Heavy flavor measurements in ALICEand future prospects
2nd TCHoU research center, member meeting, 18 Dec 2023
Jonghan ParkPhysics Motivation
A Large Ion Collider Experiment aims at investigating a strongly coupled color-deconfined
medium, known as quark-gluon plasma (QGP), created in ultrarelativistic heavy-ion collisions

Test for pQCD calculations,
Cold Nuclear Matter (CNM) effects
Reference for p–Pb and Pb–Pb
Characterization of high multiplicity eventsand search for collectivity in small systems
Jonghan Park (Univ. of Tsukuba)

Energy loss, collectivity, andhadronization modified in QGP

2nd TCHoU member meeting, 18 Dec 2023

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Physics Motivation
Why heavy quarks?

• Experience the full system evolution✓ Produced in initial hard scattering process✓ Not created and destroyed while traversing the medium➡ Flavor conservedDB

mc ∼ 1.3 GeV/c 2; mb ∼ 4.5 GeV/c 2; mQ ≫ ΛQCD
τprod = ℏ/4mc(b) ≃ 0.1(0.02) fm/c < τQGP ≃ 0.3 fm/c at LHC• Interact with medium constituents and lose their energy
via collisional and radiative processes✓ Color charge and quark mass dependence

4for quark; CA = 3 for gluon
Casimir color factor : CF =3• Participation in the collective expansion, thermalizationin the medium

Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

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ALICE detector (Run 2)
ElectroMagnetic Calorimeter

Central Barrel : |η| < 0.9• eID

Inner Tracking System• vertex reconstruction• tracking

Time Of Fight• PID

Time Projection Chamber• tracking and PID
0− +D →K πD+ → K−π +π +*+0 +D →Dπ
Ξ0c → Ξ−π +, Ξ0c → Ξ−e+νe
Ξ+c → Ξ−π +π +0− +Ωc → Ω π+− ++0Λc → pK π , Λc → pKs+ −,+Σ0,++→
Λcπcb, c → e
V0 (2.8 < η < 5.1; −3.7 < η < −1.7;)

Data samples (Run2)
min. Bias trigger~32 nb−1
pp 13 TeV
p–Pb 13 TeV. ~6 nb−1
Pb–Pb 13 TeV ~114 μb−1

Muon Arm (−4 < η < −2.5)• mID• tracking• trigger• trigger• centrality determination

Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

4Nuclear modification factor (RAA)
dN/dpT• Heavy quarks interact with medium constituents✓ Low pT : elastic collisions with medium constituents(diffusion Brownian motion, possible thermalizationin the medium)✓ High pT : radiative energy loss (gluon emission)➔ dead-cone effect

Energy loss shifts
spectrum to lower pT

p+p
A+A

1
Gluonstrahlung probability ∝[θ 2 + (mQ /EQ)2]2
RAApT

1

RAA = 1 ➔ no medium modification
Nuclear matter effects(energy loss is dominant)

1 dNAA /dpT
RAA(pT) =Ncoll dNpp /dpT
pT
Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

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Anisotropic flow
• Interaction among medium constituents converts the initialgeometrical anisotropy of the fireball into momentum
anisotropy of final-state• Quantified by the Fourier decomposition of the azimuthal
distribution of particles:∞dN∝1+2
vn ⋅ cos[n(φ − ΨRP)]∑dφn=1

Coordinate space:
Initial asymmetry
Jonghan Park (Univ. of Tsukuba)

Momentum space:
Final anisotropy

vn = ⟨cos[n(φ − ΨRP)]⟩✓ Direct flow (v1) : probes the early electromagnetic field inmedium✓ Elliptic flow (v2) :➡ low pT : sensitive to the participation in the collective motion
and in the thermalization of heavy quarks➡ high pT : sensitive to path-length dependence of energy loss
✓ Triangular flow (v3) : originate from event-by-event fluctuationsin the initial distributions of participant nucleons in the overlap
region2nd TCHoU member meeting, 18 Dec 2023

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Nuclear modification factor : prompt D mesons
R AA

JHEP 01 (2022) 174 : Pb–Pb 0–10%, 30–50%
JHEP 10 (2018) 174 : Pb–Pb 60–80%
JHEP 12 (2019) 092 : p–Pb

