Strangeness Nuclear Physics at J-PARC

Kyungpook National University

May. 26, 2009

Kiyoshi Tanida

Nuclear Physics• Study properties and reactions of nuclei

~3000 found,>5000 should exist

proton number

neut

ron

num

ber

Why interesting?

• Nuclear force

I would give you just one example here...

quarks mesons

1 fm 2 fm

ⅠⅡⅢ

2π,σ,ρ,ω, ...

(I)(I) One pion exchange tailOne pion exchange tail(II)(II) Heavier mesonsHeavier mesons

Net attractionNet attraction(III)(III)Repulsive core Repulsive core

(phenomenological)(phenomenological)

R

V(R)

1 fm 2 fm Quite different from molecularVan-der-Waals force

• State dependent• Non-central forces (LS, tensor) • Isospin dependence

Nuclear force (cont.)• is pseudscaler, i.e., J=0-

– L changes when emitting/absorbing → Mixing of L=0 and L=2 (tensor force)

• Bound state of NN exists only for J=1+, I=0(deuteron), where such mixing is allowed.

n p n p

L=0 (S)L=2 (D)

Nuclei with strangeness• Nuclei: many body systems of nucleons

– which consist of up and down quarks→ p(uud), n(udd)

– Actually, there are 6 quarks

• Baryons with strangeness= Hyperons =(uds), +(uus), =(uss),...

• Extended “space” of nuclei

u c td s b

Hyper-nuclear chart

Unexplored “space”

S=0 “surface”

Physics?• New interaction

– Extended nuclear force to flavor SU(3) world– Unified understanding of Baryon-Baryon force –

What is its origin?– Is traditional meson exchange model enough?

Need quark/gluon picture?

• Property of hyperons in nuclei?– Hyperons can mix easily (e.g., N-N, -N)

→ Dynamical systems can be made

• What happens to nuclei? Impurity effect?– Collective motion? High density matter?

B8B8 systems classified in the SU3 states with (, )

[‐(11)a+(30)]

[(11)a+(30)]

(03)

　　　 [(11)s+3(22)]

　　　 [3(11)s‐ （ 22 ） ] 　

(22)

‐3

―

(11)a

[‐(11)a+(30)+(03)]

[(30)‐(03)]

―

[2(11)a+(30)+(03)]

―

(11)s+ (22)+ (00)

(11)s‐ (22)+ (00)

(11)s+ (22)

ｰ (11)s+ (22)

(11)s － 　　 (22) － (00)

―

(22)

(30)

―

―

(22)

[‐(11)a+(03)]

[(11)a+(03)]

(30)

　　　 [(11)s+3(22)]

　　　 [3(11)s‐(22)] 　

(22)

‐1

(03)

―

―

(22)

NN(0)

NN(1)

3E, 1O (P=unsymmetric)1E, 3O (P=symmetric)B8B8(I)S

10

1

10

1

10

1

10

1

2

1

2

1

2

1

2

1

2

1

3

1

6

1

5

1

5

1

5

3

5

3

5

3

5

2

5

2

302

9

10

322

1

2

1

102

1

8

3

‐2

0

‐4

J-PARC

• J-PARC = Japan Proton Accelerator Research Complex

• Main accelerator: 50 GeV PS– 50 GeV×15 A ＝ 750 kW

x100 of KEK-PS, x10 of BNL-AGS (~x10 of FAIR)

– World leading facility with the ever strongest kaon beam

• Construction almost done– First beam extracted from 50 GeV PS on Jan. 27

– Strangeness nuclear physics experiments starts this year.

Projects in J-PARC• Material & Life science (neutron, )• Transmutation of nuclear waste• Nuclear Physics

– Strangeness nuclear physics– Hadron spectroscopy– Nucleon structure– Hot and/or dense nuclear matter– Unstable nuclei

• Particle Physics– Neutrino oscillation– Kaon rare decay – μ rare decay

Tokai Site of JAEA

Feb. 2008

June, 2007

June, 2007

Dec, 2008

K1.8

K1.8BR

K1.1

KL

Proposed experiments

• 9 SNP experiments (out of 24)– All scientifically approved, 7 full approval, 4 Day-1

S=2 system

E03

E05

E07

E03 ： Measurement of X rays from atom Spokesperson – K. Tanida (Kyoto)E05: Spectroscopic study of -hypernucleus, 12

Be, via the 12C(K,K+) reaction (Day 1 – 1st priority) Spokesperson – T. Nagae (Kyoto)E07: Systematic study of double strangeness system with an emulsion-counter hybrid method Spokespersons – K. Imai (Kyoto) K. Nakazawa (Gifu) H. Tamura (Tohoku)

E03 experiment• World first measurement of X rays from -atom

– Gives direct information on the A optical potential

• Produce - by the Fe(K-,K+) reaction, make it stop in the target, and measure X rays.

