Overview of recent ALICE results and Chinese efforts in ALICE · 6/3/2019 · Overview of recent...
Transcript of Overview of recent ALICE results and Chinese efforts in ALICE · 6/3/2019 · Overview of recent...
Overview of recent ALICE results and Chinese efforts in ALICE
Daicui Zhou (for the ALICE Collaboration)(Central China Normal University, Wuhan, China)
1
Talk at TDLI & INPAC Joint Theoretical Particle Physics Seminar SeriesJune 3, 2019, SJTU, Shanghai
Nucleus (QGP)
Extremely high temperatureand high density
Quark deconfinement
Quark confinement
QGP in early university
New state of material - QGP
2
Heavy-ion collisions at the LHC
Lattice QCD calculation
Phys. Rev. D90 (2014) 094503
• QGP behaves as perfect fluid
• Well described by ideal hydrodynamics
• Low shear viscosity/entropy density (η/s)
• Phase transition calculated by Lattice QCD
• Tc ≈ 155 MeV, εc ≈ 0.5 GeV/fm3
• Heavy-ion collisions at the LHC
• Extremely High temperature: O(1012 K)
• Vanishing baryon chemical potential
• The existence of QGP and its properties
are key issues in QCD for understanding of
confinement and chiral restoration
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 3
Evolution of heavy-ion collisions
• Initial state and pre-equilibrium
• CGC, GLASMA
• Hard parton scattering
• Jet and heavy flavour production
• Creation of Quark-Gluon Plasma
• Thermalization of strongly-interacting matter
• QGP expansion and cooling
• 3D+1 relativistic viscous hydrodynamics
• Phase transition (Tc): partons → hadrons
• Lattice QCD, cross over
• Hadronic phase
• Chemical freeze-out (Tch), rescattering, kinetic freeze-out (Tfo)
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 4
Anisotropy: Soft probe of QGP
• Quantify anisotropy: Fourier decomposition of particle azimuthal distribution
relative to the reaction plane (ΨRP) — coefficients v2, v3, v4… vn
• Elliptic flow (v2): spatial anisotropy to momentum anisotropy — large
pressure gradients and more particles emitted in plane — hydrodynamics
• Higher order flow: bring additional constraints on the initial conditions, η/s,
EoS, freeze-out conditions…
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 5
Jet: hard probe of QGP
• Jet: a spray of particles from hard parton fragmentation — get closer
access to parton energy
• Out-of-cone radiation: energy loss in jet cone — RAA < 1
➡Jet yield suppression, dijet or hadron–jet acoplanarity…
• In-cone radiation: medium modified fragmentation — RAA = 1
➡Jet shape broadening, modification of transverse energy profile…
• Hard partons produced before the QCD
medium forms
• Interact with the hot and dense medium
QCD medium
QCD vacuum
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 6
Heavy flavour: QGP medium tomography7
• Heavy quarks (mc ~ 1.5 GeV, mb ~ 5 GeV): early production (f ~ 1/2mc/b ~
0.1 fm/c << QGP ~ 5-10 fm/c) and hard fragmentation (z→1) ,Experience
full collision history:transport properties
• In-medium energy loss: radiative vs. collisional
• Radiative energy loss —> colour charge, quark mass,
medium density dependence of parton–medium coupling
➡ΔEgluon >ΔElight > ΔEcharm >ΔEbeauty;
➡RAA(B) > RAA(D) > RAA(LH) (?);
• Azimuthal anisotropic (second order flow coefficient v2)
• Low pT: degree of thermalization of heavy quarks in QCD medium
• High pT: path length dependence of heavy quark in-medium energy loss
• Quarkonia suppression and regeneration
• Resonance suppression via color screening — sensitive probe of
deconfined medium
• Regeneration via recombination of heavy quarks, mostly for charmPhys.Lett.B178 (1986) 416 ;Phys. Lett. B 490 (2000) 196; Phys. Rev. C (2001) 054905
TOF
MUON-Arm
V0, T0
EMCAL
TPC
ITS
Central Barrel (|η|<0.9)
• ITS, TPC, TOF: vertexing, 2π tracking and PID
• EMCal/Dcal, PHOS: high-pT electron trigger, PID
Muon-Arm (-4<η<-2.5):
Muon trigger, tracking, PID
Smaller detectors (V0, T0, ZDC, SPD):
Trigger, centrality selection,
event plane rec.
