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

Nuclear Matter
Probed with f Meson
- exploring the lost symmetryHideto En’yo
Kyoto University
Syllabus
Introduction
What is MASS ?
How to measure particle mass in
nuclear matter
Related Experiments
KEK-PS E325 experiment
Physics
Spectrometer
Results
Summary
Entertainment
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Mass in QCD
• Particle Data Booklet
– mu = 1.5~5 MeV
– md = 3~9 MeV
– ms = 60~170 MeV
mp = 140 MeV
mr = 770 MeV
mf = 1020 MeV
In Free Space
E2=M2+P2
Mass is effectively given,
but the state is GROUND
LEVEL
E 2 (GeV 2 )
Can we restore the symmetry ?
How we measure
?
4
3
2
1
0
0
When Particle M decays
M 2=S ei2- pi2 invariant mass
What happens in Media ?
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2
3
p 2 (GeV 2 )
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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
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Bound Nucleons
• 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 ?????
• More precisely
16O
→ π+ + e- +
15O*
(Mn +M15O ) 2 → (E15O + Eπ + Ee )2 - (P15o + Pπ + Pe )2
4
2
E
2
(GeV
2
)
3
You measure
16O levels
1
0
0
1
2
2
3
2
p (GeV )
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Moving Mesons in Media
be small
• In-media meson modification
– Observed Mass is not Lorentz Invariant
• shift of resonance position
• resonance broadening/narrowing
→ DISPERSION
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How to Measure Mass in
Media
1: Search for a deeply bound meson state,
Measure the level. (possible only at normal
nucler density)
2: Invariant Mass Spectroscopy, determine
the dispersion of mesons in nuclear media
( even in hot or dense mater)
3: Compare Decay Branching Ratios to
different channels (decay Q value must 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 Experiments
CLUES
Experiment
Measurements
Interests
CERES/HELIOS-3
KEK-TANASHI ES
GSI
r modification
Temp. dep.
r modification
Density dep.
p 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: g +A →r+A*(r→p+p-)
(Published)
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?)
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KEK-PS E325
to measure f decays
in nuclear matter
KK
Thresho
ld
in Free ?
f modification
Space
K modification ?
 f is narrow resonance (G=4.4MeV) DQ=38MeV
 G = 4.4MeV sensitive to resonance-shape change
 DQ= 38MeV sensitive to the decay branching ratios
f →K+K- (49%) f →e+e- (3x10-4)
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E325 PHYSICS
Expected Signal
(electron pairs)
• KEK-PS E325 to measure KEK-PS E325
to measure f decays inside a nucleus
– In 12GeV p+A (C/CH_2/Cu/Pb)→ f + X
– Observables
– Invariant mass spectrum; f →K+K- and f→e+e– Branching ratio; Br(f →K+K- )/Br( f →e+e-)
– Less ambiguous data on the f modification
– Also Sensitive to the production and interaction of f
in nucleus
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Mechanism of
f Production at 12 GeV
• Particle Production
follows Aa
 a~ 1 for
– Drell-Yan lepton pairs
– J/y
– perturbative production
J/y
Drell-Yan
2/3
rw
f
 a~ 2/3 for
- prw
- fragmentations
•
300GeV p+A →mm
f production ?
Br(f →K+K-) / Br(f →e+e-) Pb
Br(f →K+K-) / Br(f →e+e-)C
to be free from
production mechanism
2/3
XF
120GeV p+A→f→KK
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Some Tips of E325
• Expected mass shift is 20~40 MeV ( HatsudaLee).
• Focus on slowly moving f 's, p =~1GeV/c(lab).
About 10% of f's will decay inside a nucleus if
nothing happens.
• Secondary peak may enhance when low b f's
are selected.
• The ratio (f→K+K-)/(f→e+e-) is sensitive to
in-media modification of phi and/or K
• natural width of f is narrow (4.4MeV), but some
broadening can happen.. Estimations are:
- Gf = sfN bfr0
Gf <20MeV
- s{fN} < $10mb, total cross section (from g+A→f )
- bf=0.7,r0 =0.16/fm3
- f +*K-*(K-N→SX)
- Klingle and Weise
•
Gf ~44MeV (at rest)
109/sec primary protons on thin (0.1%) nuclear target to
suppress g conversions.
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Brief Mile Stones and Status
•
•
•
•
•
1994 March KEK-PS PAC conditionally approved
1995 March KEK-PS PAC approved
1996 July- Construction started
1996 November Engineering Run
1997 June, First Physics Run with K+K-. 17days
–
–
–
–
–
Data accumulation mainly with K+K- channel trigger
Beam Intensity 1~2 x108$ 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+eBeam 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.Ishino, 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 Counters
Lead Glass Calorimeter
TOF
GCs
AC
Karm Acccepta
AC vetos 99% of pion (P>
TOF dt~200psec
2-Stage e-ID reject 99.
Inside Magnet
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Typical Event
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Spectrometer Performance L→ppInvariant Mass Spectrum
ML= 1115.1MeV/c2
(PDG 1115.7MeV/c2)
dML = 2.2MeV/c2
 dMf = 1.2MeV/c2
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f →K+KInvariant Mass Spectrum
ALL
CH
2
C
Pb
• 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).
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Target 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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s
Target Mass Dependence of
f→K+K-
a=0.98 0.10
Absolute cross section is not well
determined yet.
a is surprisingly large
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a: Comparison to other data
• consistent with the
high energy date
(Einc > 100GeV)
where the f is
produced somewhat
perturbatively.
Surprising that similar
production mechanism
even at 12GeV
• May suggest the
perturbative
production of f even at
12 GeV
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‘99 data
• We now have enough data to identify
decays outside and inside nuclei.
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Summary and Outlook
• Study of in-media modification of meson is very
important and interesting to understand the broken chiral
symmetry in QCD.
• The experiment, E325, at KEK 12GeV PS measures
12GeV p + A →f + X reactions in both f →K+K- and
f→e+e- channels.
• To observe possible changes of the ratio,
, and of
Br(f →K+K-)/Br(f →e+e-)
the shape of the
invariant mass peak under the normal nuclear density
(r = r0 and T = 0).
• Especially we put an emphasis on the detection of slowly
moving f mesons ~ 1-2GeV/c in lab., subject to thus
decay in Nuclear Media.
• The ‘97 f→K+K- data 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 (a =0.97 +- 0.10 ) in the production
• No significant increase of a with pT
• The ‘99 f→K+K- data 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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Entertainment
General Physics Questions
Think when you are on the lift
Q1: You are freely in free space (without
gravity). Can you turn right around ? (you
can’t blow )
Q2: You have 1 litter of hot red water
(100oC) and 1 litter of cold blue water
(0oC). You want to warm up the blue
water with the red water. How high you
can warm it up ? (do not use extra energy
from outside)
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