Recent results on heavy flavour in small and large systems from - ALICE Chun Lu Huang for the ALICE collaboration

Recent results on heavy flavour in
 small and large systems from
 ALICE

 Chun Lu Huang for the ALICE collaboration
 IJCLab, CNRS, Université Paris Saclay, Orsay, France

27/05/2020 -- LHCP2020 online conference 1

QGP and heavy flavour physics
 ALICE (A Large Ion Collider Experiment ) experiment aims to study the
 quark-gluon plasma (QGP), a phase of QCD matter at high temperature
 and/or at large net baryon density
 Heavy flavour (HF) particle contains at least one charm or bottom quark

 Open and hidden HF in pp collisions: test pQCD and
 hadronisation descriptions
 HF in high multiplicity pp and p-Pb collisions: probe collective
 effects
 HF physics characterizes the QGP properties
 Hidden heavy flavour production in QGP: colour screening and
 regeneration

 Visualization by Jonghan Park, 36th WWND

27/05/2020 -- LHCP2020 online conference 2

QGP and heavy flavour physics
 ALICE (A Large Ion Collider Experiment ) experiment aims to study the
 quark-gluon plasma (QGP), a phase of QCD matter at high temperature
 and/or at large net baryon density
 Heavy flavour (HF) particle contains at least one charm or bottom quark
 Gluon radiation &
 elastic scattering
 Open and hidden HF in pp collisions: test pQCD and
 hadronisation descriptions
 HF in high multiplicity pp and p-Pb collisions: probe collective
 effects Regeneration
 HF physics characterizes the QGP properties
 Colour screening
 Hidden heavy flavour production in QGP: colour screening and
 regeneration

 Visualization by Jonghan Park, 36th WWND

27/05/2020 -- LHCP2020 online conference 3

Measurement of HF with ALICE detector
 Measure HF production via:
 Forward rapidity: muon
 • hadronic decay in central barrel detectors spectrometer
 (ITS, TPC, TOF) and PID ( |η| < 0.9 )
 • (semi-) leptonic decay:
 • electrons in central barrel trackers and ITS,
 in EM calorimeters ( |η| < 0.7 ) TPC,
 • muons in muon spectrometer TOF
 ( -4.0 < η < -2.5 )
 D meson hadronic decays Charm baryon hadronic decays EM calorimeters
 • D0 → K − π+ • Λ+c → p+ K 0s and Λ+c → p+ π+ K −
 • D+ → K − π+ π+ • Ξc0 → π+ Ξ − and Ξc+ → π+ π+ Ξ −
 • D+ + − + +
 s → φπ → K K π • Σc0 → Λ+c π− and Σ ++ → Λ+ π+
 Central barrel  prompt & non-prompt HF
Quarkonium leptonic decays Charm baryon semi-leptonic decays Muon spectrometer  inclusive HF
• J/ψ, ψ(2S), Υ → µ+ µ− • Ξc0 → νe e+ Ξ− ALICE detector measures HF down to very low pT
• J/ψ → e+ e−

27/05/2020 -- LHCP2020 online conference 4

Measurement of HF with ALICE detector
 Measure HF production via:
 Forward rapidity: muon
 • hadronic decay in central barrel detectors spectrometer
 (ITS, TPC, TOF) and PID ( |η| < 0.9 )
 • (semi-) leptonic decay:
 • electrons in central barrel trackers and ITS,
 in EM calorimeters ( |η| < 0.7 ) TPC,
 • muons in muon spectrometer TOF
 ( -4.0
 More< η

D-meson production at mid-rapidity in pp
 pT-differential cross section of D mesons  measurement provides a constraint to pQCD calculations
 New New New

 non-prompt D
 (non-) prompt D+ prompt D

 (non-) prompt +
 
 • Fraction: 5-15%
 Agreement with FONLL calculations
27/05/2020 -- LHCP2020 online conference 6

Multiplicity dependence of J/ψ production
 arXiv: 2004.12673 (submitted to JHEP) New publication

 Pb-going  backward
 p-going  forward

 • J/ψ yield increases with increasing multiplicity • J/ψ yield at backward p-Pb compatible with
 • Faster growing J/ψ yield at backward cms in p-Pb that in Pb-Pb and pp at different NN

27/05/2020 -- LHCP2020 online conference 7

Inclusive charmonium production in p-Pb
 New publication arXiv: 2003.06053 (submitted to JHEP)
 RpPb allows one to study the yield modification in pA
 (AA) wrt pp

 d2 pPb /d T d cms
 pPb = backward
 pPb d2 pp /d T d cms

 ψ(2S) forward
• Theoretical calculations, based on initial state effects
 (shadowing…) or on coherent energy loss, reproduce J/ψ
 RpPb but fail at describing ψ(2S) RpPb

• The theoretical models including the final state effects
 (comoving particles/partons) describe J/ψ and ψ(2S) RpPb

 At backward cms , ψ(2S) RpPb < J/ψ RpPb
  showing a stronger suppression

27/05/2020 -- LHCP2020 online conference 8

J/ψ production at mid- and forward-rapidity in Pb-Pb

 0-10%
From mid-rapidity to
forward-rapidity, RAA is 0-20%
more suppressed for pT < 5
GeV/c
 Extend pT reach to 20 GeV/c

 Help understand the
 interplay between the colour
 screening and energy loss

 • Charm quark density at mid-rapidity is expected to be larger than that at forward-rapidity.
 Therefore, larger probability at mid-rapidity to have more regenerated J/ψ
27/05/2020 -- LHCP2020 online conference 9

