1. Hypernuclear Physics at J-PARC
Dept. of Physics, Tohoku University
H. Tamura

2. Contents 1. Introduction 2. S=-1 2.1 g spectroscopy of hypernuclei
2.2　n-rich L hypernuclei
3. S=-2
3.1　X hypernuclear spectroscopy
3.2　LL hypernuclei
4. Experimental apparatus
5. Other plans
6. Summary

3. 1. Introduction

4. World of matter made of u, d, s quarksN Z
L, S Hypernuclei
LL, X Hypernuclei
Nu ~ Nd ~ Ns
Strangeness in neutron stars ( r > r0 )
Strange hadronic matter (A → ∞)
“Stable”
Strangeness -1 -2
Higher
density
Lower density
n-rich nuclei
３-dimensional nuclear chart
by M. Kaneta inspired by HYP06 conference poster

5. Motivation of Hypernuclear Physics
Extending “Nuclear Chart” in 3D space
Hyperons stabilize nuclei -> extend n/p drip lines
Toward multi-strange systems -> high density nuclear matter
Baryon-Baryon interaction
Unified picture of baryon-baryon interactions
Understand short-range nuclear forces in terms of quarks
Necessary to understand high density nuclear matter and strangeness mixing in neutron stars
Impurity effects in nuclear structure
Changes of size/shape, symmetry, cluster/shell structure,..
Nuclear medium effects of baryons
Probed by hyperons free from Pauli effect

6. What we know about YN, YY interactions
Established Suggested Unknown LN
Attractive (~ 2/3 of NN force) <- LZ L-single particle orbit data
Very small LS force, small spin-spin/ tensor forces <- LZ p-shell g-ray data etc.
LN-SN coupling force? <- s-shell L hypernuclei
p-wave force? Charge symmetry breaking (Lp≠Ln)?? SN
Strong isospin dependence (attractive for T=1/2,S=0) <- 4SHe
Strongly repulsive in average? <- 28Si (p-,K+) spectrum
How large is the repulsive (T=3/2,S=1) channel? XN
Weakly attractive?? <- 12C (K-,K+) spectrum
Isospin dependence??? LL
Weakly attractive <- 6LLHe
LL-XN-SS coupling force ???
LS, SS, XL, XS, XX Unknown at all ???
PRC 64 (2001)
-> UL = - 30 MeV (c.f. UN = -50 MeV)
J-PARC
will answer

7. High density matter in neutron star core
Large neutron Fermi energy -> Hyperons appear
Baryon fraction: very sensitive to YN, YY interactions
-> maximum mass, cooling speed
Hypernuclear data -> realistic calculations possible -
We need XN int., LL int., KN int. (K condensate?),
LN p-wave force, NNN and YNN force, …
帆座超新星残骸 r0
n star
かに座超新星残骸
存在比率 密度
[Credit: NASA/SAO/CXC/J.Drake et al.]
Credit: NASA/SAO/CXC/P.Slane et al.
直径が12km弱しかなく、中性子星より密度が高い。
西暦1181年に起きた超新星爆発のときにできたパルサーと考えられている。その温度が予想よりも低い。
南冠座の天体
RX J
カシオペア座の天体3C58
ストレンジネス・クォーク星の可能性

8. S=-1

9. Present Status of L Hypernuclear Spectroscopy
(2006)
Updated from: O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys. 57 (2006) 564.

10. 2.1 S=-1 g spectroscopy of L hypernuclei

11. Hypernuclear g-ray data since 1998
(p+,K+ g) at KEK-PS
(K-, p- g) at BNL-AGS
using
Ge array “Hyperball”
NaI array (13LC)
“Table of Hyper-Isotopes”
EPJ A33 (2007) 243
PRC 77 (2008)

12. LN spin-dependent interactions
Low-lying levels of L hypernuclei
Level spacing:
Linear combination
of D, SL, SN, T
Millener’s approach
Two-body LN effective interaction D SL SN T V -
Well know
from UL = - 30 MeV
p-shell: 5 radial integrals for sL pN w.f. s
D =∫V (r) |u (r)|2 r2dr, r = r - r sL pN

13. Determination of the spin-dependent force parameters
PRC 73 (’06)
D , SL, T: consistent
DE = -0.04D SL+ 0.99T
43 keV
DE = 1.29D SL T
471 keV
9LBe 2+ 0+
3/2+
5/2+
1/2+
8Be
16LO 1- 0-
1/2-
3/2-
15O
7/2+
7LLi
1/2+
3/2+
5/2+ 1+ 3+
6Li
DE = 0.70SN
-310 keV
DE = 1.44 D SL- 0.27T
692 keV
DE = D SL+ 7.85T
26 keV
D = 0.4 MeV
SN = MeV
SL = MeV
T = 0.03 MeV
PRL 86 (’00) 5963
PRL 88 (’02)
PRL 93 (2004)
-> Test and improve baryon-baryon interaction models
(meson exchange/ quark models)

14. E13 (Tamura et al.) g-ray spectroscopy of light L hypernuclei
r (sL-dN) > r (sL-pN)
sensitive to interaction range
and exchanging meson mass
(K-,p-) reaction (pK=1.5 GeV/c) at K1.8 line
using SKS + Hyperball-J (developed for higher counting rate) 　　　　
Further study of LN interaction
LN-SN coupling and three body force
Charge symmetry breaking (Ln≠Lp?)
Radial dependence (Interaction range)
　　　 LHe, 10LB, 11LB, 19LF
gL in a nucleus from spin-flip B(M1)
7LLi
(K-,p- ) ??
Very large CSB !?
Not theoretically understood.
BL(MeV)

