Measurements of meson mass at J-PARC K. Ozawa (KEK) (KEK) Contents: Physics motivation Current results Experiments @ J-PARC Summary

Measurements of meson mass

at J-PARC

K. Ozawa (KEK)

Contents:Physics motivationCurrent resultsExperiments @ J-PARCSummary

Origin of Hadron mass

2011/11/30 Zimanyi school 2011, K. Ozawa

1

10

100

1000

10000

100000

1000000

u d s c b t

QCD Mass

Higgs Mass

95% of the (visible) mass is dynamically generated by the strong interaction.

This mechanism is actively studied both theoretically and experimentally.

Current quark masses generated by

spontaneous symmetry breaking (Higgs field)

Constituent quark masses should be generated byQCD dynamical effects

2

Naïve Theory

2011/11/30 Zimanyi school 2011, K. Ozawa 3

High TemperatureHigh Density

Quark – antiquark pairs make a condensate and give a potential. Chiralsymmetry is breaking, spontaneously.

Chiral symmetry exists.Mass ~ 0 (Higgs only)

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

q

q

Vacuum Vacuum

When T and r is going down,

p as a Nambu-Goldstone boson.

Experimental approach?


When chiral symmetry is restored, mass of chiral partner should be degenerated.

Dm will decrease in finite r/T matter.

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

be restored (partially).

Vacuumr 0T 0

In finite /r T

Chiral properties can be studied at finite density and temperature.

However, measurements of chiral partner is very difficult.We measure mass modification of narrow resonance.

mass

(JP = 1-)

a1 (JP = 1+)1250

770

/r T

Dm

Dm = 0Degenerate

Best Observable…

Mass shift and Condensate


In fact, Mass modification of a vector meson can be connected to quark condensates.

q

q

Vacuum Vacuum

QCD sum rule

Average of Imaginary part of P(w2)

vector meson spectral function

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

03.0;10

*

B

V

V

m

m

Prediction

Spectrum

mV

Theoretical Assumption

Measurements of mass related information in hot/dense matter is essential!

Example:


Predicted “spectra”

• Predicted mass spectral function of vector mesons ( , , r w f) in hot and/or dense matter.– Lowering of in-medium mass– Broadening of resonance

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

r- meson

6

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

- meson

In addition, several models predict mass spectra of mesons and it can be compared with experimental results directly.

CURRENT EXPERIMENTS


Generate hot/dense media

heavy ion reactions:A+AV+X

mV(>>0;T>>0)

SPS

LHC

RHIC

82011/11/30 8Zimanyi school 2011, K. Ozawa

Measurements of Vector Meson mass spectra in hot/dense medium will provide QCD medium information.

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

Hot matter experiments

SPS-CERES results


D. Miskowiec, QM05 talk

Existing of Mass modification is established.

PLB663, 43 (2008)

NA60 Results @ SPS

10

PRL 96, 162302 (2006)


[van Hees+R. Rapp ‘06]

Next, Let’s go to RHIC!

Spectrum is well reproduced with collisional broadening.

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

Results @ 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

Excess from known hadronic sources is also observed.However, it looks different.

No concluding remarks at this moment.New data with New detector (HBD) can answer it.

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

PRC81(2010) 034911

New detector!


signal electron

Cherenkov blobs

partner positronneeded for rejection

e+

e-

qpair openingangle

~ 1 m

Constructed and installed by Weizmann and Stony Brook group.

~20 p.e.

few p.e.

Hadron

Single electron

Great performance!

Then, Nucleus!

