Heavy quark and quarkonia
Satoshi Yano(Hiroshima University)
重イオン衝突におけるダイナミクス・時空発展の統合的理解に向けた理論・実験共同研究会
2021/09/24

Open heavy flavor

2

What is heavy flavor (HF)?
•Heavy flavor (charm & beauty)– Mass: mc (~1.3 GeV/c2), mb (~4.5 GeV/c2) >> ΛQCD (~0.2 GeV)•

Produced initial hard scattering processes– Accurate interpretation by pQCD•

Short formation time– τ~1/2mq ~ 0.07 fm/c < QGP (0.1 – 1 fm/c)•Long life time
– D0: τc~ 120μm, Λ+c: τc~ 60μm
– B0: τc~500μm , Λ0b: τc~ 440μm

3Key features of using HF toinvestigate QGP properties•

Ideal probe for a tomography of QGP– Produced at only initial stage of collisions– Conservation of the number of HF quarkHadronization
Quark pair
production

QGP

hQDetector

QQ
Interact with QGP

hQ

HF is one of the cleanest probe!
4Energy loss•

Passing partons lose their energy via elastic scattering and gluon
radiation– Depending on• Color charge (Casimir factor)• Quark mass (Dead cone effect)• Path length in medium– ΔEloss(g) > ΔEloss(u,d,s) > ΔEloss(c) > ΔEloss(b)Light parton

HF quarkθ ∝ M/ERadiative energy lossθGluon radiation
Gluon emission angle θ ∝ M/ESensitive to transport coefficient: q=μ2/λ

arXiv:2106.05713

D0 pT5

Azimuthal anisotropy•

Participation in medium collective motion– Pushed by the medium as “foreign object”– Sensitive to the spatial diffusion coefficienct•Path-length dependence of energy loss
– Much energy loss with passing long distance in medium

Long L à Large ΔE

QShort L à Small ΔE

Drift in the moving medium

Medium shape insemi-central collision

Energy loss depends on L6

Coalescence•Enhancement of baryon/meson ratio w.r.t to pp collisions•Enhancement of strangeness hadron w.r.t non-strangeness hadron– In vacuum, two quark pairs should be produced at the same time to make abaryon• p:π ~ 0.2:1

In vacuumqqqqDiquark pair production

Quark pair production

meson baryonqq q

q qq

In QGPu ssd us
d ssduss

mesonqqqq

MbaryonBq

Strangeness-rich environment

Parton distribution function– Quark pair production probability depends on quark mass
• uu : dd : ss : cc ~ 1 : 1 : 0.3 : 10-11

BaryonMesonpT7

How to measure HFs?
Prompt D0

Full reconstruction– D0 à K- π+ (BR: 3.95%)– B+ à J/ψK+ à μ+μ-K+ (BR: 0.1%)•cVertex

DPartial decay product measurement– Hadron decay channel• B+ à J/ψK+– Semi-leptonic decay channel• D0 à e+ X (BR: 6.49%)• B+ à e+ X (BR: 10.99%)• B+ à D0 X (BR: 79%)

Non-prompt D0bEntries•BD105
104Vertex

ALICE Preliminarypp, s = 5.02 TeV, |y | < 0.8
PYTHIA
Dalitz electrons
Conversion electronsc→eb (→ c) → e

2.00 < p < 2.50 GeV/c
T103

Fit
Data
Data/Fit

102

DCA

101

B/D
Primary vertex

e10−−10.2 −0.15 −0.1 −0.05
ALI−PREL−329757

00.05

0.1 0.15

0.2

d 0 x sign (charge x B field) (cm)Phys. Rev. Lett. 126 (2021) 162001

8Main observation•Nuclear modification factor (RAA):– Comparison of particle production in PbPb collisions with that in pp
scaled by the number of collisions (Ncol)

RAA =

•

If no medium effects are present à RAA ~ 1
If medium effects are present à RAA ≠ 1

