Recent flow results from LHC Soft probes, hard probes and their - - PowerPoint PPT Presentation

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Recent flow results from LHC Soft probes, hard probes and their - - PowerPoint PPT Presentation

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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,

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You Zhou (NBI) @ COST workshop, Lund

Niels Bohr Institute, University of Copenhagen

Recent flow results from LHC

You Zhou

— Soft probes, hard probes and their interplay

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Anisotropic flow in Pb-Pb collisions

2

− → V2 − → V3

❖ v2, v3 and v4 are nicely described by hydrodynamic predictions

  • Similarly vn data reproduced by hydro for Xe-Xe collisions

❖ QGP: a state of perfect liquid described by hydrodynamics

  • Two main uncertainties of hydro: initial conditions and η/s

ALICE, PRL 116 (2016) 132302

Hydro: J. Noronha-Hostler etc, PRC93, 034912 (2016)

ALICE, PLB784 (2018) 82

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

What Xe-Xe collisions bring

3

, arXiv:1901.07997

❖ Flow measurements in different collision systems (Pb-Pb and Xe-Xe) will help to better understand the initial state models

  • use vn[Xe-Xe]/vn[Pb-Pb] to probe initial conditions, better description with deformed Xe
  • new collision system (e.g. O-O) will improve our understanding on IC
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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Extract initial conditions and η/s(T)

❖ 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

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

❖ Investigating p(v2) with multi-particle cumulants

  • constraints on various initial state models

Underlying p.d.f. of vn

5

ALICE, JHEP 1807 (2018) 103

vn{m} Moments p(vn)

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Correlations between vm and vn

6

❖ Comparison of SC and Normalized SC (NSC) to hydrodynamic calculations

  • Although hydro describes vn 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)

SC(m, n) = hv2

m v2 ni hv2 mi hv2 ni

Symmetric cumulants:

centrality percentile 10 20 30 40 50 60 70 SC(m,n) 3 − 2 − 1 − 1 2 3

6 −

10 ×

= 2.76 TeV

NN

s ALICE Pb-Pb SC(4,2) SC(3,2) Hydrodynamics /s=0.20 η SC(4,2), /s(T) param1 η SC(4,2), /s(T) param4 η SC(4,2), /s=0.20 η SC(3,2), /s(T) param1 η SC(3,2), /s(T) param4 η SC(3,2),

centrality percentile 10 20 30 40 50 60 70 〉

2 n

v 〈 〉

2 m

v 〈 SC(m,n)/ 0.5 − 0.5 1

〉

2 2

v 〈 〉

2 4

v 〈 SC(4,2)/ 〉

2 2

v 〈 〉

2 3

v 〈 SC(3,2)/ Hydrodynamics /s=0.20 η , 〉

2 2

v 〈 〉

2 4

v 〈 SC(4,2)/ /s(T) param1,2,3,4 η , 〉

2 2

v 〈 〉

2 4

v 〈 SC(4,2)/ /s=0.20 η , 〉

2 2

v 〈 〉

2 3

v 〈 SC(3,2)/ /s(T) param1,2,3,4 η , 〉

2 2

v 〈 〉

2 3

v 〈 SC(3,2)/

ALICE, PRL117, 182301 (2016)

Symmetri Cumulant,

  • A. Bilandzic etc,

PRC 89, 064904 (2014)

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Higher harmonic and higher order

❖ 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 (v24, v32), (v22, v34), (v24, v34) correlation
  • SC(2,3,4) -> probe (v22, v32, v42) correlation

7

ALICE, PRC 97, 024906 (2018)

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Correlations between ψn and ψm

❖ ψn and ψm correlations with ρn,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

10 20 30 40 50

n,mk

ρ 0.2 0.4 0.6 0.8 1

= 2.76 TeV

NN

s Pb-Pb ALICE

4,22

ρ

5,32

ρ

6,222

ρ

6,33

ρ

4,22

ρ

10 20 30 40 50

0.2 0.4 0.6 0.8 1

ATLAS (PRC90, 024905)

w

〉 )

4

Φ

  • 4

2

Φ cos(4 〈

w

〉 )

3

Φ

  • 3

2

Φ

  • 2

5

Φ cos(5 〈

w

〉 )

2

Φ

  • 6

6

Φ cos(6 〈

w

〉 )

3

Φ

  • 6

6

Φ cos(6 〈

5,32

ρ Centrality percentile 10 20 30 40 50

n,mk

ρ 0.2 0.4 0.6 0.8 1

IP-Glasma + MUSIC + UrQMD

4,22

ρ

5,32

ρ

6,222

ρ

6,33

ρ 6,222

ρ

Centrality percentile 10 20 30 40 50

0.2 0.4 0.6 0.8 1

6,33

ρ IP-Glasma:

  • S. McDonald et al.,

PRC 95, 064913 (2017)

ALICE, PLB773 (2017) 68

8

ρ422 = v4,22 v4{2} ⇡ hcos(4Ψ4 4Ψ2)i ρ532 = v5,32 v5{2} ⇡ hcos(5Ψ5 3Ψ3 2Ψ2)i ρ6222 = v6,222 v6{2} ⇡ hcos(6Ψ6 6Ψ2)i ρ633 = v6,33 v6{2} ⇡ hcos(6Ψ6 6Ψ3)i

