Transcript p 0 - J-PARC

J-PARCにおけるハドロン
質量起源の探索実験
小沢 恭一郎（東京大学）
Contents:
Physics motivation
Current results
Future Experiments
Summary
クォークの閉じ込
めによるハドロン
の形成
安定な物質
を作るため
の核力コア
原子核反応
による発光
超新星爆発
を起こす核
反応
太陽
Big Bang
W
Z
Higgs
相転移
ν
クォーク・
グルオン
の世界
時間
2009/10/9
超新星爆発
ハドロン
の世界
原子核
の世界
中性子星の
構造を支え
るクォーク
中性子星
反クォーク・クォーク対凝縮
によるカイラル対称性の自
発的破れと質量の獲得
J-PARC seminar, K. Ozawa
2
ハドロン質量起源
High Temperature
High Density
Quark is not confined.
Mass ~ 0 (Higgs only)
It looks real “vacuum”.
When T and r Vacuum
are going down,
Quark – antiquark pairs
make a condensate and
give a potential.
Symmetry is breaking.
q
Vacuum
q
Quark is confined.
Vacuum contains quark
antiquark condensates.
So called “QCD vacuum”.
J-PARC seminar, K. Ozawa
p as a Nambu-Goldstone
boson.
2009/10/9
3
How to study?
“QCD vacuum”, i.e. quark
condensates can be changed in
finite density or temperature.
Then, chiral symmetry will
be restored (partially).
Vacuum
r0
T0
In finite r/T
Chiral properties can be studied at finite density and temperature.
What is observable?
Mass of chiral partner should be degenerated in restored medium.
– r (JP = 1-) m=770 MeV ： a1 (JP = 1+) m=1250 MeV
– N (1/2+) m=940 MeV ： N* (1/2-) m=1535 MeV ？
Dm will decrease in finite r/T matter.
However, measurements of chiral partner is very difficult
Connect hadron properties and quark
2009/10/9
J-PARC seminar, K. Ozawa
condensate
using QCD
and/or phenomenology.
4
Theoretical efforts
• Nambu-Jona-Lasino model
– Nambu and Jona-Lasino, 1961
– Vogl and Wise, 1991
– Hatsuda and Kunihiro, 1994
Vector meson mass
G.E.Brown and M. Rho,
PRL 66 (1991) 2720
• Chiral Perturbation theory
– Weinberg 1979
– Gasser and Leutwyler, 1984, 1985
• QCD sum rule
– Shifman et al., 1979
– Colangelo and Khodjamirian, 2001
– Hatsuda and Lee, 1992
*
‘
• Lattice QCD
– Wilson, 1974
– Karsch, 2002
qq
*
m

