Quarkonia and EM probe
Satoshi Yano
Hiroshima University
POST-QM2022 @ Nagoya University
30 APRIL, 2022

Quarkonia

2

Quarkonia in QGP
Sequential melting
QQQQRegeneration
QQQQQQ•

QQ_bar pairs are produced in only the initialstage of the collision3

Nuclear modification factor of prompt-J/ψ

ALI-PREL-509400•RAA of prompt-J/ψ has been measured with full statistics in PbPb @ 5.02 TeV– Increasing RAA at low pT compatible with a regeneration model•

Regeneration effect is dominant from > 200 GeV collision energy

4Elliptic flow of J/ψ

•••J/ψ v2 at RHIC is consistent with 0, but that of LHC has it
The result indicates the importance of regeneration effect on v2How about J/ψ v2 at high pT at RHIC?

5

Nuclear modification factor of ψ(2S)•••First observation of low-pT Ψ(2S) in PbPb collisions has been done
Larger RAA suppression w.r.t J/ψ has been reported
Regeneration effect can be seen at low-pT

6

Elliptic and triangular flow of ψ(2S)•••ψ(2S) v2 is larger than that of J/ψ in wide pT range
ψ(2S) v3 is consistent with zero
The difference may come from the contribution of regeneration

7

Nuclear modification factor of Υ family••First measurement of Υ(3S) nuclear modification factor has been reported
Clear hierarchy has been observed, Υ(1S) > Υ(2S) > Υ(3S)

8Beauty quark thermalization in QGP
100% thermalization••

30% thermalization

SHM is extended to beauty quark
Beauty quark with 30% thermalization describes Υ(1S) and Υ(2S)

9Beauty quark thermalization
with double ratio of Υ(3S)/ Υ(2S)

30% b thermalization• The result of the Υ(3S)/Υ(2S) double ratio indicates more thermalization?
10

EM probe
Thermal photon and dilepton

11Thermal photon and dilepton
Real photon pTspectrum

Photon emission stages

pQCD +Pre-equilibrium

•••

QGP

Hadron gas

Dilepton massspectrum

Hadron decay

The measurement of medium temperature is accessed through thermal radiation
Real photon pT spectrum has information about the matter temperature w/ blue shift effect
The dilepton mass spectrum shape is affected by the medium temperature w/o blue shifteffect12Non-prompt direct photon extraction
Direct photon•

Non-prompt
direct photon

Photon sources

Non-prompt direct photon has been measured by extracting pQCD photon– Non-prompt direct photon = direct photon – pQCD photon•

The higher pT photon is expected to be emitted at earlier stage

13

Temperature for non-prompt direct photon•

The effective temperature at higher-pT is larger than the lower-pT region••

Pre-equilibrium contribution is described by the model (pT >3 GeV/c)
The overall yield is underestimated especially below 2 GeV/c (QGP photon dominance region)– Teffhigh-pT = 376 MeV Tefflow-pT = 260 MeV

14

LMR and IMR thermal dilepton••

Similar temperatures in LMR at three different collision energies T ~ 170 MeV has been observed
Hotter QGP creation at RHIC than SPS is suggested by the IMR result– RHIC achieves TRHIC ~ 300 MeV•

Low mass thermal dilepton is emitted from the hadronic phase, around phase transition

15

Thermal dilepton at the LHC••

Virtual photon result is consistent with the real photon method
The effective temperature has been measured as Teff = 305 MeV with large uncertainty (± 197MeV)

16Photon yield puzzle••Discrepancy between PHENIX and STAR experiment was reported
ALICE points appear to be consistent with PHENIX trend17ρ/ω peak suppression
HADES AuAu @ 2.55 GeV•••HADES has observed the unexpected ρ/ω peak suppression in AuAu collisions @ 2.55 GeV at lowpT region
The similar behavior in high multiplicity pp collisions at 13 TeV has been reported
Both measurement are similar multiplicity bin dN/dη > 3018

Summary•Quarkonia– Precise excited state results have been reported• ψ(2S) RAA is smaller than J/ψ• ψ(2S) v2 is smaller than J/ψ
• RAA Υ(1S) > Υ(2S) > Υ(3S) sequential suppression has been observed• 30 % beauty quark thermalization is estimated by Υ(1S) and Υ(2S) measurement, but Υ(2S)and Υ(3S) results indicate more thermalization•EM probe– Measurement of direct photon at early stage has been reported• Early stage thermal photon has been measured in real photon and virtual photon method• Virtual photon has been measured at LHC energy

19

Back up20

Quarkonia• 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• Heavy quark hadron fraction– Quarkonium: ~1%– Open heavy quark meson: ~90%
– Open heavy quark baryon: ~9%

