Probing the properties of

dense partonic matter at

RHIC

Y. Akiba (RIKEN)

forPHENIX collaboration

PHENIX White paper conclusion• The last paragraph of Formation of dense partonic

matter in nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration (NPA757, 184, 2005)

In conclusion, there is compelling experimental evidence that heavy ion collisions at RHIC produce a state of matter characterized by very high energy densities,......additional incisive experimental measurements combined with continued refinement of the theoretical description is needed to achieve a complete understanding of the state of matter created at RHIC.

What Additional Incisive Experimental measurements do we have in QM2005?

The matter is so opaque that even a 20 GeV 0 is stopped.

• Suppression is very strong (RAA=0.2!) and flat up to 20 GeV/c• Common suppression for 0 and it is at partonic level• > 15 GeV/fm3; dNg/dy > 1100

The matter is so dense that even heavy quarks are stopped

Even heavy quark (charm) suffers substantial energy loss in the matter

The data provides a strong constraint on the energy loss models.

The data suggest large c-quark-medium cross section; evidence for strongly coupled QGP?

(3) q_hat = 14 GeV2/fm

(2) q_hat = 4 GeV2/fm

(1) q_hat = 0 GeV2/fm

(4) dNg / dy = 1000

The matter is so strongly coupled that even heavy quarks flow

• Charm flows, but not as strong as light mesons.

• Drop of the flow strength at high pT. Is this due to

b-quark contribution?• The data favors the

model that charm quark itself flows at low pT.

• Charm flow supports high parton density and strong coupling in the matter. It is not a weakly coupled gas.

v2(D)=0.3 v2()

v2(D)=0.6 v2()

v2(D)=v2()

Greco,Ko,Rapp: PLB595(2004)202

• The first promising result of direct photon measurement at low pT from low-mass electron pair analysis.

• Are these thermal photons? The rate is above pQCD calculation. The method can be used in p+p collisions.

• If it is due to thermal radiation, the data can provide the first direct measurement of the initial temperature of the matter.

• T0max ~ 500-600 MeV !?

T0ave ~ 300-400 MeV !?

The matter is so hot that it emits (thermal?) photon copiously

PHENIX preliminary

The matter is so dense that it melts(?) J/ (and regenerates it ?)

CuCu

200 GeV/c

AuAu

200 GeV/c

dAu

200 GeV/c

AuAuee

200 GeV/c

CuCuee

200 GeV/c

• J/’s are clearly suppressed beyond the cold nuclear matter effect

• The preliminary data are consistent with the predicted suppression + re-generation at the energy density of RHIC collisions.

• Can be tested by v2

(J/)?

The matter is so dense that it modifies the shape of jets

• The shapes of jets are modified by the matter.– Mach cone?– Cerenkov?

• Can the properties of the matter be measured from the shape?– Sound velocity– Di-electric constant

• Di-jet tomography is a powerful tool to probe the matter

PHENIX preliminary

The matter may melt but regenerate J/’s

Put the results together

The matter is dense The matter is strongly coupled

The matter is hot

Can we determinethe properties of the

matter?

We look forward to working with the theory community to extract the properties of the matter

The matter modifies jets

> 15 GeV/fm3

dNg/dy > 1100

Tave = 300 - 400 MeV (?)Vs = ?(dielec) = ?PHENIX preliminary

Summary: Probing partonic state of dense matter• RHIC has produced a strongly interacting, partonic s

tate of dense matter• We now have started probing the properties of the m

atter– The energy loss mechanism and initial parton density from

jet suppression and flow data of light and heavy quarks

>15 GeV/fm3 and dNg/dy > 1100 – the initial state temperature from thermal radiation

T0ave = 300-400 MeV?

These high densities and temperatures are unprecedented

• We look forward to working with the theory community to relate the wealth of experimental observables to the properties of matter.

The matter may melt but regenerate J/’s

Probing Partonic State of Matter

The matter is dense The matter is strongly coupled

The matter is hot

We look forward to working with the theory community to extract the properties of the matter

The matter modifies jets

PHENIX preliminary

• backup

PHENIX: Reaction Plane Angle

– Study (di)jet correlations vs angle of trigger hadron relative to reaction plane

• J. Bielcikova et al,

Phys. Rev. C69:021901, 2004

trig = trig - • 6 bins from 0 to /2.

– Flow systematics change com

pletely vs trig

– Can study dependence of distortion on geometry.

Shoulder and dip seen

in all trig bins.

trig

?

From Poster by J. Jia