star results from rhic beam energy scan-i lokesh kumar (for star collaboration) outline: motivation...

STAR Results from RHIC Beam Energy Scan-I

Lokesh Kumar (for STAR Collaboration)

Outline:

Motivation Accessing QCD Phase Diagram: T and mB

Searching QCD Phase Boundary: Turning-off QGP signatures

Searching QCD critical point: Enhanced fluctuations BES Phase-II Summary Quark Matter 2012

August 12-18, 2012, Washington, DC

Lokesh Kumar, QM2012 1

Lokesh Kumar, QM2012

STAR BES Program: MotivationMain goals:

Study the QCD phase diagram:

- Search for the signals of possible

phase boundary- Search for softening of EOS

- Search for the possible QCD Critical Point

2

QCD Phase Diagram:

http://drupal.star.bnl.gov/STAR/starnotes/public/sn0493: arXiv:1007.2613

Important Steps:

Proposal: Year 2008Feasibility: Au+Au 9.2 GeV test run [STAR: PRC 81, 024911 (2010)]

Year 2010: First phase started Year 2011: Two more energy points

2

http://drupal.star.bnl.gov/STAR/starnotes/public/sn0493


STAR Experiment

3

MRPC ToF Barrel

BBC

PMD

EMC Barrel EMC End

Cap

TPCHLT

FTPC

Coverage:0 < f < 2p|h| < 1.0

Uniform acceptance: All energies and particles

Year √sNN (GeV) Events(106

)

2010 39 130

2011 27 70

2011 19.6 36

2010 11.5 12

2010 7.7 5

2012* 5 Test Run

Uncorrected Nch

dNev

t / (

Nev

t dN

ch)

BES-I Data:

Rapidity

p T (

Ge

V/c

)

Au+Au 7.7 GeV Au+Au 200 GeV

p p

p p

3


Particle Identification

4

PID (TPC+TOF):pion/kaon: pT~1.6 GeV/cproton pT~3.0 GeV/cStrange hadrons: decay topology & invariant mass

TPC TPC+TOF

Au+Au 39 GeV

4


Two Considerations

5

Changing energy in RHIC BES (higher to low √sNN) and look at the energy dependence trend of various observables

J. Randrup & J. Cleymans,Phys. Rev. C 74 (2006) 047901

RHIC BES

Discuss the observations seen from the data at RHIC BES in view of above two possibilities

Encounter varying net-baryon density Change in baryon to meson ratio 1st order phase transition effects

If lower energy only allows system to enter hadronic phase – Turn off of QGP signatures

Two perspectives:

In this talk:

5


(A) Accessing Phase Diagram

6

T-mB:From spectra and ratios

6


p, K, p Spectra

7

STAR PreliminarySlopes: p > K > p

Proton spectra: - without feed-down correction

p,K,p yields within measured pT ranges:70-80% of total yields

7

STAR Preliminary

X-

Au+Au 39 GeV


Strange Hadron Spectra

Au+Au 39 GeV

K0s L

Au+Au 39 GeV

f, K0s: Levy function fit

, L X : Boltzmann fit L: feed-down corrected

STAR Preliminary

8


Freeze-out Parameters

Centrality dependence of freeze-out temperature with baryon chemical potential observed for first time at lower energies

THERMUS Model:Tch and mB

S. Das: Fri, 6B

Particles used: p, K, p, L, K0

s, X

9

STAR Preliminary

STAR Preliminary

Au+Au


Freeze-out Parameters

Higher kinetic temperature corresponds to lower value of average flow velocity and vice-versa

Blast Wave: Tkin and <b>

S. Das: Fri, 6B

Particles used: p,K,p

10

STAR Preliminary


(B) Turn-OFF of QGP Signals/Softening of Equation of State/1st Order Phase Transition

Au+Au 9.2 GeVAMPT:

<p x

> (

Ge

V/c

)

v1 vs. y: NCQ Scaling: Rcp :

Charge Separation:

1st order phase tranisition?

QGP?

NCQ breaking in hadronic matter?

Dense medium (QGP)

L.P. Csernai et al., PLB 458, 454 (1999)

F. Liu et al., JPG 37 094029 (2010)

K. Fukushima et al., PRD 78, 074033 (2008)

11

Turn-off of QGP?

