Gamma spectroscopy ofhypernuclei--E13 and beyond-H. Tamura
Tohoku University
1. Introduction
2. E13: purposes and present status
3. Beyond E13
4. Summary

1. IntroductionHyperball Hypernuclear
1998~g-ray data before 1998

Hypernuclear g-ray data

1- 6.041
3/2-

M1

2-

Hyperball
Hypernuclear g-ray data before 1998

Hypernuclear g-ray data

LN spin-dependent interaction strengths determined:
Spin-spin: D = 0.33 MeV (A>10), 0.42 MeV (A<10)
L spin-orbit: SL = -0.01 MeV
N spin-orbit: SN = -0.4 MeV
Tensor: T =0.03 MeV

 Almost all these p-shell levels are reproducedby this parameter
set. (D.J. Millener)
1 6.041-3/2-2-

 LN-SN coupling force from NSC models looks good.
 Feedback to BB interaction models
M1

An example of 12C (p+,K+g)12LC at KEK
Unbound region

Unbound region

Bound excited states
w/o Doppler corr.
Bound excited states

Bound excited states
w/ Doppler corr.

Hosomi et al.
To be published

Reaction angle
qpK

DL = 1
non-spin-flip
production

Spin-flip
production(p,K) Reaction angle

Level scheme of 12LC (Updated Analysis)
PRC 64 (2001) 044302(p+,K+)

12C(e,e’K+)12 B
L@ JLab Hall CpL

Ex (MeV)6.09±0.08 (E336)
6.30±0.11 (E369)
5.0±0.1 (FINUDA)

6.050 ± 0.010

sL(p+,K+)

2.63±0.06 (E336)
2.51±0.17 (E369)
2.5±0.2 (FINUDA)

2.833 ± 0.003
12C (p+,K+) 12 C
L

@ KEK-PS

0.1615± 0.0003-> LN Spin-dependent interaction
This precise 12LC level scheme is useful for testing new reactions and apparatus

2. E13: Purposes andPresent Status

Hyperball-JGe cooled down to ~70K
by pulse-tube refrigerator(c.f. 92K w/LN2)
Fast backgroundsuppressor made of PWO
Eff. ~ 6% @1 MeV
with 32 Ge(re=60%)

Hyperball-J
installed in front of SKS magnet at K1.8

Hyperball-J performance in beam
Ge Adc (added for 16 detectors)

Measured range : 0.1 - 8MeV

e-(511 keV)Count19F(197.1 keV)

FWHM: 3.8±0.3 keV

74Ge

10B(718.4 keV)

18F(937 keV)

27Al or 56Fe

CF2(20g/cm2) target
8 hours
Red: g-rays from beam reaction
on target nuclei
Energy [keV]

17O(870.7 keV)

FWHM: 4.3±0.5 keV

Purpose of E13 experiment
Approved as DAY1, Second priority

LN interaction

1st Part: 10--40kW, 2013.6 -> 2015.2~(1) Charge symmetry breaking in LN interaction
4 He :LConfirm (or deny) CSB effects suggested by old data
1.5,1.8 GeV/c (K-,p-) @K1.8(2) Radial dependence of LN interaction
19 F : The first sd-shell hypernuclei
L
1.8 GeV/c (K-,p-) @K1.8
2nd Part: >50kW, after 2016?
(3) Study LN-SN coupling force
10 B and 11 B: Inconsistency in p-shell data.
LL
1.1 GeV/c (K-,p-) @K1.1

g-factor of L in nucleus(4) Spin-flip B(M1) measurement for gL in a nucleus- 7 Li : g measurement in ~3% accuracy 1.1 GeV/c (K ,p ) @K1.1
LLExperimental approaches toCharge Symmetry Breaking puzzle in A=4
Origin: LN-SN coupling?
But theoretically difficult

Will be measuredvia (e,eK+) at Jlab

Experimental confirmation of CSB
J-PARC E13 (+ more)Will be measurd  4He(K-,p-g) 4LHe(1+->0+)
by Ge at J-PARC  4He (K-,p0g) 4 H(1+->0+)
LOld NaI datawith a few keV accuracy(K-,p-4)

4 HLLHe?
4He + p-Being measured
at ManizOld emulsion
dataDifficult
by counter experiments

Experimental approaches toCharge Symmetry Breaking puzzle in A=4
Origin:LN-SN
Bedjidian
et al, coupling?
PLB 83 (1979) 252
But theoretically difficult

Will be measuredvia (e,eK+) at Jlab

Experimental confirmation of CSB
J-PARC E13 (+ more)Will be measurd  4He(K-,p-g) 4LHe(1+->0+)
by Ge at J-PARC  4He (K-,p0g) 4 H(1+->0+)
LOld NaI data

4 HL

4He + p-Being measuredat Maniz

Old emulsion
not a significant
datapeakwith a few keV accuracy

4 H]：・Eg[4LHe] =(K-Eg,p-4) [ HeLL
Clear evidence of CSB.
?
Spin dependenceof CSB int.
・ Eg[4LHe] = Eg [4LH] :Strongly suggests CSB does
not exist Difficult

by counter experiments

19 F spectroscopy
L
The first study of sd-shell hypernuclei
Separated from(K,p) angular distribution
1.12 MeV

1.01 MeV(3) shrinkage andN-spin-orbit force(byproduct)

0.88 MeV

E1

0.30 MeV

Calc. (Millener)
16O core

Lsd orbitpn(1) LN spin-spin interaction in sd shell(2) spin-flip B(M1) -> gL (byproduct)