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

, . p - beams

J-PARCCLAS

At Nuclear Density


Stable systemSaturated density

Experiments, CBELSA/TAPS KEK-E325 @KEK-PS (Japan)CLAS g7 @ J-Lab

Cold matter experiments

Two Experimental methods– Direct measurements of mass spectra

Emitted Proton Neutronp, , p g

Nucleon Hole

Target

Decay

Meson

– Meson bound state spectroscopy


Results with Bound states K. Suzuki et al., Phys. Rev. Let., 92(2004) 072302

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

Reduction of the chiral order parameter, f*p(r)2/fp

2=0.64 at the normalnuclear density, r = r0 is indicated.


p bound state

Y. Umemoto et al., Phys. Rev. C62(2004) 02460615

Direct Measurements of MassKEK-PS E325: 12 GeV proton induced.

p+A r, w, f + XElectron decays are detected.


E325 Spectrometer


E325 Results I

mr = m0 (1 - /0) for = 0.092011/11/30 Zimanyi school 2011, K. Ozawa 18

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

Cu we+e-

re+e-

w/ /r f

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

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

KEK E325, / r w e+e-

Note: 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.

mr = m0 (1 - /0) for = 0.02 ± 0.02

No peak shift of r

Only broadening is observed

g w/ /r f

R. Nasseripour et al., PRL 99 (2007) 262302


E325 Result II: f e+e-

Cu

bg<1.25 (Slow)

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.

20

First measurement of f meson mass spectral modification in QCD matter.

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

Excess!!

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


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

mf = m0 (1 - /0) for = 0.0321

Target/Momentum dep.

NEW EXPERIMENTS@ J-PARC



Performance of the 50-GeV PS

• Beam Energy ： 50 ＧｅＶ(Currently, 30GeV)

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

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

• Beam Power: 750kW (270kW)

Numbers in parentheses are ones for the Phase 1.

23


Linac

J-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

24

Hadron Hall


Hadron HallNP-HALL

56m(L)×60m(W)

Upgrade of E325Large statistics

25

Stopped w for Clear mass

modification

Exp1: Upgrade of KEK-E325• Large acceptance (x5 for pair )• Cope with high intensity beam and high rate (x10)• Good mass resolution ~ 5 MeV/c2

• Good electron ID capability

2011/11/30 Zimanyi school 2011, K. Ozawa 26100 times higher statistics!!

What can be achieved?


Pb

fModified f

[GeV/c2]

f from Proton

Invariant mass in medium

ff

ff

ff

ff

p dep

.

High resolution

Kinematic dependence

Detector components


Tracker~Position resolution 100μmHigh Rate(5kHz/mm2)Small radiation length(~0.1% per 1 chamber)

Electron identificationLarge acceptanceHigh pion rejection @ 90% e-eff.

100 @ Gas Cherenkov25 @ EMCal

R&D Items


Develop 1 detector unit and make 26 units.① GEM foil

③ Hadron Blind detectorGas Cherenkov for electron-ID

② GEM Tracker

Ionization (Drift gap)+ Multiplication (GEM)

High rate capability + 2D strip readout

CsI + GEMphoto-cathode

50cm gas(CF4) radiator~ 32 p.e. expectedCF4 also for multiplication in GEM

Exp 2: stopped w meson


g g

gp

w p0

n

p-A + N+X

p0g

2ppm

Beam momentum is ~ 1.8 GeV/c. As a result of KEK-E325,9% mass decreasing (70 MeV/c2) can be expected.

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

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

w m

om

entu

m [

GeV

/c]

0.2

0.4

0 2 4p momentum [GeV/c]

0


Experimental setupp-p wn @ 1.8 GeV/c

p0 g gg

Target: Carbon 6cmSmall radiation lossClear calculation of w bound state Also, Ca, Nb, LH2

Neutron DetectorFlight length 7m60cm x 60 cm (~2°)

Gamma DetectorGood resolution75% of 4p

Beam Neutron

Gamma Detector

Detectors


Timing resolutionTiming resolution of 80 ps is achieved (for charged particle).It corresponds to mass resolution of 22 MeV/c2.

Neutron EfficiencyIron plate (1cm t) is placed.Efficiency is evaluated using a hadron transport code, FLUKA.Neutron efficiency of 25% can be achieved.

