J-PARC におけるハドロン質量起源の探索実験

J-PARCJ-PARC におけるハドロにおけるハドロン質量起源の探索実験ン質量起源の探索実験

小沢　恭一郎（東京大学）小沢　恭一郎（東京大学）Contents:Contents:

Physics motivationPhysics motivation

Current resultsCurrent results

Future ExperimentsFuture Experiments

SummarySummary

J-PARC seminar, K. Ozawa2

時間

Big BangW

Z

ν

クォークの閉じ込めによるハドロンの形成

クォーク・グルオンの世界

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

ハドロンの世界原子核

の世界

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

太陽

超新星爆発

中性子星

超新星爆発を起こす核反応

中性子星の構造を支えるクォーク

Higgs相転移

2009/10/9

ハドロン質量起源ハドロン質量起源

2009/10/9 J-PARC seminar, K. Ozawa 3

High TemperatureHigh Density

Quark – antiquark pairs make a condensate and give a potential.Symmetry is breaking.

Quark is not confined.Mass ~ 0 (Higgs only)

It looks real “vacuum”.

Quark is confined.Vacuum contains quark antiquark condensates.So called “QCD vacuum”.

q

q

Vacuum VacuumWhen T and are going down,

as a Nambu-Goldstone boson. as a Nambu-Goldstone boson.

How to study?How to study?


Mass of chiral partner should be degenerated in restored medium. (JP = 1-) m=770 MeV ：　 a1 (JP = 1+) m=1250 MeV

– N (1/2+) m=940 MeV 　：　 N* (1/2-) m=1535 MeV ？

m will decrease in finite /T matter.

However, measurements of chiral partner is very difficultHowever, measurements of chiral partner is very difficult

“QCD vacuum”, i.e. quark condensates can be changed in finite density or temperature.Then, chiral symmetry will

be restored (partially).

Vacuum 0T 0

Connect hadron properties and quark condensate using QCD and/or phenomenology.

Connect hadron properties and quark condensate using QCD and/or phenomenology.

In finite

Chiral properties can be studied at finite density and temperature.

What is observable?

Theoretical effortsTheoretical efforts• Nambu-Jona-Lasino model

– Nambu and Jona-Lasino, 1961– Vogl and Wise, 1991– Hatsuda and Kunihiro, 1994

• 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

• Empirical models– Potential model (De Rujula et al., 1975), Bag model (Chdos et

al., 1974)• In addition, Collisional broadening, nuclear mean field …


‘

G.E.Brown and M. Rho,PRL 66 (1991) 2720

0

**

8.0qq

qq

mm

T.Hatsuda and S. Lee,PRC 46 (1992) R34

18.0;1mm

0

B

V

*V

Vector meson mass

2009/10/9 J-PARC seminar, K. Ozawa

Predicted Predicted ““spectraspectra””

• several theories and models predict spectral function of vector mesons ().– Lowering of in-medium mass– Broadening of resonance

R. Rapp and J. Wambach, EPJA 6 (1999) 415

- meson

6structure due to coupling to S11,P13 resonances

P. Muehlich et al. , Nucl. Phys. A 780 (2006) 187

- meson

As the first step, experiments try the comparison between

predicted spectra and measurements.

As the first step, experiments try the comparison between

predicted spectra and measurements.

MEASUREMENTSMEASUREMENTS


Create QCD medium Create QCD medium

heavy ion reactions:A+AV+X

mV(>>0;T>>0)

SPS

LHC

RHIC

elementary reaction:, p, V+XmV(=0;T=0)

, . p - beams

J-PARCCLAS

At Nuclear Density

82009/10/9 8J-PARC seminar, K. Ozawa

Measurements of Vector Meson mass spectra in QCD medium will provide QCD condensates information.

Leptonic (e+e-, +-) decays are suitable, since lepton doesn’t have final state interaction.

Measurements in Nucleus• Stable system

– No (small) need for time development

• Saturated density

ECT*-WS, K. Ozawa

Link vector meson masses and the quark condensate.

Link meson bound states and the quark condensate.

Two approaches,


Bound State (Emitted Proton/Neutron)p

Nucleon Hole

TargetDecay

Meson

bound stateK. Suzuki et al., Phys. Rev. Let., 92(2004) 072302

bound state is observed in Sn(d, 3He) pion transfer reaction.

