collective dynamics · au+au 30%-60% bes-i bes-ii but models with magnetic field-independent...

Realizing the Long Range Plan at RHIC

When you make things complicated enough, they become simple again.

Paul Sorensen

June 10, 2016

Collective Dynamics

The Phase Transitions in the Early Universe

RHIC is ideally suited to study the phase transition that occurred a few microseconds after the Big Bang

One microsecond after the Big Bang, the universe was filled with Quark Gluon Plasma: Quantum Chromodynamics describes how

that QGP froze into the nuclear matter we are made of today

Region Covered by RHIC Energy Scan

2

Lattice QCD: Borsanyi et.al. arXiv:1007.2580

2

Key Discoveries in Collective Dynamics

Discoveries and theory advances enabled by RHICs flexibility give us a detailed model of the evolution of nuclear collisions

Data can only be described using: •  an equation-of-state consistent with first principles QCD calculations •  a plasma phase with a viscosity smaller than any other known fluid

The hottest matter ever created is also the most perfect fluid known in nature!

Transverse Slice

4

Emergence of near-perfect fluidity: characterization (η/s(T) for example) and understanding

Can the same fluctuations that could have created the asymmetry between matter and anti-matter during the electro-weak phase transition be measured in the QGP phase in heavy ion collisions (chiral anamoly)?

Breaking of chiral symmetry in QCD generates 99% of the visible mass of the universe. Is chiral symmetry restored in these collisions?

Goals for Collective Dynamics

Quark Gluon Plasma Mapping the phase diagram: At low density, the phase transition between QGP and hadrons is smooth. Is there a 1st order transition and a critical point at higher density?

Probing Chiral Symmetry with Quantum Currents

(GeV)NNs10 210 310

4 1

0×

) O

S-H

SS

(H 0

1

2

0.5 0.4 0.3 0.2 0.1

(GeV)B

µ

Au+Au 30%-60%

BES-I

BES-II

But models with magnetic field-independent backgrounds can also be tuned to reproduce the observed charge separation

charge separation

The chiral anomaly of QCD creates differences in the number of left and right handed quarks.

In a chirally symmetric QGP, this imbalance can create charge separation along the magnetic field

+ -

B=1018 Gauss

a similar mechanism in electroweak theory is likely responsible for the matter/antimatter asymmetry of our universe

observed at all but the lowest energy

General Consistency

6

Chiral Magn. Wave as Predicted

0

0.1

0.2

0.3

0.4

0.025 0.035 0.045

U+U 193 GeV 0-10%∆η>0.025

STAR Preliminary(γO

S -γSS

) × 1

04

v2 {2}

Multiplicity binningSpectator binningSTAR QM12 (1210.5498)

Charge Separation ∝ B not v2

Phys.Rev.Lett. 107 (2011) 052303

charge distribution

Questions of Interpretation Remain

7

Current understanding: backgrounds unrelated to the chiral magnetic effect may be able to explain the observed charge separation

-0.01

0

0.01

0.02

0.03

0.04

0 10 20 30 40 50 60 70

M/2

(γos

- γ s

s)

% centrality

STARBlastWave (σφ=0)

BlastWave

-0.01

0

0.01

0.02

0.03

0.04

0 10 20 30 40 50 60 70

M/2

(γos

- γ s

s)

% centrality

v2 CB (σφ=0)v2 CB

-0.01

0

0.01

0.02

0.03

0.04

0 10 20 30 40 50 60 70

M/2

(γos

- γ s

s)

% centrality

v2c (σφ=0)v2c

-0.01

0

0.01

0.02

0.03

0.04

0 10 20 30 40 50 60 70

M/2

(γos

- γ s

s)

% centrality

v2s (σφ=0)v2s

background model charge separation in Au+Au at 200 GeV

Difficult to draw definitive conclusions without well understood, independent lever arms for B and v2. Better statistics from BESII won’t be enough.

