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11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
1
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
2
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 ?
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
3
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
4
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
5
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
6
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”.
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
7
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.
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
8
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?)
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
9
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 ?
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
10
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
11
• 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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
12
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} < $10mb, total cross section (from +A→) =0.7,0 =0.16/fm3
→+*K*(KN→X) Klingle and Weise ~44MeV (at rest)
• 109/sec primary protons on thin (0.1%) nuclear target tosuppress conversions.
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
13
Brief Mile Stones and Status
• 1994 March KEK-PS PAC conditionally approved• 1995 March KEK-PS PAC approved • 1996 July- Construction started• 1996 November Engineering Run• 1997 June, First Physics Run with K+K. 17days
– Data accumulation mainly with K+K channel trigger– Beam Intensity 1~2 x108$ 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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
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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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
15
E325 SETUP
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
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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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
17
Typical EventTypical Event
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
18
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
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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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
20
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.
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
21
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
22
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
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
23
‘99 data
• We now have enough data to identify decays outside and inside nuclei.
Very
Preliminary
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
24
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.
11-JAN-2000 @ RIKEN Winter School
Hideto En'yo, Kyoto University
25
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)
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