New Experimental Results from RHIC

Mark D. Baker (BNL)

Current and Future Directions at RHIC August 6, 2002

Many thanks to: Thomas Ullrich, Sergei Voloshin, Thomas Peitzmann

Mark D. Baker

Organization

• Initial State• “Bulk” Matter• Boost (Non)-Invariance• “Jet quenching”

Or failure to scale with Ncoll...

• Opacity/Explosiveness

• High2002 pT puzzles

• Summary

Mark D. Baker

PRL 88 (2002) 022302

• Start with low entropy• Final state interactions just reshuffle

Multiplicity is a window on the initial state

s (GeV)

Mark D. Baker

RHIC: Nch at mid-rapidity

Consistency of RHIC resultsPHENIX: PC, STAR: TPC

PHOBOS: Si BRAHMS: Si & Scint.

A. Bazilevsky (PHENIX)

PHENIX & STARpreliminary

Ratio R(200/130):BRAHMS: 1.14 0.05PHENIX: 1.17 0.03PHOBOS: 1.14 0.05STAR: 1.19 (no sys. yet)

QM2002 summary slide (Ullrich)

Mark D. Baker

Nch: Centrality Dependence at RHIC (SPS)

_pp

PHOBOS Au+Au ||<1

19.6 GeVpreliminary

130 GeV

200 GeV

Au+Au

(preliminary)

M. Baker (PHOBOS)

Everything counts:• Nch|=0 described nicely by KN (hard + soft)• Nch scales with Npart

collpp

partpp

Nxn

Nnx

d

dN

2

)1(

QM2002 summary slide (Ullrich)

Mark D. Baker

Nch(sNN) – Universality of Total Multiplicity?

pQCD e+e- Calculation

)/exp( sBsch CAN

Total charged particle multiplicity / participant pair

Total particle multiplicity reflects the initial state?Note: Still interesting dynamics in the final state interactions!

(A. Mueller, 1983)

2/sseff

Same for all systems at same s(seff for pp)

Mark D. Baker

e+e- measures dN/dyT

(rapidity relative to“thrust” axis)

200 GeV

More detailed comparison of AA, ee

Mark D. Baker

Understanding “Bulk” MatterStudying Matter:

Global Observables Nch, ET, pT

, S, …

Particle Yields & Ratios Tch, B, S, …

Particle Spectra Tfo, flow, stopping, …

Correlations

… and all that in pp, pA, AA

STAR preliminary

99.5%

QM2002 summary slide (Ullrich)

Mark D. Baker

Statistical Model: First Look at AuAu @ 200 GeV

All 200 GeV data taken from QM talks:F. Wang (STAR)/G. Van Buren (STAR)/T. Chujo (PHENIX)/Ouerdane (BRAHMS)J. Lee (BRAHMS)/B. Wosiek (PHOBOS)New 130 GeV data are:C. Suire (STAR)/J. Castillo (STAR)

Predictions:phenomenologically: B ~ 1.3 GeV (1+s/4.5 GeV)-1

assume unified freeze-out condition: E/N ~ 1.1 GeV T

QM2002 summary slide (Ullrich)

Mark D. Baker

K-/K+ and p/p from AGS to RHICI. Bearden (BRAHMS)

Becattini caluclation usingstatistical model: T=170, s=1 (weak dependency)

vary B/T K+/K- andp/p

K- /K+=(p/p)1/4 is a empirical fit to the data points

KK driven by s

~ exp(2s/T)

p/p driven by B

~ exp(-2B/T)

s = s (B) since <S> = 0BUT: Holds for y 0 (BRAHMS y=3)

QM2002 summary slide (Ullrich)

Mark D. Baker

Radial flowM. Kaneta/N. Xu (STAR)

<pT> prediction with Tth

and <> obtained from blastwave fit (green line)

<pT> prediction for Tch = 170 MeV and <>=0pp no rescattering, no flowno thermal equilibrium

STAR

preliminaryF. Wang

Mark D. Baker

Identified Particle Spectra at RHIC @ 200 GeV

Feed-down matters !!!

