Heavy-flavour productions in the relativistic
heavy ion collisions at the LHC
Shingo Sakai, Univ. of Tsukuba

Heavy Flavour (HF) in pp, p-Pb & Pb-Pb! Heavy-flavour (charm & beauty) production!

Initial hard scatterings (MHF >> ΛQCD)! pp collisions

Test for perturbative QCD (pQCD)! Reference for heavy ion collisions (both experiment & theory)!

! Heavy ion collisions

Created in initial parton-parton scatterings! Traverse and interact with the hot & dense QCD matter!

A good probe to study properties of the QCD matter! Energy loss (RAA), collectivity (v2), hadronization!

! pA collisions!

Control measurement for heavy ion collisions to disentangle
initial from final state effects!

2

Cold nuclear matter effect on heavy-flavour production

Energy Loss of heavy flavours! In-medium parton energy loss
! Radiative energy loss (PLB 632, 81)! gluon bremsstrahlung! smaller energy loss for heavy than for light quarks
due to “dead cone” effect (PLB 519 (2001) 199.)! energy loss depends on the colour charge and islarger for gluons than for quarks! Collisional energy loss (PLB 649, 139)
! energy loss via elastic scattering! Theoretical predictions:! mass & colour charge dependence of energy loss
! Eloss(g) > Eloss(u,d,s) > Eloss(c) > Eloss(b)Nuclear modification factor

π
AA

R
3

D
AA

<R

B
AA

<R

?

d N AA dpTRAA ( pT ) =TAA × dσpp dpT

Azimuthal anisotropy of Heavy flavoursｙ" Elliptic flowdN/d(φ-ψRP) = …+ N0(1+2v2cos(2(φ-ψRP))) +…

ｘ! Transfer initial spatial anisotropy

to momentum anisotropy
Initial spatial anisotropy# macroscopic: hydro model=> pressure gradient# microscopicpｙ=> scattering in the medium! Low pT
! coupling of heavy quarks withthe medium and their thermalizationp! Intermediate pT!Hadronization mechanism (recombination)ｘ! High pT
Momentum space anisotropy! Path-length dependence of energy loss
4of particle emission

! Heavy-flavour results in pp collisions

5Charm production in pp collisions
CMS-HIN-16-005

JHEP1603(2016)159

pp, s=7 TeV
102
Prompt D0, |y|<0.5
ALICE

T

d2σ/(dp dy ) (µb GeV-1 c )JHEP 1201 (2012) 128

10

FONLL

5 TeV
1

7 TeV
10−1
0

13 TeV± 3.5% lumi, ± 1.3% BR uncertainty not shown

2

4

6

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10

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p (GeV/c )ALI−PUB−111909

T! D meson production mid- and forward-rapidity is in good agreementwith pQCD calculations! upper side of the FONLL uncertainty band
! various energies: 5.02, 7 and 13 TeV! from pT = 0 to 100 GeV/c
6

Beauty production in pp collisions
CMS-DP-2016-016

JHEP 04 (2012) 084

b-jets! B meson production is in good agreement with pQCD calculations! FONLL is better agreement from low pT to high pT! PYTHIA overestimates at lower pT! b-jet production is also well represented by a pQCD (NLO)
7

HF production in pp collisions
Phys. Rev. D 86, 112007

c->e + b->e (eHF)

Phys. Lett. B 708(2012) 265

c->µ + b->µ (µHF)! Productions of leptons (e,µ) from charm+ beauty decays in different rapidity ranges
are also well described by pQCD calculations
8

! Heavy-flavour results in p-Pb collisions

9p-A collisions! Heavy-flavour in p-A collisions!

control measurement for heavy-ion collisions todisentangle initial (cold nuclear matter effects) from final
state effects! Cold nuclear matter effects!

nuclear modification of Parton
distribution Functions (PDF):
shadowing or gluon saturation
K.J. Eskola et al., JHEP 0904(2009)65
H. Fuji & K. Watanabe, NPA 915 (2013) 1

energy loss I. Vitev et al., PRC 75(2007) 064906! kT broadening (Cronin enhancement)! multiple collisions!