Probing Chiral Symmetry with Quantum Currents

8

Current understanding: backgrounds unrelated to the chiral magnetic effect may be able to explain the observed charge separation

Isobar collisions in 2018 can tell us what percent of the charge separation is due to CME to within +/- 6% of the current signal

4096Zr + 40

96Zr vs. 4496Ru+ 44

96Ru

Background level (%)0 50 100

(R

uR

u-Z

rZr)

γ∆

Re

l. d

if.

in

0

0.05

0.1

0.15

Sig

nif

ica

nc

e

0

2

4

6

8

10

12

14

16

18

case 1

case 2

32

σ5

= 200 GeVNNs

20 - 60%

projection with 400M events

Rel

ativ

e di

ffere

nce

in c

harg

e se

para

tion

(Ru

vs Z

r)

9 9

Models show that higher harmonic ripples are sensitive to the presence of a QGP: v3 goes away when the QGP goes away

Data show v3 is present even at the lowest energies and far stronger than can be explained by non-QGP models

But it disappears at lower energies for Npart<50

t = 0 fm t = 2.5 fm t = 5 fm B. Schenke et.al., Phys. Rev. C 85, 024901

Elliptic n=2 flow (image of an atomic fermi gas)

All harmonic flow (QGP simulation)

Mapping the Phase Diagram: QGP at 7 GeV?

0 100 200 300

0

0.02

0.04

0.06

0.08

0.1

AMPT Default; 7.7 GeV

{2}23vpartN

partN

=200 GeVNN

s 62.4 39 27 19.6 14.5 11.5 7.7

Non-QGP Model

10

)2

(fm

2 sid

e -

R2 o

ut

R

6

8

10

12

0.5 0.4 0.3 0.2 0.1

(GeV)B

µ

= 0.26 GeVT

0%-5%; m

/dy

1dv

0

0.01

10%-40%; net-proton

(GeV)NNs10 210 310

ch,p

p/n

{2}

2 3v

0.04

0.05

0.06

0.07

0.08

>0.2 GeVT

0%-5%; p

Maximum in lifetime?

Minimum in pressure?

Region of interest √sNN≲20 GeV, however, is complicated by a changing B/M ratio, baryon transport dynamics, longer nuclear crossing times, etc. Requires concerted modeling effort: the work of the BESTheory topical collaboration is essential

BESI: Anomalies in the Pressure?

11

Non-monotonic trend observed but statistical precision is limited

The moments of the distributions of conserved charges are related to susceptibilities and are sensitive to critical fluctuations

BESI: Critical Behavior?

