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Nuclear Matter Probed with Meson
- exploring the lost symmetry-
Hideto En’yo Hideto En’yo Kyoto UniversityKyoto University
SyllabusSyllabus Introduction Introduction
What is MASS ?What is MASS ? How to measure particle mass in How to measure particle mass in
nuclear matternuclear matter
Related Experiments Related Experiments KEK-PS E325 experimentKEK-PS E325 experiment
PhysicsPhysics SpectrometerSpectrometer ResultsResults
SummarySummary EntertainmentEntertainment
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Mass in QCDMass in QCD• Particle Data Booklet
– mu = 1.5~5 MeV m = 140 MeV– md = 3~9 MeV m = 770 MeV– ms = 60~170 MeV m= 1020 MeV
0
1
2
3
4
0 1 2 3
p2 (GeV2)
E2 (G
eV2)
When Particle M decays M 2=ei
2pi2 invariant
massWhat happens in Media ?
In Free SpaceE2=M2+P2
Mass is effectively given, but the state is GROUND LEVEL
Can we restore the symmetry ?How we measure ?
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What Theorists Say ?What Theorists Say ?
•<qq> quark condensate : order parameter • to indicate how much the symmetry broken• but not an observable
→ Mass of Vector Meson, Mv = 2 x Mq
eff + small interaction term
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Bound NucleonsBound Nucleons
• Imagine that a neutron ( or proton ) in Oxygen nuclei made GUT decay in Kamiokande. (assume that you have a perfect detector )
n → π+ + e
Mn2 → Eπ
+ Ee)2 Pπ + Pe)2
Mn = 939.6 MeV , Mn
= 938.3MeV ?????
• More precisely16O → π+ + e + 15O*
(Mn +M15O ) 2 → 15O + Eπ
+ Ee )2 P15o + Pπ
+ Pe )2
0
1
2
3
4
0 1 2 3
p2 (GeV2)
E2 (
GeV
2)
You measure 16O levels
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Moving Mesons in MediaMoving Mesons in Media
• In-media meson modification– Observed Mass is not Lorentz Invariant
• shift of resonance position
• resonance broadening/narrowing→ DISPERSION
be smallbe small
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How to Measure Mass How to Measure Mass in Mediain Media
1: Search for a deeply bound meson sta1: Search for a deeply bound meson state, Measure the level. (possible only at te, Measure the level. (possible only at normal nucler density)normal nucler density)
2: Invariant Mass Spectroscopy, determ2: Invariant Mass Spectroscopy, determine the dispersion of mesons in nuclear ine the dispersion of mesons in nuclear media ( even in hot or dense mater)media ( even in hot or dense mater)
3: Compare Decay Branching Ratios to 3: Compare Decay Branching Ratios to different channels (decay Q value must different channels (decay Q value must be sensitive) be sensitive)
Meson spectroscopy ( in free space) can be considered as the mass spectroscopy for the valence quarks in normal vacuum, with which it is difficult to answer “what is the origin of the mass”.
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Hurdles
• Many Unknown ( theories exist but almost no experiments )
– Temperature & dependence of <qq>– Temperature & time evolution
→CERN/RHIC/LHC
– Density & dependence of <qq>– Density & time evolution
→BNL/JHF
– Dispersion & Broadening
A lot of inputs from experiments needed, even at the normal nuclear matter density.
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Present and Future ExperimentsPresent and Future Experiments
CLUES
Experiment Measurements Interests
CERES/HELIOS-3 modification Temp. dep.
KEK-TANASHI ES modification Density dep.
GSI modification Density dep.
The efforts to be continued at RHIC and LHC (temperature dependence)
Present & future experiments to measure the mass of vector mesons at normal nuclear matter density.
KEK-ES: +A →+A*(→+) (Published)
KEK-PS: p+A→+X(→K+K/e+e) (Running)
SPring-8: + →+A*(→ K+K) (Ready to run )
GSI: d +A→3He+A*(bound states) (Ready to run )
GSI-HADES: +A→ +A* (→e+e) (Preparation, 2001?)
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KEK-PS E325 KEK-PS E325 to measureto measure decays decays in nuclear matterin nuclear matter
is narrow resonance (is narrow resonance (=4.4MeV) =4.4MeV) Q=38MeVQ=38MeV = 4.4MeV sensitive to resonance-shape change = 4.4MeV sensitive to resonance-shape change Q= 38MeV sensitive to the decay branching ratiosQ= 38MeV sensitive to the decay branching ratios
→K+K (49%) →e+e (3x10-4))
KK Thresholdin Free Space
K modification ?
modification ?
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E325 PHYSICSE325 PHYSICS
Expected Signal(electron pairs)
• KEK-PS E325 to measure KEK-PS E325 to measure decays inside a nucleus
– In 12GeV p+A (C/CH_2/Cu/Pb)→ + X– Observables
– Invariant mass spectrum; →K+K and →e+e – Branching ratio; Br( →K+K )/Br( →e+e
– Less ambiguous data on the modification – Also Sensitive to the production and interaction of
in nucleus
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• Particle Production follows
A
for – Drell-Yan lepton pairs
– J/
– perturbative production
for - fragmentations
• production ?
Br( →K+K) / Br( →e+ePb Br( →K+K) / Br( →e+eC
to be free from
production mechanism
Mechanism of Mechanism of Production at 12 GeVProduction at 12 GeV
J/
Drell-Yan
2/3
2/3
XF
300GeV p+A →
120GeV p+A→→KK
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Some Tips of E325• Expected mass shift is 20~40 MeV ( Hatsuda-Lee).• Focus on slowly moving 's, p =~1GeV/c(lab). Abo
ut 10% of 's will decay inside a nucleus if nothing happens.