ALICE apparatus
DCAL
PHOS
Countries: 41Institutes: 176Members: 1800
Detector:
Length: 26 meters
Height: 16 meters
Weight: 10,000 tons
TDR
Dedicated to measure
hadrons, electrons,
muons and photons
to cope with very high
multiplicities
8
ALICE performance
• Efficient low-momentum tracking — down to ~150 MeV/c
• Excellent particle identification (hadrons, leptons and photons)
• Excellent vertex capability (HF, V0, cascades, conversions)
• Di-jet trigger via combined calorimeters (EMCal – DCal)
• High precision muon measurement at forward rapidity
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 9
➢ v2 mostly driven by overlapgeometry
➢ higher orders mostly driven by fluctuations
(odd harmonics non-existent in averagegeometry)
➢ compare different systemsusing multiplicity as scaling variable
― finite vn in pp:
similar values as peripheral Pb–Pb/Xe–Xe― different geometry at given multiplicity:
→ v2 does not scale withmultiplicity
Anisotropic expansion
0
0.02
0.04
0.06
0.08
0.1
vn{2
}
0.12
(a)
0.16 PYTHIA 8 Hydro ALICE
pp pp p-Pb Xe-Xe Pb-Pb pp p-PbXe-Xe Pb-Pb
13 5.02 5.02 5.44 5.02 13 5.02 5.44 5.02 sNN
(TeV)0.14 v 2{2, || > 1.4}
v 3{2, || > 1.0}
v 4{2, || > 1.0}
102 103
N ch (|| <0.8)
0.08
0.06
0.04
0.02
0
0.1
0.16
v2{k
}
0.18 (b)
0.14 || < 0.8
T
0.12 0.2 < p < 3.0 GeV/c
Hydro ALICEXe-Xe Pb-Pb pp p-Pb Xe-Xe Pb-Pb
5.44 5.02 13 5.02 5.44 5.02 sNN
(TeV)
3-sub
v 2{4}
v 2{4}
v2{6}
v2{6}
2
2-sub
v {8}
2-subv2{8}
vn vs multiplicity
multiplicity
➢ quantify azimuthal anistropy by Fourier coefficients:v2 v3 v4
. . .
[arXiv:1903.01790]
ALICE Overview and Chinese Eff, Daicui Zhou, SJTU, Shanghai, June 3, 2019Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 10
Charged
High-Precision Correlations of CorrelationsJH
EP
09
(20
17
)03
2P
RC
97
(20
18
)02
490
6
Symmetric cumulants Factorization ratios
How are vn and vm correlated? Do vn factorize in pT?
Characterization with unprecedented detail!
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, SJTU, June 3, 2019, SJTU, Shanghai 11Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 11
Charged
v2 vs. pT
• D0 mesons exhibit v2 >0 →charm quarks flow with medium
• Event Shape Engineering
– At fixed impact parameter, select shape of collision region
• Heavy flavour v2 “follows” shape fluctuations q2
D0 anisotropya
rXiv
:18
09.0
9371
20% largest q2
60% smallest q2
20% largest q2
Overview of the ALICE recent results, Daicui Zhou, Fudan, Shanghai 12
60% smallest q2
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 12
• Spectator charge causes large magnetic
field (~1018 Gauss)
– Aligns spins
• Domains with non-zero topological charge
(local) → chirality flip
• Leads to charge separation
• Experimental correlator
– Same sign = signal
– Opposite sign = control
Overview of the ALICE recent results, Daicui Zhou, Fudan, Shanghai 13
Chiral Magnetic Effect
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 13
• Signal observed increasing with increasing
centrality
• Magnitude similar at 0.2 TeV (STAR) and2.76 TeV (ALICE)
• Magnitude similar in Pb-Pb and p-Pb
• Issue: Large backgrounds due to local charge
conservation (resonance decays, momentum
conservation, parton fragmentation)
Earlier ResultsP
RL
110
(20
13
),01
230
1
112 vs. centrality
Overview of the ALICE recent results, Daicui Zhou, Fudan, Shanghai 14Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 14
• Event shape engineering, modelling of magnetic
field + initial state models allows limit on CME
• fCME = maximal signal contribution in correlator
– Limit set on signal 7-33% at 95% C.L.[PLB 777(2018)151,PRC 97(2018)044912]