Reduction of the chiral order parameter, f*()2/f2=0.64 at the normalnuclear density ( = 0 ) is indicated.


as a NG boson

10New exp. is in preparation at RIKEN

D. Jido et al., arXiv:0805.4453PLB670 (2008) 109

Jido-san et al. shows that -nucleus scattering length is directly connected to quark condensate in the medium.

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。

11

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）


注意

12J-PARC seminar, K. Ozawa

INS-ES TAGX experiment INS-ES TAGX experiment

E STT model

Present work

Previous

work

800-960

MeV

700-710 MeV

672±31

MeV

960-1120

MeV

730

MeV

743±17

MeV

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 cos analysis to quantify the strength of rho like excitation

• Phys.Rev.C68:065202,2003. In-medium 0 spectral function study via the H-2, He-3, C-12 (+ -) reaction.

2009/10/9

Try many models, and channels Δ, N*, 3π,…

CBELSA/TAPSCBELSA/TAPS

disadvantage:

• 0-rescattering

advantage:

• 0 large branching ratio (8 %)

• no -contribution ( 0 : 7 10-4)

p

A + X

0

2ppm

D. Trnka et al., PRL 94 (2005) 192203after background subtraction

%.mm 03

m = m0 (1 - /0) for = 0.13

TAPS, TAPS, 00 with with +A+A


E325 @ KEK-PSE325 @ KEK-PS12 GeV proton induced.

p+A + XElectrons from decays are detected.

TargetCarbon, Cupper0.5% rad length


KEK E325

E325 SpectrometerE325 Spectrometer


Mass spectra measurements

m = m0 (1 - /0) for = 0.092009/10/9 J-PARC seminar, K. Ozawa 16

Induce 12 GeV protons to Carbon and Cupper target, generate vector mesons, and detect e+e- decays with large acceptance spectrometer.

Cu e+e-

e+e-

/

The excess over the known hadronic sources on the low mass side of peak has been observed.

M. Naruki et al., PRL 96 (2006) 092301

KEK E325, e+e-

CLAS g7a @ J-LabCLAS 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

m = m0 (1 - /0) for = 0.02 ± 0.02

No peak shift of

Only broadening is observed

/

Contradiction?Contradiction?

• Difference is significant

• What can cause the difference?– Different production

process– Peak shift caused by

phase space effects in pA?• Need spectral function of

without nuclear matter effects

Note: • similar momentum range• E325 can go lower slightly


In addition, background issue is pointed out by CLAS

CLASKEK


Results: Results: e e++ee- - (E325)(E325)

Cu

<1.25 (Slow)

Invariant mass spectrum for slow mesons of Cu target shows a excess at low mass side of .

Measured distribution contains both modified and un-modified mass spectra. So, modified mass spectrum is shown as a tail.

19

First measurement of meson mass spectral modification in QCD

matter.

R. Muto et al., PRL 98(2007) 042581

Excess!!

20

<1.25 (Slow) 1.25<<1.75 1.75< (Fast)


Mass modification is seen only at heavy nuclei and slowly moving Mass Shift:

m = m0 (1 - /0) for = 0.03

Target/Momentum dep.

NEXT STEPNEXT STEP@ J-PARC@ J-PARC


Condensates to SpectrumCondensates to Spectrum


We should revisit the relation between quark condensate and vector meson spectrumWe should revisit the relation between quark condensate and vector meson spectrum

q

q

Vacuum Vacuum

QCD sum rule

Average of Imaginary part of (2)

vector meson spectral function



T.Hatsuda and S. Lee,PRC 46 (1992) R34

03.0;10

*

B

V

V

m

m

Prediction

Spectrum

mV

Original idea by Hatsuda and Lee shows the relation

Assume

Using this relation,

Spectrum to condensate


Evaluate quark condensate using QCD-SR.

Experimental requirements

1. High statics2. Clear initial condition

Beyond comparisons with models

q

q

Vacuum Vacuum

QCD sum rule





Replace by average of measured spectra

p

Condensates and SpectrumCondensates and Spectrum


New exp 1: High StatisticsNew exp 1: High Statistics• Extended to vertical direction

Side viewPlain view

KEK spectrometer

Cope with 10 times larger beam intensity!!100 times higher statistics!! 24

What can be achieved?What can be achieved?


Pb

Modified

[GeV/c2]

from Proton

Invariant mass in medium

p dep

.