 0 .8  r  r 0 
m
qq
T.Hatsuda and S. Lee,
PRC 46 (1992) R34
m*V 
r 
  1   B  ;   0.18
mV 
r0 
• Empirical models
– Potential model (De Rujula et al., 1975), Bag model (Chdos et
al., 1974)
• In addition, Collisional broadening, nuclear mean field …
2009/10/9
J-PARC seminar, K. Ozawa
5
Predicted “spectra”
As the first step,
experiments try the comparison between
predicted spectra and measurements.
• several theories and models predict spectral function of
vector mesons (r, w, f).
– Lowering of in-medium mass
– Broadening of resonance
P. Muehlich et al. , Nucl. Phys. A 780 (2006) 187
r- meson
w- meson
structure due to coupling to
S11,P13 resonances
R. Rapp and J. Wambach, EPJA
6 (1999)
415 K. Ozawa
2009/10/9
J-PARC
seminar,
6
MEASUREMENTS
2009/10/9
J-PARC seminar, K. Ozawa
7
Create QCD medium
Measurements of Vector Meson mass spectra in QCD
medium will provide QCD condensates information.
At Nuclear Density
heavy ion reactions:
A+AV+X
mV(r>>r0;T>>0)
SPS
RHIC
, p. p - beams
J-PARC elementary reaction:
CLAS
, p, p  V+X
mV(r=r0;T=0)
LHC
Leptonic (e+e-, m+m-) decays are suitable, since
2009/10/9
J-PARC seminar, K. Ozawa
lepton doesn’t have final state interaction.
8
Measurements in Nucleus
• Stable system
– No (small) need for time
development
• Saturated density
Two approaches,
Link vector meson masses and the quark condensate.
 Link meson bound states and the quark condensate.
Nucleon Hole
p, p, 
2009/10/9
Meson
J-PARC
ECT*-WS,
seminar,
K. Ozawa
K. Ozawa
Target
Bound State (Emitted
Proton/Neutron)
Decay
9
p bound state
K. Suzuki et al., Phys. Rev. Let., 92(2004) 072302
p as a NG boson
p bound state is observed in
Sn(d, 3He) pion transfer reaction.
Reduction of the chiral order parameter,
f*p(r)2/fp2=0.64 at the normal
nuclear density (r = r0 ) is indicated.
Jido-san et al. shows that pnucleus scattering length is
directly connected to quark
condensate in the medium.
D. Jido et al., arXiv:0805.4453
PLB670 (2008) 109
2009/10/9
New exp. is in preparation at RIKEN
J-PARC seminar, K. Ozawa
10
Mass spectra measurements
• 現在までに主に4例の実験結果
– TAGX 実験
– CBELSA/TAPS 実験
– KEK陽子シンクロトロン（KEK-E325実験)
– J-Lab CLAS実験
• 軽い原子核と重い原子核で比較することで、媒質効果を導き出す。
注意
得られるものは、自由空間中で崩壊
した粒子の分布との重ね合せ
予想される質量分布（KEK実
験、銅標的の場合）
2009/10/9
J-PARC seminar, K. Ozawa
11
11
INS-ES TAGX experiment
Eγ~0.8-1.12.GeV, sub/near-threshold ρ0 production
• PRL80(1998)241,PRC60:025203,1999.: mass reduced in
invariant mass spectra of 3He(γ, ρ0)X ,ρ0 --> π+π−
• Phys.Lett.B528:65-72,2002: introduced cosq analysis to
quantify the strength of rho like excitation
• Phys.Rev.C68:065202,2003. In-medium r0 spectral function
study via the H-2, He-3, C-12 (,p+ p-) reaction.
Try many models, and channels
Δ, N*, 3π,…
2009/10/9
E
STT model
Present
work
Previous
work
800-960
MeV
700-710
MeV
672±31
MeV
730
MeV
743±17
MeV 12
960-1120
MeV
J-PARC seminar, K. Ozawa
CBELSA/TAPS
TAPS, w  p0 with +A
D. Trnka et al., PRL 94 (2005) 192203
p

w

p0

mw 
advantage:
after background subtraction
A  w + X
m
p0


p p  p  2
m
 3.0 %
• p0 large branching ratio (8 %)
• no r-contribution (r  p0 : 7  10-4)
disadvantage:
• p0-rescattering
2009/10/9
mw = m0 (1 -  r/r0) for  = 0.13
J-PARC seminar, K. Ozawa
13
E325 @ KEK-PS
12 GeV proton induced.
p+A  f + X
Electrons from f decays are detected.
Target
Carbon, Cupper
0.5% rad length
KEK E325
2009/10/9
J-PARC seminar, K. Ozawa
14
E325 Spectrometer
2009/10/9
J-PARC seminar, K. Ozawa
15
Mass spectra measurements
KEK E325, r/w  e+eInduce 12 GeV protons to Carbon and Cupper target, generate
vector mesons, and detect e+e- decays with large acceptance
spectrometer.
M. Naruki et al., PRL 96 (2006) 092301
Cu
re+e-
w/r/f
we+e-
The excess over the
known hadronic sources
on the low mass side of w
peak has been observed.
mr = m0 (1 -  r/r0) for  = 0.09
2009/10/9
J-PARC seminar, K. Ozawa
16
CLAS g7a @ J-Lab
Induce photons to Liquid dueterium, Carbon, Titanium and
Iron targets, generate vector mesons, and detect e+e- decays
with large acceptance spectrometer.
R. Nasseripour et al., PRL 99 (2007) 262302