• Interesting opportunity: Isobar run at RHIC
– Test Z2 magnetic field dependence
• Sub-percent precision with run 3 and 4
Now & FutureP
LB
77
7(2
01
8)1
51
fCME vs. centrality
Overview of the ALICE recent results, Daicui Zhou, Fudan, Shanghai 15Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 15
• Passing nuclei → strong magnetic field → C-odd directed flow v1
• Electric field → same effect with opposite direction
• Measured for hadrons and D mesons
– Earlier formation time→ sensitivity to stronger magnetic field
D Directed Flow
Theory expects that B dominates,
but opposite slope measured
(with limited significance)
Signal larger
Overview of the ALICE recent results, Daicui Zhou, Fudan, Shanghai 16Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 16
J/ψ anisotropy
v2
v3
• J/ v2 well measured:-- Forward in di-muon channel
➢ J/ψ flows ⇒ coupling to medium (consistent with recombination)
➢ ordering: v2(J/ψ) < v2(D0) < v2(h±)
➢ First evidence for v3 > 0 (3.7 )
arXiv:1811.12727
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 17
ϒ anisotropy
Tp (GeV/c)
2 4 6 8 10
v2
−0.05
0
0.05
0.1
0.15
0.2
(1S), KSU model, arXiv:1809.06235
ALICE Preliminary Pb−Pb sNN = 5.02 TeV
5−60%2.5 < y < 4
Inclusive J/
(1S)
ALI−PREL−314841
v2 (1S), TAMU model, PRC 96 (2017) 054901
Centrality
5−60% 5−20% 20−60%
v2
−0.05
0
0.05
0.1
0.15(1S)
Inclusive J/
ALICE Preliminary Pb−Pb sNN = 5.02 TeV
2 < p < 15 GeV/cT
2.5 < y < 4
ALI−PREL−314845
➢ first measurement of v2 for Υ: consistent with 0
first particle measured not to have flow!
➢ not dragged along by flow of medium,
not produced by recombination
Pb–Pb 2018!
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 18
• HI collision more than superposition of nucleon- nucleon collisions
with incoherent fragmentation?
Hadron energy Loss
dN / dpTpp
Ncoll
dN / dpTAA
AAR =
RAA = 1 → no modification
RAA = 1 → medium effects
RAA vs. pT Significant suppression of hadrons w.r.t pp
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Hint of ordering of energy loss:
➢ charged hadrons
➢ D mesons
➢ Ds
➢ Λc
→ mass-dependent energy energy loss
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
⚫ Significant energy loss
– Consistent picture of charged and D jets, and hadrons
⚫ Quark-mass dependent energy loss involving b
Heavy quark and jet energy loss
B→ J/
D
20
D jetsCharged jetsD mesons
PRC93,034913(2016) pT (GeV/c)
⚫ described by models implementing mass-ependent energy loss
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
Jet energy loss
➢ also jets are strongly suppressed in medium➢ excellent tool to study medium interaction
JetsJets
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 21
• Characterize and understand parton-medium
interactions by exploring splitting phase space
• First splitting at small angles:– Pb-Pb jets ~ vacuum reference
• First splitting at large angles:
– Overall suppression, steeper zg distribution
Jet Substructure
R < 0.1
22
R > 0.1
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
Small Systems
JHEP09(2010)091ALICE
p-Pb
PLB719(2013)29
p-Pb
23
PLB726(2013)164
P-Pb
Double ridge resembles the structure attributed to collectiveflow in p-Pb
Clear indication for mass ordering in p-Pb resembles Pb-Pb and supports “flow” picture
➢ Models including hydrodynamical expansion
can describe the observations
Alternative interpretations:
➢ CGC: many-gluon correlations
(Dusling, Venugopalan, PRD 87 (2013) 094034)
➢ MPIs and “colour reconnections”(Ortiz et al, PRL 111 (2013) 042001
pp
Nch
Collective phenomena observed
in pp and p-Pb collisions have
caused a paradigm shift.