A.M. Glenn et al., PLB 644(2007)11910€

d N pPb dpT
R pPb ( pT ) =TAA × dσpp dpT

RpPb of D, B and eHF at mid-rapidity
R pPb

PRL 113 (2014) 232301

PRL 115 (2016) 032301

Phys. Lett. B 754 (2016) 81-93
2.5

ALICE

1.6
1.4

0

+

*+

Average D , D , D-0.96<y cms<0.04

2

1.2

eHF

R pPb

0.8

1

0.6

0.2

ALICE

1.5

1

0.4

p−Pb, s NN = 5.02 TeV
c,b → (e+ + e-)/2, −1.065 < y cms < 0.135

p-Pb, s NN=5.02 TeV

D mesonKang et al.: incoherent multiple scattering
Sharma et al.: coherent scattering + CNM
FONLL + EPS09NLO shad.
Blast wave calculation
Normalisation uncertainty

0.5

CGC (Fujii-Watanabe)
pQCD NLO (MNR) with CTEQ6M+EPS09 PDF
Vitev: power corr. + k broad + CNM Eloss
T

0
0

5

10

15

20

25

p (GeV/c )T

ALI−PUB−79415

0

2

4

6

8

10

p (GeV/c )ALI−PUB−100497

T! RpPb of D mesons, B mesons and eHF is consistent with unity! No significant cold nuclear matter effects on heavy-flavour production! Theoretical calculations with CNM effects are consistent with data
! predict a small suppression at low pT due to gluon saturation at low x! Possible enhancement due to radial flow is predicted small based on
Blast-wave model [PLB 731 (2014) 51]
11

12

RpPb of c-jets and b-jets at mid-rapidity
CMS-HIN-15-012

PLB 754 (2016) 59

c-jet
b-jet

! Measured c-jet cross section in p-Pb is consistent with PYTHIA simulation! RpPb of b-jet with PYTHIA-based estimation is consistent with unity! considering the uncertainty on the PYTHIA reference12

D production at forward-backward rapidity
2
LHCb
CTEQ6M+EPS09NLO

2

LHCb preliminarysNN=5 TeV
Backward

1.5

RFB

1.5

2.5

LHCb preliminarysNN=5 TeV
Forward

RpPb

RpPb

LHCB-CONF-2016-003

LHCb
CTEQ6M+EPS09NLO

LHCb preliminary
pPb sNN=5 TeV

2.5 < |y*| < 4

1

1.5

1
1

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0.5

0
0

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pT [GeV/c]

0
0

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pT [GeV/c]

00stat. uncert.
total uncert.
CTEQ6M+EPS09NLO

2

4

6

! D0 production at forward and backward rapidity! forward: p-going, 1.5 < y < -4
! backward: Pb-going, -5 < y < -2.5
! Significant D0 production asymmetry in forward – backward rapidity regions! Measurements are consistent with a theoretical calculation! NLO with CTEQM and EPS09NLO
13

8pT [GeV/c]

B->J/Ψ production at forward-backward rapidity
JHEP 02 (2014) 072! B->J/Ψ production at 1.5 < η < 4.0 (forward) and -5 < η < -2.5 (backward)! RFB of B->J/Ψ is asymmetry! backward yield is suppressed w.r.t. forward yield! RFB of B->J/Ψ is larger than RFB of prompt J/Ψ
! indicate cold nuclear matter effect is less pronounced for b hadrons14

! Heavy-flavour results in Pb-Pb collisions

15

D mesons in central Pb-Pb collisions
JHEP 03 (2016) 081, JHEP 03 (2016) 082

CMS-HIN-16-001! Strong suppression of D mesons production! similar magnitude of suppression in 2.76 and 5.02 TeV! suppression observed up to 100 GeV/c at 5.02 TeV! DS tends to larger : a hint of recombination process! Suggest significant energy loss of charm in the medium
16

eHF & µHF production in Pb-Pb collisions
40-50% (eHF), 40-80%(µHF)

2
Pb-Pb, sNN = 2.76 TeV
Centrality class 0-10%

1.8

RAA

R AA

0-10%
ALICE Preliminary

1.8

1.6
1.4
1.2

2

e±←HF*, -0.6<y<0.6

1.6µ±←HF, 2.5<y<4

1.4

Syst. uncertainty

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p (GeV/ c )ALI−PREL−101085

T

Heavy flavour decay µ± 40-80% central, 2.5<y<4.0
Heavy flavour decay e± 40-50% central, |y|<0.6
with pp ref. scaled cross section at s = 7 TeVwith pp ref. FONLL calculation at s = 2.76 TeV

0.4±(*) e ←W contribution not subtracted

0

Pb-Pb, sNN = 2.76 TeV

0.2
0
0

HFM: Phys. Rev. Lett. 109 (2012)
2

4

6

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T

! Strong suppression of eHF (|y|<0.6) & µHF (2.5<y<4) in central collisions! similar suppression of eHF & µHF in different rapidity regions! less suppression in mid-central collisions in both rapidity regions! high pT: large contribution from beauty! Suggest significant energy loss of charm and beauty in the medium
ALI−DER−53851

17

16

18

p (GeV/c)