w/r/f
No peak shift of r
Only broadening is
observed
2009/10/9
J-PARC seminar, K. Ozawa
mr = m0 (1 -  r/r0)
for  = 0.02 ± 0.02
17
Contradiction?
• Difference is significant
• What can cause the
difference?
CLAS
KEK
– Different production
process
– Peak shift caused by
phase space effects in pA?
• Need spectral function of r
without nuclear matter
effects
Note:
• similar momentum range
• E325 can go lower slightly In addition, background issue is
pointed out by CLAS
2009/10/9
J-PARC seminar, K. Ozawa
18
Results: f  e+e- (E325)
b<1.25 (Slow)
Excess!!
Cu
R. Muto et al., PRL 98(2007) 042581
Invariant mass spectrum for
slow f mesons of Cu target
shows a excess at low mass
side of f.
Measured distribution contains both
modified and un-modified mass
spectra. So, modified mass spectrum
is shown as a tail.
First measurement of f meson mass
2009/10/9
19
J-PARC seminar, K. Ozawa
spectral
modification
in QCD matter.
Target/Momentum dep.
b<1.25 (Slow)
1.25<b<1.75
1.75<b (Fast)
Mass modification is seen only at heavy nuclei
and slowly moving f
Mass Shift:
2009/10/9
J-PARC seminar, K. Ozawa
20
mf = m0 (1 -  r/r0) for  = 0.03
NEXT STEP
@ J-PARC
2009/10/9
J-PARC seminar, K. Ozawa
21
Condensates to Spectrum
We should revisit the relation between
quark condensate and vector meson spectrum
Original idea by Hatsuda and Lee shows the relation
Vacuum
q
Vacuum
q
QCD sum rule
Average of Imaginary
part of P(w2)
vector meson
spectral function
Using this relation,
Assume
Prediction
T.Hatsuda and S. Lee,
PRC 46 (1992) R34
mV
2009/10/9
Spectrum
J-PARC seminar, K. Ozawa
mV* 
r 
 1   B  ;   0.03
mV 
r0 
22
Spectrum to and
condensate
Condensates
Spectrum
Replace by average
of measured spectra
Vacuum
q
Vacuum
QCD sum rule
q
Average of Imaginary
part of P(w2)
vector meson
spectral function
p
Evaluate quark condensate using QCD-SR.
Beyond comparisons with models
Experimental
requirements
2009/10/9
1. High statics
2. Clear initial condition
J-PARC seminar, K. Ozawa
23
New exp 1: High Statistics
• Extended to vertical direction
KEKSide
spectrometer
view
Plain view
Cope with 10 times larger beam intensity!!
2009/10/9
J-PARC seminar, K. Ozawa
100 times
higher statistics!!
24
What can be achieved?
Pb
f
f
Modified f
f
f
f
ff f
f
f from
Proton
[GeV/c2]
High
resolution
Invariant
mass in
medium
seminar, K. Ozawa
calculate quarkJ-PARC
condensate
2009/10/9
25
New exp 2: Clear Initial condition
n
w

mw 

p0
A  w + X

p p  p  2
Generate w meson using p + p.
Emitted neutron is detected at 0.
Decay of w meson is detected.
p0

