Heavy Flavours in ALICEmoriond.in2p3.fr/QCD/2014/FridayAfternoon/Pachmayer.pdf · 2014. 3. 28. ·...

Heavy Flavours in ALICE

Yvonne Pachmayer, University of Heidelbergfor the ALICE Collaboration

Motivation

Cold nuclear matter effects

Results from p-Pb collisions

Open heavy flavour

J/ψ, ψ(2S), ϒ(1S)

Comparison with models and Pb-Pb results

Conclusion

Moriond 2014 Yvonne Pachmayer (University of Heidelberg) 2

Physics MotivationHeavy Flavour in Pb-Pb Collisions

Cold nuclear matter effects+ hot nuclear matter effects (related to the Quark-Gluon Plasma)

D meson RPbPb

RPbPb(pT )=1

⟨T PbPb ⟩×

dN PbPb /dpT

d σ pp /dpT

Heavy-flavour quarks (c, b)

Originate from initial scattering processes

Sensitive to the full history of the collision

Excellent probes to study the de-confined medium produced in Pb-Pb collisions

Elementary collisionNo nuclear matter effects


Physics MotivationHeavy Flavour in Pb-Pb Collisions


ALICE: arXiv:1202.1383PHENIX: Phys. Rev. Lett. 98 (2007) 232301; Phys.Rev. C 84 (2011) 054912; Phys. Rev. C (2005) 049901

J/ψ RPbPb

J/ψ Meson (cc)

Original idea (1986): J/ψ suppression via colour screening discussed as probe of de-confinement

Quark-Gluon Plasma screens all charmonia, but charmonium production takes place at the phase boundary


C o l o r S c r e e n i n g

cc

Matsui, Satz PLB 178 (1986)Braun-Munzinger, Stachel PLB 490 (2000)Thews et al. PRC 62 (2000)


Control experiment for Pb-Pb measurements

Cold nuclear matter effects

Gluon shadowing or saturation

Initial state energy loss

Energy loss of incoming parton

Coherent energy loss

kT broadening of initial partons

Physics MotivationHeavy Flavour in p-Pb Collisions



Cold nuclear matter effects -without Quark-Gluon Plasma

Eskola et al., JHEP 0904 (2009) 65Kharzeev et al., arXiv:1205.1554Dominguez et al. ArXiv:1109.1250Vogt PRC 81 (2010) 044903 Arleo arXiv:1204.4609Lourenco et al., JHEP 0902 (2009) 14


A Large Ion Collider ExperimentMuon Spectrometer

Forward Muon Arm Acceptance in p-Pb/Pb-p:Forward: 2.03 < y

cms < 3.53

Backward: -4.46 < ycms

< -2.96

pT > 0 GeV/c

Semi-muonic decays:Semi-muonic decays:D, B, Λ

c, … → μ + anything

Charmonium and Bottomonium:Charmonium and Bottomonium:J/ψ, ψ(2S), Y(1S) → μ+ + μ-

p/Pb

Pb/p

μ

μ

Iron Wall 7 λi

Front Absorber 10 λi

Trigger Chambers

Tracking Chambers

μ-ID via tracksmatched withtrigger system


Central Barrel:-0.9 ≤ η ≤ 0.9p

T > 0 GeV/c

A Large Ion Collider ExperimentCentral Barrel

ITS

TPC

TRD

TOF

Semi-electronic decays:Semi-electronic decays:D, B, Λ

c, … → e + anything

Hadronic decays:Hadronic decays:D0 → K-π+ D+

s → K+K-π+

D+ → K-π+π+ D*+ → D0π+ Charmonium:Charmonium:J/ψ → e+ + e-

K π

e e

Track impact parameter and PID

D*+J/ψ


Electrons from Semi-electronic c/b Decays

Analysis strategy

Electron Identification with TOF+TPC (more suited for low pT) or

EMCal+TPC (more suited for high pT)

Subtraction of the background sources via data-tuned MC cocktail or invariant mass analysis

→ RpPb

consistent with unity

within uncertainties

RpPb( pT )=1

⟨T pPb⟩×

dN pPb /dpT

d σ pp /dpT

RpPb

= 1 → no nuclear effects



Analysis strategy




RpPb( pT )=1

⟨T pPb⟩×

dN pPb /dpT

d σ pp /dpT

RpPb


→ Prediction including initial state effects agrees with data within uncertainties


D Meson RpPb

→ Compatible results for D0, D+, D*+ and D+

S

→ All results consistent with unity

→ Models including initial state effects describe data

Comparison with models

pQCD calculation for heavy-flavour production with EPS09 parametrizations of nuclear PDF (Mangano et al., Nucl. Phys. B 373 (1992) 295. Eskola et al., JHEP 0904 (2009) 065)

CGC predictions (Fujii-Watanabe, arXiv:1308.1258)


D meson: Comparison R

pPb(p

T) and R

PbPb(p

T)

RPbPb

: suppression up to a factor of 5

at pT ~10 GeV/c for 0-7.5% most central

collisions

RpPb

: results consistent with unity

→ Suppression observed in Pb-Pb is a final state effect – charm quark in-medium energy loss


Quarkonia

Mocsy, Eur. Phys. J.C61, 2009

Matsui, Satz PLB 178 (1986)Karsch, Satz Z. Phys. C 51 (1991) 209Braun-Munzinger, Stachel PLB 490 (2000)Thews et al. PRC 62 (2000)