Ncol xElliptic flow (v2):– Study azimuthal distribution of produced particle with respect to thereaction plane (ψRP)
N(φ) ∝ 1+2
ψRP

Σ v cos{n(φ - ψ )}nRP

If the collectivity effects are present à v2 > 0 (low-pT)
If the path-length effects are present à v2 > 0 (high-pT)9Latest results

10

2.4
2.2
2
1.8

Energy loss

1.6
1.4
1.2

ALICE Preliminary
0−10% Pb−Pb, s NN = 5.02 TeV
0++Average D , D , D* , |y | < 0.5π±, |y | < 0.5R AA

R AA

Nuclear modification factor RAA
Light v.s. Charm
1.4
1.2
1

arXiv:1910.07678 (2019)
Charged particles, |η| < 0.8
JHEP 1811 (2018) 013

0.8
0.6
0.4
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5p (GeV/ c )
T

1
0.8
0.6
0.4
0.2
00

102030JHEP 1810 (2018) 174
ALI−PREL−320198

4050p (GeV/c )T•

At low-pT (<10 GeV/c): ΔEloss(light) > ΔEloss(c)•At high-pT (>10 GeV/c): ΔEloss(light) ~ ΔEloss(c)– Indicating smaller energy loss in charm hadron– Indicating the same energy loss mechanism in light and charm hadron

11R AA

Nuclear modification factor RAA
Charm v.s. Beauty
1.6

Non-prompt D0

ALICE Preliminary

Pb-Pb, s NN = 5.02 TeV
0-10%, |y |<0.5

1.4
0Non-prompt D

Energy loss

1.2

Prompt D0

10.8
0.6
0.4
0.2
0
ALI−PREL−332574•

102030JHEP 1810 (2018) 174

4050p (GeV/c)TAll pT (<20 GeV/c): ΔEloss(c) > ΔEloss(b)– Indicating smaller energy loss in beauty hadron

12Enhancement

Nuclear modification factor RAA
Meson v.s. Baryon
Charm with Strangeness v.s. Charm

JHEP 1810 (2018) 174
Phys.Lett. B793 (2019) 212-223•

At low-pT (<10 GeV/c): Baryon > Meson, Ds > D(non-strangeness)•

At high-pT (>10 GeV/c): Baryon = Meson, Ds = D(non-strangeness)– Indicating coalescence contribution– Indicating the same production mechanism

13v2

Elliptic flow (v2)Light v.s. Charm
ALICE
0.3

30−50% Pb−Pb, s NN = 5.02 TeV
π± |y | < 0.50++
Prompt D , D , D* average |y | < 0.8
Inclusive J/ ψ 2.5 < y < 40.20.1

0.05101520

PLB 813 (2021) 136054
ALI−DER−354787

2530 35p (GeV/c )T•

Almost the same v2 as light hadron•

Flattened and compatible with light hadron at high-pT ( > 7GeV/c)– Contribution from thermalized charm?
– Energy loss path-length dependence?

14

v 2 {SP, |∆η |>0.9}

Elliptic flow (v2)
Charm v.s. Beauty
0.4

ALICE 30−50% Pb−Pb, s NN = 5.02 TeV0++

Prompt D , D , D* average, |y |<0.8
Syst. from data
Syst. from B feed-down

0.3

0.2

0.1

0.0
TAMU
LGRPHSD
POWLANG HTLBAMPS elDAB-MOD M&T−0.1

1
ALI−DER−348327

23

MC@sHQ+EPOS2
LIDOCatania
LBT
BAMPS el+rad

4 5 6 7 8 910

PLB 813 (2021) 136054

20 30p (GeV/ c )TPhys. Rev. Lett. 126 (2021) 162001•Positive beauty v2!

•Beauty v2 compatible with charm v2 at high-pT– Different shape from the other particle (no significant pT dependence)– Energy loss path-length dependence?

151.8BAMPS el.+rad.

BAMPS el.