If p momentum is chosen carefully,
momentum transfer will be ~ 0.
0.4
As a result of KEK-E325,
We can expect 9% mass decreasing.
It corresponds to 70 MeV/c2.
To generate stopped modified w
meson, beam momentum is ~ 2
GeV/c. (K1.8 can be used.)
2009/10/9
w momentum [GeV/c]
p
Stopped w meson
0.2
Mass dependence
(Mw = 783 MeV/c2)
-100 MeV/c2
-50 MeV/c2
0
0
J-PARC seminar, K. Ozawa
DM = 0 MeV/c2
6
2
4
p momentum [GeV/c]
26
Expected results
Initial condition is measured
by forward neutron.
w can be bounded in nucleus.
Emitted
Neutron
p
Bound
w
p0  decay
Expected Invariant mass spectrum
DM=9%
ΔＥ/E =
3 %/√E
DM=0
DM=13%
Show mass
shift at p=0.
2009/10/9
Invariant mass in
medium
J-PARC seminar, K. Ozawa
Dm
27
Chiral symmetry with Baryon
LOI by K. Itahashi et. al
h bound state
N*(1535)
KS-KL s-wave resonance (Chiral Unitary model)
Chiral partner of nucleon (Chiral Doublet model)
Calc. by H. Nagahiro
How to study N* experimentally?
h – N is strongly coupled with N*
h in nucleus makes N* and hole
Generate slowly moving h in nucleus
2009/10/9
J-PARC seminar, K. Ozawa
28
Experiment for h
LOI by Dr. K. Itahashi’s
Calc. by H. Nagahiro, D. Jido,
S. Hirenzaki et. al
Forward neutron is detected.
missing mass distribution is measured.
Simulation
2009/10/9
In addition, measurements of
invariant mass of N* decay
J-PARC seminar, K. Ozawa
29
f bound state?
b<1.25 (Slow)
Cu
Bound?
pp -> ff
fp -> K+L
Φ s
s
u
p u
d
s K+
u
s
u Λ
d
See details in Dr. H. Ohnishi’s proposal
2009/10/9
J-PARC seminar, K. Ozawa
30
GEM DEVELOPMENT
2009/10/9
J-PARC seminar, K. Ozawa
31
GEM
• High Field in hole induces avalanche Multiplication
QIN
ED=500V/cm
EI=1000V/cm
QOUT
GAIN = QOUT / QIN
10~30 per foil
TYPICAL GEM:
50 µm Kapton
5 µm Copper
70 µm holes at 140 µm pitch
F. Sauli, Nucl. Instr. and Meth. A386(1997)531
2009/10/9
J-PARC seminar, K. Ozawa
32
Gain
Typically, 3 layers are used.
Ar(90%)-CH4(10%)
Gain
3-GEM
104
2-GEM
・CERN-GEM
Ar(70%)-CO2(30%)
Gain
55Fe
104
3-GEM
2-GEM
X-ray
5.9 keV
３００
４００
[V]
Effective Gain mesasured w X-ray
2009/10/9
J-PARC seminar, K. Ozawa
33
Japanese GEM
CERN-GEM
Etching
method
wet etching
SciEnergy GEM
dry etching
The cross
section of
a hole
Cost
2009/10/9
A hole with
double-conical
shape
A hole with
cylindrical
shape
\60k per foil
\80k per foil
*CERN-like GEM can be produced
in Japan (Ray-Tech
Co.)
also.
J-PARC
seminar,
K. Ozawa
• Dry etching
method is
applied.
– Hole shape is
improved and
cylindrical hole
GEM has better
Gain stability.
34
Another advantages in Japan
• 100mm thickness GEM is successfully developed
by Dry etching method and LCP base material.
– Higher gain is expected with thicker GEM
● 150mm-GEM VGEM=750V
● 100mm-GEM VGEM=500V
● Standard-GEM (50mm)
VGEM=250V
● 150mm-GEM
● 100mm-GEM
● Standard-GEM
(50mm)
Electric field along the
center of a GEM hole
2009/10/9
J-PARC seminar, K. Ozawa
35
Easy signal handling
Pulse shape

