Recent flow results from LHC — Soft probes, hard probes and their interplay You Zhou Niels Bohr Institute, University of Copenhagen You Zhou (NBI) @ COST workshop, Lund
Anisotropic flow in Pb-Pb collisions Hydro: J. Noronha-Hostler etc, PRC93, 034912 (2016) − → ALICE, PRL 116 (2016) 132302 V 2 − → V 3 3.2264d0 ❖ v 2 , v 3 and v 4 are nicely described by hydrodynamic predictions • Similarly v n data reproduced by hydro for Xe-Xe collisions ALICE, PLB784 (2018) 82 ❖ QGP: a state of perfect liquid described by hydrodynamics • Two main uncertainties of hydro: initial conditions and η /s 2 You Zhou (NBI) @ COST workshop, Lund
What Xe-Xe collisions bring , arXiv:1901.07997 3.2264d0 ❖ Flow measurements in different collision systems (Pb-Pb and Xe-Xe) will help to better understand the initial state models • use v n [Xe-Xe]/v n [Pb-Pb] to probe initial conditions, better description with deformed Xe • new collision system (e.g. O-O) will improve our understanding on IC 3 You Zhou (NBI) @ COST workshop, Lund
Extract initial conditions and η /s(T) 3.2264d0 ❖ Theory can be further constrained by combined Pb-Pb & Xe-Xe fits • Initial conditions by the same initial state model; common η /s(T) and ζ /s(T) ❖ Theory can be further constrained by sensitive flow observables 4 You Zhou (NBI) @ COST workshop, Lund
Underlying p.d.f. of v n v n {m} Moments p(v n ) 3.2264d0 ALICE, JHEP 1807 (2018) 103 ❖ Investigating p(v 2 ) with multi-particle cumulants • constraints on various initial state models 5 You Zhou (NBI) @ COST workshop, Lund
Correlations between v m and v n Symmetric cumulants: SC ( m, n ) = h v 2 m v 2 n i � h v 2 m i h v 2 n i SC(m,n) 〉 3 6 2 n − 10 × v 1 〈 2 2 ALICE Pb-Pb s = 2.76 TeV 〉 SC(4,2)/ 〈 v 〉 〈 v 〉 m NN 4 2 2 Symmetri Cumulant, 2 v 〈 2 2 SC(4,2) SC(3,2)/ 〈 v 〉 〈 v 〉 SC(m,n)/ 3 2 A. Bilandzic etc, 1 SC(3,2) 0.5 PRC 89, 064904 (2014) 0 0 1 Hydrodynamics − SC(4,2), η /s=0.20 Hydrodynamics SC(4,2), η /s(T) param1 2 2 − 2 SC(4,2)/ 〈 v 〉 〈 v 〉 , η /s=0.20 SC(4,2), /s(T) param4 η ALICE, 4 2 2 2 3.2264d0 SC(4,2)/ v v , /s(T) param1,2,3,4 〈 〉 〈 〉 η SC(3,2), η /s=0.20 0.5 − 4 2 2 2 SC(3,2)/ v v , /s=0.20 〈 〉 〈 〉 η SC(3,2), η /s(T) param1 PRL117, 182301 (2016) 3 − 3 2 2 2 SC(3,2), /s(T) param4 SC(3,2)/ 〈 v 〉 〈 v 〉 , η /s(T) param1,2,3,4 η 3 2 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 centrality percentile centrality percentile ❖ Comparison of SC and Normalized SC (NSC) to hydrodynamic calculations • Although hydro describes v n fairly well, there is not a single centrality for which a given η /s parameterization describes simultaneously SC and NSC -> tighter constraints! • NSC(3,2) measurements provide direct access into the initial conditions (despite details of systems evolution) 6 You Zhou (NBI) @ COST workshop, Lund