• Secondary peak may enhance when low 's are selected.
• The ratio (→K+K)/(→e+e) is sensitive to in-media modification of phi and/or K
• natural width of is narrow (4.4MeV), but some broadening can happen.. Estimations are:
= N 0 <20MeV {N} < $10mb, total cross section (from +A→) =0.7,0 =0.16/fm3
→+*K*(KN→X) Klingle and Weise ~44MeV (at rest)
• 109/sec primary protons on thin (0.1%) nuclear target tosuppress conversions.
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Brief Mile Stones and Status
• 1994 March KEK-PS PAC conditionally approved• 1995 March KEK-PS PAC approved • 1996 July- Construction started• 1996 November Engineering Run• 1997 June, First Physics Run with K+K. 17days
– Data accumulation mainly with K+K channel trigger– Beam Intensity 1~2 x108$ protons/spill– 0.6% interaction target (106 interaction/spill)– C/CH2/Pb 3 targets in-line– 165GByte Data (160M events) collected in 50 shifts
• 1998 March, Completion of Spectrometer, • 1998 April -May: Production Running of 29 days
– Parallel Trigger. K+K-/ e+e- – Beam Intensity 1~2 x 109 protons/spill– 0.1% interaction target (106$ interaction/spill)– $C/CH2/Cu 3 targets inline– 502GByte Data (180M events) collected in 85 shifts
• 1999 June 60 shifts Data Taking performed– Parallel Trigger. K+K-/ e+e- – Beam Intensity 1~2 x 109 protons/spill– 0.2% interaction target (106$ interaction/spill) – 360GByte Data (180M events) collected in 85 shifts
• 2000 May 80-100 shifts Data Taking Expected
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E325 collaboration
• Kyoto University– H.Enyo, H.Funahashi, T.Haseyama, M.Ish
ino, H.Kanda, M.Kitaguchi, S.Mihara, M.Miyabe, T.Miyashita, K.Miyazaki, T.Murakami, R.Muto, M.Naruki, K.Ozawa, H.D. Sato, T.Tabaru, S.Yamada, S.Yokkaichi, Y.Yoshimura
• T.I.T. – K.Hamada, Y.Sakemi, T.A.Shibata
• CNS, University of Tokyo – H.Hamagaki
• KEK– J.Chiba, M.Ieiri, O.Sasaki, M.Sekimoto, K.
Tanaka
• RCNP– M.Nomachi
\250,000,000/5students/5years=\10,000,000
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E325 SETUP
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Trigger CountersTrigger Counters
TOF
ACGCs
Lead Glass Calorimeter
Karm Accceptance
Inside Magnet
AC vetos 99% of pion (P>0.55GeV/c)TOF t~200psec
2-Stage e-ID reject 99.9% pions
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Typical EventTypical Event
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Spectrometer Spectrometer PerformancePerformance→p→p
Invariant Mass SpectrumInvariant Mass Spectrum
M= 1115.1MeV/c2
(PDG 1115.7MeV/c2)
M= 2.2MeV/c2
→ M= 1.2MeV/c2
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→ →KK++KK Invariant Mass SpectrumInvariant Mass Spectrum
• 0.4<Mkk<0.6 GeV/c2 , Pk<1.2GeV/c
• Two kaons are in the same arm.
• Mixed event background is over-plotted (shaded area).
ALL CH2
C Pb
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Target Dependence of WidthTarget Dependence of Width
• Resonance positions & widths are consistent with those in free space (within the statistic of ‘97 data)
• Pb data looks wider though.
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Target Mass Dependence ofTarget Mass Dependence of →K→K++KK
=0.98 0.10
Absolute cross section is not well determined yet. is surprisingly large
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Comparison to other dataComparison to other data
• consistent with the high energy date (Einc > 100GeV) where the is produced somewhat perturbatively. Surprising that similar production mechanism even at 12GeV
• May suggest the perturbative production of even at 12 GeV
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‘99 data
• We now have enough data to identify decays outside and inside nuclei.
Very
Preliminary
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Summary and OutlookSummary and Outlook• Study of in-media modification of meson is very important a
nd interesting to understand the broken chiral symmetry in QCD.
• The experiment, E325, at KEK 12GeV PS measures 12GeV p + A → + X reactions in both →K+K and →e+e channels.
• To observe possible changes of the ratio, Br(
→K+K)/Br( →e+e), and of the shape of the invariant mass peak under the normal nuclear density ( and T = 0).
• Especially we put an emphasis on the detection of slowly moving mesons ~ 1-2GeV/c in lab., subject to thus decay in Nuclear Media.
• The ‘97 →K+Kdata have been analyzed so far (1/5 of the data already collected, 1/10 of data to be acquired). The results shows
– No statistical significance on the mass shape deformation (YET)
– Strong A dependence ( =0.97 0.10 ) in the production• No significant increase of with pT
• The ‘99 →K+Kdata are still preliminary, with some hint of in-media decay component in the mass shape.
• Many new experimental results including this experiment will be available soon, from GSI, Spring-8, and KEK.
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EntertainmentEntertainmentGeneral Physics QuestionsGeneral Physics QuestionsThink when you are on the liftThink when you are on the lift
Q1: You are freely in free space Q1: You are freely in free space (without gravity). Can you turn (without gravity). Can you turn right around ? (you can’t blow )right around ? (you can’t blow )
Q2: You have 1 Q2: You have 1 llitteritter of of hot red hot red water (100water (100ooC)C) and 1 and 1 llitteritter of of cold cold blue water (0blue water (0ooC)C). You want to . You want to warm up the warm up the blue waterblue water with the with the red waterred water. How high you can . How high you can warm it up ? (do not use extra warm it up ? (do not use extra energy from outside)energy from outside)