Prof. S. Uno @ MPGD WS
GEM Response function
No magnetic Field/ No Drift region
σ＝359.7±0.4 μm
Signal from GEM foil
150mV
P10
σ＝181.2±0.3 μm
Ar-CO2
(70/3
0)
Signal from
Readout pad
80ns
Response function
Width of signal spread is consistent with
Time constant is from the drift
time in the last gap. (No ion tail) transverse diffusion in GEM (along
It can be reduced to ~20ns. 3layers ).
It can be reduced by magnetic field.
Intrinsic multi-track resolution DV ~ 1 mm3
(Standard MWPC TPC ~ 1 cm3)
2009/10/9
J-PARC seminar, K. Ozawa
36
Good @ high rate counting
• MWPC limitation
– Wire spacing: 1~2 mm
– Gain dropping @ high rate
• Micro strip gas chamber
– Discharge problem
• Micromegas
MWPC
– Another candidate
• GEM
– Flat gain over 105 Hz/mm2
– I like flexibility of configuration
– Good characteristics of signal
• Signal is generated by electron
• Not by ion
• No ion tail and pole cancellation
electronics
104 105
GEM
I took these ideas and figures from F. Sauli’s presentation at XIV
GIORNATE
RIVELATORI
Villa
Gualino 10-13 Febbraio 2004
2009/10/9 DI STUDIO SUIJ-PARC
37
seminar, K.
Ozawa
Beam Line tracker
Collaboration with KEK
2009/10/9
J-PARC seminar, K. Ozawa
38
Hadron Blind Detector
CsI光電面を用いた光検出器の開発
• 紫外域に感度を持つ光検出器
を開発する。
チェレンコフ光
電子
• 実験では、Cherenkov光検出
器として電子識別に用いられる。
– 電子は、ガス中で光を出す。
– p中間子は、出さない。
• 具体的には、
– GEM上面にCsI光電面を蒸着
– GEM３層を電子増幅に使用
• 読み出しにStripやPadを用い
ることで位置情報も得られる
2009/10/9
References
1. NIM A523, 345, 2004
2. NIM A546, 466, 2005
J-PARC seminar, K. Ozawa
39
R&D @ RIKEN
Beam Test @ LNS Tohoku Univ.
100 um thick CsI coated GEM as
a photo cathode
Reverse bias btw mesh and CsI
GEM to suppress ionization
electrons
dE/dx
(Blind ON)
dE/dx + Light
(Blind OFF)
1~2 photo electrons
2009/10/9
J-PARC seminar, K. Ozawa
40
GEM TPC
Use GEM for signal avalanche
• Low ion feed back
– No Gate operation
• Easy signal handling
– Small time constant
– Narrow signal distribution
 Flexible readout configuration
– No wire
– Resolution
10cm
• Diffusion
• Pad configuration
2009/10/9
GEM TPC
@ CNS
10cm
J-PARC seminar, K. Ozawa
41
GEN TPC R&D @CNS
1.
Hit positions in pad-row direction (X) and drift direction (Z) are
determined by simple weighted mean of charge.
2.
Spatial resolution is estimated from a residual between the
1st
position of the middle pad row and the interpolated position.
1
2
Res X  X 2   X 1  X 3 ,  X 
 ResX 2nd
2
Result
6

Best resolution was 80mm (X-direction) and 310mm(Z-direction)
with Ar-C2H6 gas, with rectangular pad, for drift length of 13mm. 3rd