RAA of B meson decays (B->e & B->J/Ψ)RAA

JHEP 1205 (2012) 063
2.5

Pb-Pb, s NN = 2.76 TeV, 0-20% centrality2b (A c) A e, |y| < 0.8
syst. uncertainty
nomalization uncertainty

1.5

1

0.5

ALICE Preliminary
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6

7

8

p (GeV/c )ALI−PREL−74678

T! Suppression of B->e and B->J/Ψ at high pT! lower pT : tends to follow binary scaling (consistent with unity)! high pT (> 3 GeV/c): RAA ~ 0.4-0.5! Suggestions of beauty energy loss in the dense QCD matter
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RAA of charged particles, D and B->J/Ψ
CMS-PAS-HIN-16-001
R AA

JHEP 1511 (2015) 205, CMS-PAS-HN-12-014
1.4

Pb-Pb, sNN = 2.76 TeV
π± (ALICE) 8<p <16 GeV/ c , |y |<0.8
T
D mesons (ALICE) 8<p <16 GeV/ c , |y |<0.5
T
Non-prompt J/ ψ (CMS Preliminary)
6.5<p <30 GeV/ c , |y |<1.2 CMS-PAS-HIN-12-014

1.2

T

1

(empty) filled boxes: (un)correlated syst. uncert.
(*) 50-100% for non-prompt J/ ψ

0.8
0.6
0.4

50-80%*

40-50%
30-40%

0.2

20-30%±π shifted by +10 in 〈N part〉00
ALI−DER−93725

50

100

150

200

10-20%

250

300

0-10%

350

400

〈N part〉! The magnitude of D meson suppression is similar to charged particles (π)
within uncertainties! can’t conclude on the expectation : RAA (D) > RAA (π)! RAA of D meson is smaller than RAA of B->J/Ψ
! indication of smaller energy loss of beauty than charm
19

Beauty jet
PRL 113 (2014) 132301! Heavy-flavour jets: allow to address energy loss at parton level! Observed strong suppression of b-jets in most-central collisions! similar magnitude of suppression to inclusive jet! high pT b-jets: largely comes from gluon splitting
20

Imbalance of pairs of b jets

CMS-HIN-16-005! Sub-leading recoil jets
! larger path-length, primary b-jets from flavour creation! Toward increasing imbalance with increasing centrality! similar imbalance as inclusive dijet
21b-bAzimuthal anisotropy of D mesonsv2

PRC 90 (2014) 034904
0.6

Pb-Pb,

0

Prompt D |y |<0.8, v 2{EP}

0.6

ALICE

0.6

Syst. from datasNN = 2.76 TeV

Syst. from B feed-down

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Centrality 10-30%

Centrality 0-10%
2Charged particles, v 2{EP,|∆ η|>2}

10 12 14 16 18

p (GeV/c )
T

2

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Centrality 30-50%

10 12 14 16 18

p (GeV/c )
T

2

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10 12 14 16 18

p (GeV/c )T

ALI−PUB−70100! Non zero D v2 at low pT! Tends to get large from central (0-10%) to mid-central (30-50%)! Hydrodinamical behavior! Consistent with charged particle v2! Charm quarks participate to the collective motion of the system
22

Azimuthal anisotropy of eHF and µHF
v2

eHF : arXiv: 1606.00321, µHF: PLB 753 (2016) 41-56
0.5

0-10% Pb-Pb, s NN = 2.76 TeV

0.5
0.4

0.4

10-20% Pb-Pb, sNN = 2.76 TeV
e± ← HF, v 2{EP, |∆η| > 0.9}, |y | < 0.7

0.5
0.4

0.3

µ± ← HF, v 2{2, |∆η| > 1.7}, 2.5 < y < 40.3

0.2

0.2

0.2

0.1

0.1

0.1

0

0

0

−0.1

0.1

0.1

0.3

−0.2

ALICE

0

2

4

ALI−PUB−106769

6

8

0.2
10 12
0
p (GeV/ c )
T

2

4

6

8

0.2
10 12
0
p (GeV/c )20-40% Pb-Pb, s NN = 2.76 TeV

2

4

6

8

T

! Non-zero v2 of eHF at |y|<0.7 and µHF at 2.5<y<4! the magnitude is compatible in mid- and forward-rapidities! v2 of eHF measured from pT > 0.5 GeV/c! similar pT dependence to other light hadron v2! v2 at high pT eHF and µHF reflects beauty! Charm quarks participate to the collective motion of the system
23