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
Strangeness production
NEW
24
Nature Phys.13(2017)535
➢Particle identification capabilities down to low pT
➢ Integrated particle yields
➢Fully characterized by thermal model:
―baryon chemical potential β=0
―temperature T ≈ 153 MeV
―volume V ≈7000 fm3
(for Pb–Pb √sNN
= 5.02 TeV)
➢Thermodynamic description ↔
➢Microscopic fundamental interactions
➢Particle ratios as function of multiplicity
show smooth evolution from pp to Pb–Pb
collisions, transition between different
mechanisms?
Yields normalized to pions
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
• Run 3 can reach extremely rare (10-11) pp events
– 200 pb-1 | Sampling 1013 events
• Significant overlap between pp and PbPb
– In multiplicity up to ~65% centrality
• If pp behaves HI, we shall see “standard” HI physics
– Including jet quenching if effects driven by final state
– If not, we can see the differences
• In addition: MB sample for low-multiplicity limit
– What is smallest droplet of matter showing
collective behavior?
– Origin of collectivity in few particle system?
(color reconnection, gluon interference, escape, …)
Understanding Small Systems
Pb-Pb
p-Pb
pp
Today
65% central
14-16 <Nch>
>25k events
P(Nch) vs. Nch
25Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
LHC run 2
Upgrades “LHC LS2”• LHC: collimators + injectors
• ALICE: Tracking, DAQ (rate x100)
LHC Run 3 + 4 (numbers for Pb-Pb)
• L = 6 ·1027 cm-2s-1 ~ 50 kHz rate
• 10 nb-1 (ALICE)
2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029
Upgrades “LHC LS3"
26
Precision measurements of ➢heavy flavour and quarkonia➢ Jets➢ low-mass dileptons➢ light (hyper-)nuclei
Future physics goals
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
ALICE detector upgrade27
Increase of luminosity and improve vertexing and tracking at low-pT
27Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
LS2 upgradesobjective: operation at high interaction rates (50 kHz of Pb–Pb collisions)
⇒ continuous (i.e. untriggered) read-out for core detectors
Time Projection Chamber
(not toscale)
GEM readout chambers
Muon Forward Tracker
MAPS-based forward tracker
Inner TrackingSystem
Monolithic Active Pixel Sensors
Forward Interaction Trigger
Cherenkov + scintillator
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 28
Construction & commissioningTPC ITS Inner/Outer Barrel
Half-layer0 Half-Layer1 Half-Layer2
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 29
Beyond LS2ITS3
➢ wafer-sized sensors
➢ on-chip powerdistribution
➢ cooling by forced air flow
➢ significant reduction of material budget
FoCal
➢ forward region so far uninstrumented
➢ FoCal-E: photons and π0s
➢ FoCal-H: photon isolation and jets
➢ constrain gluon PDFs at low x
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 33330
• Legacy of results from first 8 years of heavy-ion collisions at the LHC
– Participant picture, medium properties, energy Loss in 100 GeV regime, quarkonia
regeneration, and so on.
– Paradigm shift of understanding of small collision systems
• Next decade expects 100x larger data sample
– Macroscopic long-wavelength QGP
– Microscopic parton dynamics underlying the QGP properties
– Investigate unified picture of particle production from small to large systems
Opportunities detailed in community document: arXiv:1812.06772
Summary
31Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
Chinese efforts in ALICE
• Hardware contributions
• Physics contributions
• Perspective HL and HE running at the LHC
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 32
Hardware contributions⚫ PHOS FEE development
⚫ A DCAL supermodule development
⚫ DCAL/EMCAL/PHOS SRU development
⚫ ITS upgrade + MFT upgrade
ALICE Experiment41 Countries177 Institutes1800 Members
PHOSDCal
Muon Spectrometer
-2.5 >eta > -4
Physics Goal
Detection of QGP signal and properties at TeV energiesDetector:
Length: 26 meters
Height: 16 meters
Weight: 10,000 tons
33
China Team:
CCNU, CIAE, HUST, HTU,
USTC and Fudan/SINAP
Physics on:
• Photons and jets
• Heavy-floavours
• Exotic particle properties
34
PHoton Spectrometer(PHOS) FEE
⚫ Development of full PHOS FEEs (R&D, production and commissioning);
⚫ Development of three sets of software of PHOS (FEE, Triger and RCU);
⚫ Objective: dedicated to measurement of photons and jets
FEE arrayFront-end electronics (FEE)
34
35
PHOS FEE R&D, production and commissioning
R&D in 2002 - 2005
First batch of FEEs delivered in Jan. 20063nd batch of FEEs delivered in June 2008
FEE Review Meeting, on May 30/31 2005, Wuhan