Zigzag pad and rectangular pad have similar spatial resolution.
ResX
Large offset
due to GEM
and
electronics
Pad-row
direction
Drift
direction
Z  T  vdrift
2009/10/9
J-PARC seminar, K. Ozawa
42
Summary
• According to the theory, Hadron mass is
generated as a results of spontaneous
breaking of chiral symmetry.
• An experimental efforts are underway to
investigate this mechanism. Some results
are already reported.
– Still, there are problems to extract physics
information.
• New experiments for obtaining further
physics information are proposed.
– Explore large kinematics region
– Measurements with stopped mesons
– Measurements of bound states
2009/10/9
J-PARC seminar, K. Ozawa
43
Back up
ハドロン質量の起源
Current quark masses
generated by
spontaneous symmetry
breaking (Higgs field)
1000000
100000
QCD Mass
Higgs Mass
10000
1000
100
10
1
u
d
s
c
b
t
Constituent quark
masses generated by
QCD dynamical effects
(spontaneous chiral
symmetry breaking ).
95% of the (visible) mass is generated by the strong interaction,
dynamically. Only 5% of the mass is due to the Higgs field.
The hadron mass is strongly related to chiral
properties of “QCD medium”, which can be
2009/10/9
45
J-PARC seminar, K. Ozawa
changed as a function of Temperature and Density.
Chiral symmetry
Gluon
Divide with
quark chirality
Neglect
mass
(if m ~0)
V(q)
The lagrangian does not change
under the transformation below .
This symmetry is called as
Chiral symmetry.
2009/10/9
J-PARC seminar, K. Ozawa
Symmetric
in rotation
q
46
Breaking of symmetry
When the potential is like
V(f) = f4,
Potential is symmetric and
Ground state (vacuum) is at symmetric position
If the interaction generate
additional potential automatically,
V’(f) = -a*f2
Potential is still symmetric, however,
Ground state (vacuum) is at non-symmetric
position
This phenomenon is called
spontaneous symmetry breaking
dV
~ self energy of ground state ~ mass
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J-PARC seminar, K. Ozawa
47
Background is not an issue
• Combinatorial background is evaluated by a mixed event
method.
The problem:
• Form of the background is determined by acceptance and
Each
experiment can’t apply another method.
reliable.
• We should be careful on normalization.
CLAS
KEK
Normalized
using mass
region
above f.
There is
enough
statistics
Absolute
normalization
using likesign pairs
2009/10/9
J-PARC seminar, K. Ozawa
48
Experimentalists face to reality
- E325 simulation- e+e-
 V  A 1 , Bremsh  Z 2 , Background  Z 4
KEK-E325 Target
material
C
C
Cu X4
1g/c
m2
2009/10/9
beam
(p/spill)
0.64x109
Interaction radiation
Cu length(%)
length(%)
0.2%
0.4%
0.05% X4
0.5% X4
1g/c
m2
J-PARC seminar, K. Ozawa
49
Performance of the 50-GeV PS
Numbers in parentheses are ones for the Phase 1.
• Beam Energy：
• Repetition:
• Flat Top Width：
• Beam Intensity:
• Beam Power:
2009/10/9
50ＧｅＶ
(30GeV for Slow Beam)
(40GeV for Fast Beam)
3.4 ~ 5-6s
0.7 ~ 2-3s
3.3x1014ppp, 15mA
(2×1014ppp, 9mA)
ELinac = 400MeV (180MeV)
750kW (270kW)
J-PARC seminar, K. Ozawa
50
J-PARC
• Cascaded Accelerator Complex:
Materials and Life
Science Facility
Hadron Hall (Slow
Extracted Beams)
3GeV Rapid Cycling
(25Hz) Synchrotron
Linac
2009/10/9
Neutrino Beamline to
Super-Kamiokande
J-PARC seminar, K. Ozawa
50GeV
Synchrotron
51
Let’s go to J-PARC
• Beam Energy：
• Beam Intensity:
2009/10/9
50ＧｅＶ
(30GeV for Slow Beam)
3.3x1014ppp, 15mA
(2×1014ppp, 9mA)
J-PARC seminar, K. Ozawa
Hadron Hall
52
Beam Line
NP-HALL
56m(L)×60m(W)
ここでやります。
お願いします。
2009/10/9
J-PARC seminar, K. Ozawa
53
Experimental setup
Beam
Neutron
p-C  wnX @ 1.8 GeV/c
 p0 
 
