Electrophoto-production of strangeness and Hypernuclei

Osamu HashimotoDepartment of Physics, Tohoku University

October 21-22, 2004Jeju University

Strangeness production by pions and photons

21 1.2 1.4 1.6 1.8

σto

tal(

b)

1.0

2.0

Eγ(GeV)

p(,K+) Total cross section

Phys. Lett. B 445, 20 (1998)M. Q. Tran et al.

Basic characteristics of the (e,e’K+) spectroscopy

Proton converted to Neutron rich hypernuclei

Large angular momentum transfer Similarly to (+,K+) reactionSpin-flip amplitude Unnatural parity hypernuclear statesHigh quality primary beam Sub MeV resolution

The (e,e’K+) reactions --- elementary and hypernuclear ---

termsdependentspinggg

termtindependenspinf

gggfkEEEpk

EEEpdd

LKK

K

lab

:,,

:

)(cos)((

)2(

110

0

21

21

20

20

24

Elementary process

Hypernuclear production

2tan

21

1

2,

12

22

2

2'

22

*

'

3

e

pe

e

KKe

Qq

mqE

EEE

Q

dd

dddd

nK0reaction data near the threshold play an important role

• No contribution from the t-channel Born term• Less contribution of resonances terms

Isobar model

Elementary processes of photo-strangeness production

•g(K00n) = -g(K+0p)

Coupling constantsResonances to be included

New high-quality data being available for K+

However,

Six possible isospin channels: (1) p(,K+) (2) p(,K+)0

(3) p(,K0)+

(4) n(,K+)-

(5) n(,K0) (6) n(,K0)0

n(,K) Model calculation

γ + n → K0 + Λ

Energy dependence Angular distribution

calculated by Sotona’s code

γ + p → K+ + ΛEγ = 1.05 GeV

Eγ = 1.05 GeV

Kaon-MAID: T.Mart, C.Bennhold, Phys. Rev. C61 (2000) 012201(R)　 http://kph.uni-mainz.de/MAID/ kaon/kaonmaid.htmlSLA: T.Mizutani et al., Phys. Rev. C58 (1998) 75.

Laboratory for Nuclear Science, Tohoku University at Sendai

Neutral Kaon Spectrometer

( NKS )

•　 200 MeV LINAC• 1.2 GeV 　　 Booster/stretcher ring• エネルギー標識化光子ビーム

• up to 1.1 GeV/c•　 Good duty factor

First observation of neutral kaons in the threshold region

K0 ~ 450

Background

Invariant Mass () (GeV/c2)

coun

ts/2

0MeV

K0s: c2.68cm

12C target

Ks0 + + - (64 %)

solid: Kaon-MAID n(,K0)onlydashed: Kaon-MAID include p(,K0)+ + n(,K0)0

solid: SLA n(,K0)

Neff = 4.2kF

0=0.22GeV/c

Comparison with recent models + 12C K0 + X

( Quasi-free K0 production)

preliminary

preliminary

Neutral kaons from the liquid deuterium targetK0

S : c ～ 2.68 cm

x ～ 1.6mm

Comparison of D2 target data

with theoretical models

preliminary

Upgrade plan at LNS, Tohoku

STB ringradiator

1.2 GeV e-

NKS2

Pole diameter : 160 cmBMAX : 0.5 T

High momentum & mass resolutionEfficiency more than 2X for K0

Efficiency more than 10 x for Ready in 2005

K+ detection At very forward angle (~ 0 degrees) Maximum hypernuclear production cross section

e’ detection At extremely forward angles Advantage : Large virtual photon flux Disadvantage : Huge backgrounds from Bremsstrahlung

Hypernuclear production by the (e,e’K+) reaction

pe=0.3GeV/c e’