Higher harmonic and higher order ALICE, PRC 97, 024906 (2018) 3.2264d0 ❖ Higher harmonic SC (NSC) could provide tighter constraints on models • Initial conditions & η /s(T) ❖ Outlook : higher order (6- and 8-particle) SC and NSC • SC(2,2,3), SC(2,3,3), SC(2,2,3, 3) -> probe (v 24 , v 32 ), (v 22 , v 34 ), (v 24 , v 34 ) correlation • SC(2,3,4) -> probe (v 22 , v 32 , v 42 ) correlation 7 You Zhou (NBI) @ COST workshop, Lund
Correlations between ψ n and ψ m L. Yan etc, PLB744 (2015) 82 n,mk Pb-Pb s = 2.76 TeV ρ 422 = v 4 , 22 v 4 { 2 } ⇡ h cos(4 Ψ 4 � 4 Ψ 2 ) i NN 1 1 ρ ALICE ρ 0.8 0.8 ρ 532 = v 5 , 32 4,22 ρ v 5 { 2 } ⇡ h cos(5 Ψ 5 � 3 Ψ 3 � 2 Ψ 2 ) i 5,32 ρ 0.6 0.6 6,222 ATLAS (PRC90, 024905) ρ 6,33 cos(4 -4 ) ρ 6222 = v 6 , 222 〈 Φ Φ 〉 v 6 { 2 } ⇡ h cos(6 Ψ 6 � 6 Ψ 2 ) i 4 w 0.4 0.4 2 cos(5 -2 - 3 ) 〈 Φ Φ Φ 〉 2 3 w 5 〈 cos(6 Φ -6 Φ ) 〉 2 0.2 0.2 w ρ 633 = v 6 , 33 6 〈 cos(6 Φ -6 Φ ) 〉 v 6 { 2 } ⇡ h cos(6 Ψ 6 � 6 Ψ 3 ) i ρ ρ 3 w 6 4,22 5,32 0 10 20 30 40 50 0 10 20 30 40 50 n,mk IP-Glasma + MUSIC + UrQMD ALICE, 1 1 ρ ρ 4,22 PLB773 (2017) 68 ρ 0.8 0.8 5,32 ρ 3.2264d0 6,222 0.6 0.6 ρ ATLAS Collaboration, 6,33 PRC90, 024905 (2014) 0.4 0.4 0.2 0.2 IP-Glasma: ρ ρ 6,222 6,33 S. McDonald et al., 0 10 20 30 40 50 0 10 20 30 40 50 PRC 95, 064913 (2017) Centrality percentile Centrality percentile ❖ ψ n and ψ m correlations with ρ n,mk • Agreement between ALICE and ATLAS (different eta coverage) • Results are compatible with hydrodynamic calculations using IP-Glasma & η /s=0.095 • Precise measurements using Pb-Pb 5.02 TeV data are available 8 You Zhou (NBI) @ COST workshop, Lund
Individual constraints Y. Zhou, Nuclear Physics A 982 (2019) 71 3.2264d0 9 You Zhou (NBI) @ COST workshop, Lund
Differential flow (soft probe) ALICE, JHEP 09 (2017) 032 n Hydrodynamics Pb-Pb = 2.76 TeV ALICE s v NN {2} , MC-KLN & /s=0.20 η {2,| |>0.8} ∆ η v Centrality: 20-30% v n 2 {2} , MC-Glb & η /s=0.08 0.2 0.2 {2,| |>0.8} 0.2 v ∆ η v n | η | < 0.8 3 {2} , Trento & /s(T) η {2,| |>0.8} v ∆ η v n 4 {2} , AMPT & /s=0.08 η v n 0.1 0.1 0.1 v 2 v 3 v 4 3.2264d0 0 0 0 0 1 2 3 0 1 2 3 0 1 2 3 (GeV/ ) (GeV/ ) (GeV/ ) p c p c p c ALI − DER − 139356 T T T ❖ More detailed information are carried by differential measurements ❖ comparisons of data and hydrodynamic calculations show: • strong constraints on the initial state and η /s(T) of QGP • calculations with AMPT -initial conditions give the best description of data 10 You Zhou (NBI) @ COST workshop, Lund
Differential flow (hard probe) PLB776 (2017) 195 3.2264d0 ❖ SHEE describes the data better than CUJET3.0 • modeling the initial-state fluctuations are crucial ingredient to describe the experimental data related to parton energy loss • (For SHEE) Linear path-length dependence of the energy loss works better than quadratic ones 11 You Zhou (NBI) @ COST workshop, Lund