Higher moments like kurtosis*variance κσ2 change sign near the critical point

Mapping the region of interest: BES-II

12

0 0.1 0.2 0.3 0.4 0.5

Mill

ion

Eve

nts

10

210

310

7.7

9.1

11.5

14.5

19.6

273962.4

200

(GeV)NNs

Cu

rre

nt

Da

ta S

ets BES-II

0 0.1 0.2 0.3 0.4 0.5

/dy

1dv

0

0.01

0.02net-proton

10%-40% BES-I

10%-15% BES-II

(GeV)B

µ

0 0.1 0.2 0.3 0.4 0.5

ne

t-p

roto

n2

σκ

0

1

2

3

0%-5% Au+Au; |y|<0.5

< 2.0 GeV (Prelim.)T

0.4 < p

BES-II

rapidity width0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

net-

pro

ton

2σ

κ

0

1

2

3

=7.7 GeVNNs

=27 GeVNNs

7.7 GeV BES-II

0 0.1 0.2 0.3 0.4 0.5

Mill

ion

Eve

nts

10

210

310

7.7

9.1

11.5

14.5

19.6

273962.4

200

(GeV)NNs

Curr

ent D

ata

Sets BES-II

0 0.1 0.2 0.3 0.4 0.5

/dy

1dv

0

0.01

0.02net-proton

10%-40% BES-I

10%-15% BES-II

(GeV)B

µ

0 0.1 0.2 0.3 0.4 0.5

ne

t-p

roto

n2

σκ

0

1

2

3

0%-5% Au+Au; |y|<0.5

< 2.0 GeV (Prelim.)T

0.4 < p

BES-II

rapidity width0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

ne

t-p

roto

n2

σκ

0

1

2

3

=7.7 GeVNNs

=27 GeVNNs

7.7 GeV BES-II

More Data RHIC Luminosity Upgrade needed for Low Energies

Better Coverage

BES-II: detector and accelerator upgrades for 2019 and 2020

RHIC Run Plan

13

By 2022, large acceptance BESII detector will never have seen 200 GeV Au+Au

Untapped potential for a broad physics program including longitudinal dynamics complimentary to the jet and Quarkonium program of sPHENIX

2016 2017 2018 2019 2020 2021 2022+-200GeVAu+Au-d+AuEnergyScan

-500GeVp+p-62.4or27GeV?

IsobarZr+ZrandRu+Ru BES-II BES-II FullEnergyAu+Au

2η+

1η

0 1 2 3 4 5

cove

rage

η∆

0

1

2

3

4

5

TPC

iTPC

STAR Forward Upgrades FCS/FTS

at 14.5 GeV

beam

y

No. of Particles Correlated

0 1 2 3 4 5

iTP

C B

oost

0

1

2

3

4

5

Spectra

, Ridgen v

di-leptons

2σκ RP Corr.

CME

4N)δ (RP. Corr.

{4}n v

← di-baryons x11

astrophysical implications

Early Time Dynamics

14






Early Time Dynamics

15






Current Measurements

16






Temperature Dependence of η/s

17






18

RHIC provides access to emergent phenomena of QCD: •  Hottest man-made temperature: 300k times hotter than the center of the sun •  Data shown to prefer an Equation-of-State consistent with lattice QCD •  The QGP created at RHIC is the most perfect liquid ever known •  Exploratory scan finds QGP and intriguing behavior below 20 GeV

Following this progress we want to make measurements needed •  to define the phase structure in the QCD phase-diagram (critical point?) •  study the chiral properties of the QGP •  map the T dependence of η/s and other transport properties

In 2018: Isobar collisions will provide definitive evidence on the chiral magnetic effect in 2019-2020: Detector and accelerator upgrades will provide key abilities in the search for a critical point Extended coverage intended for BESII opens up many opportunities for a diverse program in 2022+

Steps toward fulfilling the promise of RHIC

Thanks

BESI: Do We Create QGP at Lower Energies?

The minimum εcτ for QGP formation is between 0.6-1.8 GeV/fm2

BES-I exploratory scan was carried out to shed light on this question

Energy density measurements from exploratory scan: BES-I 2010-2014

21

A. Adare et al. Phys. Rev. C 93, 024901

Head-on Collisions Npart~350

Grazing Collisions small Npart

well above

too close to call

22 22

Models show that higher harmonic ripples are very sensitive to the existence of a QGP phase

v3 goes away when the QGP phase disappears

← n=2 →

J. Auvinen, H. Petersen, Phys. Rev. C 88, 64908

t = 0 fm t = 2.5 fm t = 5 fm B. Schenke et.al., Phys. Rev. C 85, 024901

Elliptic n=2 flow (image of an atomic fermi gas)

All harmonic flow (QGP simulation)

Do We Create QGP at Lower Energies?

23 23

10 210 310

0.04

0.06

0.08

0.1

0.12

0.14

3−10×

ch,PP/n{2}23v

(GeV)NNs

0-5% 10-20% 30-40% 50-60%

Higher energy collisions producing more particles and higher pressure should more effectively convert fluctuations into v3.

Deviations from that expectation could be indicative of interesting trends like a slowing of the speed of sound. What does v3

2/Nch look like?

Critical Behavior: Anomalies in the Pressure?

collective dynamics · au+au 30%-60% bes-i bes-ii but models with magnetic field-independent...

Documents