BRAHMS: 10% centralPHOBOS: 10%PHENIX: 5%STAR: 5%

QM2002 summary slide (Ullrich)

Mark D. Baker

Elliptic Flow

V2

Normalized Multiplicity

Particle asymmetry

dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R)) + ... )

midrapidity : || < 1.0

STAR

Mark D. Baker

Centrality dependence @ RHIC.

STAR

v2=0.05

130 GeV: 0.075< pt < 2.0 200 GeV: 0.150< pt < 2.04-part cumulants

200 GeV: 0.2< pt < 2.0

Preliminary

200 GeV: Preliminary

Note possible dependence on low pt cut

- Consistent results- At 200 GeV better pronounced decrease of v2 for the most peripheral collisions.

STARPreliminary

QM2002 summary slide (Voloshin)

Mark D. Baker

v2 vs pseudorapidity

Talk by S. Manly

PHOBOS: No boost invariance !

QM2002 summary slide (Voloshin)

Mark D. Baker

p + p inel.

UA5, Z.Phys.C33, 1 (1986)

dN

/d

Systematic errors not shown

19.6 GeV is preliminaryPHOBOS Au+Au

dN

ch/d/<

Np

art>

beamy

6% central

beamy

Growth of Limiting Fragmentation Region

Mark D. Baker

Interlude: Many ways to slice pz

FTTz xs

pymp2

sinhsinh:

Away from mid-rapidity:

epem Ty

T TT pmy ln

Rapidity: Generalized velocity

Pseudorapidity: ~y: easier to measure

Feynman x: scaled pz

Mark D. Baker

Rapidity dists.: Boost-Invariance at RHIC ?

M. Baker (PHOBOS)

D. Ouerdane (BRAHMS)

1cosh)/(

cosh)/(),( :Jacobian

22

mp

mpp

y

QM2002 summary slide (Ullrich)

Mark D. Baker

NEW: Rapidity dependence of ratios at RHICI. Bearden (BRAHMS)

BRAHMS 200 GeV

At mid-rapidity:Net-protons: dN/dy 7proton yield: dN/dy 29 ¾ of all protons from pair-production

QM2002 summary slide (Ullrich)

Mark D. Baker

Boost-Invariance at RHIC ?

Boost invariance only achieved in small region |y|<0.5

Thomas Ullrich,

QM2002

Mark D. Baker

Suppression of Hadron Production (130 GeV)

ratio of pT-spectra AA central / pp

RAA < 1 for central Au+Aureactions at RHIC (130 AGeV)

observed in neutral pions and charged hadrons (PHENIX and STAR)

RAA d 2N AA dydpT

d 2N pp dydpT NcollAA

RAA =1 for scaling with number of binary collisions

J.C. Dunlop et al. , Nucl. Phys. A 698, 515c (2002)

K. Adcox et al. , Phys. Rev. Lett. 88, 22301 (2002)

QM2002 summary slide (Peitzmann)

Mark D. Baker

Energy Dep. of pT-spectra in pp and AA

spectra in pp strong variation

with beam energy “flattening”

of spectra power law

influence of hard scattering

K. Reygers et al., Hirschegg 2002

spectra in AA little variation

with beam energy almost exponential

influence of thermal production?

QM2002 summary slide (Peitzmann)

Mark D. Baker

Preliminary sNN = 200 GeV

Preliminary sNN = 200 GeV

C. Jorgensen, BRAHMS Parallel Saturday

C. Roland, PHOBOS Parallel Saturday

J. Jia, PHENIX Parallel Saturday

J. Klay, STAR Parallel Saturday

200 GeV results from all experiments

Charged Hadron Spectra

QM2002 summary slide (Peitzmann)

Mark D. Baker

The 4 experiments

Thomas Peitzmann, QM2002

Mark D. Baker

Normalize by Npart/2. Divide by the value at Npart=65

PHOBOS Preliminary:

Au+Au 200 GeV

UA1 pp (200 GeV)

Participant scaling of AuAu vs. AuAu??