High resolution

calculate quark condensate

New exp 2: Clear Initial conditionNew exp 2: Clear Initial condition


-50 MeV/c2

= 0 MeV/c2

-100 MeV/c2

0 2 4 6 momentum [GeV/c]

m

om

entu

m [

GeV

/c]

0

0.2

0.4Mass dependence(M = 783 MeV/c2)

Stopped meson

n

A + X

0

2ppm

As a result of KEK-E325,We can expect 9% mass decreasing.It corresponds to 70 MeV/c2.To generate stopped modified meson, beam momentum is ~ 2 GeV/c. (K1.8 can be used.)

Generate meson using + p.Emitted neutron is detected at 0.Decay of meson is detected.

If momentum is chosen carefully, momentum transfer will be ~ 0.

Invariant mass in medium

Expected resultsExpected results


Show mass shift at p=0.

Emitted Neutron

0 decayBound

Initial condition is measured by forward neutron. can be bounded in nucleus.

Δ Ｅ /E = 3 %/√E

Expected Invariant mass spectrum

M=0

M=9%

M=13%

m

Chiral symmetry with Baryon Chiral symmetry with Baryon


bound stateN*(1535)

K-K s-wave resonance (Chiral Unitary model)Chiral partner of nucleon (Chiral Doublet model)

– N is strongly coupled with N*

How to study N* experimentally?

in nucleus makes N* and hole

Generate slowly moving in nucleus

LOI by K. Itahashi et. al

Calc. by H. Nagahiro

28

Experiment for Experiment for


Calc. by H. Nagahiro, D. Jido, S. Hirenzaki et. al

Forward neutron is detected.missing mass distribution is measured.

In addition, measurements of invariant mass of N* decay

Simulation

29

LOI by Dr. K. Itahashi’s

bound state?bound state?


Cu

<1.25 (Slow)

Bound?ss

uud

K+

Λ

Φ

p ud

s

us

p -> K+

pp ->

See details in Dr. H. Ohnishi’s proposal

30

GEM DEVELOPMENTGEM DEVELOPMENT


ED=500V/cm

EI=1000V/cm

• High Field in hole induces avalanche Multiplication

GEMGEM

QIN

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


Typically, 3 layers are used.


GainGain

Effective Gain mesasured w X-ray

Ar(90%)-CH4(10%)

3-GEM

2-GEM

3-GEM 2-GEMGain

・ CERN-GEM

３００４００ [V]

104

Gain

104

Ar(70%)-CO2(30%)

55FeX-ray5.9 keV

• Dry etching method is applied.– Hole shape is

improved and cylindrical hole GEM has better Gain stability.


Japanese GEMJapanese GEM

CERN-GEM

wetwet etching

SciEnergy GEM

drydry etchingEtching method

The cross section of

a hole

A hole with cylindricalcylindrical

shape

A hole with double-conicaldouble-conical

shape

Cost \80k per foil\60k per foil

*CERN-like GEM can be produced in Japan (Ray-Tech Co.) also.

• 100m thickness GEM is successfully developed by Dry etching method and LCP base material.– Higher gain is expected with thicker GEM


Another advantages in JapanAnother advantages in Japan

● 150m-GEM

● 100m-GEM

● Standard-GEM (50m)

Electric field along the center of a GEM hole

● 150m-GEM VGEM=750V

● 100m-GEM VGEM=500V

● Standard-GEM (50m) VGEM=250V

Pulse shape


Easy signal handlingEasy signal handling

Intrinsic multi-track resolution V ~ 1 mm3

(Standard MWPC TPC ~ 1 cm3)

Signal from Readout pad

Signal from GEM foil

80ns

150mV

GEM Response function

Time constant is from the drift time in the last gap. (No ion tail)

It can be reduced to ~20ns.

σ ＝ 181.2±0.3 μm

Ar-CO2

(70/30)

Width of signal spread is consistent with transverse diffusion in GEM (along 3layers ).

It can be reduced by magnetic field.

No magnetic Field/ No Drift region

σ ＝ 359.7±0.4 μmP10

Response function

Prof. S. Uno @ MPGD WS


Good @ high rate countingGood @ high rate counting• MWPC limitation

– Wire spacing: 1~2 mm– Gain dropping @ high rate

• Micro strip gas chamber – Discharge problem

• Micromegas– 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

GEM

MWPC

104 105

37

I took these ideas and figures from F. Sauli’s presentation at XIV GIORNATE DI STUDIO SUI RIVELATORI Villa Gualino 10-13 Febbraio 2004

Beam Line trackerBeam Line tracker

2009/10/9 38

Collaboration with KEK

J-PARC seminar, K. Ozawa

Hadron Blind DetectorHadron Blind Detector

• 紫外域に感度を持つ光検出器を開発する。

• 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。– 中間子は、出さない。

• 具体的には、– GEM 上面に CsI 光電面を蒸着– GEM ３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

