PHENIX???? ????????????

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PHENIX????????????????

• ?????
• ???

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Open Questions
Formation of hot and dense matter is
established. Still, we have many important
questions to answer.

• Is the matter deconfined?
• J/y suppression
• How does Heavy-flavor act?
• Heavy flavor measurements
• Is Chiral symmetry restored?
• Vector meson
• Radiation? Mass shift?
• Di-lepton continuum

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_at_SPS
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CERES
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CERES 2
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NA60

• ? and ? fix yields such as to get, after
  subtraction, a smooth underlying continuum
• ?
• (?) set upper limit, defined by saturating the
  measured yield in the mass region close to 0.2
  GeV/c2 (lower limit for excess).
• (?) use yield measured for pT gt 1.4 GeV/c

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Whats this?
van HeesRR 06

• absolute norm., melting r
• Mgt0.9GeV 4p?mm w and f ?!

• baryon effects essential

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Model 2
Contributions included in our calculation
QGP quasi-particle picture, (Schneider et al.
(2002))
In-medium Rho spectral function (Eletsky et. al.
(2001))
In-medium Omega spectral function (Martell
Ellis (2004))
In-medium Phi not (yet) included
Renk, Ruppert (2006)
(Results were obtained by folding with the
schematic acceptance matrix, not the full MC
acceptance simulation.)
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f? _at_RHIC
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Chiral Symmetry in Hadronic matter

• Mass shift and/or modification of vector mesons
  are expected
• Lepton decays become good probes
• Not interacting strongly.
• However, we only see integrated information from
  all stages of collisions.
• QGP, Mixed, Hadron gas
• Comparisons between lepton decays and hadron
  decays in several collision systems are important

R. Rapp (Nucl. Phys A661(1999) 238c
After Freeze Out
Hadron gas
QGP

• Integrated information

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Observables in vector meson measurements

• Line shape
• Direct measurements
• Yield
• Q value of f ? KK is small
• Should be sensitive to mass changes in either f
  or K
• pT slope
• Difference between hadron decays and lepton
  decays
• It could show the difference of collision stage.

Lissauer and Shuryak, Phys. Lett. B253, 15 (1991).
T.Hatsuda and S.Lee (Phys.Rev.C46-R34-38, 1992)
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Measurement
Dalitz Conversion g
After BG subtraction
Raw spectrum (Combinatorial BG included)
Invariant mass spectrum of ee- in PHENIX
0
1
2
3
GeV/c2
Clear f, w, and J/y peaks with very good mass
resolution!!
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f hadron and lepton decays
Main issue KK- and ee- seem not consistent
Many efforts are on-going to understand the
difference btw K and e.
We have to prove that the difference is not made
artificially. Analysis in dAu and pp data is
important as baseline.
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Baseline - dAu
d Au collisions at vsNN 200 GeV
f? ee-
f? KK-
Combinatorial Background
Counts per 10 MeV/c2

• N?120

PHENIX Preliminary
PHENIX Preliminary
ee- invariant mass (GeV/c2)
To settle cold nuclear matter effect, Both f?
ee- and f? KK- are measured in d-Au collisions
and results are compared.
KK- invariant mass (GeV/c2)
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dN/dy in dAu

• dN/dy is compared between ee and KK.

dN/dy
KK channel dN/dy 0.0468 /- 0.0092(stat)
(0.0095,-0.0092) (syst.) ee channel dN/dy.056?.
015(stat) ?50(syst)
dN/dy
KK
No significant difference between ee and KK
within statistical and systematic errors.
ee
PHENIX preliminary
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pp
omega
phi
ds/dy Extracted by integration OMEGA 3.50037 /-
0.175942 (stat) /- 0.875 (sys) 4.37554 (upper
sys) 2.62521 (lower sys) PHI 0.369182 /-
0.0195987 (stat) /- 0.0894 (sys) 0.458564
(upper sys) 0.2798 (lower sys)
??
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w spectra

• Spectra of w meson are measured in several
  collision systems.

• pp

• AuAu

• dAu

• Results are mainly obtained using hadron decays.
• Analysis for electron decay mode is underway.