K+

pK=1.2 GeV/c

Ee=1.8 GeVe- Beam

Target nucleus

E=1.5 GeV

Angular distribution of electrons and kaons

Ee = 1.864 GeVEe’=0.4 GeVEe = 1.864 GeVEe’ = 0.38 GeV

angle (deg)

d/d

(nb/

sr)

electrons kaons(degrees) Calculated

by Sotona’s code

Jlab Accelerator

Hall BHall A Hall C

Beam characteristicsEmax 6 GeV Max. Current 200 ADuty factor 100%Emittance 2.0 m·mradEbeam 2.510-5 (FWHM)

E89-009E01-011

E97-107

E89-009 experimental setup

To beam dump

E89-009 calibration

p(e,e’K+) p(e,e’K+)

12C(e,e’K+) quasi-free

Accidental

e

e’ e+ e-

815 keV(FWHM)

CHx target

A(e,e’;(e+,e-))A

138nb/sr

12B spectrum of E89-009

d/d

nb/

sr/0

.3 M

eV

-B(MeV)

-15 0 5 10 15-5-10

(2+,3+)(1-,2-)

(1-,0-)

(2-,1-)

40

50

60

70

80

90

Ground state doublet

B = 11.52±0.35 MeV

Cross section 140±17(stat) ±18(sys) nb/sr

Motoba’s calculation

J cross section 1- 23.4 nb/sr 2- 114.5 nb/sr

Binding energy

Emulsion data B = 11.37 MeV

750 keV(FWHM)

1 month data

7He Spectrum of E89-

009

• No peaks observed in the bound region• A suggestive bump at around 7-8 MeV

d/d

nb/

sr/0

.3 M

eV120

140

160

180

200

7Li(e,e’K+)7He

20

40

60

80

-20-10 10 200

-B ( MeV)-10 -5 10 15 2050

0.01

0.02

0.03

0.04

)/( srbdd

6

He + n6He +

5/2+

3/2+

3/2-

1/2+

5/2-

7/2-3/2-

5/2-

-B ( MeV)Shell model calc. by Sotona

E~400 keV

12C (e,e’K)12BVery Preliminary

Data

with Multiple Uncorrected Beam Energies

“Standard” PID

Full statistics with fitted peaks. Resolution still not fully optimizedSubsets of data appear to have better resolutionLimited statistics

+ cut on Beam x position at 1C12+ ± 50 keV on relative beam energy

E=1.3 MeV (FWHM)

Guarantees beam within specs

Projected Data

Beam energy spread and spectrometer resolutions as planned

E~800 keV

From Prof. Garibaldi

HALL A

Hypernuclear spectroscopy experiments at Jlab

Area Ee(GeV)

E

(GeV)

e

(deg.)

pK

(GeV/c)

K

(deg.)Spectromete

rsRun year

E89-009

Hall C

1.7-1.8 1.5 0 1.2 0-7

SOS+ENGE,

Splitter2000

E94-107

Hall A 4 1.9 6 1.9 6 HRS+HRS,

Septum 2004

E01-011

Hall C 1.8 1.5 4.5 1.2 0-14

HKS+ENGE (Tilt),

Splitter2005

??? Hall C

2.2-2.5 1.5 ~3 1.2 0-14

HKS+HES,New

splitter2007?

MAINZ to join

The tilt method for higher luminosity

Side view

Future spectrometer system for the (e,e’K+) reaction

High resolution Electron Spectrometer

HES

(2.2~2.5GeV)

Yield comparison of E01-011 and E89-009

Item E01-011 E89-009 Gain

factorVirtual photon flux per

electron(x10-4)0.2-0.35 4 0.05-

0.0875Target

thickness(mg/cm2) 100 22 4.5

Scattered electron momentum

acceptance(MeV/c)150 120 1.2

Kaon survival rate 0.35 0.4 0.88Solid angle of K arm 16 5 3.2

Beam current(A) 30 0.66 45Estimated yield (12

Bgr:counts/h) ~500.9

(measured)