References1. NIM A523, 345, 20042. NIM A546, 466, 2005


CsI 光電面を用いた光検出器の開発電子

チェレンコフ光

R&D @ RIKENR&D @ RIKEN


1~2 photo electrons

Beam Test @ LNS Tohoku Univ.100 um thick CsI coated GEM as a photo cathodeReverse bias btw mesh and CsI GEM to suppress ionization electrons

dE/dx (Blind ON)

dE/dx + Light (Blind OFF)

• Low ion feed back – No Gate operation

• Easy signal handling – Small time constant– Narrow signal distribution Flexible readout configuration– No wire– Resolution

• Diffusion• Pad configuration

GEM TPCGEM TPC


10cm

10cm

GEM TPC @ CNS

Use GEM for signal avalanche

GEN TPC R&D @CNSGEN 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 position of the middle pad row and the interpolated position.

Result Best resolution was 80m (X-direction) and 310m(Z-direction)

with Ar-C2H6 gas, with rectangular pad, for drift length of 13mm. Zigzag pad and rectangular pad have similar spatial resolution.

ResXXX XXXRes 6

2 ,

2

1312

1st

2nd

3rd

ResX

Pad-row direction

Drift direction

driftvTZ

Large offset due to GEM and electronics

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


Back upBack up

ハドロン質量の起源ハドロン質量の起源


1

10

100

1000

10000

100000

1000000

u d s c b t

QCD Mass

Higgs Mass

95% of the (visible) mass is generated by the strong interaction, dynamically. Only 5% of the mass is due to the Higgs field.

Current quark masses generated by spontaneous

symmetry breaking (Higgs field)

Constituent quark masses generated byQCD dynamical effects (spontaneous chiral symmetry breaking ).

The hadron mass is strongly related to chiral properties of “QCD medium”, which can be changed as a function of Temperature and

Density.

45

Chiral symmetryChiral symmetry


The lagrangian does not change under the transformation below .

This symmetry is called as Chiral symmetry.

V(q)

q

Symmetric in rotation

GluonDivide with chirality Neglect (if m ~0)quark mass

Breaking of symmetryBreaking of symmetry


Potential is symmetric andGround state (vacuum) is at symmetric position

Potential is still symmetric, however,Ground state (vacuum) is at non-symmetric position

This phenomenon is called

spontaneous symmetry breaking

When the potential is like V() = 4,

V ~ self energy of ground state ~ mass

If the interaction generate additional potential automatically,

V’() = -a*2

Background is not an issueBackground is not an issue• Combinatorial background is evaluated by a mixed event

method.• Form of the background is determined by acceptance and

reliable.• We should be careful on normalization.


Absolute normalization using like-sign pairs

CLAS KEKNormalized using mass region above . There is enough statistics

The problem:Each experiment can’t apply another method.


1g/cm2

1g/cm2

C Cu

421 ,, ZBackgroundZBremshAV

Experimentalists face to reality - E325 simulation- e+e-

KEK-E325 Target

material beam (p/spill)

Interaction length(%)

radiation length(%)

C 0.64x109 0.2% 0.4%

Cu X4 0.05% X4 0.5% X4


Performance of the 50-GeV PSPerformance of the 50-GeV PS

• Beam Energy ： 50 ＧｅＶ(30GeV for Slow Beam)(40GeV for Fast Beam)

• Repetition: 3.4 ~ 5-6s• Flat Top Width ： 0.7 ~ 2-3s• Beam Intensity: 3.3x1014ppp, 15A

(2×1014ppp, 9A) ELinac = 400MeV (180MeV)

• Beam Power: 750kW (270kW)

Numbers in parentheses are ones for the Phase 1.

50


Linac

J-PARCJ-PARC• Cascaded Accelerator Complex:

3GeV Rapid Cycling (25Hz) Synchrotron

50GeV Synchrotron

Materials and Life Science Facility

Hadron Hall (Slow Extracted Beams)

Neutrino Beamline to Super-Kamiokande

51

Let’s go to J-PARCLet’s go to J-PARC


• Beam Energy ： 50 ＧｅＶ(30GeV for Slow

Beam)• Beam Intensity: 3.3x1014ppp, 15A

(2×1014ppp, 9A)

Hadron Hall


Beam LineBeam LineNP-HALL

56m(L)×60m(W)

ここでやります。お願いします。

53

Experimental setup-C nX @ 1.8 GeV/c

0

Beam: 107 -

Target: Carbon 6cmSmall radiation lossClear calculation of bound state

Neutron DetectorFlight length 7m

Gamma DetectorAssume T-violation’s

Charged Track sweepSKS

Beam Neutron

Gamma Detector


Measurement I: missing massMeasurement I: missing mass


0 2 4 6 momentum [GeV/c2]

0

0.8

0.4 = 0

= 5

= 10

1.2Neutron dependence

m

om

entu

m [

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.