1.6

POWLANG HTL

PHSD

1.4

LIDO

Catania

TAMU

MC@sHQ+EPOS2

1.2

0++

Prompt D , D , D* average, |y |<0.8
Syst. from data
Syst. from B feed-down

0.3

0.2

prompt

ALICE 30−50% Pb−Pb, s NN = 5.02 TeV/ R AA

20.4

non-prompt

ALICE Preliminary
0−10% Pb−Pb, s NN = 5.02 TeV
0++
Prompt D , D , D* average, |y |<0.5

3.0

D0 meson

ALICE Preliminary

Pb-Pb, s NN = 5.02 TeV2.50-10%, |y |<0.5R AA

2.2v 2 {SP, |∆η |>0.9}

R AA

Comparison with models

2.00.1

1pp reference
Filled markers: measured
Open markers: p -extrapolated

0.8T

1.50.00.60.4

TAMU
LGR
PHSD
POWLANG HTLBAMPS elDAB-MOD M&T−0.1

0.201

ALI−PREL−320238

102
JHEP 1810 (2018) 174 p (GeV/c )10T

1
ALI−DER−348327

23

MC@sHQ+EPOS2
LIDOCatania
LBT
BAMPS el+rad

4 5 6 7 8 910

PLB 813 (2021) 136054

1.00.520 30p (GeV/ c )5TALI−PREL−332624

Data

TAMU 0-20%

CUJET3

MC@sHQ+EPOS2 el.

LGR

MC@sHQ+EPOS2 el.+rad.+gluon damping

1015

JHEP 1810 (2018) 17420p (GeV/c)• There are many models, and they describe the trend well

16

T

Quarkonium

17Quarkonium•

Bound state of ccbar and bbbar– Charmonium (ccbar state)• J/ψ: M = 3.096GeV/c2• Ψ(2S): M = 3.686GeV/c2– Bottomonium (bbbar state)• Υ(1S): 9.46 GeV/c2• Υ(2S): 10.023 GeV/c2• Υ(3S): 10.3552 GeV/c2•

About 1 % heavy quark pairs form quarkonium– Open heavy quark meson: ~90%
– Open heavy quark baryon: ~9%18

Melting v.s. regeneragtion
Quarkonium melting caused by Debye screening•– Depends on hadron radius (hierarchy)

RobustQ
QQ•

QQuarkonium regeneration– ~30 ccbar pairs in a collision (0-5%:PbPB@5.02TeV)

QQ
Q

QQQ

19

Comover interaction•

Quarkonium is produced in initial stage of collisions– Hadronization at very early formation time• τψ(2S) ~ 0.35 fm/c
– Dense condition even in small collision system• Possible to see the effect in small collision system (w/o QGP)

•Break-up quarkonium with passing soft particles– Depending on the radius– Sequential break-up in J/ψ, ψ(2S), Υ(1S) , Υ(2S) , Υ(3S)…

QQ

QQ

20

Latest results21

Nuclear modification factor RAA
Melting v.s. regeneration

ALI-PREL-358983

PLB 805 (2020) 135434

Obvious energy dependence of RAA(5.02 TeV) > RAA(2.76 TeV) >RAA(0.2 TeV)
• Regeneration > melting @ LHC!

•22

v2

Elliptic flow (v2)Light v.s. Open-charm v.s. Hidden CharmALICE
0.3

30−50% Pb−Pb, s NN = 5.02 TeV
π± |y | < 0.50++Prompt D , D , D* average |y | < 0.8
Inclusive J/ ψ 2.5 < y < 40.2

0.1

0.0

5
ALI−DER−354787

101520JHEP 10 (2020) 141

2530 35p (GeV/c )T•

Positive J/ψ v2•Light hadron, D, J/ψ v2 converge into single value at high-pT– Clear mass hierarchy with π±, D, J/ψ

– Energy loss path-length dependence?

23

R AAComparison with theory
1.6
ALICE Preliminary, Pb-Pb sNN = 5.02 TeV, 0-20%
2.5 < y < 4, inclusive J/ ψ

1.4
1.2
1Data, Lint ≈ 750 µb-1
Uncorrelated syst. uncertainty
Transport (Du et al.)Statistical hadronization (Andronic et al.)