J/ψ production at forward-rapidity in Pb-Pb
 New New

 20-40% 40-90%

 Flat over full pT

Enhanced
at low pT
 More suppressed at high pT

 • Statistical hadronization model: • In transport model:
 • regenerated J/ψ  low pT • regenerated J/ψ  low pT
 • initially produced J/ψ survived in nucleus corona • primordial J/ψ survived in QGP  high pT
  high pT

27/05/2020 -- LHCP2020 online conference 10

J/ψ polarization at forward-rapidity in Pb-Pb
 arXiv: 2005.11128 (submitted to PRL) New publication
 First measurement of J/ψ polarization in AA

 • Additional study of J/ψ production mechanisms with
 polarization measurement
 • The angular distribution of the two leptons decayed from a
 quarkonium is expressed:
 cos , 
 1
 ∝ 1 + λ cos 2 + λ sin2 cos 2 + λ sin(2 )
 3 + λ 
 ( , , ) = (0,0,0)  J/ψ not polarized
 ( , , ) = (-1,0,0)  J/ψ longitudinally polarized
 ( , , ) = (+1,0,0)  J/ψ transversally polarized

 A hint for non zero polarization in Pb-Pb with a
 maximum significance of ~2 sigma
27/05/2020 -- LHCP2020 online conference 11

HF production in Pb-Pb collisions
In hot medium , heavy New publication
quarks are expected to lose
energy via:
• elastic scattering
• radiative process

 electrons from semileptonic HF
 hadron decays

 TAMU calculation also Non-
 includes shadowing effect  prompt D0
 compatible with the data for
 pT < 3 GeV/c Prompt D0

 Phys. Lett. B 804 (2020) 135377

 Electron RAA for pT > 5 GeV/c is described by theoretical Non-prompt D0 RAA less suppressed for 5
 calculations that include the radiative and collisional energy loss < pT < 9 GeV/c
27/05/2020 -- LHCP2020 online conference 12

Charm elliptic and triangular flow in Pb-Pb
 arXiv: 2005.11131 (submitted to PLB) New publication
Azimuthal distribution of particles:
 ∞ D-meson v2 increases
 d 
 ∝ 1 + 2 � cos[ ( − Ψ )] from most central to
 d semi-central collisions
 =1 v2
• 2nd-order
 coefficient v2  elliptic flow
• 3rd-order coefficient v3  triangular flow Prompt D
 π±
 p
 Inclusive J/ψ
 • For 3 < pT < 6-8 GeV/c: D-meson v3 is
 • π± vn ≈ D meson vn < p vn  compatible in the two
 consistent with the number of centrality classes
 constituent quarks v3
 • J/ψ vn < D meson vn  fraction
 of J/ψ from bottom, whose
 flow is less than charm

27/05/2020 -- LHCP2020 online conference 13

Beauty elliptic flow in Pb-Pb
 PRL 123 (2019) 192301 arXiv: 2005.11130 (submitted to PRL)

 Beauty flow
 Υ(1S)
 New publication
 5-60%
 30-50%

 • Compatible with zero in the full pT range • First time observation non-zero flow at low pT
 • Described by models including: • No strong pT dependence
 • path-length dependent dissociation of bottomonia in QGP • b quarks may not be fully thermalized in this pT
 • regeneration of bb� range
27/05/2020 -- LHCP2020 online conference 14

Conclusions
 • Open and hidden HF are useful tools to probe the QGP in heavy-ion collisions
 • pp collisions:
 • D-meson production is described by FONLL pQCD calculations

 • p-Pb collisions:
 • Similar trend observed for J/ψ as function of multiplicity in pp, backward p-Pb and Pb-Pb
 • ψ(2S) RpPb at backward cms  described by models including final state effects

 • Pb-Pb collisions:
 • J/ψ is enhanced at mid-rapidity wrt forward-rapidity
 • HF electron RAA is described by models including radiation and collisional energy loss
 • HF flow is observed and helps to understand the collective behaviour

 Zoom meeting room: https://cern.zoom.us/j/3460282632?pwd=ejBicStsbVMxTzVqdDZXYU5NNktrQT09
27/05/2020 -- LHCP2020 online conference 15

Backup

27/05/2020 -- LHCP2020 online conference 16

QGP and heavy-ion collisions
 T = 157 MeV from PLB 795 (2019) 15
  ALICE experiment aims to study the quark-gluon
 plasma (QGP), a phase of QCD matter at high
 temperature and/or at large net baryon density
  Heavy-ion collisions at high collision energy create
 the QGP state in the laboratory.
  ALICE (A Large Ion Collider Experiment) at the LHC
 studies the region at high temperature but at low net
 baryon density.

27/05/2020 -- LHCP2020 online conference 17

Inclusive charmonium production in p-Pb
 New publication arXiv: 2003.06053 (submitted to JHEP)

27/05/2020 -- LHCP2020 online conference 18

Inclusive J/ψ RAA in Pb-Pb

27/05/2020 -- LHCP2020 online conference 19

Inclusive J/ψ RAA in Pb-Pb

27/05/2020 -- LHCP2020 online conference 20

J/ψ polarization at forward-rapidity in Pb-Pb
 New

27/05/2020 -- LHCP2020 online conference 21

Upsilon production in Pb-Pb collisions
 Paper preparation

 Υ(1S)

27/05/2020 -- LHCP2020 online conference 22