STAR Preliminary

v 1


Directed Flow

Mid-central collisions:Pion v1 slope: Always negative (7.7-39 GeV)(Net)-proton v1 slope: changes sign between 7.7 and 11.5 GeV

Y. Pandit: Tue, 1A

€

vn = cosn φ −ψ n( ) ,n =1

12

STAR Preliminary

STAR Preliminary

STAR Preliminary


Elliptic Flow

Difference in baryon-antibaryon v2

increases with decreasing √sNN: S. Shi: Fri, 6B

€

vn = cosn φ −ψ n( ) ,n = 2

- - J. Dunlop et al., PRC 84, 044914 (2011)

- - J. Xu et al., PRC 85, 041901 (2012)

13

Poster: A. Schmah #141

For anti-particles: Baryons and mesons show no splitting at 11.5 GeV f-meson v2 deviates (~2s) from others for √sNN ≤ 11.5 GeV: less collectivity contribution from partonic interactions

baryon transport / hadronic interactions

STAR Preliminary


Dynamical Charge Correlations

Splitting between same and opposite-sign charges: Decreases with decreasing √sNN and disappears below √sNN=11.5 GeV

G. Wang: Thu, Plenary RPad

dN

sin21

14

STAR Preliminary


Rcp Measurements

RCP (K0s) < 1 at √sNN > 19.6 GeV

RCP > 1 for √sNN ≤ 11.5 GeV

For pT > 2 GeV/c:X. Zhang: Thu, 5A

E. SangalineThu, 5C

15

Poster: S. Horvat # 94

(Un)-Identified Rcp:


Phase Boundary Search With Nuclei

Need higher statistics to makeconclusive statement

Y. Zhu: Thu, 5A

16

Strangeness Population Factor:

Beam energy dependence of S3 behaves differently in QGPand pure hadron gas

- S. Zhang et al., PLB 684 (2010) 224

- J. Steinheimer et al.,PLB 714 (2012) 85


(C) Searching QCD Critical Point

√sob

serv

ab

le Enhanced Fluctuationsnear Critical Point

T. Andrews. Phil. Trans. Royal Soc., 159:575, 1869

CO2 nearliquid-gas transition

Particle ratio fluctuations (2nd moments) - K/p, p/p, K/p Conserved number fluctuations - Higher moments of net-protons, net-charge,..

17


Particle Ratio Fluctuations

STAR observed monotonic behavior for particle ratio fluctuations vs. √sNN

P. Tribedy: Tue, 2C

€

σdyn = sign(σ data2 −σ mixed

2 ) σ data2 −σ mixed

2

€

σdyn2 ≈ vdyn

dyn,K NK NK 1 NK

2 N N 1 N

2 2NKN

NK N

18

STAR Preliminary STAR Preliminary

K/p

STAR Preliminary

p/p

Poster: Z. Ahammed # 124


Higher Moments: Net-protons

0-5% central collisions: Deviations below Poisson observed for √sNN > 7.7 GeV Peripheral collisions: Deviations above Poisson observed for √sNN < 19.6 GeV Higher statistics needed at 7.7 GeV and 11.5 GeV and possibly a new data point around ~15 GeV

X. Luo: Fri, 7B

2( )N Nσ = < −< > >3

3

( )N Ns

σ< −< > >

=4

4

( )3

N Nκσ

< −< > >= −

S ~

19

Poster: Z. Li # 215


Higher Moments: Net-charge2( )N Nσ = < −< > >

3

3

( )N Ns

σ< −< > >

=4

4

( )3

N Nκσ

< −< > >= −

S ~

STAR Preliminary

Data lies in between Poisson and HRG model expectations

Higher statistics needed at 7.7 GeV and 11.5 GeV and possibly a new data point around ~15 GeV

D. McDonald: Fri, 7B

20

Posters: N. Sahoo # 557, A. Sarkar # 394


Beam Energy Scan Phase- II

21


BES Phase-II proposal Electron cooling will provide increased luminosity ~ 10 times

Proposal BES-II (Years 2015-2017):

A. Fedotov, W. Fischer, private discussions, 2012.

√sNN (GeV) μB (MeV) Requested Events(106)

Au+Au 19.6 206 150

Au+Au 15 256 150

Au+Au 11.5 316 50

Au+Au 7.7 420 70

U+U: ~20 ~200 100

1% Au target

- Annular 1% gold target inside the STAR beam pipe - 2m away from the center of STAR- Data taking concurrently with collider mode at beginning of each fill

: No disturbance to normal RHIC running

Fixed Target Proposal:Poster: B. Haag # 385

22


STAR BES Program Summary

206 5851120 420

2.557.719.639

775

√sNN (GeV)

mB (MeV)

QG

P p

rope

rtie

s

BE

S p

hase

-I

Test

Run

Fix

ed T

arge

t

BE

S p

hase

-II

Large range of mB in the phase diagram !!!