Neutron Detector EM calorimeter

CsI EMCalorimeterExisting detector + upgrade

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

912

mass resolution of 18 MeV/c2 can be achieved.

Expected results


H. Nagahiro et al, Calculation for 12C(p-, n)11Bw

Final spectrum is evaluated based on a theoretical calculation and simulation results.

Expected Invariant mass spectrum

Stopped w is selected by forward neutron

Generation of w is based on the above theoretical calculation.

Detector resolution is taken into account.

Yield estimation is based on 100 shifts using 107 beam.

Estimated width in nucleus is taken into account.

Exp 3: Study of Baryon sector


h bound stateN*(1535)

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

h – N is strongly coupled with N*

How to study N* experimentally?

h in nucleus makes N* and hole

Generate slowly moving h in nucleus

LOI by K. Itahashi et. al

Calc. by H. Nagahiro

34

Experiment for h


LOI by K. Itahashi et. al 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

35

Exp 4: f bound state?


Cu

bg<1.25 (Slow)

Bound?

ss

uud

K+

Λ

Φ

p ud

s

us

Detection:fp -> K+L

Generation:pp -> ff

36

Exp 5: h’ @ J-PARC


It’s under discussion with Prof. T. Csorgo.Please join us and come to Japan!

Summary• According to the theory, Hadron mass is

generated as a results of spontaneous breaking of chiral symmetry.

• Many experimental efforts are underway to investigate this mechanism. Some results are already reported.

• New experiments for obtaining further physics information are proposed.– Explore large kinematics region– Measurements with stopped mesons


Back up

Chiral 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 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(f) = f4,

dV ~ self energy of ground state ~ mass

If the interaction generate additional potential automatically,

V’(f) = -a*f2

Theoretical efforts

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

• Chiral Perturbation theory– Weinberg 1979

• QCD sum rule– Shifman et al., 1979– Hatsuda and Lee, 1992

• Lattice QCD– Wilson, 1974

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

1974)• In addition, Collisional broadening, nuclear mean field …2011/11/30 Zimanyi school 2011, K. Ozawa 42

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

18.0;1mm

0

B

V

*V

Vector meson mass

Connect hadron properties and chiral properties using QCD and/or phenomenology.

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

0

**

8.0qq

qq

mm

RHIC&PHENIX


Not only mass spectra, K. Suzuki et al., Phys. Rev. Let., 92(2004) 072302

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

Reduction of the chiral order parameter, f*p(r)2/fp

2=0.64 at the normalnuclear density (r = r0 ) is indicated.


p bound state

Y. Umemoto et al., Phys. Rev. C62(2004) 024606

44New exp. will be done at RIKEN

D. Jido et al., arXiv:0805.4453

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

Mass spectra measurements• Following four experiments,

– TAGX experiments @ INS-Japan– CBELSA/TAPS experiments– KEK-E325 @KEK-PS-Japan– CLAS g7 experiment @ J-Lab-USA

• Use heavy and light nucleus and extract mass modification

45

Obtained spectra is combination of two spectra, such as decayed in nucleus and free space.

Expected mass spectra


Note

46Zimanyi school 2011, K. Ozawa

INS-ES TAGX experiment

Eg STT modelPresent

work

Previouswork

800-960MeV

700-710 MeV

672±31MeV

960-1120MeV

730MeV

743±17MeV

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 ( ,g p+ p-) reaction.

2011/11/30

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

Background 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 f. 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

Condensates and Spectrum


Unfortunately, quark condensates is not an observable.We can link condensates and vector meson spectrum.

How to access quark condensate experimentally?

q

q

Vacuum Vacuum

QCD sum rule


vector meson spectral function

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

03.0;10

*

B

V

V

m

m

Prediction

Spectrum

mV

The relation is established by Prof. Lee and Prof. Hatsuda.

Assume

Next step


Then, calculate quark condensate using QCD sum rule.

