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

Measurements of in-medium decay of
vector mesons
Hideto En’yo
RIKEN / Kyoto University
for
The KEK-PS E325 Collaboration
Physics motivation
Status Experiment
f →K+K－ results & w/r →e＋e－ results
Discussion & Summary
JPS meetig, March 2001
Hideto En'yo, RIKEN
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Tantalizing hints for new state of matter
CERN Press Release
Feb. 2000
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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
JPS meetig, March 2001
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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
JPS meetig, March 2001
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
JPS meetig, March 2001
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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 He
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?)
JPS meetig, March 2001
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KEK-PS E325
to measure ρωφ decays in nuclear matter
KK Threshol
in Free Spac
K modification ? f modification
Shape modification can be
measured in
 / / → e+eJPS meetig, March 2001
f(G=4.4MeV) DQ=38MeV
 →K+K- / → e+eHideto En'yo, RIKEN
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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} < $10mb, total cross section (from g+A→f ) bf=0.7,r0 =0.16/fm3
- f +*K-*(K-N→SX)
- Klingle and Weise
JPS meetig, March 2001
Gf ~44MeV (at rest)
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Brief Mile Stones and Status
Analysis
•
•
•
KK ee•
•
1994 March. KEK-PS PAC conditionally approved
1995 March. KEK-PS PAC approved
1996 July. Construction started
1996 November. Engineering Run (40.5shift of beam test)
1997 June, First Physics Run with K+K-. 17days 50 shifts
– Data accumulation mainly with K+K- channel trigger
– Beam Intensity 1~2 x108$ protons/spill on 0.6% interaction targets (106 interaction/spill)
• 1998 March. Completion of Spectrometer,
• 1998 April –May. Production Running of 29 days 74shifts.
– Parallel Trigger. K+K-/ e+e– Beam Intensity 1~2 x 109 protons/spill on 0.1% interaction target (106$ interaction/spill)
• 1999 June 57 shifts Data Taking performed
– Parallel Trigger. K+K-/ e+e– Beam Intensity 1~2 x 109 protons/spill on 0.2% interaction target (106$ interaction/spill)
• 2000 Jun, 35shifts
• 2000 Dec. Data Taking to start now.
• 104 shifts to go in 21st Century !
JPS meetig, March 2001
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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
ICEPP, U-Tokyo
S.Mihara
M.Ishino
– H.Hamagaki, K.Ozawa
• Tohoku University
– H. Kanda
• KEK
– J.Chiba, M.Ieiri, O.Sasaki, M.Sekimoto, K.Tanaka
• Osaka University
– M.Nomachi
Companies
T.Miyashita
Y.Yoshimura
K.Hamada
• RIKEN
– S.Yokkaichi, T.Tabaru, H. Enyo
JPS meetig, March 2001
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E325 SETUP
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JPS meetig, March 2001
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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
JPS meetig, March 2001
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‘98 data (Electron Channel)
Nucl-ex-0011013
to appear in PRL
[events / 50MeV/c 2]
100
30
a)
from light
targets
80
fit result
w,r,f e+e w p 0e+e combinatorial
60
40
from heavy
target
25
20
fit result
w,r,f e+e w p 0e+e combinatorial
15
10
20
0
b)
5
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
[GeV/c 2]
e+e- invariant mass
0
0 0.2 0.4 0.6 0.8
1 1.2 1.4 1.6 1.8 2
[GeV/c 2]
e+e- invariant mass
• ω→e+e－ Significant Difference between C and Cu
• The first observation of in-medium decay of vector mesons.
JPS meetig, March 2001
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‘99 data (KK mode)
JPS meetig, March 2001
to be published
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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
JAM
2. a0/f0
All come from string decays
3. Non resonant (not large)
4. 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
％ 2001
JPS meetig, March
Kinematical Distributions are well
Described by JAM
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s
Target Mass Dependence of
f→K+K- (’97+’99 Data)
a=1.010.09
a=1.080.01
EXP
JAM
a is surprisingly large but
explained by JAM.
For Carbon
Ωσ= 0．19 0.030.09 μｂ EXP
Ωσ= 0．31 0.03 μｂ
JAM
σ= 15.5 Aαμｂ
JPS meetig, March 2001
JAM
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s
Target Mass Dependence of
( , →e+e- (’99 Data)
a=
a=
0.63 ± 0.07 for ωpeak
1.03 ± 0.15 for φpeak
ω→e+e－
C/CH2
φ→e+e－
JPS meetig, March 2001
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What we have learned ?
• Meson modification is observed in
nucleus 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）
JPS meetig, March 2001
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What is missing then ?
• Theoretically
– How large the in-media broadening ?
• SHAPE
• DECAY RATE
Many theoretical works, not conversing
– Other trivial reasons ?
• Collisional broadening
• Phase space (not important in E325)
• Experimentally
– Statistics, Statistics, Statistics, to give
• Accurate shape
• Dispersion
– φ→e+e－
By Akaishi, Yamazaki
JPS meetig, March 2001
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Summary and Outlook

The ’97+’99 f→K+K- data have been analyzed. The results shows




The ‘98 ω→e+e- spectrum shows a surprising indication of inmedium decay of ρ/ω mesons



The first observation of mesons decayed in nuclear matter.
The physics underneath is not apparent yet, but very promising to go further.
The ‘99 e+e- data are still preliminary, with a clear peak of φ →e+e

No significant mass shape deformation (a0/f0 are problematic)
Strong A dependence (a =1.01 +- 0.09 ) in the production
Reasonable agreement with the cascade model JAM.
A dependence of ω and φ productions are ~2/3 and ~3/3 , respectively
Statistics will be ＞5times at the end of assigned beam time,
φ→e+e- and dispersion data will be available
Will hopefully be the first measurements to address the
chiral property of dense nuclear matter.
JPS meetig, March 2001
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