ATLAS Collaboration, PRC90, 024905 (2014)

  • L. Yan etc, PLB744 (2015) 82
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3.2264d0 You Zhou (NBI) @ COST workshop, Lund 9

Individual constraints

  • Y. Zhou, Nuclear Physics A 982 (2019) 71
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3.2264d0 You Zhou (NBI) @ COST workshop, Lund 10

Differential flow (soft probe)

❖ 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

ALICE, JHEP 09 (2017) 032

) c (GeV/

T

p 1 2 3

n

v 0.1 0.2 = 2.76 TeV

NN

s Pb-Pb Centrality: 20-30% | < 0.8 η | ) c (GeV/

T

p 1 2 3 0.1 0.2 ALICE |>0.8} η ∆ {2,|

2

v |>0.8} η ∆ {2,|

3

v |>0.8} η ∆ {2,|

4

v ) c (GeV/

T

p 1 2 3 0.1 0.2 Hydrodynamics /s=0.20 η , MC-KLN & {2}

n

v /s=0.08 η , MC-Glb & {2}

n

v /s(T) η , Trento & {2}

n

v /s=0.08 η , AMPT & {2}

n

v

ALI−DER−139356

v2 v3 v4

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

❖ 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

Differential flow (hard probe)

PLB776 (2017) 195

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Connection of low and high pT

12

PLB776 (2017) 195

❖ Correlation between high-pT and low-pT v2

  • Investigate connection between v2 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 v2 at both low and high pT

❖ Outlook:

  • quantify the correlation strength with <v2(pTLow)2 v2(pTHigh)2> - <v2(pTLow)2><v2(pTHigh)2>
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3.2264d0 You Zhou (NBI) @ COST workshop, Lund 13

What about intermediated pT

❖ Low pT -> “hydrodynamic flow” (soft probe) ❖ High pT -> “parton energy loss” (hard probe) ❖ What about 2 ≲ pT ≲ 10 GeV/c -> “recombination? coalescence?”

  • interplay of soft and hard probes? Discussions in this COST workshop!
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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

D meson Flow

❖ D0 vs charged hadron (or light flavor)

  • D0 v2 and v3 show smaller but similar

pT dependence

❖ Data vs theory

  • at low pT, comparisons suggest that the

charm quarks flow

  • For pT > 6 GeV/c, v2(D0) ≃ v2(ch), the path

length dependence of charm quark energy 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:

14

CMS, PRL120, 202301 (2018)

K.GULBRANDSEN @ Wed. 14:45

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

❖ Charged hadrons:

  • almost no pT dependence (up to 12 GeV/c)
  • the usage of q2 provides a selection of a global property of the collision

❖ D meson

  • q2 selection effect seems similar with charged hadrons within large uncertainty

15

D meson flow with ESE

ALICE, arXiv:1809.09371

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

❖ 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!

Summary

16 Thanks for your attention!

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

New PhD position at NBI

❖ New PhD position in ALICE group, APPLY now

17

Villum Young Investigator program

— “Creating a smallest droplet of early universe in the Laboratory”

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

backup

18

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Global Bayesian Analysis

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  • S. Bass, QM2017

using Pb-Pb data only

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund 20

Flow as hard probes

ATLAS, EPJC78 (2018) 784

❖

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

Anisotropic flow and QGP

21

ALICE, PRL107, 032301 (2011)

EKRT: H. Niemi et. al, PRC 93, 024907 (2016)

❖ vn also quantitatively described by hydrodynamics using EKRT, AMPT, Trento initial conditions (but not MC-Glauber, nor MC-KLN) with different η/s(T)

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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

) c (GeV/

T

p 1 2 3 4 5 |>2} η Δ {2, |

4

v 0.05 0.1 0.15

±

π

±

K p p+

= 5.02 TeV

NN

s Pb − ALICE Pb | < 0.5, 10-20% y |

❖ Higher order vn and the component from non-linear hydrodynamic response vn,mk

  • Mass dependence at low pT, described by hydrodynamic model iEBE-VISHNU
  • Baryon meson grouping (recombination or coalescence?) at intermediated pT

22

vn and vn,mk of identified particles

) c (GeV/

T

p

1 2 3 4 5

4,22

v

0.02 0.04 0.06 0.08 0.1 = 5.02 TeV

NN

s Pb-Pb 10-20% |<0.8 η | ALICE Preliminary

±

π

±

K p p+

ALI-PREL-157977

ALICE, JHEP 1809 (2018) 006

  • v4. : total flow

v4,22: v4 from ε22

  • v4L. : v4 from ε4
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3.2264d0 You Zhou (NBI) @ COST workshop, Lund

❖ SHEE:

  • Includes initial-state geometry fluctuations
  • use viscous hydrodynamics including event-by-event fluctuations in the soft sector, in

addition to an energy loss model

  • performed with a low shear viscosity to entropy density ratio (η/s), less than or equal

to 0.12

❖ CUJET3.0

  • uses a smooth hydrodynamic back- ground
  • uses pQCD calculations to describe the hard parton interactions in the QGP

, complemented by a perfect-fluid hydrodynamic expansion of the medium.

  • 23