1.8

ALICE

1.6

Pb-Pb, sNN = 5.02 TeV

1.40+

1 dNAA /dpTRAA(pT) =Ncoll dNpp /dpT

0-10%30-50%

60-80%

p-Pb• Prompt D meson average nuclear modification
factors in different centrality classes in Pb–Pbcollisions and p–Pb collisions+Average D , D , D*|y | < 0.5• Observed suppression at intermediate and high pT

1.2✓ Suppression increases from peripheral to central
collisions in Pb–Pb collisions✓ Increasing medium density, size, and lifetime of thefireball10.80.6• RAA in p–Pb collisions is compatible with unity within
uncertainty

0.40.205

10 15

20 2530 3540 4550

✓ Suppression in PbPb collisions is due to final-state
effects induced by the formation of a hot and dense
QGP mediump (GeV/c )ALI−PUB−501932

Jonghan Park (Univ. of Tsukuba)T

2nd TCHoU member meeting, 18 Dec 2023

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0
Nuclear modification factor : non-prompt D

JHEP 12 (2022) 126• Observed larger suppression for prompt D0
compared to non-prompt D0✓ Mass dependence of in-medium energy loss▵Ec > ▵Eb✓ Well described by TAMU, CUJET3.1, LGR
and MC@sHQ+EPOS2 model predictions
within uncertainties → all models include
both collisional and radiative energy lossmechanisms• Coalescence can explain the intermediatepT trend: prompt D0 acquire a higher
momentum than the parent charm quark→ hardening of the pT spectra

Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

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Nuclear modification factor : heavy flavor electrons• Large suppression in the intermediate and high pT region✓ RAA(b(→c)→e) ≈ RAA(b(→c)→μ) → no dependence on decay channel✓ No significant pT dependence for pT > 8 GeV/c✓ RAA of b(→c)→e is slightly higher than that of b,c→e while both are merged at high pT→ beauty contribution is dominant

1.8R AAR AA• Comparable with various models within uncertainties
ALICE

1.6

0−10% Pb−Pb, sNN = 5.02 TeV

1.4c, b → e
PLB 804 (2020) 135377

1.2ATLAS, c → µ, |η|<21

PLB 829 (2022) 137077

1.8b (→ c) → e|y|<0.8|y|<0.6

1.2

0.6

0.4

0.40.20.200152025300p (GeV/c )ALI-PUB-566933

Jonghan Park (Univ. of Tsukuba)

MC@sHQ+EPOS2PHSD
LIDO

10.6

100−10% Pb−Pb, sNN = 5.02 TeV

1.4b (→ c) → e|y|<0.8|y|<0.6

0.8

5ALICE

1.6

0.80

Phys. Rev. C 108 (2023) 034906

T510152025p (GeV/c )ALI-PUB-566943

T

2nd TCHoU member meeting, 18 Dec 2023

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Elliptic flow (v2) : heavy flavor hadrons• Elliptic flow (v2) of heavy flavor hadrons✓ Positive v2 for prompt non-strange D mesons✓ Positive v2 for J/ψ
✓ Positive v2 for b→e• ϒ(1S) v2 compatible with zero
• Looking more in details at different pT regions:✓ For pT < 3 GeV/c → quark-mass ordering➡ v2(ϒ(1S)) ≲ v2(b→e) ~ v2(J/ψ) < v2(D) < v2(π)✓ For 3 < pT < 6 GeV/c → effects of coalescence for Dmesons (c quark + light quarks)➡ v2(J/ψ) < v2(D) ~ v2(π)

ALI-PUB-352028

JHEP 09 (2018) 006 : pions
PLB 813 (2021) 136054 : prompt DJHEP 10 (2020) 141 : include J/ψ
PRL 126, 162001 (2021) : b→ePRL 123, 192301 (2019) : ϒ(1S)
Jonghan Park (Univ. of Tsukuba)✓ For pT > 6 GeV/c → consistent with similar path-length
dependence of the energy loss for light and heavyquarks➡ v2(J/ψ) ~ v2(D) ~ v2(π)

2nd TCHoU member meeting, 18 Dec 2023

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0Elliptic flow (v2) : non-prompt D• Observed lower non-prompt D0 v2 than prompt D meson v2 in 2 < pT < 8 GeV/c and compatiblewith b→e elliptic flow

✓ Different degree of participation to the collective motion of the medium between charm and beautyquarks• Comparable with models including hadronization via coalescence in addition to fragmentation
EPJC 83 (2023) 1123

Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

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Heavy flavor hadrons in small systems• Production cross section of heavy flavor hadrons can be described by the factorization approach:parton distribution functions (PDFs), partonic cross section, and fragmentation fuctions (FFs)
hard22
hard22σAB→h = PDF(xa, Q )PDF(xb, Q ) ⊗ σab→c(xa, xb, Q ) ⊗ Dc→h(z = ph /pc, Q )parton distributionfunction (PDFs)

hard scatteringcross section(pQCD)

fragmentation
function(hadronization)

Fragmentation functions (non perturbative) are
assumed to be universal among collision systems
and constrained from measurements in e+e− ande−p collisions

Ratios of particle species are sensitive to heavy quark hadronization
Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

120+
Production cross section : prompt/non-prompt D /D
d2σ/(dp dy ) (µb GeV-1 c )|y | < 0.5pp, s = 5.02 TeV

0102
10110-1

10-2

data
model

data
model

pp, s = 5.02 TeV

102101• Precise measurements of|y | < 0.5prompt and non-prompt D
meson production crosssections over wide pT range

Prompt D+
Data
GM-VFNS
Non-prompt D+
Data
GM-VFNS b Æ D
GM-VFNS b Æ Hb Æ D

10-1

10-2
10-3±2.1% lumi. unc. not shown±0.8% BR unc. not shown

321100

data
model

data
model

10-3

10ALICET

Prompt D
Data
GM-VFNS
Non-prompt D0
Data
GM-VFNS b Æ D
GM-VFNS b Æ Hb Æ D

35101520253035p (GeV/c )T

53021505101520253035p T (GeV/c )1015

ALI−PUB−496371

Jonghan Park (Univ. of Tsukuba)

20253035p (GeV/c )
T

data
model

10ALICE

data
model

3

T

d2σ/(dp dy ) (µb GeV-1 c )JHEP 05 (2021) 220±2.1% lumi. unc. not shown±1.7% BR unc. not shown

32
1100

51015202535p (GeV/c )
T

530
21505

ALI−PUB−496375

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101520253035✓ Described within
uncertainties by pQCDmodel calculations✓ GM-VFNS predictions
underestimate non-prompt
D meson cross section✓ Data provides good
constraints for models(experimental uncertainties
are smaller than that oftheoretical ones)p T (GeV/c )101520253035

p (GeV/c )T

2nd TCHoU member meeting, 18 Dec 2023

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Charm meson production in pp collisions• Independent meson-to-meson ratios in transverse momentrum pT• FONLL calculations (pQCD) correctly describe the data
✓ Using fragmentation functions from e+e−, e−p measurements

1.2ALICE|y | < 0.5

pp, s = 5.02 TeV
Prompt
Data
FONLL

1.0

Non-prompt
Data
FONLL + PYTHIA8 Dec.

0.8

D+s / (D0+D+)+D /D0•Higher Ds/D0+D+ ratios for non-prompt D mesons, due to relevant contribution to Ds from B0, B+decays
0.8

ALICE pp, s = 5.02 TeV |y | < 0.5
0.7
0.6

PromptData

Non-prompt
Data
FONLL + PYTHIA8 Dec.
+0+00
Ds ← B +B +Bs+ΛbD+s ← B0+B+D+s ← B0s

0.5
0.4

0.6

JHEP 05 (2021) 220

0.3
0.4
0.2
0.2

0.1
±1.9% BR uncertainty not shown02468101214160Jonghan Park (Univ. of Tsukuba)

T4681012p (GeV/c )p (GeV/c )ALI−PUB−496383

2

ALI−PUB−496387

T

2nd TCHoU member meeting, 18 Dec 2023

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Charm baryon production in pp collisions• First measurement of Λc production down to pT = 0in small system+0Λc / DPRL 127, 202301 (2021)

1• Enhancement of prompt Λc/D0 ratio at low andALICEpp, s = 5.02 TeVPYTHIA 8 (Monash)
PYTHIA 8 (CR Mode 2)
HERWIG 7Catania, fragm.+coal.
M. He and R. Rapp:
SH model + PDG
SH model + RQM

0.50
ALI−PUB−499774

Jonghan Park (Univ. of Tsukuba)