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New approaches for f and w

• No PID method for f ? KK-

• f in pp

• It works very well especially in high pT region
• Combinatorial BG is decreased

• Improved BG estimation

• w in AuAu

w?p0g
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Next steps

• Analysis for run4 should be completed soon
• Improved statistics and background in run7
• Improved understanding for dAu
• Figure out how to analyze r mesons (short lived)
• r? pp- at STAR (Phys. Rev. Lett. 92, 092301)
• Try many measurements to figure out chiral
  symmetry restoration
• Line shape?
• Yield? Slope?
• Ratio between hadron and electron or f and w
• Ratio to p0

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electron positron continuum
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electron-positron continuum

• Broadening of r meson makes continuum on the
  invariant mass of electron-positron pair
• In addition, thermal radiation by the system via
  quark anti-quark annihilation also makes
  continuum and it carries direct information from
  the matter.
• Matter is formed
• Deconfinement
• Thermalized
• Experimentally, combinatorial background is very
  large and must be subtracted properly.
• Also, useful for charm measurements

• A prediction

• R. Rapp, nucl-ex 0204003

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Results

• Clear enhancement is observed in the mass region
  below w.

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pp AuAu comparison
pp NORMALIZED TO meelt100 MeV
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Centrality Dependence
LOW MASS

• p0 production scales with Npart
• If in-medium enhancement from pp or qq
  annihilation
• ?yield should increase faster than proportional
  to Npart

INTERMEDIATE MASS

• p0 production scales with Npart
• charm follows binary scaling? yield should
  increase proportional to Ncoll

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Further analysis
CuCu

• Comparison with CuCu
• Comparison with SPS
• Finalizing pp
• Reasonable normalization of pp
• Npart for low mass?
• Ncoll for charm?
• Improved statistics in run7
• pT dependence
• reaction plane dependence
• Use HBD to suppress background

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Hadron Blind Detector

• Background is made by combination of
  non-correlated ee- pair,
• ee- from Dalitz and g rejected by new detector

combinatorial pairs
all signal
Dalitz rejector Hadron Blind Detector
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photon
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Thermal photon
Turbide, Rapp, Gale, Phys. Rev. C 69 (014903),
2004

• Direct photon
• Directly emitted from the medium
• Not from hadron
• Hard photon
• Initial pQCD
• Thermal photon
• Hadron gas
• QGP

• After subtraction of large background from hadron
  decays,

• Window for thermal photons from QGP in this
  calculation pT 1 - 3 GeV/c
• pQCD calculation should be confirmed in High pT
  region

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Idea - g ? ee-
Any source of real g emits virtual g with very
low mass
Dalitz decay
Use lepton pairs to measure virtual g and
extrapolate to real g
PHENIX can measure low mass ee- pairs hadron
decays and direct photon
In the analysis, Mee distribution for Dalitz and
direct photon is calculated theoretically.
Therefore, the ratio of Nee in two different mass
region is converted to the ratio between direct
and inclusive photons. The systematic error is
reduced.
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gdirect / ginclusive
Significant 10 excess of
very-low-mass virtual direct photons
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gdirect / ginclusive
Significant 10 excess of
very-low-mass virtual direct photons
Results agrees well with Conventional result
One can extract the direct photon yield from the
inclusive photon yield.

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Direct photon yield
Direct photon yield is calculated from the
inclusive photon yield.
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Direct photon yield
Direct photon yield is calculated from the
inclusive photon yield.
Compare to NLO pQCD L.E.Gordon and W.
Vogelsang Phys. Rev. D48, 3136 (1993)
Excess above the calculation
It might include contribution from thermal photons
Reference measurement needed pp and dAu Using
same analysis method
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Thermal photon?
Compare to thermal model

• D. dEnterria, D. Perresounko
• nucl-th/0503054

21 hydro T0ave360 MeV(T0max570 MeV) t00.15
fm/c

• data above thermal at high pT

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pp
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Recalculation of Rg in pp
PHENIX Preliminary
Stat.errors on simulation are included in
sys.errors on Rg. It should be reduced.
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Comparison of Rg with Run4-central result
PHENIX Preliminary
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Summary

• So many interesting analysis topics are on-going
  at PHENIX
• Such as, Heavy flavor measurements, J/y, f, and
  lepton pair continuum
• Measurement for chiral symmetry is underway.
• First result will publish soon.
• Enhancement is observed in ee- continuum!
• Interesting results in Direct photon measurements.

We are still in an exciting time!