60

Expected 28Al hypernuclear

spectra

SKS E140a

28Si(+,K+)28Si

Summary

Photo strangeness production in the 1 GeV regionNeutral kaon measurement plays a unique roleNKS at LNS, Tohoku measured neutral kaonsNKS2 for further experimental study of neutral kaon production is under construction

Hypernuclear production by the (e,e’K+) reactionThe first 2 experiments were successfully carried out at Jlab Hall C and Hall A2nd generation hypernuclear spectroscopy by the (e,e’K+) reaction is to be carried out in 2005High resolution electron spectrometer is under construction for the 3rd generation (e,e’K+) spectroscopy

Etop2pass

(GeV)

Acceptable energy windows of HKS systemwith ENGE or HES revised 04/10/10

10.55

0.40.3 0.6 0.8

Ee’ (GeV)2.51.8 1.9Ee at Hall

(GeV)

Acceptable Central Energy

(GeV)

HESENGE

2.0 2.2 2.4

Etop1pass

(GeV)

4.4 4.55 5.0 6.0

9.45 10.3 10.8 12.0

2.05

0.65

2.15

Invariant mass spectrum

Invariant mass [GeV/c2]

K0 mass region 0.46 – 0.54 GeV/c2

accidental events

miss ID events

k0 candidates

Momentum distribution

Error : statistical only

Virtual photon energy E1.5 GeV

Beam energy Ee= 1.721, 1.864 GeV

Reaction Threshold(MeV)p KKKK*(892)

21 1.2 1.4 1.6 1.8

σtotal(b)

1.0

2.0

Eγ(GeV)

Tota

l cro

ss se

ctio

n

Phys. Lett. B 445, 20 (1998)M. Q. Tran et al.

Experimental Experimental conditioncondition

Limited by bremsstrahlung electrons at 0 deg.in scattered electron spectrometer

p(, K+)

Beam current < 2 A

< 0.6 A for 12C target

Target thickness < 100 mg/cm2

natC 22 mg/cm2

CH2 8.8 mg/cm2

XN

i totalKTK dNNdd

1

11

NT : target densityNX : or 12

B g.s yield N : Number of virtual photon integrated over Ee’ and e’ total : total correction factor

Cross sectionCross section

Cross sections were extracted with experimental yields

.deg0''

KKee dd

ddEdd

Triple-differential cross section

)2

tan/2(1

1

'1

)2/(

222

22

e

e

e

Qq

EEE

QΓ

1212B spectrum fitting resultsB spectrum fitting results

Fitted by 3 Gaussians and a constant Energy resolution was fixed 0.9 MeV(FWHM) Constant = 5±1 nb/sr/400keV

Energy level of Energy level of 1212B B

spectrumspectrum

Emulsion dataB=11.37±0.06 MeV

3/2 -

1/2 -

3/2 -5.0

2.10.26

0.20

1.72

S factor12C(e,e’p)11B

11B x s 12B

Ex(MeV) d/d(nb/sr)

2.51

5.44Ex(MeV)

B(g.s)=12.20±0.06±0.25 MeV :

30±15±4

59±14±7

122 ±12 ±15

1212B spectrum v.s B spectrum v.s 1212

C spectrumC spectrum

12C KEK E369

Structure is similarS and P states are observed

S

P

S

P

E=1.3GeV, =3deg., 900 keV(FWHM), NSC97f

DWIA calculation with phenomenological potential by Motoba

Theoretical prediction of Theoretical prediction of 1212B B

spectrumspectrum

Theoretical calculation of Theoretical calculation of 2828Al Al

spectrumspectrum

300 keV(FWHM)

ls splitting ???high spin and unnatural parity states

Calculated by Sotona et al.

DWIA calculation by a code of M.Sotona

Angular distributionAngular distribution of 12

B states

(p3/2)-1(p3/2) 3+

(s1/2)-1(p1/2) 2-

(p3/2)-1(s1/2) 2-

(s1/2)-1(s1/2) 1+

Expected yield ratio between g.s.