FEE and PHOS installation, 2008, p2/LHC 35
2009年3月3日, 兰州
PbW04 crystal
APD CSPPWO
Readout
光子探测器模块重12吨 PWO array
TRU
联合安装和调试PHOS超级模块 FEE array一个超级模块 36
FEE
Contribution on PHOS(red arrow)
ALICE-DCAL Proposal
PHOS
DCAL
● ALICE Di-jet Electromagenetic Calorimeter (DCAL) proposed by China and Japan team
in 2009 and approved by ALICE after 6 months;construction in two years and
taking data from 2015
● Measure energy of photon and jet precisely
Je
t
γ
jet
jet
π0
γ-jet
Jet-jet
π0-jet
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 37
代表性成果 1-1: 研制双喷注电磁量能器的一个超级模块
38
Di-jet EMCAL(DCAL) contribution
SRU development for EMCAL /DCAL /PHOS
39
◼ Scalable Multi-channel parallel
p2p transmission mode, high
Speed, low noise, high stability
◼For DCAL firstly; then applied
to EMCal; Improved for PHOS
◼ Building a SRU prototype at Lab
For monitoring the on site at CERN
◼ Published on Nucl. Inst. Meth.
Phys. Res. A (2014), pp. 157-162
39
Neutral pion measurement in pp and Pb-Pb collisionsEur. Phys. J. C77 (2017) 339
• Neutral pion: measured up to pT = 40 GeV/c
➡Thanks to the shower shape method for high-pT
π0 identification
• New constraint on model prediction
➢ Suppression increase with centrality, achieve to a factor about 10 in most 5%central collisions at high pT -- two times as larger as at RHIC
➢ Larger energy loss resulted by highly denser QCD medium at LHC
Eur. Phys. J. C 10 (2014) 3108
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 40
π0–hadron correlation in pp and Pb–Pb collisions
• Measurement has been extended to lower pT w. r. t. di-hadron correlations
➡Near side enhancement: modification of jet fragmentation, quark- / gluon-jet ratio
and/or the bias on parton pT spectra…
➡Away side suppression at high pT: hard parton energy loss
➡Away side enhancement at low pT: favor the jet-medium excitation scenario
➡Provided baseline for the study of γ-hadron / jet correlations
Phys. Lett. B763 (2016) 238
Away side
Near side
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 41
Jet production in pp and Pb-Pb collisions
• Charged-particle jet RAA at 5.02 TeV
• Consistent with RAA of full-jet RAA at 2.76 TeV
• Cross section ratio measured in pp collisions
• Jet structure in vacuum — consistent with model predictions• Baseline for heavy-ion collisions — understanding of the medium modified jet
fragmentation
• pp reference: paper proposal has been accepted by ALICE collaboration
New for QM’18
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 42
HF muon production in LHC RUN-I
• Observed strong suppression of yield of open heavy-flavour decay muons in central Pb–Pb
collisions w. r. t. pp collisions
➡Nuclear modification factor in p–Pb collisions consistent with unity at high pT
➡Strong suppression is due to the hot medium effects
• Positive v2 of open heavy-flavour decay muons at forward rapidity
➡Significant interaction of heavy quarks with the QCD medium in a wide rapidity range
• Phys. Lett. B708 (2012) 265
• Phys. Lett. B753 (2016) 41• Phys. Rev. Lett. 109 (2012) 112301
• Phys. Lett. B770 (2017) 459
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 43
HF muon production in LHC RUN-II
44
• Production of open heavy-flavour decays muons was measured up to pT = 20 GeV/c
• Reduced uncertainty w. r. t. RUN-I measurement — new constraint on model
predictions
• Corresponding paper proposals have been received by ALICE
➡Target journal: Phys. Lett. B (pp collisions) and Phys. Rev. Lett. (Pb–Pb collisions)
• Xe–Xe at 5.44 TeV: compatible with Pb–Pb at 5.02 TeV with similar event multiplicity
ALICE-China group has dominated almost all of HF decay muon
measurements in ALICE
Xe–Xe at 5.44 TeV
New for QM’18
Pb–Pb at 5.02 TeV
Production of D mesons
Core contribution of ALICE-China group• First measurement of D meson production cross section in pp collisions at LHC energies• First measurement of D meson RAA in Pb–Pb collisions in ALICE LHC RUN-II
JHEP 1201 (2012) 128
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 45
JHEP 1810 (2018) 174
Collectivity of (Multi-)strangeness
46
➢ First observation of significant parton collectivity at the LHC, indicating the QGP
produced in Pb-Pb collisions closing to idea fluid
➢ Scaling violation of number of quarks with level ~20% observed firstly at the LHC
JHEP 1506, (2015) 190
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 46
Strangeness enhancement
• Smooth evolution of particle ratios with
multiplicity
• Strangeness enhancement considered
defining feature of heavy-ions — now also
seen in high-multiplicity pp / p–Pb!