Explore QCD Diagram

23


Summary

Phase Diagram: - Large mB range covered by the STAR in the phase diagram - Centrality dependence of Tch vs. mB observed for the lower energies Phase Boundary: - Proton v1 slope changes sign between 7.7 GeV and 11.5 GeV - Particles-antiparticles v2 difference increases with decreasing √sNN

- f-meson v2 deviates from others for √sNN ≤ 11.5 GeV - Dynamical charge correlations: vanish below 11.5 GeV - Rcp > 1 for pT > 2 GeV/c and √sNN ≤ 11.5 GeV Critical Point: - Ratio fluctuations (2nd moment) show monotonic behavior vs. √sNN

- Deviation from Poisson observed for higher moments of net-protons BES-II: - Propose higher statistics data below 20 GeV - Fixed target proposal to extend mB coverage up to 800 MeV

24

ThanksThanks to STAR Collaboration

Argonne National Laboratory, Argonne, Illinois 60439Brookhaven National Laboratory, Upton, New York 11973University of California, Berkeley, California 94720University of California, Davis, California 95616University of California, Los Angeles, California 90095Universidade Estadual de Campinas, Sao Paulo, BrazilUniversity of Illinois at Chicago, Chicago, Illinois 60607Creighton University, Omaha, Nebraska 68178Czech Technical University in Prague, FNSPE, Prague, 115 19, Czech RepublicNuclear Physics Institute AS CR, 250 68 \v{R}e\v{z}/Prague, Czech RepublicUniversity of Frankfurt, Frankfurt, GermanyInstitute of Physics, Bhubaneswar 751005, IndiaIndian Institute of Technology, Mumbai, IndiaIndiana University, Bloomington, Indiana 47408Alikhanov Institute for Theoretical and Experimental Physics, Moscow, RussiaUniversity of Jammu, Jammu 180001, IndiaJoint Institute for Nuclear Research, Dubna, 141 980, RussiaKent State University, Kent, Ohio 44242University of Kentucky, Lexington, Kentucky, 40506-0055Institute of Modern Physics, Lanzhou, ChinaLawrence Berkeley National Laboratory, Berkeley, California 94720Massachusetts Institute of Technology, Cambridge, MA Max-Planck-Institut f\"ur Physik, Munich, GermanyMichigan State University, East Lansing, Michigan 48824Moscow Engineering Physics Institute, Moscow Russia

NIKHEF and Utrecht University, Amsterdam, The NetherlandsOhio State University, Columbus, Ohio 43210Old Dominion University, Norfolk, VA, 23529Panjab University, Chandigarh 160014, IndiaPennsylvania State University, University Park, Pennsylvania 16802Institute of High Energy Physics, Protvino, RussiaPurdue University, West Lafayette, Indiana 47907Pusan National University, Pusan, Republic of KoreaUniversity of Rajasthan, Jaipur 302004, IndiaRice University, Houston, Texas 77251Universidade de Sao Paulo, Sao Paulo, BrazilUniversity of Science \& Technology of China, Hefei 230026, ChinaShandong University, Jinan, Shandong 250100, ChinaShanghai Institute of Applied Physics, Shanghai 201800, ChinaSUBATECH, Nantes, FranceTexas A\&M University, College Station, Texas 77843University of Texas, Austin, Texas 78712University of Houston, Houston, TX, 77204Tsinghua University, Beijing 100084, ChinaUnited States Naval Academy, Annapolis, MD 21402Valparaiso University, Valparaiso, Indiana 46383Variable Energy Cyclotron Centre, Kolkata 700064, IndiaWarsaw University of Technology, Warsaw, PolandUniversity of Washington, Seattle, Washington 98195Wayne State University, Detroit, Michigan 48201Institute of Particle Physics, CCNU (HZNU), Wuhan 430079, ChinaYale University, New Haven, Connecticut 06520University of Zagreb, Zagreb, HR-10002, Croatia