• Aiming at establishing the experimental method

K- K+

X ray

Fe target (dss)

Fe

X ray

Physics Motivation• Strangeness nuclear

physics at S=-2– A doorway to the multi-

strangeness system– Very dynamic system?

• Large baryon mixing? Inversely proportional tomass difference.

• H dibaryon as a mixed state of -N-?

• Little is known so far Main motivation of the J-PARC

Importance of systems• Valuable information on N (effective) interaction

– e.g., How strong N (and thus N- mixing) is? • Relevant to the existence of H dibaryon• N component in -hypernuclei

– Exchange interaction is prohibited in one-meson exchange models

• How about A dependence?– Most OME models predict large A dependence.

• Impact on neutron stars– Does play significant role in neutron stars because of its

negative charge?– was supposed to be important, but its interaction with

neutron matter is found to be strongly repulsive.

Principle of the experiment• Atomic state – precisely calculable if there is no

hadronic interaction• 1st order perturbation

– If we assume potential shape,we can accurately determine its depth with only one data

– Shape information can be obtained with many data

– Even if 1st order perturbation is not good, this is still the same.

• Peripheral, but direct (-nuclei spectroscopy)

∫ Ψ=Δ drrUrE )(|)(| 2

l (orbital angular momentum)

Ene

rgy

(arb

itrar

y sc

ale)

...

...

...

...

l=n-1 (circular state)l=n-2l=n-3

nuclear absorption

atom level scheme

Z

Z

X ray energy shift – real partWidth, yield – imaginary part

Successfully used for , K,p, and

Experimental setup

K

K

• Long used at KEK-PS K2 beamline (E373, E522, ...)– Minor modification is necessary to accommodate high rate.

• Large acceptance (~0.2 sr)

1.8 GeV/c1.4x106/spill (4s)

X-ray detector• Hyperball-J

Yield & sensitivity estimation• Total number of K-: 1.0x1012 for 800 hours.• Yield of

– production: 3.7×106

– stopped: 7.5×105

• X-ray yield ：　 2500 for n=65 transition– 7200 for n=76

• Expected sensitivity– Energy shift: ~0.05 keV (systematic dominant)

Good for expected shift (~1 keV, 4.4 keV by Koike ) < 5% accuracy for optical potential depth– Width: directly measurable down to ~ 1 keV– X-ray yield gives additional (indirect) information on

absorption potential.

Expected X-ray spectrum

n= 65

shift & width0 keV

Expected X-ray spectrum(2)

n= 65

shift & width4 keV

E07 Hypernuclei

Goal: • 10000 stopped on emulsion• 100 or more double- HN events• 10 nuclides

Chart of double- hypernuclei

Hybrid emulsion method

Production of hypernuclei

~10% of aretrapped in nuclei

p

Example event in emulsion• Track length, thickness

– PID/energy

• Presume what are produced at each vertex – Then check consistency– Unique assignment is

sometimes possible

• Calculate binding energyΔB= B2B

gives net interaction

Systematics of binding energy• ΔBmay different for each nucleus

– For example by hyperon mixing effect

p n

6He

p n

5He

p n

Suppressed Enhanced

p n

S ＝－１• E10: Production of neutron-rich Lambda-hypernuclei with the

double charge exchange reaction Spokespersons – A. Sakaguchi (Osaka), T. Fukuda (Osaka E. -C.)

• E13 ： Gamma-ray spectroscopy of light hypernuclei Spokesperson – H. Tamura (Tohoku)

• E15 ： A search for deeply-bound kaonic nuclear states by in-flight 3He(K-,n) reaction Spokespersons – M. Iwasaki (RIKEN), T. Nagae (Kyoto)

• E17: Precision spectroscopy of kaonic 3He 3d2p X-rays Spokesperson – R. S. Hayano (Tokyo), H. Outa (RIKEN)

• E18: Coincidence measurement of the weak decay of 12C and

the three-body weak interaction process Spokespersons: H. C. Bhang (Seoul), H. Outa (RIKEN), H. Park (KRISS)

• E22: Exclusive study on the N weak interaction in A=4 -Hypernuclei Spokespersons: S. Ajimura (Osaka), A. Sakaguchi (Osaka)

S=+1?

S=+1; -hypernuclei?