19 F spectroscopy
LThe first study of sd-shell hypernuclei(4) Cross checkof (1)p18
Separated fromLO + p(K,p) angular distribution

1+0+

1.12 MeV

3+2+

1.01 MeV
18(3) shrinkage andN-spin-orbit force(byproduct)

0.88 MeV

E1LO

16O core

0.30 MeVLnsd orbit

Calc. (Millener)
16O core

Lsd orbitpn(1) LN spin-spin interaction in sd shell(2) spin-flip B(M1) -> gL (byproduct)

A-dependence ofLN spin-spin int. strength=> Information onwave functions and interaction range=> confirm short-range nature of LN int.

sLsN

sLpN
r (sL-dN) > r (sL-pN) > r (sL-sN)

sLdN

Magnetic moment of a L in a nucleus
Baryon magnetic moment in nucleus:
affected by partial restoration of chiral symmetry?
-> Origin of baryon spin and massL, free from Pauli effect, is a good probe.

mq=eh2mqc

mq : Constituent
quark mass

mq decrease -> mq increase ？

 Direct measurement is difficult (t ~ 0.1-- 0.2 ns)
 L-spin-flip M1 transition: B(M1) -> gL

gL
Jc
core nucleus

gc

Jc +1/2

in s-orbit "hypernu

M1fine stru

Jc -1/2

L in s-orbit

hypernucleus~100% Doppler Shift Attenuation MethodψL↑ψψL↓ψPreliminary data on gL
 BNL E930 (M. Ukai)
10B (K-, p-) 10

gL = -1.1 +0.6 mN

LB*-> 7LLi*+ 3He-0.4

t from DSAM

3/2+1+6Li

7 Li
L

1/2+

 KEK E566 (Y. Ma)

gL > -1.76 mN
t from DSAM

12C (K-, p-) 12 C*L-> 11LB* + p

gL = -1.04±0.41 mN

7/2+3+10B

11 B
L

5/2+

12C (K-, p-) 12 C*L

2-3/2-・Yield ratio for [ 2-→1- ] / [1-2→2-] g-rays-> Br(2-1-) = 0.19±0.12 (80% of 2- weakly decays)

11C

12 C
L

1-・ Weak decay rate of 2- and 1- are assumed
to be the same, Gweak = (lifetime 230.7±6.3 ps)-1=> GM1 = Br /(1 - Br) GweakgL(free) = -1.226 mN

Preliminary data on B(M1) in 7LLi (BNL E930)
10B (K-, p-) 10LB*,

10+7+LB*(3 ) -> LLi*(3/2 )+ 3He indirect population
simulation3+

7/2+5/2+1+3/2+1/2+6Li

7LLi- gL = 1.1 -+0.4
mN
0.6

preliminary(statistical error only)- gL(free) = 1.226 mN

First data of gL in nucleus-> Precise(~5%) B(M1) measurement of 7LLi
at J-PARC E13

Preliminary data on B(M1) in 7LLi (BNL E930)
10B (K-, p-) 10LB*,

10+7+LB*(3 ) -> LLi*(3/2 )+ 3He indirect population
simulation

E13 (2nd): Simulation
Nucl.Phys. A881 (2012) 310

3+7/2+5/2+1+3/2+1/2+

6Li7LLi- gL = 1.1 -+0.4
mN
0.6

 Stat. error Dt/t = 5.6%
D|gL-gc|preliminary=>~ 3%|g-g|
Lc(statistical error only)- gL(free) = 1.226 mN

First data of gL in nucleus-> Precise(~5%) B(M1) measurement of 7LLi
at J-PARC E13

3. Beyond E13

Future Plans Systematic study of gL (7LLi, 12LC, 19LF, …)
 r dependence -> chiral symmetry restoration
 Isospin dependence -> effect of S mixing
Doppler shift attenuation method+ Weak-gamma coincidence method Impurity effects in p and sd shell hypernuclei
 Shrinkage/ deformation change (9LBe, 13LC, 20LNe,...) Disappearance of neutron halo (7LHe)
 Study structure of normal nuclei using a L
Triaxial deformation (25LMg), a-cluster gas (12C(0+2)+ L) L’s single particle energies for a wide range of A
1hw energy LS splittingfrom E1: (p1/2L->sL, p3/2L->sL) for a wide mass range

L’s single particle energy

L Binding Energy BL (MeV)

Plot by D. J. MillenersLpLdLfLgL

E1 g-rayerror ~ 1 keV
LS splitting Density dependenceof LN interaction-> EOS and hyperon puzzle(Y.Yamamoto’s talk) Origin of LS splitting(2B-LS force, tensor force,many body effects)(K-,p-), (p+,K+) -> DE~200 keV @J-PARC Ext-HH(e,e’K+) DE~500 keV, syst.err. ~100 keV@Jlab Hall-A (HKS+HRS)

E1 measurement for heavy hypernuclei
g-spectroscopy of 208LPb
H.Tamura et al., J-PARC LOI(K-,p-) at 1.8 GeV/c
10 g target
3x106K-/4s (~270 kW)

500 h
p3/2(5-) ~500 events
p1/2(7-) ~200 events
p3/2(7-) ~130 events

Higher intensity isnecessary!

4. Summary
 E13-1st will study 4LHe and 19LF for CSB and LN interaction
in sd-shell hypernucleus.
 Hyperball-J is ready and commissioning has been done.
 E13-2nd will study gL in nucleus from B(M1) measurement.
 Beyond E13, we plan E1 (pL->sL) measurement for heavy
hypernuclei, as well as systematic study of gL andimpurity effects.