C o l o r S c r e e n i n g

cc

Kluberg and Satz, arXiv:0901.3831

Start of Collision Development ofQGP

Hadronisation

Braun-Munzinger and Stachel, arXiv:0901.2500


J/ψ RpPb

vs rapidity

Significant suppression at mid- and forward rapidity

Backward rapidity result consistent with no suppression

Pbp

pPb

Systematic uncertainties:coloured boxes: uncorrelatedshaded areas: (partially) correlatedgrey box at unity: fully correlated

Forward and backward: ALICE: arXiv:1308.6726

small x-rangelarge x-range


J/ψ RpPb

vs rapidity

Pbp

pPb

Systematic uncertainties:coloured boxes: uncorrelatedshaded areas: (partially) correlatedgrey box at unity: fully correlated

Forward and backward: ALICE, arXiv:1308.6726 Significant suppression at mid- and forward rapidity

Backward rapidity result consistent with no suppression

Models of CNM effects

Shadowing model CEM + EPS09 NLO (Vogt, arXiv:1301.3395)

Coherent energy loss (Arleo et al., arXiv:1212.0434) with pp data parametrization

Gluon saturation (Fuji et al., arXiv:1304.2221): Color Glass Condensate framework with CEM LO with saturation scaleQ2

s,A(x=0.01) = 0.7-1.2 GeV/c2

→ Shadowing: backward rapidity data well reproduced, strong shadowing favoured at forward rapidity

→ Coherent energy loss: y-dependence well reproduced

→ CGC calculations: underestimate the data


J/ψ RpPb

vs pT

Backward rapidity: RpPb

shows small pT dependence close to unity

Mid-rapidity: RpPb

tends to increase with pT, more precision needed

Forward rapidity: RpPb

increases with pT, consistent with unity for p

T > 5 GeV/c

Backward rapidity Mid-rapidity Forward rapidity

→ At forward rapidity data tends to favour strong shadowing→ CGC calculations underestimate data→ Coherent energy loss model overestimates suppression at forward rapidity for p

T < 2 GeV/c

p Pbp PbPb p

Vogt, arXiv:1301.3395, Arleo et al., arXiv:1212.0434, Fuji et al., arXiv:1304.2221


J/ψ: Comparison RpPb

(pT) and R

PbPb(p

T)

Backward rapidity & Forward rapidity Mid-rapidity

→ Different pT dependencies in Pb-Pb and p-Pb/Pb-p

→ Small CNM effect for pT > 4 GeV/c


One among several possible implications of RpPb

on RPbPb

interpretation

→ Small effects from extrapolated shadowing at pT > 7 (4) GeV/c

at mid (forward) rapidity→ At low p

T in Pb-Pb collisions the J/ψ yield is enhanced (or equal to)

compared with the expectation from CNM effects

Assuming 2 → 1 kinematics + factorization of nuclear effect (only nPDF as nucl. effects in pA)

Backward rapidity & Forward rapidity Mid-rapidity

J/ψ: Comparison RpPb

(pT) and R

PbPb(p

T)


ψ(2S) RpPb

vs rapidity

RpPbψ(2S)

=RpPbJ / ψ σpPb

ψ(2S)

σpPbJ /ψ

σppJ / ψ

σ ppψ(2S)

→ Strong decrease of ψ(2S)/J/ψ from pp to p-Pb→ Not described by initial state CNM effect and coherent energy loss→ Similar result as PHENIX experiment at √s

NN = 0.2 TeV (arXiv:1305.5516)


ϒ(1S) RpPb

vs rapidity

→ Similar RpPb

of J/ψ and ϒ

→ EPS09 shadowing in fair agreement within uncertainties


Conclusion

Open heavy-flavour results

Good agreement with pQCD calculations including shadowing predictions

p-Pb results confirm that the suppression in central Pb-Pb collisions is a final state effect – charm quark in-medium energy loss

J/ψ measurements

Support strong shadowing at forward rapidity and/or the coherent energy loss model

J/ψ suppression observed in Pb-Pb collisions cannot be ascribed to cold nuclear matter effects alone

ψ(2S) suppressed relatively to J/ψ by up to 45% at backward rapidity

Final state effect?

(1S) measurements show a similar suppression as the ones from ϒ J/ψ but large uncertainties (pp interpolation, limited statistics)

More measurements to come, stay tuned!More measurements to come, stay tuned!


Back-Up



→ Similar result as PHENIX experiment (√s

NN = 0.2 TeV)

PHENIX: Phys. Rev. Lett. 109 (2012) 242301

Analysis strategy




RpPb( pT )=1

⟨T pPb⟩×

dN pPb /dpT

d σ pp /dpT

RpPb



D Meson RpPb

: Comparison with Models

→ Compatible results for D0, D+, D*+ and D+

S

→ All results consistent with unity

→ No rapidity dependence observed (within narrow y range)

Comparison with models

pQCD calculation for heavy-flavour production with EPS09 parametrizations of nuclear PDF (Mangano et al., Nucl. Phys. B 373 (1992) 295. Eskola et al., JHEP 0904 (2009) 065)

CGC predictions (Fujii-Watanabe, arXiv:1308.1258)

→ Models including initial state effects describe data

Heavy Flavours in ALICEmoriond.in2p3.fr/QCD/2014/FridayAfternoon/Pachmayer.pdf · 2014. 3. 28. ·...

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