10 12
p T (GeV/c )Comparison with models (1)+*+ALICE D , D , D average, |y|<0.5

1

Pb-Pb, sNN = 2.76 TeV
Centrality 0-20%

0.8

WHDG rad+coll
POWLANG
Cao, Qin, Bass
Aichelin et al, Coll+LPM radBAMPSTAMU elastic
UrQMD

0.6
0.4
0.2
0
0

2

4

6

8

10

12

14 16
p (GeV/c)T

ALI−DER−48662

2

1.8
1.6

µ ←HF

0

ALICE Preliminary
Pb-Pb, sNN = 2.76 TeV, 0-10% central

R AA

1.2

Heavy flavour decay electron RAA

RAA

JHEP09(2012)112

1.2

1.4
1.2

1

1

0.8

0.8

0.6

0.6

0.4

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0.2

0.2

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ALI−PREL−77686

0

10 12 14 16 18
p (GeV/c)

0

2

4

6

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ALICE Preliminary

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14

16

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20

p (GeV/c )ALI−PREL−101250! Theoretical calculations! initial: with/without cold nuclear matter from PDF! medium modeling: Hydro, Glauber, parton transportation! interaction: radiative, collisional, resonant interaction! hadronization: fragmentation, coalesence! Models represent RAA of D mesons, eHF and µHF! mid- and forward-rapidity regions! high pT leptons (e,µ) mainly from beauty decay
24

Pb-Pb, sNN = 2.76 TeV
2.5 < y < 4Centrality class 0-10%µ±←HF
MC@sHQ+EPOSBAMPS elastic
TAMU elastic
Syst. uncertainty

1.8
1.6

with pp ref. from scaled cross section at s = 7 TeVwith pp ref. from FONLL calculation at s = 2.76 TeVBAMPS el.
BAMPS el. + rad.
TAMU
POWLANG
MC@sHG+EPOS,Coll+Rad(LPM)

1.4

2

T

BAMPS: J. Phys. G 38 (2011) 124152,
POWLANG: Eur. Phys. J C
71(2011)1666,
UrQMD: arXiv:1211.6912,J. Phys. Conf.
Ser. 426,012032(2013),
TAMU: Phys. Rev. C 86 (2012) 014903,
WHDG: J. Phys. G38(2011)124114,
Aichelin: Phys. Rev. C79(2009)044906,
J. Phys. G37(2010)094019
Cao,Qin, Bass: arXiv:1308.0617

Comparison with models (2)0+1

Pb-Pb, sNN = 2.76 TeV
Centrality 0-20%

0.8

WHDG rad+coll
POWLANG
Cao, Qin, Bass
Aichelin et al, Coll+LPM radBAMPSTAMU elastic
UrQMD

0.6
0.4

0.4

4

6

8

10

12

14
16
p (GeV/c)T*+

Pb-Pb, sNN = 2.76 TeV
Centrality 30-50%

0.2
0.1

-0.1
2

+

ALICE D ,D , D average
Syst. from data
Syst. from B feed-down

0.3

0

0.2

ALI−DER−48662

0*+

ALICE D , D , D average, |y|<0.5

00

PRC 90 (2014) 034904
v2

RAA

JHEP09(2012)112
1.2

0
ALI−DER−48710

WHDG rad+coll
POWLANG
Cao, Qin, Bass
Aichelin et al, Coll+LPM rad
BAMPS

2

4

6

8

TAMU elastic
UrQMD

10

12

14
16
p (GeV/c)T! Theoretical calculations! initial: with/without cold nuclear matter from PDF! medium modeling: Hydro, Glauber, parton transportation! interaction: radiative, collisional, resonant interaction! hadronization: fragmentation, coalesence! Large suppression and non-zero v2 (at low pT) are represented by models,
but simultaneous reproduction of the RAA and v2 is challenging
25

Comparison with models (3)! Experimental result! RAA(D) < RAA(B->J/Ψ)! Theoretical model! radiative + collisional energy loss
! used two masses (charm andbeauty) for calculating B->J/Ψ RAA
to study mass dependence! result using beauty mass well
represents centrality dependenceof RAA (B->J/Ψ)! the difference between D meson
and B->J/Ψ is mainly from massin this model

26

Summary! Heavy-flavour measurements at LHC

D, B, leptons from heavy flavours, c-jet and b-jet! The productions are well described by pQCD calculations in pp
collisions!

! Pb-Pb collisions!

Strong suppression of heavy-flavour yield!

Clear indication for substantial energy loss of charm and beauty inthe hot and dense matter$ Not observed such suppression in pPb!

!

Results indicate beauty lose smaller energy than charm

Non-zero & centrality dependence of v2!

Suggest strong re-interaction in the medium! Heavy flavours observed to be significantly affected by

hot and dense QCD medium

27