0.8
0.6
0.4
0.2
0
ALI−DER−342092

•
•

2468

10JHEP 02 (2020) 041

1214

161820p (GeV/ c )TALI-PUB-347891

Phys. Rev. Lett. 119 (2017) 242301

Well description of RAA with transport model including primordial, melting,and regeneration with thermalized charmGood agreement with v2 for pT < 4 GeV/c, but large deviation from data for
4 < pT < 10 GeV/c24

Charmonium sequential
suppression in pA collisions

JHEP 06 (2016) 50••

Sequential suppression in pPb collisions!
Not described by conventional model (Eloss in nucleus + nPDF)– The same suppression for J/ψ and ψ(2S)•

Need to be considered the interaction to discuss sequential melting

25

Bottomonium
Sequential suppression

PLB 805 (2019) 270-293•Sequential suppression for Υ family– RAA(Υ(1S)) > RAA(Υ(2S)) > RAA(Υ(3S))

26

v2

Elliptic flow of bottomonium
ALICE Pb − Pb

0.2s NN = 5.02 TeV

5 − 60%2.5 < y < 4Inclusive J/ψϒ (1S)
ϒ (1S), TAMU modelϒ (1S), BBJS model

0.15
0.1
0.05
0−0.05
2
ALI−PUB−325477

46

PLB 819 (2021) 136385

810p (GeV/c )T• Υ(1S) v2 is significantly smaller than J/ψ– Υ(1S) is the only particle without v2!
– No thermalization for beauty

27

Bottomonium sequential
suppression in pA collisions••

Bottomonium sequential suppression in pPb collisions!
Same hierarchy in comover interaction model– Still tension at Pb-going direction (y<0)

28Conclusion from the experiments•Open heavy flavor– Energy loss hierarchy is observed at pT < 10 GeV/c– Energy loss hierarchy is disappeared at pT > 10 GeV/c– Charm and beauty have positive v2, but no pT dependence in beauty– Strangeness meson and baryon is enhanced•

Quarkonium– Regeneration contribution is larger than melting for J/ψ at LHC– Sequential melting is observed for Υ family in PbPb collisions– J/ψ has positive v2, but zero consistent v2 for Υ(1S)– Sequential suppression for charmonium and bottomonium in pPb
collisions (possibly) due to comover interaction has been observed29What’s next for HF?
•Why don’t you measure all objects at forward rapidity in PbPb
collisions?
– Large Lorentz boost at low-pT particle– Longer life time for low-pT (~10 times longer @ y~4)
• Precise measurement of heavy flavor baryons– Open low-pT muonic channel (e.g. BàJ/ψK, Bà J/ψXàμμX, BàμX)

Event display of B-meson decay (orange point) from LHCb

30

Short-term future•

ALICE experiment installs high precision Si tracker at forwardrapidity– Access to measure muon decay point precisely

ALICE-LoI-MFTALICE-LoI-MFT

31

Unique idea(Long-term future)•

Fixed target experiment at LHC (AFTER@LHC)– Collision energy √sNN ~ 72 GeV• Enough energy to produce QGP– With high luminosity and polarized several targets•

Forward in lab-frame, but mid-rapidity in physics (Δy~4.3)– Measure mid-rapidity physics with boosting!
– Very good opportunity for HF measurement•Novel way to search QCD phase diagram– Baryon chemical potential depends on rapidity

Phys. Rev. C98 (2018) 034905

32

Back up33

ATLAS open heavy flavor

34

BAMPS el.+rad.

BAMPS el.

