probing the properties of dense partonic matter at rhic
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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
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