Mysteries about pentaquark

• Does it really exist?– Need confirmation/rejection

• Width? Why so narrow?– No doubt < 1MeV– Not observed in K+n

elastic scattering/charge exchange

• Spin-Parity ？– 1/2+?, 3/2+?, 1/2-?, ....

• What is the nature?

LEPS 1st publication

d

u

d

u

s

Confirmation of

• High resolution width • First exp. @J-PARC: E19

(Spokesperson: M. Naruki)– p(,K) reaction– A good resolution:

~2 MeV (FWHM)expected thanks toK1.8 beamline and SKS

– Sensitivity: ~ 100 nb/sr– Stage 2 approved: Day-1– Even better resolution is

possible (~0.1 MeV)

T2

An example of extension plan (by Noumi)

Hypernuclei?• Extend Baryon-Baryon interaction to include anti-

decuplets• May give a hint about the nature of

– For example, [D. Cabrera et al., nucl-th/0407007] calculated self-energy of -KN channel (i.e., K-exchange) weak, not enough to give bound states

– If -KN channel is taken into account, strong binding can be obtained (cf. N(1710) strongly couples to N)

– There are many other scenarios...

• Well, it’s interesting in itself, isn’t it?

Production methods?

• (K+,+) reaction: Proposed by Nagahiro et al.[PLB 620 (2005) 125]– Momentum transfer ～ 500 MeV/c– Elementary cross section: < 3.5 b/sr (KEK-PS E559)

[Miwa et al., arXiv:0712.3839]... Not good

• (,K): Momentum transfer ~1 GeV/c small cross section (< a few b/sr: E522)

We propose (K+,p) reaction[K. Tanida and M. Yosoi, J-PARC LOI

http://j-parc.jp/NuclPart/pac_0801/pdf/LOI_Tanida_pentahyper.pdf]

The (K+,p) reaction• Elementary process d(K+,p)+

• Small momentum transfer

• High resolution missing massspectroscopypossible

npK

Θ

Status and prospects

• First beam successfully extracted in Jan. 2009– To K1.8BR beamline

• Expected schedule– Apr.-Sep., 2009 (now): fast extraction for neutrino exp.

Finishing K1.8 beamline construction– Oct.-, 2009: commissioning of K1.8, E15&17@K1.8BR

beam intensity: ~1% of designed value– 2010~: experiments at K1.8

starting from experiments using pions (E19, 18, 10, 22)10%~full intensity

– E03: 2011?

Silicon Strip Detectors• J-PARC beam intensity

– 106~107/s for K-, much more for pions

• Rate limit for gas-wire chambers– We are going to use 1 mm MWPC

105 cps/mm ~5 x 106 cps (rms beam size ~ 20 mm)– Tracking detectors are the bottle neck

• SSD: even finer pitch (~50 m) up to 108 cps possible– Higher position resolution is a favorable side effect.

Requirements for SSD• Strip pitch < 100 m• Timing resolution < 10 ns

– Expected accidental hit rate: < 1 at 108 cps

• Detector size: > 60 x 20 mm2

– Covering K1.8 beam size (rms: 20 x 3 mm2) • High radiation tolerance

– Stable operation for > 1 month at 108 cps

We are developing SSD that satisfy those requirements

SSD sensor• Developed for ATLAS collaboration• Thickness: 285 m• Effective area:

62 x 61 mm2 – OK• Strip pitch & number

80 m x 768 strips• High radiation tolerance

– up to 3 x 1014 p/cm2

for 24 GeV/c protons– > 3 months with 108 cps

• DSSD not available – Hamamatsu has withdrawn– Can KNU help?

Readout – APV25• Developed by CMS collaboration• Preamp. + shaper + multiplexer

– 128 ch/chip– Quite similar to IDEAS VA1

• Shaping time ~ 50 ns• Multiple sampling with

40 MHz clock time resolution: ~3 ns

• High radiationtolerance

peaking time

Hybrid board• Sensor + 6 APV25 chips• 1st prototype under construction coming soon

Rin-ei ( 林栄 ),Japan

DAQ• APVDAQ system – developed by HEPHY, Wien

Summary• Utilizing the world ever-strongest kaon beam

at J-PARC, we are planning to attack S=-2 sector.– E03: precision spectroscopy of -atomic X rays to study

A interaction– Many other SNP experiments are planned

• S=+1 hypernuclei might be accessible– Confirmation experiment first– Need detailed experimental design for hypernuclei

• Silicon strip detector– Up to 108 cps

Important for the highest beam intensity at J-PARC– Developing a prototype with ATLAS sensor + APV25 chip– Sensor is a problem for DSSD