Hadron Spectroscopy with high momentum beam line at J-PARC

K. Ozawa (KEK)

ContentsCharmed baryon spectroscopyNew experiment at J-PARC

On-going Joint Project• Joint project between J-PARC theory center,

KEK, and RCNP. – Proposing construction of new high-momentum

high-resolution beam line

• Collaboration– H. Kamano, T. Nakano, H. Noumi, A. Hosaka

(RCNP), T. Sato (Osaka)– M. Oka, T. Hyodo (TIT), D. Jido(Kyoto)– K. Ozawa, S. Yasui (KEK)

2012/2/10 2Future prospect of Hadron physics

Hadron Physics

• Origin of Hadron interaction?– Nuclear Force inside nuclei– Meson-Baryon, Baryon-Baryon interaction

• Property of Nuclear (QCD) matter?– Origin of hadron mass– Neutron Star

• Inside structure of Hadron? – Naïve quark model needs to be extended– Roper, Penta quark , Exotic mesons @ Belle

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Beyond the quark model

• According to the naïve quark picture, the first excited state should be negative.

• However, observed state is positive. (It’s called Roper.)– Long standing problem

• In addition, several exotic hadrons are observed recently.

Roper

Exotics Width v.s. Mass[MeV] of Excited Nucleon

Belle, PRL 99(2007), 142002Y LEPS, PRC 79, 025210Θ+

Need further study.2012/2/10 4Future prospect of Hadron physics

Issues and Solution

• Several effects are competed in light hadrons – Gluon interaction , Chiral properties, Di-quark

correlation, Three body effects, Spin dependent interaction, Dynamical orbital excitation

• Current experimental data includes all above effects. – Every effect should be measured separately.

• Heavy Quark spectroscopy is key!– Many of above complex effects are suppressed.

– Spin dependent interaction, Three body effects, Chiral effects

Ｃ2012/2/10 5Future prospect of Hadron physics

Charmed Baryons• Wccc : Triple charmed baryon

– It only have color interactions.– Experimentally, it’s not observed yet.

• Xcc : Doubly charmed baryons – Effects of chiral symmetry are suppressed. – Other effects can be studied easily. – One experiment (SELEX) reported.– It can be produced at J-PARC.

• L+c, Sc : Charmed baryons– Spin dependent interaction is suppressed– Interactions can be simplified. – Let’s start here!2012/2/10 Future prospect of Hadron physics 6

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Single charmed Baryons

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Predicted states using a quark model(L.A. Copley et. al, Phys. Rev. D 20 (1979) 768) Observed charmed baryons

Lc p

Sc p

DN

Threshold

Several states are missing

Di-quark correlation?

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Charmed baryon system can be understood as Heavy Quark – di-quark system

?“Roper”

In addition, exotics in charm sector

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• If exotic baryons exist in charm sector, it can be observed easily compared to light quarks.– Narrow width– Large mass window below DN threshold

Candidate of exotics Mass window

for exotics

Charm Baryon spectroscopy @ J-PARC

• Mass Spectra of excited charmed baryon contains basic information of quark interaction

• Many states are still missing– Few states are observed in invariant

mass plot.• Observed states has relatively

narrow width – Good for spectroscopy!

Roper candidate

Observed charmed baryons2012/2/10 10Future prospect of Hadron physics

Several missing states and exotic candidates Observe all excited states of

single charmed baryon below 3 GeV.

Purpose

New Experiment @ J-PARC

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p- p -> S0c + D0

p+ n(d) -> L+c + D0

D0 -> p+ K-

Detect p, K and reconstruct D meson. Then, missing mass is calculated.

Dispersive Focal PointDp/p~0.1%

Construct new high resolution, high momentum beam line

Beam

Experimental Setup

• Magnetic field: 1 [T]• 50% of D meson can be detected• Poor mom. res. at very forward

Candidate 1: Solenoid type

Candidate 2: Dipole type

f2m

2m

p- p -> S0c + D0

p+ n(d) -> L+c + D0

D0 -> p+ K-

Detect p, K and reconstruct D meson. Then, missing mass is calculated.

Size of Gap

2m

• Magnetic field: 1 [T]• 50% of D meson can be detected

1m

1m

Size of inside coil

2012/2/10 12Future prospect of Hadron physicsParticle identification and trigger scheme are issues for both cases.

dp/p ~ 1% is required

Kinematics & Acceptance• Beam Momentum: 15GeV/c• Lc (2940 ) (Roper candidate) is assumed.

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p from D0 decays

K acc. is similar

Both p and K are in acceptance

Solenoid D-magnet

PT PZ

[GeV/c]0 1 0 42

[GeV/c]8

Momentum Resolution

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• Beam Momentum: 15GeV/c• Lc (2940 ) (Roper candidate) is assumed.

p from D0 decays

K is similar

Both p and K are in acceptance

Solenoid D-magnet

DpZ/ pz

D-magnet configuration has better momentum resolution.Further check for the calculation is needed.

0 0.1-0.1

Dx = 100mm

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PT PZPT PZ

p from L decays Proton from L decays

PT PZPT PZ

Decay products from Lc

p from Lc(2940) 3body decays p from Lc(2286) decays

Decayed products can be measured using the same configuration.

Summary• To understand structure of light hadrons,

charmed baryon spectroscopy is an important tool.

• charmed baryon spectroscopy can give basic information about Roper state, Exotic state, and di-quark correlations.

• A new beam line and new experiment is proposed to perform charmed baryon spectroscopy.

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Physics topics @ new beam line

• Charm baryon bound state• Color transparency • Short range structure • Drell-Yan process (P04)• c-bar c contents in nuclei• Multi-fragmentation • omega bound state (E26) and eta’• Basic cross section of pi N -> pi pi N• Exotic in light quark • Mass modification of f (E16)• Heavy ion physics2012/2/10 Future prospect of Hadron physics 17

BACK UP

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Note: Existing experimental results• Currently, charmed baryons are identified using its decays in

collider experiments.

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BaBar, Lc -> LK0sK+

(Phys. Rev. D72 052006)

N ~ 4600

• Our experiment measure productions of baryons and it gives different information.

• Statics will be similar • Intensity of 107 ~ 108 / spill

• Sensitive to relatively wide width states• Background will be suppressed at

threshold region.

• Exclusive measurements can be done. • Decays can also be measured.

The J-PARC E16 spectrometer

20

X 26

Magnet (used for KEK E325)

Candidates of large D-magnet spectrometer

Cross Section & Yield

• No reliable calculation in such threshold region– At least, 10 nb can be assumed.

• Yield – Lq H2 1g/cm2

– 107 / spill, 6 second– 1 baryons per spill

• D meson Branch and acceptance – 1%

• Integrated Yield per month – ~ 102 per month

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Note: Doubly charmed meson

• Threshold of p momentum: 27.5 GeV– p+ + p -> D0 + D0 + Xcc

++

• After upgrade of MR energy to 50 GeV, there is a hope.

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