Connection of low and high p T PLB776 (2017) 195 3.2264d0 ❖ Correlation between high-p T and low-p T v 2 • Investigate connection between v 2 induced by hydrodynamic flow and the path-length dependence of parton energy loss • Data described by linear function, initial-state geometry and its fluctuations are likely to be the common causes of the observed v 2 at both low and high p T ❖ Outlook: • quantify the correlation strength with <v 2 (p TLow ) 2 v 2 (p THigh ) 2 > - <v 2 (p TLow ) 2 ><v 2 (p THigh ) 2 > 12 You Zhou (NBI) @ COST workshop, Lund
What about intermediated p T 3.2264d0 ❖ Low p T -> “ hydrodynamic flow ” (soft probe) ❖ High p T -> “ parton energy loss ” (hard probe) ❖ What about 2 ≲ p T ≲ 10 GeV/ c -> “recombination? coalescence?” • interplay of soft and hard probes? Discussions in this COST workshop! 13 You Zhou (NBI) @ COST workshop, Lund
D meson Flow ❖ D 0 vs charged hadron (or light flavor) CMS, PRL120, 202301 (2018) • D 0 v 2 and v 3 show smaller but similar p T dependence ❖ Data vs theory • at low p T , comparisons suggest that the charm quarks flow • For p T > 6 GeV/ c , v 2 (D 0 ) ≃ v 2 (ch), the path length dependence of charm quark energy 3.2264d0 loss is similar to that of light quarks ❖ Results for charmonium are also available ❖ Question: non-flow in data and theory? • vs. ? • Outlook: multi-particle cumulants? • More non-flow, see: K.GULBRANDSEN @ Wed. 14:45 14 You Zhou (NBI) @ COST workshop, Lund
D meson flow with ESE ALICE, arXiv:1809.09371 3.2264d0 ❖ Charged hadrons: • almost no p T dependence (up to 12 GeV/ c ) • the usage of q 2 provides a selection of a global property of the collision ❖ D meson • q 2 selection effect seems similar with charged hadrons within large uncertainty 15 You Zhou (NBI) @ COST workshop, Lund
Summary ❖ Anisotropic flow, services as soft and hard probes, enable more possibilities to explore the QGP properties ❖ LHC Run3 program (high luminosity, new collision systems) as well as new theoretical efforts provide new opportunities! 3.2264d0 Thanks for your attention! 16 You Zhou (NBI) @ COST workshop, Lund
New PhD position at NBI Villum Young Investigator program — “Creating a smallest droplet of early universe in the Laboratory” 3.2264d0 ❖ New PhD position in ALICE group, APPLY now 17 You Zhou (NBI) @ COST workshop, Lund
backup 3.2264d0 18 You Zhou (NBI) @ COST workshop, Lund
Global Bayesian Analysis S. Bass, QM2017 using Pb-Pb data only 3.2264d0 19 You Zhou (NBI) @ COST workshop, Lund
Flow as hard probes ATLAS, EPJC78 (2018) 784 3.2264d0 ❖ 20 You Zhou (NBI) @ COST workshop, Lund
Anisotropic flow and QGP ALICE, PRL107, 032301 (2011) EKRT: H. Niemi et. al, PRC 93, 024907 (2016) 3.2264d0 ❖ v n also quantitatively described by hydrodynamics using EKRT, AMPT, Trento initial conditions (but not MC-Glauber, nor MC-KLN) with different η /s(T) 21 You Zhou (NBI) @ COST workshop, Lund
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