• Not reproduced by traditional soft QCD
models (e.g. Pythia)
➡Challenges universality and factorization of
fragmentation
➡Study of hadronization mechanisms
• Multiple Parton Interactions lead to
densely packed strings in the transverse
plane (e.g. EPOS and DIPSY)
Nature Physics 13 (2017) 535
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 47
Chinese-team effort on ITS upgrade
48
Chinese team involved in R&D of the MAPS; Taking 20% of chip module assembly, installation and calibration of upgrade ITS
7 layers (10 m2) silicon pixel (MAPS)
sensor traker from 22-406 mm to IP with
spatial resolution O(5 um)
Bs, Bc,Λb , b-jet measurement available
ITS upgrade HIC assembly at CCNU
48
Involvement on Muon Tracker Forward (MFT)
49
More precise measurements of heavy
flavours and low mass dileptons
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 49
ALICE Chinese Team●华中师范大学(CCNU)
transport and collective properties of QGP
●中国原子能科学研究院(CIAE)
Cold nuclear effects
● 中科院上海应用物理研究所(SINAP)
Exotic particle properties in nuclear matter
●中国科学技术大学(USTC)
Charmonia and collectivities of QGP environment
● 华中科技大学(HUST)
Readout electronics
● 湖北工业大学(HUT)
Readout electronics
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 50
谢谢!
Thanks
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 51
Backup
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 52
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 54
v3
arXiv:1804.02944
v2
arXiv:1805.04390
54
v4
conditions and medium propertiesp differential v constrains initialT n
v2
Inclusive charged particle
anisotropic flow fluctuations:
vn ratios constrain medium
properties: /s, /s
v4
v2
Overview of the ALICE recent results, Daicui Zhou, Fudan, Shanghai
High-Precision Measurements of Collective Flow
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 55
J/ψ anisotropy
v3 (0-50 % integrated)
Tp (GeV/c)
2 4 6 8 10 12
v3/v
2
0
0.5
1 Pb-Pb sNN = 5.02 TeV 5-40%
Tp (GeV/c)
2 4 6 8 10 12
Inclusive J/, 2.5<y<4.0, ALICE
Prompt D0, |y |<1.0, CMS
h, ||<0.8, ALICE
10-50%
v3/v2: 5-40 % (left), 10-50 % (right)
➢ v3/v2 significantly smaller for J/ψ
➢ Underlines importance of regeneration component
[arXiv:1811.12727]
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai 56
➢ How does charm recombine from the QGP?
– Baryon/meson ratios Ds/D, c/ D0,b/B
– Very challenging: e.g.c c ~ 60 m
c arX
iv:1
80
9.1
0922
– c /D0 increases considerably from pp/p-Pb to Pb-Pb
→favours recombination from quarks in the medium
(instead of primordial production)
56
➢ c composed of udc
(heavy quarks produced early in the collision)
➢First measurement at LHC
Recombination:
➢ similar fect seen for J/Ψ
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
• LHC provided a few hours of Xe-Xe collisions in 2018 (as a proof-of-principle)
– Resulted in a number of results and publications
Xe-Xe
arXiv:1805.04432
PL
B7
84(2
018
)82
Charged-particle density
Anisotropic flow
57Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai
• RAA suppression Pb-Pb vs. Xe-Xe
– weaker at same centrality
– identical at same dN/d or Npart
for central events
– deviations above 30% centrality but
within uncertainties
Xe-Xe
PLB788(2019)166Centrality
58
Centrality
Daicui Zhou, ALICE Overview and Chinese Efforts in ALICE, June 3, 2019, SJTU, Shanghai