To keep momentum lower, small neutron scattering angle is needed.Bound state of has strong scattering angle dependence.In addition, to achieve good timing resolution, small counter is needed.

Relatively small (30cm x 30cm) neutron detector is used.

Neutron DetectorTiming resolution

Beam test is done at Fuji test lineTiming resolution of 80 ps is achieved (for charged particle).It corresponds to mass resolution of 22 MeV/c2.

Scintillator


Time of flight [ps]

Energy DistributionCalculated by FLUKA

Neutron EfficiencyLead plate (1cm t) is placed to increase neutron efficiency.

Efficiency is evaluated using a hadron transport code, FLUKA.Neutron efficiency of 27% can be achieved.

Both resolution and efficiency should be checked using a neutron beam.

Measurement II: Invariant massMeasurement II: Invariant mass


Mass decreasing of 70 MeV/c2 is expected using E325 result. (Note: CLAS has no mass shift results.)

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 meson is generated and decayed gamma rays go to back to back directions.

Large acceptance is essential to detect mesons.

M = 24MeV/c2

E325

TAPS

Gamma detectorCsI EMCalorimeter

T-violation’s one is assumed “at this moment”.

Δ Ｅ /E = 1.62%/√E + 0.8%Δ Ｅ /E = 3 %/√E (conservative)

（ D.V. Dementyev et al., Nucl. Instrum. Meth. A440(2000), 151 ）


21 MeV/c2

29 MeV/c2

Acceptance for is evaluated as 58%.

• Strong positive ion feedback suppression


Ion feedbackIon feedback

ElectronsIons

S. Bachmann et al, Nucl. Instr. and Meth. A 438(1999)376

GEM HV configuration should be determined carefully .


• Several gas can be used for GEM– p10, Ar-C2H6, Ar-CO2 (70/30)

• An interesting gas is CF4

– Large drift velocity – 8.9 [cm/s] @ 570V/cm

– Small Diffusion – 104(Transverse) and 82(Longitudinal) [m/cm]

60

GEM TPC Gas GEM TPC Gas

No Magnetic field

Resolution

S. X. Oda et al, Nucl. Instr. and Meth. A 566(2006)312

Drift velocity

Diffusion

CF4

p10

Ar-C2H4

CF4

p10

Ar-C2H4

CF4

p10

Ar-C2H4

Position Resolution

• You can choose your favorite one.


Read out patternRead out pattern

1-D STRIPS

2-D STRIPS

PADS

PAD ROWS

CERN-TS-DEM ODA ET AL: GEM TPC

• Size– Enough

primary electron should be produced per pad length

– Narrower than Diffusion• 2~3 pad hits

in one raw


Pad size and patternPad size and pattern

Readout plane

Pattern

Rectangular Stagger Chevron

•Flexible configuration with GEM•Number of pad can be reduced using de-focusing effects at GEM.

•Diffusion between GEM foils.•Resistive Foil

63

Front-End ElectronicsFront-End Electronics

• Originally, it’s developed for CMS Si detector.• Also, it’s used for COMPASS GEM

Example: APV-S1 chip


Results @ SPS

64

PRL 96, 162302 (2006)


[van Hees+R. Rapp ‘06]

(NA60)

Next,We should try to extract of a quark condensate information from the data.

Spectrum is reproduced with collisional broadening.

Muon pair invariant mass in In-In at sNN=19.6 GeV

Results @ RHICResults @ RHIC


• 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

Advantages of RHICQGP generatedClear initial conditionTime developing

calculated by Hydrodynamics

Advantages of RHICQGP generatedClear initial conditionTime developing

calculated by Hydrodynamics

No concluding remarks at this moment.Currently, we are working for detector upgrade.

Electron pair invariant mass in Au-Au at sNN=200 GeV

arXiv:0706.3034

J-PARC におけるハドロン質量起源の探索実験

Documents

Transcript of J-PARC におけるハドロン質量起源の探索実験