Systematic measurements of light vector mesons in RHIC-PHENIX

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Systematic measurementsof light vector mesons
in RHIC-PHENIX

• Yoshihide Nakamiya
• Hiroshima University, Japan
• for the PHENIX collaboration
• Quark Matter 2008, Jaipur, India

Contents Topics in this talk PHENIX
experiment Results Summary
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Topics in this talk
ltTopic 1gt Mass modification of light vector
mesons - as a probe of the chiral
phase transition - in the low pT
region
Question 1 Have we observed changes in line
shape and/or yield?

• Mass Line Shape
• Possible modification of line shape of the
  invariant mass distribution for f/w/r is expected
  to be observed.
• -gtEffects are small and cant be detected
  with current statistics and
• signal to background ratio.

• Yield difference between f?ee- and f? KK-
• Branching ratio between ee- and KK- may be
  sensitive to mass modification, since Mphi is
  approximately 2 ? MK.
• -gt Compare yields of f?ee- and f? KK-

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Topics in this talk (Contd)
ltTopic 2 gt Particle yield suppression of light
vector mesons in medium - as a
probe of medium effects - at
relatively high pT
Systematic measurements give information about
properties of the medium

• pT/mT spectra of f and w in several decay
  channels
• Nuclear modification factors (RAA and RdA) as
  functions of pT

We are trying to answer the following questions
Question 1 Does the particle yield suppression
depend on mass or on quark
number ? -gt Nuclear
modification factor RAA of the f meson
is compared to proton results.
Question 2 Does RAA of mesons have a mass or
flavor dependence? -gtRAA
of several mesons are compared to each other.
(p, h, w, f, )
ltBaselinegt Results of pp and dAu are also shown.
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Electron, hadron and photon in PHENIX
f/w ? ee-

• PHENIX acceptance
• -0.35 lt ? lt 0.35
• 2 x 90in azimuthal angle for two arms
• Event selection
• BBC
• Electron ID
• RICH
• EMCal

• photon ID
• EMCal

• Hadron ID
• TOF
• EMCal-TOF

w ? pp-p0, p0g
f ? KK-
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Results for pp and dAu as baseline measurement
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Extended f ? KK- analysis
Consistency between f ? KK- and f ?ee-
f
dAu
0-20
M.B.
pp

• f?KK- measurements have been extended to both
  higher and lower pT using new methods, i.e. no
  kaon ID and single kaon ID methods.
• The three independent kaon analyses are
  consistent with each other.

In pp, spectra of ee- and KK- show reasonable
agreement!
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Measurements of w in wide pT range
pT spectra of w are measured for several decay
modes in dAu and pp.
w
dAu
pp
Spectra show good agreement among several decay
channels.
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RdA of f and w mesons in 200 GeV
As a baseline check, RdA is calculated for f and
w and compared to other mesons.
RdA f
RdA w
0-20
0-20
M.B.
M.B.

• RdA does not show suppression in central arm.
• f and w results are consistent with p0 and h.

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f/p, w/p ratios in pp and dAu 200 GeV
f/p, f/K
w/p
dAu
f/p dAu
f/K pp
pp
f/p pp
f/p and w/p ratio have little or no pT
dependence at pT gt2.0 GeV/c.
?/?0 in pp Run5 _at_ vs 200 GeV 0.81
0.02(stat) 0.07(syst) ?/?0 in dAu Run3 _at_ vsNN
200 GeV 0.94 0.08(stat) 0.12(syst)
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Topic 1 Chiral symmetry restoration
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Yield comparison between f?ee- and f? KK-
Question 1 Have we observed changes of yield
between ee- and KK- ?
Comparison of integrated yield is not enough,
because mass modification effects depend on the
pT region. Low pT mesons tend to decay inside the
hot/dense matter
f
f
Low pT
High pT
In addition, To determine the integrated yield,
an extrapolation to lower pT is needed. There is
a large uncertainty in the calculation.
Thus, pT-dependent information is essential for
comparison.
Now, we should ask
Have we observed changes of spectra between ee-
and KK- ?
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Spectra comparison between f?ee- and f? KK-
AuAu
M.B.
40-92
20-40
Errors are too large to make any clear statement
about the comparison of spectra for f ? ee- and
f ? KK-.
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Topic 2 Nuclear modification factors
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f?KK- in AuAu is also extended to higher mT

• f?KK- measurement has been extended to higher
  mT using no kaon ID method.
• mT region is extended to 5 GeV.

The two independent hadron decay analyses are
consistent with each other in AuAu.
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Is RAA suppression carried by mass or quark
number?
Question 1 Is particle yield suppression
carried by mass or quark number ?
RAA of proton (mp938 MeV/c2)
Comparison between f and p
RAA of f meson (mf1019 MeV/c2)
60-93

• RAA of f in central collisions is lower than in
  peripheral at high pT.
• RAA of protons is nearly independent of
  centrality.

f RAA shows a different trend as compared to the
proton.
Difference of RAA between f and proton suggests
that energy loss occurs at the partonic level.
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w mesons in AuAu
Background estimate is improved in ??p0? analysis
pT spectra of w are measured for several
centralities and at high pT.
0-20
M.B.
Details are in M.Ouchidas poster
20-60
Background and shape are carefully estimated.
60-92

• Measurement of w mesons up to 10 GeV/c is made.

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Mass dependence of RAA between mesons
Question 2 Does RAA of mesons have a mass or a
flavor dependence?
f meson has a different RAA for pT lt 5 GeV/c.
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Summary
ltTopic 1gt Mass modification of light vector
mesons - as a probe of chiral
phase transition - in low pT
region
Question 1 Have we observed changes of line
shape, yield, and/or spectra? Answer 1 We are
still trying to quantify the difference.
Improvement of statistics and signal to
background ratio in the next
run will improve existing measurements.
ltTopic 2 gt Particle yield suppression of light
vector mesons in medium - as a
probe of medium effect - at
relatively high pT
Question 1 Is particle yield suppression
carried by mass or quark number ? Answer 1
Difference between RAA of f meson vs proton
suggests that energy loss
occurs at the partonic level . Question 2 Does
RAA of mesons have a mass or flavor dependence ?
Answer 2 f meson has a different RAA compared
to other mesons (p, h).
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Thank you for inviting me to Quark Matter 2008
! Id like to say thanks to all participants and
collaborators
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Back up
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Yield and temperature for f mesons

• After several experimental checking, we found
  integrated
• information is not enough to determine the
  difference between
• ee- and KK-.
• Need a careful check of mT spectra.

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The invariant mass spectra for f mesons
f-gt ee- dAu
f-gtee- AuAu
f-gt ee- pp
f
f
f-gtKK- (double PID) dAu
f-gt KK- (double PID) AuAu
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The invariant mass spectra for f mesons
f-gtKK- (single PID) pp
f-gtKK- (no PID) pp
f-gtKK- (no PID) AuAU
f-gtKK- (no PID) dAu
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The invariant mass spectra for ? mesons
w-gt ee- pp
w-gtee- dAu
w-gtee- AuAu
?
?
w-gtp0pp- pp
w-gtp0g pp
w-gtp0g AuAu