Spectra Physics at RHIC :Highlights from 200 GeV data

Spectra Physics at RHIC :Highlights from 200 GeV data

Manuel Calderón de la Barca Sánchez

ISMD ‘02, Alushta, Ukraine Sep 9, 2002

2

Understanding “Bulk” Matter in HI collisions

Studying Matter:

Global Observables Nch, ET, pT

, S, …

Particle Yields & Ratios Tch, B, S, …

Particle Spectra Tfo, flow, stopping, …

STAR preliminary

99.5%

3

Nch: Centrality Dependence at RHIC (SPS)

_pp

PHOBOS Au+Au ||<1

19.6 GeVpreliminary

130 GeV

200 GeV

Au+Au

(preliminary)

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

collpp

partpp

Nxn

Nnx

d

dN

2

)1(

4

ET/ Nch from SPS to RHIC

Independent of energyIndependent of centrality

PHENIX preliminaryPHENIX preliminary

Surprising fact: SPS RHIC: increased flow, all particles higher pTstill ET/ Nch changes very littleDoes different composition (chemistry) account for that?

5

pT of Charged Hadrons from SPS to RHIC

STAR preliminary

2212

R

ddNccp ch

T

Saturation model:J. Schaffner-Bielich, et al. nucl-th/0108048D. Kharzeev, et al. hep-ph/0111315

Many models predict similar scaling (incl. hydro) Need data around s = 70 GeVto verify (or falsify)

increase only ~2%

6

Ratios

Huge amount of results from all 4 RHIC experiments:• systematic studies of: -/+, K-/K+, p/p/ ,/,/,

/p, K/ , /, /h, K, K*/K, … many as function of pT, Npart

at s of (20), 130, and 200 GeV Problem: with and without feed-down correction

BRAHMS large y coverage and reach to high pT

PHENIX reach to high pT

STAR multi-strange baryons

7

Ratios at RHIC I : vs. p

All experiments: 1K/K 0.95

Does p/p also stay constant, or does it begin falling?

8

Ratios at RHIC II: vs. y

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

BRAHMS 200 GeV

9

K-/K+ and p/p from AGS to RHIC

Slightly different view of statistical model.

Becattini calculation 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)

10

Rapidity Spectra: Boost-Invariance at RHIC ?

D. Ouerdane (BRAHMS)

1cosh)/(

cosh)/(),( :Jacobian

22

mp

mpp

y

11

Boost-Invariance at RHIC ?

• dN/dy of pions looks boost-invariant BUT

• change in slopes for rapidity already from 0 1

• BRAHMS (J.H. Lee): no change in proton slope from y = 0 3 BUT increase in dN/dy Boost invariance only achieved in small region |y|<0.5

12

Identified Particle Spectra at RHIC @ 200 GeV

Feed-down matters !!!

BRAHMS: 10% centralPHOBOS: 15%PHENIX: 5%STAR: 5%

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Interpreting the Spectra

The shape of the various particle spectra teach us about: Kinetic freeze-out temperatures Transverse flow

The stronger the flow the less appropriate are simple exponential fits: Hydrodynamic models (a la Heinz/Kolb/Shuryak/Huovinen/Teaney) Hydro inspired parameterizations (Blastwave)

Blastwave parameterization: Ref. : E.Schnedermann et al, PRC48 (1993) 2462 (modifications by Snellings, Voloshin) Very successful in recent months

Spectra HBT (incl. the Rout/Rside puzzle) Flow

spectra ()

HBT

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Blastwave Fits at 130 & 200 GeV

Fits M. Kaneta (STAR)

200 GeV

Results depend slightly on pT coverageSTAR:Tfo ~ 100 MeV T ~ 0.55c (130) & 0.6c (200)PHENIX:Tfo ~ 110 MeV (200)T ~ 0.5c (200)

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What flows and when?

<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

and appear todeviate from commonthermal freeze-out Smaller elast? Early decoupling from expanding hadronic medium? Less flow?What about partonic flow?

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Does it flow? Fits to Omega mT spectra

• What do we now about elast of and ?• May be it flows, and may be they freeze out with the others• Maybe and are consistent with a blastwave fit at RHIC• Need to constrain further more data & much more for v2 of

SPS/NA49

RHIC

STAR preliminary

T is not well constrained !

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Other Attempts: The Single Freeze-Out Model

Single freeze-out model (Tch=Tfo)

(W. Broniowski et. al) fit the data well (and reproduce , K*, ,

Thermal fits to spectra are not enough to make the point.

To discriminate between different models they have to prove their validity by describing:

Spectra (shape & yield) Correlations (HBT,

balance function, etc.) Flow

Only then we can learn …

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Conclusions

• Flood of data from SPS & RHIC new probes correlations between probes higher statistics & precision

• Models (Generators) are behind The majority of models in RHI fail already describing global

observables (possible exception AMPT) Many models describe “A” well but fail badly at “B” can still be useful but limited scope

We learn more by combing various pieces and putting them into context

Thermalization, Chemical and Kinetic Freeze-out Conditions, and System Dynamics can only be studied (and are studied) using all the pieces together

Agreement between thermal fits to particle spectra and ratios + flow makes a very strong case for thermalization of matter created at RHIC