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)…

Q
Q

Q

Q

22

ATLAS

23

24

25

Bottomonium family suppression
Comparison with pPb
Stronger suppression w.r.t. pPb collisions has been observed
pPb 34.6 nb-1, pp 28.0 pb-1 (5.02 TeV)

1.6CMSΥ (1S)

RpPb•

1.4

Υ (2S)

1.2

Υ (3S)

Preliminary|yΥ | < 1.93CM

10.8
0.6
0.4
0.2001020pΥ (GeV/c)
T30

26

PR 889 (2020) 1-106

27

R AA

1Pb-Pb s NN = 5.02 TeV¯ (1S)Aµ+µ<

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

0.500
ALIéPRELé307082

24y28

Photon source

29

Open heavy flavor

30

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

31Key features of using HF to investigate QGP
properties•

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

QGPhQDetector

QQInteract with QGPhQ

HF is one of the cleanest probe!
32

Energy loss•

Passing partons lose their energy via elastic scattering and gluonradiation– 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/E

Radiative energy lossθGluon radiation
Gluon emission angle θ ∝ M/E
Sensitive to transport coefficient: q=μ2/λ

arXiv:2106.05713

D0 pT

33

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

Q
Short L à Small ΔE

Drift in the moving medium

Medium shape insemi-central collision

Energy loss depends on L34

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 vacuumqqq
qDiquark pair production

Quark pair production

meson baryonqq qq q
q

In QGPu ssd usd ssdussmesonqqqq

Mbaryon

Bq

Strangeness-rich environment

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

BaryonMesonpT35

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

D

Partial 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 D0b

Entries

•

B

D

105
104

Vertex

ALICE Preliminarypp, s = 5.02 TeV, |y | < 0.8
PYTHIA
Dalitz electrons
Conversion electronscAeb (A c) A e

2.00 < p < 2.50 GeV/cT103

Fit
Data
Data/Fit

102

DCA

101B/D
Primary vertex

e10<<10.2 <0.15 <0.1 <0.05
ALIéPRELé329757

00.05

0.1 0.15

0.2

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

36

Main observation•Nuclear modification factor (RAA):– Comparison of particle production in PbPb collisions with that in pp scaled by the number ofcollisions (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 the reaction plane (ψRP)
N(φ) ∝ 1+2ψRPΣ 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)

37

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 | < 0.5/±, |y | < 0.5

R AA

R AA

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

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

0.80.60.40.20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5p (GeV/ c )
T

10.8
0.6
0.40.200102030

JHEP 1810 (2018) 174
ALIéPRELé320198

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

38

R AA

Nuclear modification factor RAACharm v.s. Beauty
1.6Non-prompt D0ALICE Preliminary

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

1.40Non-prompt D

Energy loss

1.2

Prompt D0

10.8
0.6
0.4
0.2
0ALIéPRELé332574•

102030JHEP 1810 (2018) 174

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

39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

40

v2

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

30<50% Pb<Pb, s NN = 5.02 TeV/± |y | < 0.5
0++Prompt D , D , D* average |y | < 0.8
Inclusive J/ s 2.5 < y < 40.2

0.1

0.05

101520

PLB 813 (2021) 136054
ALIéDERé354787

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?

41v 2 {SP, |6d |>0.9}

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

ALICE 30<50% Pb<Pb, s NN = 5.02 TeV
0++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
LGR
PHSD
POWLANG HTLBAMPS elDAB-MOD M&T<0.11
ALIéDERé348327

23

MC@sHQ+EPOS2
LIDOCatania
LBTBAMPS 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?

42

1.8

BAMPS 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-down0.30.2prompt

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 TeV

2.50-10%, |y |<0.5

R AA

2.2v 2 {SP, |6d |>0.9}

R AA

Comparison with models

2.00.1

1

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

0.8

T

1.5
0.0

0.60.4TAMU
LGRPHSD
POWLANG HTLBAMPS elDAB-MOD M&T

<0.1

0.201

ALIéPRELé320238•102
JHEP 1810 (2018) 174 p (GeV/c )10T

1
ALIéDERé348327

23

MC@sHQ+EPOS2LIDO
Catania
LBT
BAMPS el+rad

4 5 6 7 8 910

PLB 813 (2021) 136054

1.00.520 30p (GeV/ c )5T

ALIéPRELé332624

Data

TAMU 0-20%

CUJET3

MC@sHQ+EPOS2 el.

LGR

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

1015

JHEP 1810 (2018) 17420p (GeV/c)T

There are many models, and they describe the trend well43