Experimental requirements

1. High statics2. Clear initial condition


Assumed Spectrum

Evaluate quark condensate directly.Not comparison btw predictions and measurements.

Replace by average of measured spectra

p

GEM foils

• Dry etching method is developed in Japan.– Hole shape is improved and

cylindrical hole GEM has better Gain stability.

– Thicker GEM foils is generated.


wet etching dry etching

Hole shape

A hole with cylindrical

shape

A hole with double-conical

shape

WetDry

10

100

1000

10000

250 275 300 325 350 375 400

Gai

n

Δ Vgem/ 2 (100μ ) ・Δ Vgem （50μ ）[V]

100μ ｍ(single)

50μ ｍ(triple)

100mm1 foil

50mm3 foils

Applied Voltage per 50 mm [V] 300 350

102

103

Thicker GEM foil

Stability of GEM gain

GEM Tracker


Gas: Ar/CO2

2D readout: kapton t=25mm(Cu: t=4mm both side) 290 mm

Test @ KEK

σ~105μm

Residual [mm]

HBD: in the beginning…


1~2 photo electronsToo small…

dE/dx (Blind ON)

dE/dx + Light (Blind OFF)

Compare Measured Charge w/wo Cherenkov light blind

Charge [A.U.]

This part of evaporated CsI looks gone!!Low Q.E.?

Beam test results


GEM Configuration

2mm

2mm

2mm

11mm

Drift gap 11mm, 500V/cmAmplifing part 50μm GEM×3

Xi – XSSD [mm]Charg

e d

ivis

ion

Response Function

Weighted mean of Strip Charge

σ~105μm

Residual [mm]

Position Resolution:spos = Charge spread / Neff Worse resolution for tilted trackspos = 470 mm @ 15Require good resolution @ 30

Charge Spread

③ Hadron Blind Detector

• 紫外域に感度を持つ CsI 光電面– Cherenkov 光検出に最適– GEM 上面に CsI 光電面を蒸着

– 100 mm GEM を用いる• Radiator ガス : CF4

– High transmission @ UV

2011/11/30 55

CsI 光電面による Cherenkov 光検出器

MESH

2 mm

1.5 mm

3.25 mm

5.25 mm

LCP(100um)

CsI

pad

Cer

enko

vph

oton

Ionization(40)

Phot

oelec

tron (

32)

50um

GEM

50um

GEM

32 x 800

– p Threshold 4 GeV/c • GEM ３層を電子増幅に使用

– Gain ~ 800 @ CsI GEM Important for e/p

• Pad 読み出しで位置情報も

• Reverse Bias to suppress ionization!!

Ref. NIM A523, 345, 2004

ElectronCF4 Radiator

By K. AokiZimanyi school 2011, K. Ozawa

56

HBD @ J-PARC

2011/11/30 Zimanyi school 2011, K. OzawaCerenkov blob, f ~34mm

Beam

• Beam– 600 MeV

positron

• Defined are• 1cm x 1cm

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 r

without nuclear matter effects

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


We need to have a new experiment to investigate the problem.

CLAS

KEK

R.S. Hayano and T. Hatsuda, Ann. Rev.

Results from CBELSA/TAPS

disadvantage:

• p0-rescattering

advantage:

• p0g large branching ratio (8 %)

• no -contribution ( 0 : 7 10-4)

g g

gg

w p0

p

gA + X

p0g

2ppm

TAPS, w p0g with g+A

2011/11/30 Zimanyi school 2011, K. Ozawa 58m = m0 (1 - /0) for = 0.13No sensitivities for mass modification

arXiv: 1005.5694V. Metag at Hawaii JPS-DNP meeting

TAPS results II


M. Kotulla et al, PRL 100 (2008) 192302 E= 900 – 1400 MeV

Large w width in nuclei due to w-N interaction.

