Transcript PHENIX for the First Collider,RHIC Hideto En’yo Kyoto

Nuclear media effects on production
and decay of vector meson studied in
12 GeV p+A interaction
Hideto En’yo
RIKEN / RIKEN-BNL Research Center
for
The KEK-PS E325 Collaboration
Physics motivation
Our Experiment
Results (K+K－ & e＋e－ Channels)
Discussion & Summary
YITP Kyoto, Oct 2002
Hideto En'yo, RIKEN/RBRC
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Tantalizing hints for new state of matter
CERN Press Release
Feb. 2000
YITP Kyoto, Oct 2002
Hideto En'yo, RIKEN/RBRC
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What Theorists Say ?
•<qq> quark condensate : order parameter
• to indicate how much the symmetry broken
• but not an observable
→ Mass of Vector Meson, r w f
Mv = 2 x Mqeff + small interaction term
YITP Kyoto, Oct 2002
Hideto En'yo, RIKEN/RBRC
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Bound Nucleons, Mesons
• Imagine that a neutron ( or proton ) in Oxygen nuclei made GUT
decay in Kamiokande. (assume that you have a perfect detector )
n → π + + eMn2 → ( Eπ + Ee)2 -(Pπ + Pe)2
Mn = 939.6 MeV , Mn = 938.3MeV ????? 4
• More precisely
e-
+
15O*
3
2
→
π+ +
E (GeV )
16O
You measure
16O levels
2
2
(Mn +M15O ) 2
→ (E15O + Eπ + Ee )2 - (P15o + Pπ + Pe )2
1
0
0
1
p
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2
2
(GeV
2
3
)
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Moving Mesons in Media
Outside
be small
Inside
• In-media meson modification
– Observed Mass is not Lorentz Invariant
• shift of resonance position
• resonance broadening/narrowing
→ DISPERSION
YITP Kyoto, Oct 2002
Hideto En'yo, RIKEN/RBRC
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Experiments
CLUES
Experiment
CERES/HELIOS-3
KEK-TANASHI ES
GSI
Measurements
r modification
r modification
p modification
Interests
Temp. dep. ρis modified in Hot Matter
Density dep. ρis modified in He
Density dep. πis modified in Nucleus
Present & future experiments
.
RHIC(running)/LHC(2006)
KEK-PS: p+A→f+X(fK+K-/e+e-) (Running)
SPring-8: g + →f+A*(f→ K+K-)
(Ready to run )
GSI: d +A→3He+A* (hw bound states) (Ready to run )
GSI-HADES: p +A→ w+A* (w→e+e-) (Preparation, 2001?)
YITP Kyoto, Oct 2002
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KEK-PS E325
to measure ρωφ decays in nuclear matter
KK Threshold
in Free Space
f modification ?
K modification ?
Shape modification can be
measured in
   → e+eYITP Kyoto, Oct 2002
f(G=4.4MeV) DQ=38MeV
 →K+K-  →e+eHideto En'yo, RIKEN/RBRC
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Some Tips of E325
• 109/sec primary protons on thin (0.1%) nuclear target to suppress g
conversions.
• Focus on slowly moving f,w,r 's, p =~1GeV/c(lab). About 10% of f's
will decay inside a nucleus if nothing happens.
• Expected mass shift is 20~40 MeV for φ ～140MeV for ρ、ω
– ( Hatsuda-Lee).
• Secondary peak may enhance when low b f's are selected.
• The ratio (f→K+K-)/(f→e+e-) is sensitive to modification of phi
and/or K
• natural width of f, w is narrow (4.4, 8.4MeV), but some broadening can
happen.. Estimations are:
- Gf = sfN bfr0
Gf <20MeV
- s{fN} < $10mb, total cross section (from g+A→f ) bf=0.7,r0 =0.16/fm3
- f +*K-*(K-N→SX)
- Klingle and Weise
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Gf ~44MeV (at rest)
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History
1995 March. KEK-PS PAC approved
1996 July. Construction started
ω→e+e−
φ→K+K−
1997 June First Physics Run with K+K−
φ→e+e−
99
1998 May Already Published
95
12
(P.R.L. 86 (2001) 5019 )
1999 July Hawaii JPS/QM2002/PANIC02
～700
～125
178
2000 June Production Run with newly installed
Dec. Vertex Chamber & Lead Glass Calorimeter
2001 Nov. Production Run
～4800×2
～570
～930×2
2002 Feb. LAST Production Run
YITP Kyoto, Oct 2002
Hideto En'yo, RIKEN/RBRC
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E325 collaboration
• Kyoto University
H.Funahashi,, M.Kitaguchi, M.Miyabe, T.Murakami, R.Muto,
M.Naruki, F.Sakuma, H.D. Sato, S.Yamada
• CNS, University of Tokyo
– H.Hamagaki, K.Ozawa
• ICEPP, U-Tokyo
– S.Mihara, M.Ishino
• RIKEN
– S.Yokkaichi, T.Tabaru, H. Enyo
• Tohoku University
– H. Kanda
• KEK
– J.Chiba, M.Ieiri, O.Sasaki, M.Sekimoto, K.Tanaka
• Osaka University
– M.Nomachi
YITP Kyoto, Oct 2002
Graduation
T.Miyashita
Y.Yoshimura
K.Hamada
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E325 SETUP
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Set up
Hodoscope
Forward LG Calorimeter
Aerogel Cherenkov
Rear LG Calorimeter
Forward TOF
Side LG Calorimeter
B
Barrel Drift Chamber
Cylindrical DC
Rear Gas Cherenkov
Vertex DC