510p (GeV/c )Tintermediate pT w.r.t e+e− results• Described by :✓ Significantly underestimated by PYTHIA 8 Monash tune
(which incorporates fragmentation parameters frome+e− data)✓ PYTHIA 8 with color-reconnection beyond leading color(CR-BLC) → "junction" topology enhances charmbaryon production✓ Catania model → thermalized system of u, d, s andgluons; hadronization via coalescence in addition tofragmentation✓ Statistical Hadronization Model and Relativistic Quark
Model → strong feed-down from augmented set ofexcited charm baryons➡ PDG : 5Λc, 3Σc, 8Ξc, 2Ωc➡ RQM : 18Λc, 42Σc, 62Ξc, 34Ωc
2nd TCHoU member meeting, 18 Dec 2023

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Charm baryon production in pp collisions
PRL 127 (2021) 272001

arXiv:2308.04877

ALI-PUB-561515

ALI-PUB-521755• Clear pT dependence• Significantly underestimated bymodels

Jonghan Park (Univ. of Tsukuba)• Agreement with PYTHIA 8•

Monash tune
Similar enhancement w.r.t e+e−0,+0,+,++for Ξc and Σc• No pT dependence• Catania closer to themeasurements when additional
resonances are considered

2nd TCHoU member meeting, 18 Dec 202316

f (c Æ Hc)

Charm fragmentation fractions at LHC
1.0
ALICE, pp, s = 5.02 TeV(PRD 105, L011103 (2022))

0.8

ALICE Preliminary, p-Pb, sNN = 5.02 TeV+ -B factories, e e , s = 10.5 GeV+ -LEP, e e , s = m Z

0.6

HERA, ep, DIS
HERA, ep, PHP

0.4

0.2

0.00DD+D+sΛ+cΞ0c

ALI−PREL−541012• Charm fragmentation fractions at LHC✓ Independent of center-of-mass energy and system size
✓ Significant enhanced for charm baryons w.r.t dd and ep collisions➡ breaking of the universality of fragmentation functions• Charm quark production cross section at midrapidity is at the upper boundary of state-of-the-art
pQCD calculations

Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

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ALICE detector in Run 3
In Run 3 and Run 4✓ 500 kHz in pp / up to 50 kHz in Pb–Pb✓ 200 pb−1 in pp / 10 nb−1 in Pb–Pb

Inner Tracking System• 7 pixel layers• More granularity• Closer to the beam pipe
• Reduce material budget• Improved pointing resolution

Muon Forward Tracker• 5 planes of MAPS
• vertexing and tracking for muon

Improved impact parameter resolution, in particular
for low pT, in order to select more effectively decay
vertices of heavy-flavor mesons and baryons
Jonghan Park (Univ. of Tsukuba)

Time Projection Chamber• New readout chambers with GEM• Continuous readout

2nd TCHoU member meeting, 18 Dec 2023

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• Ability to measure B hadrons via full reconstruction✓ Significant increase of signal to background ratio for Bs• Understanding of in-medium energy loss, hadronization

mechanism, thermalization in the medium via B hadrons

R AAPerformance in Run 3
3.5 ALICE Upgrade Projection
0-10% Pb-Pb, s NN = 5.5 TeV-10
3.0 L int = 10 nb
Bs Æ D-s π+
ITS2
2.5
ITS3TAMU
2.0B0sB (non-strange)
1.5

S/B

1.0
0.5

1010-1

ALICE Upgrade Projection

0Bs Æ D-s π+

00 -10% Pb-Pb, s NN = 5.5 TeVL int = 10 nb-1

246810 12 14 16 18 20p (GeV/c )ALI−SIMUL−348369

T-2

ITS2
ITS3
10-3

Unc. signal estimation
Unc. background estimation

05

ALI−SIMUL−348451

1015p (GeV/ c )T

ALI-SIMUL-308758

ALI-SIMUL-308740

Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

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Summary and Outlook• Heavy flavor measurements with ALICE detector in pp, p–Pb, Pb–Pb collisions• Strong suppression of heavy-flavor production in central Pb–Pb collisions✓ Mass ordering of the RAA at intermediate pT✓ Compared with various model predictions implementing different energy loss and hadronization• Strong coupling of charm quark with medium constituents at low pT✓ Smaller v2 for beauty → weaker thermalization than charm• Charm baryon-to-meson ratios in pp collisions present significant differences to e+e−, ep
collisions✓ Charm fragmentation fractions not universal across collision systems• Upgraded ALICE detector during LS2✓ Better pointing/tracking resolution, higher statistics✓ Extend heavy flavor physics program with better precision

Thank you for your attention!
Jonghan Park (Univ. of Tsukuba)

2nd TCHoU member meeting, 18 Dec 2023

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