60 MeV/c2 even at stopped w.

In-medium decays

Essential:Focus on Small momentumIssue:Yield estimation of decays

Branching Ratio

60% 26.1

conversion

% 92.8

space freeat

MeV 60 , MeV 49.8

*

*

2222*

0

0

total

abstotal

absabsfreetotal

total

absfree

M. Kotulla et al, PRL 100 (2008) 192302

60 MeV/c2 even at stopped w.


Decay Yield EvaluationBased on measured crosssection of p-p wn for backward w (G. Penner and U. Mosel, nucl-th/0111024,J. Keyne et al., Phys. Rev. D 14, 28 (1976))

Production cross section0.02 mb/sr (CM) @ s = 2.0 GeV 0.17 mb/sr (Lab) @ s = 2.0 GeV Beam intensity107 / spill, 6 sec spill lengthNeutron Detector acceptanceDq = 2°(60 cm x 60 cm @ 7m)Gamma Detector acceptance90% for wRadiation loss in target 11%Survival probability in final state interaction 60%Beam Time 100 shiftsBranching Ratio 1.3 % 8.9 %


H. Nagahiro et al calculation based on the cross section and known nuclear effects.Assumed potential is consistent with w absorption in nucleus.

Interact w nuclei

No interact

Total

Large width ~ 60 MeV/c2

% 26.1*

0,

*

totalabstotal

Neutron MeasurementTiming resolution

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


Neutron EfficiencyIron plate (1cm t) is placed to increase neutron efficiency.Efficiency is evaluated using a hadron transport code, FLUKA.Neutron efficiency of 25% can be achieved.

Bound region

We can not see a clear bound peak.At this moment, there is no beam line at J-PARC to have enough TOF length and beam energy

Gamma detectorCsI EMCalorimeter

T-violation’s one is assumed.（ D.V. Dementyev et al., Nucl. Instrum. Meth. A440(2000), 151 ）


Assumed Energy Resolution

Obtained p meson spectra for stopped K decays

Muon holes should be filled by additional crystals.Acceptance for w is evaluated as 90%.

Fast simulation is tuned to reproduce existing data.

Simulation1. Assume base resolution as shown

in the previous slide

2. Apply additional smearing to match the existing data.

– Depend on crystal position


Tail due to holes w. Fiducial cut

pdata

pdata

pSim.

pSim.

wo. Fiducial

Simulation Tune

w. Fiducial

Simulation results for w

Fiducial Cut for w meson

Direct g from w decay hits away from holes (red crystal)

Final Spectrum


Including Background: Main background is 2p0 decays and 1g missing

Bound region

One can select bound region as Energy of w < E0, which is measured by the forward neutron counter.

Invariant Mass spectrum for the bound region

Strong kin. effects

Expected results


H. Nagahiro et al

2366 2755 938

Generation of w

Decay of w (Invariant Mass)

Large abs.No int.

Large abs.Large int.

“Mass” correlation?


Neutron energy spectrum

Interact w. nuclei andMass modification

No interactNo mass mod.

Smearing

Correlation to invariant mass reconstructed by p0g (Mass @ decay)

Expected Missing mass spectrum(Mass @ generation)

Non-correlation? Same mass?

“Mass” Correlation


Invariant Mass VS Missing EnergyNon-correlated model

Correlated model

Correlation analysis will useful for reducing kinematical effects.

simulation

Issue: Final state interaction

2011/11/30 Zimanyi school 2011, K. Ozawa 69no distortion by pion rescattering expected in mass range of interest.

P. Mühlich, PhD-thesis, Giessen, 2006

GiBUU simulationassuming droppingin-medium ω massOpen symbol

Scattered p

ω

J. G. Messchendorp et al., Eur. Phys. J. A 11 (2001) 95

Re-scattering of p is governed by D dynamics Our decayed p has Tp of 256 MeV

Similar kinematics range

However, 0.13/(0.22+0.13) = 0.37 is missing.

Documents

Measurements of meson mass at J-PARC K. Ozawa (KEK) (KEK) Contents: Physics motivation Current results Experiments @ J-PARC Summary