Beam: 107 pTarget: Carbon 6cm
Gamma
Detector
Small radiation loss
Clear calculation of w
bound state
Neutron Detector
Flight length 7m
Gamma Detector
Assume T-violation’s
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Charged Track sweep
SKS
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J-PARC seminar, K. Ozawa
Measurement I: missing mass
Relatively small (30cm x 30cm)
neutron detector is used.
To keep w momentum lower, small
neutron scattering angle is needed.
Bound state of w has strong
scattering angle dependence.
In addition, to achieve good timing
resolution, small counter is needed.
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w momentum [GeV/c2]
Missing mass resolution of 25 MeV/c2
is required to see a significant signal
in bound region.
Missing mass is measured by TOF of
neutron.
Timing resolution of 90 ps is required
for neutron detector using 7 m flight
path.
1.2
Neutron q dependence
q = 10
0.8
q = 5
0.4
q = 0
0
0
6
2
4
p momentum [GeV/c2]
J-PARC seminar, K. Ozawa
55
Neutron Detector
Timing resolution
Beam test is done at Fuji test line
Timing resolution of 80 ps is
achieved (for charged particle).
It corresponds to mass resolution of
22 MeV/c2.
Scintillator
Neutron Efficiency
Lead plate (1cm
t) is placed to
increase neutron
efficiency.
Time of flight [ps]
Efficiency is evaluated using a hadron
transport code, FLUKA.
Neutron efficiency of 27% can be
achieved.
Both resolution and efficiency should
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J-PARC seminar, K. Ozawa
be checked using a neutron beam.
Energy Distribution
Calculated by FLUKA
56
Measurement II: Invariant mass
Mass decreasing of 70 MeV/c2 is
expected using E325 result.
(Note: CLAS has no mass shift results.)
E325
Invariant mass resolution of 35 MeV/c2
is required to see a clear shifted peak.
Good energy resolution (few %) is
needed for gamma-ray detection.
Almost stopped w meson is generated
and decayed gamma rays go to back to
back directions.
Large acceptance is essential to
detect w mesons.
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J-PARC seminar, K. Ozawa
TAPS
DM =
24MeV/c2
57
Gamma detector
CsI EMCalorimeter
T-violation’s one is assumed “at this moment”.
（D.V. Dementyev et al., Nucl. Instrum. Meth. A440(2000), 151）
21 MeV/c2
29 MeV/c2
ΔＥ/E = 1.62%/√E + 0.8%
ΔＥ/E = 3 %/√E (conservative)
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J-PARC seminar,
K. evaluated
Ozawa
Acceptance
for w is
as 58%.
58
Ion feedback
• Strong positive ion feedback suppression
Ions
Electrons
S. Bachmann et al, Nucl. Instr. and Meth. A 438(1999)376
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GEMJ-PARC
HV configuration
should be determined carefully
.
59
seminar, K. Ozawa
GEM TPC Gas
Drift
velocity
CF4
• Several gas can be used for GEM
Ar-C2H4
– p10, Ar-C2H6, Ar-CO2 (70/30)
p10
• An interesting gas is CF4
– Large drift velocity – 8.9 [cm/ms] @ 570V/cm
S. X. Oda et al, Nucl. Instr. and
Position Resolution
Meth. A 566(2006)312
– Small Diffusion – 104(Transverse)
and Resolution
82(Longitudinal) [mm/cm]
No Magnetic
Diffusion
field
p10
Ar-C2H4
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CF4
J-PARC seminar, K. Ozawa
p10
Ar-C2H4
CF4
60
Read out pattern
• You can choose your favorite one.
PADS
1-D STRIPS
2-D STRIPS
CERN-TS-DEM
ODA ET AL: GEM TPC
PAD ROWS
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J-PARC seminar, K. Ozawa
61
Pad size and pattern
• Size
Readout plane
– Enough
primary
electron
should be
produced per
pad length
– Narrower than
Diffusion
• 2~3 pad hits
 Pattern in one raw
•Flexible configuration with GEM
•Number of pad can be reduced
using de-focusing effects at
GEM.
•Diffusion between GEM foils. Rectangular Stagger
2009/10/9
•Resistive Foil J-PARC seminar, K. Ozawa
Chevron
62
Front-End Electronics
Example: APV-S1 chip
• Originally, it’s developed for CMS Si detector
• Also, it’s used for COMPASS GEM
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63
Results @ SPS (NA60)
Muon pair invariant mass in In-In at sNN=19.6 GeV
PRL 96, 162302 (2006)
[van Hees+R. Rapp ‘06]
Spectrum is reproduced
with collisional broadening.
Next,
We should try to extract of a quark
condensate information
from the data.
J-PARC seminar, K. Ozawa
2009/10/9
64
64
Results @ RHIC
Electron pair invariant mass
in Au-Au at sNN=200 GeV
arXiv:0706.3034
Advantages of RHIC
QGP generated
Clear initial condition
Time developing
calculated by
Hydrodynamics
• Black Line
– Baseline calculations
• Colored lines
– Several models
Low mass
• M>0.4GeV/c2:
– some calculations OK
• M<0.4GeV/c2:
not reproduced
– Mass modification
– Thermal Radiation
No concluding remarks at this moment.
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seminar, K. Ozawa
Currently,
we areJ-PARC
working
for detector upgrade.