression observed for 3(4) <p T <18(10) GeV/c for the most central collisions Final state effects: HF decay e R pPb compatible with unity (cf. S.9) Similar suppression at central (electrons) and forward (muons) rapidity Muons results: Phys. Rev. Lett. 109 (2012)

as a function of p T Suppression up to a factor of 5 at p T ~10 GeV/c for 0-7.5% central collisions. Hot medium effect: D R pPb measurement compatible with unity (cf. S.9) R AA (D) ~ R AA (charged π ) within large uncertainties Not trivially linked to ΔΕ (g) and ΔΕ (c): different fragmentation, spectral shape, bulk properties arXiv:

13 Smaller suppression in peripheral than in central collisions at high-p T for D mesons Indication of a larger suppression for charm than for beauty Supported by predictions from energy-loss models for R AA D and non-prompt J/ Ψ => Hint of the quark-mass dependence of energy loss: ΔΕ (c) > ΔΕ (b) as a function of N part J. Phys. G 38 (2011) ; J. Phys. G 38 (2011) ; Phys. Rev. C 80 (2009)

D mesonsHF decay electrons and muons v 2 (D) ~ v 2 (charged π ) within uncertainties v 2 (HF-e) ~ v 2 (HF- μ ) within uncertainties in different rapidity regions All channels show positive v 2 (>3 σ effect) Information on the initial azimuthal anisotropy transferred to charm quarks Phys. Rev. Lett. 111 (2013) The anisotropy is quantified via a Fourier expansion in azimuthal angle φ with respect to the reaction plane Ψ RP 14

A global picture of QGP from the D mesons Simultaneous description of R AA and v 2 gives insight on quark transport coefficients of the medium Still a challenge for models Low p T D mesons thermalized in the formed medium and acquire properties of the expanding bulk Only models with predictions for both RAA and v2 are shown J. Phys.G38 (2011) , Eur. Phys J. C 71 (2011) 1666; arXiv: ; Phys. Rev. C 79 (2009) ; arXiv: ; arXiv: ; arXiv: JHEP 09 (2012) 112PRL 111 (2013)

Conclusions HF measurements in pp collisions HF measurements in p-Pb collisions HF measurements in Pb-Pb collisions  Production cross sections in all channels described within uncertainties by pQCD-based calculations (at both 7 and 2.76 TeV)  More exclusive study ongoing (D and non prompt J/ Ψ vs. mult and D-h correlations)  Good agreement with pQCD calculations including nuclear modification of PDFs and CGC predictions  R pPb (D,e) ~ 1 within uncertainties  HF decay e-h correlations show similar structure as for h-h correlations in p-Pb collisions (double ridge structure)  R AA < 1 at high p T for all HF channels for central Pb-Pb collisions final state effects due to parton energy loss in the hot and dense medium  R AA (D) ~ R AA (charged π ) for central collisions  R AA (D) > R AA (B->J/ Ψ ) for central collisions Difference between charm and beauty hadrons at high p T  v 2 > 0 for all HF channels measured at low p T Suggests that charm takes part in the anisotropic evolution of the system 16

BACK-UP SLIDES 17

LHC schedule belong LS1 18 LS2 starting in 2018 (July) 18 months + 3months BC (Beam Commissioning) LS3LHC: starting in 2023 => 30 months + 3 BC injectors: in 2024 => 13 months + 3 BC approved by CERN management and LHC experiments spokespersons and technical coordinators Monday 2 nd December 2013 Run 2Run 3 Run 4 LS 2 LS 3 LS 4LS 5Run 5

ALICE running conditions during RUN II ( ) 19 Values to be compared to:  L = cm -2 s -1 in pp collisions 2012 (8 TeV)  L = cm -2 s -1 in Pb-Pb collisions 2011 (2.76 TeV)  L = cm -2 s -1 in p-Pb/Pb-p collisions 2013 (5.02 TeV)

Centrality Measurement 20 Collision centrality determine the number of participating nucleons and the remaining spectators.  ZDCs (~116m from IP) measure spectator nucleons  V0, SPD, TPC are sensitive to participating nucleon “Fit” multiplicity distributions with a Glauber MC (V0 amplitude, SPD clusters, TPC tracks) Energy deposit on the ZDCs and ZEMs

D mesons reconstruction strategy 21 D 0 -> K - π + M = ± 0.13 MeV; c τ = μ m D + ->K - π + π + M = ± 0.15 MeV; c τ = μ m D *+ -> D 0 π + M = ± 0.13 MeV Invariant mass analysis mainly based on secondary vertex reconstruction and kaon identification.  Vertex reconstruction Impact parameter resolution ~ 60 μ m for p T = 1 GeV/c JHEP 09 (2012) 112 Main topological cuts: Impact parameter of the tracks Angle between the meson flight line and the particle momentum

D mesons reconstruction strategy 22  Kaon identification Energy loss deposit in the TPCVelocity measurement in TOF TPC allows K/ π separation up to ~0.6 GeV/c TOF allows K/ π separation up to ~2 GeV/c

Heavy-flavour decay electrons 23 Low p T : TPC (dE/dx) + TOF + TRD High p T : TPC (dE/dx) + EMCAL  Electron identification  Background subtraction Cocktail method: MC hadron generator for different background sources e + e - invariant mass method to remove Dalitz decay and photon conversion

24 Heavy-flavour decay muons Phys. Lett. B 708 (2012) Main source: muon from pions and kaons decay, subtracted by MC dN/dp T normalized to data at low p T Background contribution decreases with p T => measurement for p T > 2 GeV/c Remove beam-gas and secondary muons by requiring a muon trigger signal + a cut on the p x DCA Remove punch-through hadrons by muon trigger matching  Muon track selection  Background subtraction In Pb-Pb: no subtraction of decay muons, but analysis restricted to high p T region where background is small

Charm and Beauty cross sections Evaluation of the total charm and beauty production cross sections 25

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Compatible results for the four D-meson species (including the D s ) All measurements compatible with unity within uncertainties 28

No rapidity dependence observed in <y CMS <

Compatible D meson production ratios between pp at 7 TeV and p-Pb at 5.02 TeV 30

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Upgrades Inner Tracking System 32 Reduces the material budget (X/X0 per layer): from 1.14% to 0.3% for the inner layers. Get closer to IP (first layer): 39 mm to 22 mm. Improves the pointing resolution by x3 (r φ ) and x5 (z). Increase granularity (6 layers to 7 layers) and reduce pixel size (from 50 x 425 μ m to 20 x 20 μ m). Fast readout: pp at 1 MHz and Pb-Pb at 50 kHz.

Upgrades Muon Forward Tracker 33 ψ ’: improve the S/B by x6 with respect to the current performance. B->J/ ψ : prompt/displaced J/ ψ separation for measuring B down to zero p T. MFT 5 silicon pixel discs located in front of the absorber. MFT will improve the pointing accuracy in the vertex region. OHF: separate charm and beauty contributions at the (di)muon level.