Than

k Yo

u


BES Related Talks at QM2012

1). Beam Energy Dependence of Strange Hadron Production at RHIC: Xiaoping Zhang, Thu-5A, 15:002). Beam Energy Dependence of Hypertriton Production and Lifetime Measurement: Yuhui Zhu, Thu-5A:15:403). Centrality dependence of freeze-out parameters from the Beam Energy Scan at STAR: Sabita Das, Fri-6B:15:004). Di-electron production dependence on transverse momenta, reaction plane, centralities and collision

energies in Au+Au collisions at STAR: Bingchu Huang, Wed-3C: 09:105). $R_{CP}$ and $R_{AA}$ Measurements of Identified and Unidentified Charged Particles at High $p_{T}$ in Au+Au Collisions at $\sqrt{s_{NN}}=$7.7, 11.5, 19.6, 27, 39, and 62.4 GeV in STAR: Evan Sangaline, Thu-5C: 15:00 6). Event anisotropy $v_2$ of charged and identified particles in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7,

11.5, 19.6, 27, 39 and 62.4 GeV with STAR: Shusu Shi, Fri-6B: 15:207). Study of Net-proton High Order Cumulant in STAR at RHIC: Lizhu Chen, Tue-2C: 15:40 8). Search for the QCD Critical Point by Higher Moments of Net-proton Multiplicity Distributions at STAR:

Xiaofeng Luo, Fri-7B:

17:30 9). Beam energy and centrality dependence of the statistical moments of the net-charge, net-kaon and

total pion multiplicity distributions in Au+Au collisions at STAR: Daniel McDonald, Fri-7B: 16:50 10). Beam Energy Dependence of First and Higher-Order Flow Harmonics from the STAR Experiment at RHIC: Yadav Pandit, Tue-1A: 14:5511). Search for QCD Phase Transitions and the Critical Point Utilizing Particle Ratio Fluctuations and Transverse Momentum Correlations from the STAR Experiment: Prithwish Tribedy, Tue-2C: 16:4512). Search for the Chiral Magnetic Effects in High-Energy Nuclear Collisions: Gang Wang, Thu-IVB: 12:2013). Femptoscopy of identified particles at STAR: Neha Shah, Tue-1C: 14:35


BES Related Posters at QM2012


Poster # Presenter Title

215 Zhiming Li Dynamical higher cumulant ratios of net and total protons at STAR

269 Bingchu Huang Low mass di-electron production in Au+Au collisions at $\sqrt{s_{_{NN}}} = 19.6$ GeV at STAR

385 Brook Haag Results from Fixed-Target Collisions at RHIC: Au+Al at $\root{S_{NN}}$ = 4.5, 3.5 and 3.0 GeV

113 Patrick Huck Dielectron Production in Au+Au-Collisions at $\sqrt{s_{NN}}$ =39 \& 62.4 GeV at STAR

94 Stephen Horvat Collision energy dependence of high transverse momentum $R_{CP}$ of charged hadrons in STAR

557 Nihar Sahoo Higher moments of net-charge multiplicity distributions at RHIC energies from STAR

308 Bill Llope Light (anti)nucleus production in $\sqrt{\rm s_{\rm NN}}$$=$7.7-200 GeV Au$+$Au collisions in the STAR Experiment

124 Zubayer Ahmed Measurement of energy dependence of K/pi fluctuation in STAR experiment at RHIC

394 Amal Sarkar Higher moments of Net Kaon multiplicity distributions at RHIC energies for the search of QCD Critical Point

BES Related Posters at QM2012


Poster # Presenter Title

263 John Novak Incident Energy Dependence of Transverse Momentum Correlations in Au+Au collisions at sqrt(sNN) = 7.7 - 200 GeV in STAR

141 Alexander Schmah Observation of a difference in v2 between particles and anti-particles in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7-62.4 GeV with STAR

121 Hui Wang Beam energy dependent charge balance functions in heavy ion collisions at STAR


Back up

29


Chemical Freeze-out

Statistical-Thermal Model (THERMUS):

€

n =1

V

∂(T lnZ)

∂μ=VTmi

2gi2π 2

(±1)k+1

kk=1

∞

∑ eβkμ i( )K2

kmiT

⎛

⎝ ⎜

⎞

⎠ ⎟

Fitted particle ratios with THERMUS Used grand-canonical approach Two main parameters: Tch and mB

b=1/T; -1(+1) for fermions (bosons), Z=partition function; mi = mass of hadron species i; V = volume; T = Temperature; K2= 2nd order Bessel function; gi = degeneracy; mi = chemical potential

30


Chemical Freeze-out

31


Elliptic Flow

Rate of increase of v2 is slow from 7.7-39 GeV

32


Baryon-Meson Ratio

33

STAR Preliminary


C6/C2

34

L. Chen: Tue, 2C


Fixed Target Set-up

35

star results from rhic beam energy scan-i lokesh kumar (for star collaboration) outline: motivation...

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