C. Roland, QM2002

S. Mioduszewski, QM2002

Mark D. Baker

Jet Evidence in Azimuthal Correlations at RHIC

near-side correlation of charged tracks (STAR)

trigger particle pT = 4-6 GeV/c

distribution for pT > 2 GeV/c

signature of jets

also seen in (0) triggered events (PHENIX)

trigger particle pT > 2.5 GeV/c

distribution for pT = 2-4 GeV/c

M. Chiu, PHENIX Parallel Saturday

QM2002 summary slide (Peitzmann)

Mark D. Baker

Counter-Jet Suppressionjet suppression measure as a function of centrality

trigger-jet little modification(?)

most trigger particles from jets!

counter-jet strong suppression

with increasing Npart jet quenching?

inconsistencies for smallertrigger momentum

to be investigated

D. Hardtke, STAR Plenary Tuesday

QM2002 summary slide (Peitzmann)

Mark D. Baker

Surface Emission?

Jets ~ Npart??

How about Ncoll / V ?Future measurements may clarify this...

Idea from X.N.Wang, QM2002

Mark D. Baker

Opaque expanding source would mean:

Heiselberg, Levy,.PRC 59 (1999) 2716

)/(2 Tpufv TT

Mark D. Baker

High pT v2 reaches geometric surface limitv 2

impact parameter (fm)

QM2002 (Voloshin)

E. Shuryak, nucl-th/0112042

QM2002 (Filimonov, STAR)

)/()cos(

;)sin(

max,

Rb

v

262

2

ααα

Mark D. Baker

Opaque, expanding source would mean:

2222222 2)()( xtso YXRR

)(outX

)(sideY

29.13

5)(

)(

spheres

shellhalfs

R

R

65.012

5)(

)(

sphereo

shellhalfo

R

R

Opaque Expanding

Rischke RIKEN workshop (2002): Such strong xt correlations probably require a lack of boost-invariance...

Mark D. Baker

kT dependence of Rout/Rside

A. EnikizonoQM2002

C.M. Kuo, QM2002 poster (PHOBOS) 200 GeV:

.)(25.009.016.1 syst @0.25 GeV/c

Mark D. Baker

p/

• Proton yield is comparable with pions @ 2 GeV in central collisions, less in peripheral

Central

p/

Peripheral

Tatsuya Chujo (PHENIX)

Mark D. Baker

High pT Puzzle I:

T. Sakaguchi, PHENIX Parallel Saturday

Important baryon and/or kaon contribution out to pT = 8 GeV/c?

S. Mioduszewski, PHENIX

Mark D. Baker

Adler et al., nucl-ex/0206006

High pT puzzle II:

Still flowing at pT = 8 GeV/c?

Mark D. Baker

Our state is extreme• Hot dense state

Freezeout temperature near theoretical transition High Energy Density

• Very black source. v2 ~pT and ~ maximum allowed from surface

HBT Ro/Rs

Approximate Npart scaling of high pT particles

• Explosive source. Radial flow at roughly the speed of sound HBT Ro/Rs

(Unlike 2-particle correlations)• Alternatively (or additionally):

Magic near-instantaneous freezeout Blast wave or Humanic model

• Puzzles left at high pT

Mark D. Baker

Oh, what one day can do...

CERN baseline (17.3 GeV) PHOBOS preliminary

& NA49PbPb* WA98 (0-5%)

PbPb* NA50 (0-5%)

PbPb* NA50 (5-10%)

PbPb EMU13 (0-9%)

PbPb NA49 (0-5%)

PbPb 17.3 GeV (0-5%)

AuAu 19.6 GeV (0-6%)

Mark D. Baker

Energy Density Estimate (Bj)

Latticec

Bj~ 5 GeV/fm3

Bj~ 25 GeV/fm3

02j

TB

1 1 d

c dy

E

R

formation time: 0.2 - 1 fm

PRL 87 (2001) 052301