1.6

POWLANG HTLPHSD

1.4

LIDO

Catania

TAMU

MC@sHQ+EPOS2

1.2

0++Prompt D , D , D* average, |y |<0.8
Syst. from data
Syst. from B feed-down

0.3

0.2

prompt1.8

ALICE 30−50% Pb−Pb, s NN = 5.02 TeV

3.02.5/ R AA

20.4

non-prompt

ALICE Preliminary
0−10% Pb−Pb, s NN = 5.02 TeV
0++Prompt D , D , D* average, |y |<0.5D0 meson

ALICE Preliminary

Pb-Pb, s NN = 5.02 TeV
0-10%, |y |<0.5

R AA

2.2

v 2 {SP, |∆η |>0.9}

R AA

Comparison with models

2.00.1

1pp reference
Filled markers: measured
Open markers: p -extrapolated

0.8

T

1.5
0.0

0.6
0.4

TAMU
LGR
PHSD
POWLANG HTLBAMPS elDAB-MOD M&T−0.1

0.201

ALI−PREL−320238•10102p (GeV/c )T1
ALI−DER−348327

23

MC@sHQ+EPOS2
LIDOCatania
LBT
BAMPS el+rad

4 5 6 7 8 910

1.00.520 30p (GeV/ c )5Data

TAMU 0-20%

CUJET3

MC@sHQ+EPOS2 el.

LGR

MC@sHQ+EPOS2 el.+rad.+gluon damping

10T

1520p (GeV/c)T

ALI−PREL−332624

There are many models, and they describe the trend well
1.5 < 2πDsTc < 7 with Tc=155 MeV

35

R AA

2.2

ALICE Preliminary
0−10% Pb−Pb, s NN = 5.02 TeV
0++Prompt D , D , D* average, |y |<0.5

2
1.8

BAMPS el.+rad.

BAMPS el.

1.6

POWLANG HTL

PHSD

1.4

LIDO

Catania

TAMU

MC@sHQ+EPOS2

1.21pp reference
Filled markers: measured
Open markers: p -extrapolated

0.8

T0.6
0.4
0.201102p (GeV/c )10T

ALI−PREL−320238

R AA

2.221.8

ALICE Preliminary
0−10% Pb−Pb, s NN = 5.02 TeV
0++Prompt D , D , D* average, |y |<0.5

1.6

Djordjevic
CUJET 3.0
SCET M,G g=1.9-2

1.4
1.2
1

Filled markers: pp measured reference

0.8Open markers: pp p -extrapolated reference
T0.6
0.40.2
5
ALI−PREL−320246

10 15 20 25 30 35 40 45 50
p (GeV/c )T36f (c ® Hc)

1.0
ALICE, pp, s = 5.02 TeV
B factories, e e-, s = 10.5 GeV+

0.8

LEP, e e-, s = mZ
+HERA, ep, DIS

0.6

HERA, ep, PHP

0.4

0.2

D0D+

D+sL+cX0c

D*+

ALI-PUB-488617

37

38

Nuclear modification factor RAA
Melting v.s. regeneration
Collision energy dependence

ALI-PREL-358983

Regeneration > melting @ LHC

Rapidity dependence

ALI-PREL-335823

Larger energy density39

v2 {EP}

0.25
ALICE 20 - 40% Pb-Pb, s NN = 5.02 TeVInclusive J/ψ
e e , |y | < 0.9, v 2{EP, ∆ η = 0}µ+µ-, 2.5 < y < 4, v 2{EP, ∆ η = 1.1}
- global syst : 1%

0.2+ -

0.15
0.1
0.05
0−0.05−0.10

K. Zhou et al. (2.5 < y < 4)
Inclusive J/ ψ w non-collective
Inclusive J/ ψ w/o non-collective
Primordial J/ ψX. Du et al.
Inclusive J/ ψ , |y | < 0.9
Inclusive J/ ψ , 2.5 < y < 4
Primordial J/ ψ , 2.5 < y < 424681012p (GeV/ c )T40

Fragmentation into charmonium

41

PR 889 (2020) 1-10642

43

R AA

1Pb-Pb s NN = 5.02 TeV

ϒ (1S)→µ+µ−

ALICE, Cent. 0-90% (arXiv:1805.04387)
CMS, Cent. 0-100% (arXiv:1805.09215)

0.500
ALI−PREL−307082

24y44

45