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Front Gas Cherenkov
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YITP Kyoto, Oct 2002
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Around the targets
• 3 target plate inline
– C/CH2/Cu
– 109/s protons，
– 106/s interactios
• Vertex chamber
– 1.75mm drift length
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Spectrometer Performance (Invariant Mass Spectrum)
L→pp0→p-p+
ML= 1115.4-5MeV/c2 (PDG 1115.7MeV/c2)
dML = 1.8-2.4MeV/c2 (Sim 1.9MeV)
M= 494.8MeV/c2 (PDG 497.7MeV/c2)
dMk = 6.1MeV/c2 (Sim 6.3MeV )
φ→KK 2．4MeV φ→ee 9MeV
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‘98 data (Electron Channel)
PRL, 2001
28 May, page 5019
w  e+e-
• ω→e+e－ Significant Difference between C and Cu
• The first observation of in-medium decay of vector mesons.
YITP Kyoto, Oct 2002
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Combinatorial background
K0s
Major background souces are
• π0→γγ （γ→ee)
• π0→ eeγ
•π+ π－ invariant mass is well
described with the mixed events.
•π+ π－ Correlation is only
significant for K0s
Spectrum of p pair
YITP Kyoto, Oct 2002
It is reasonable to use ee mixed event
for the combinatorial background
Hideto En'yo, RIKEN/RBRC
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•450GeV p+Be→e+e- Helios/Na34
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Acceptance Corrected
Cross Section
channnel α
ω electron 0.849
JAM
0.805
φ electron 1.268
φ kaon
1.014
JAM
1.172
±
±
±
±
±
Error
0.0800
0.0003
0.2127
0.0769
0.0030
JAM Comparison
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Nuclear Mass Number
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ω Meson Kinematics
pT Dependence
Absolute Cross Sections are ~6x
larger in JAM
Kinematical Distributions are well
reproduced by JAM
xF Dependence
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How w & f are produced
JAM
w
f
Our Acceptance
Our Acceptance
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Feynman X
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‘98 data (Electron Channel)
PRL, 2001
28 May, page 5019
w  e+e-
• ω→e+e－ Significant Difference between C and Cu
• The first observation of in-medium decay of vector mesons.
YITP Kyoto, Oct 2002
Hideto En'yo, RIKEN/RBRC
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Invariant Mass Spectrum of e+e- (’02 Data)
Counts/20MeV/c2
Counts/20MeV/c2
Preliminary
Fit Result
ω
ρ
φ
Back Ground
Light Target
(Carbon)
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GeV/c2
Heavy Target
(Copper)
Hideto En'yo, RIKEN/RBRC
GeV/c2
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BackGround Subtracted
Invariant Mass Spectrum of e+e- (’02 Data)
Counts/20MeV/c2
Counts/20MeV/c2
Preliminary
Fit Result
ω
ρ
φ
Light Target
(Carbon)
YITP Kyoto, Oct 2002
GeV/c2
Not large mass
rSome
is 0.4hints
timesfor
dependence
smaller
than
(wait
for momentum
f modification
dependence
analysis)
pp data
Heavy Target
(Copper)
Hideto En'yo, RIKEN/RBRC
GeV/c2
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‘99 data (KK mode)
YITP Kyoto, Oct 2002
to be published
Hideto En'yo, RIKEN/RBRC
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JAM (Y.Nara, RBRC)
Intra Nuclear Cascade Code
Pt
βγ
Y
Ｙ－Pt
Resonance Production ( Low Energy)
String Excitation (Mid Energy)
Parton-parton (High Energy)
K+K- Sources
1. φ
2. a0/f0
3.
4.
JAM
All come from string decays
Non resonant (not large)
PID back ground
Experiment
C,CH2 data (χ2 = 34.5/37)
a0/f0 to φ 37．7±10 %
Gd,Cu data (χ2 = 38.8/37)
a0/f0 to φ 27.2±10．1％
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Kinematical Distributions are well
Described by JAM
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What we have learned ?
• Meson modification is observed at
normal nuclear density firstly in
electron pair channel.
• Does it means QCD chiral symmetry
restoration ?
Toy Model Calc.
– NOT YET ( life is more complicated)
– mass shift as predicted by Hatsuda
– in-media broadening of 3 × free
space ( D. Cabera et al.)
– production of ρ・ω at the surface
of a nucleus （A 2/3）
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What is missing then ?
• Theoretically
– How large the in-media broadening
shift ?
• SHAPE
• DECAY RATE
Many theoretical works, not conversing
– Other trivial reasons ?
• Collisional broadening
• Phase space (not important in E325)
• Experimentally
– Statistics to give
• Accurate shape (Partially achieved)
• Dispersion (to come)
– φ→e+e－ / K+K－ comparison
By Akaishi, Yamazaki
YITP Kyoto, Oct 2002
Hideto En'yo, RIKEN/RBRC
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Conclusions

The ‘98 ω→e+e- spectrum has shown an indication of in-medium
decay of ρ/ω mesons, over the known hadronic sources below
the ω peak.

The first observation of mesons decayed in nuclear matter.
In the 2002 e+e- data, we have confirmed the above excess.
Obtained ρ/ω ratio supports that this excess is mainly due to the
modifications of ρ meson.



The physics underneath is not apparent yet, but very promising to go further.
Some hint on φ meson modifications is seen.

Low mass side enhancements (a0/f0 or f modification ?) seen.
The ’97+’99 f→K+K- data have shown
PRODUCTION


The measured production cross section of ω is consistent with the previouse
measurement. JAM calculation predict ~6 times larger.
A dependence of φ and ω productions can be reproduced by JAM.
KEY is in detail analyses we have in our hand.
YITP Kyoto, Oct 2002
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Origine of Large α observed in φ production
s(f)s(w)
ee
KK
JAM
JAM
• αf seems to be larger than αw
• Same tendency also in JAM.
• Most of φ production is from
secondary interactions (JAM).
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’99+’98 data (Electron Channel)
Statistics improved by
factor 5. Consistently
the excess was seen.
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Electron efficiency and pion contamination
• We evaluated the electron
efficiency and pion
contamination in the
momentum range greater than
400 MeV/c.
EM cal Energy.vs.Momentum


The remaining ep pair background was estimated to be
about 13% in the final e+e- pair sample.
The contaminations like pp pair to be negligibly small.
YITP Kyoto, Oct 2002
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Kinematical distribution of electron pair
• The kinematical coverage of the present data is shown.
• The combinatorial background is subtracted.
Opening
angle
Transverse
Momentum
bglab
Rapidity
Light Target
YITP Kyoto, Oct 2002
Opening
angle
bglab
Transverse
Momentum
Rapidity
Heavy Target
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Meson production in JAM
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