15. mL in nucleus -> medium effect of baryons
g factor of L in nucleus eh
2mqc
mq=
mL in nucleus -> medium effect of baryons
mq : Const.
quark mass
Direct measurement extremely difficult
(tL ~ ns)
B(M1) of L-spin-flip M1 transition -> gL
reduction of mass
-> enhancement of m??
in s-orbit gc
Doppler Shift Attenuation Method :
~100%
applied to “hypernuclear shrinkage”
in 7LLi from B(E2) : PRL 86 (’01)1982
-> Precise B(M1) measurement (~5%) of 7LLi at J-PARC

16. 2.2 S=-1 n-rich hypernuclei

17. Search for n-rich hypernuclei by (Stopped K-, p+)
9LHe
6LH
12LBe
7LH
16LC
Only upper limit
Background from Sigma decay

18. Neutron-rich hypernucleus
(KEK E521, K6+SKS)
Physics Interest
L-S coherent coupling
-> more bound?
Behavior of n-halo
with a L
Production mechanism?
2-step charge exch.
(p-p->p0n, p0p->K+L etc.)
S- admixture
(p- p->S- K+, S- p->Ln)
p- p p -> L n K+
10B (p-, K+) 10LLi
pp~1.2 GeV/c
L-S coherent coupling
Akaishi et al.,
PRL 84 (2000) 3539
11.1±1.9 nb/sr
Almost no
background
Saha et al., PRL 94 (2005)
First data on n-rich hypernucleus

19. E10 (Sakaguchi et al.) Study on Neutron-Rich Hypernuclei
Produce neutron-rich hypernuclei
by the double charge-exchange (DCX) reaction
NCX: (K-,p-), (p+,K+) reaction
L-hypernuclei
SCX: (e,e’K+), (K-,p0), (p-,K0) reaction
DCX: (K-,p+), (p-,K+) reaction
NCX
ordinary nuclei
SCX
this study
DCX
Akaishi:
Glue-like role of L (BL=4.4 MeV) +
LNN coherent
coupling ( +1.4 MeV)
6LH p 5H n n n L p n n n n n
unbound
“Hyperheavy hydrogen”: deeply bound

20. S= -2
X-hypernuclei

21. E05 (Nagae et al.) X-hypernuclear spectroscopy by (K-,K+)
K- p -> X- K+
1st priority
First spectroscopic study of
S=-2 systems in (K-,K+) reaction
First step to multi-strangeness
baryon systems
-> Take a similar spectrum
for (K-,K+) reaction
XN Interaction
Attractive or repulsive? How large?
<- X-nuclear potential depth
Isospin dependence ?
<- Different targets
XN-LL coupling force ?
<- Xp→LL conversion width
<- X and LL hypernuclear mixing states

22. Previous data on XN interaction (BNL AGS E855)
PK=1.8 GeV/c
ΔM=9.9 MeV/c2 (FWHM) for p(K−,K+)Ξ−
−20 < EΞ < 0 MeV
89±14 nb/sr θ< 8°
42± 5 nb/sr θ<14°
VΞ = -14 MeV?

23. Expected 12C (K-,K+) 12XBe Spectrum
ΔEmeas. = 3 MeVFWHM pX
VΞ= -20MeV
VΞ= -14MeV
[counts/0.5MeV] sX
Precision:
Peak Position: MeV
Width: MeV
-BΞ [MeV]

24. 3.2 S=-2 LL hypernuclei (and X- atoms)

25. A golden event of LL Hypernuclei
Nagara event
The first well-identified
double L hypernucleus event L n p
“Triple magic nucleus”
p(0s)2 n(0s)2L(0s)2
produced from
K- p -> X- K+ reaction
Mass ->
DBLL =1.01± MeV
- 0.11
Interaction between L-L
is weekly attractive.
Takahashi et al., PRL 87 (2001)
KEK E377
Emulsion-counter hybrid method
~103 stopped X-
PRL 87 (2001)

26. E03 (Tanida et al.) X- atomic X rays
E07 (Nakazawa, Imai, Tamura et al.)　 S=-2 Systems with Emulsion-Counter Hybrid Method
Measure tracks by counters
Ten times more events of LL hypernuclei
>104 stopped X-, ~102 LL hypernuclei
Details of LL interaction strength
L-L correlation (H dibaryon-like state)
in nucleus from “LL” -> S-p decay
Measure X- -atomic X-rays with Hyperball-J
Shift and width of X-rays -> X-nuclear potential
Stopped X- events identified from emulsion
“LL” -> S-p decay event
E03 (Tanida et al.)　 X- atomic X rays
by (K-,K+)X- on Fe target

27. Experimental Apparatus
K1.8

28. Hadron Hall Handron Hall SKS X hypernuclei LL hypernuclei
X-atomic X rays
g spectroscopy
n-rich L hypernuclei
Q+ search
w nucleus
SKS
Beam
Dump
K- nucleus bound states
K- atomic X rays
h, f nucleus
K1.8 (Fall,2009~) KL
Handron Hall
K1.8BR (Dec.2008~)
Production
target (T1)
K1.1 (when?)
30 (→ 50) GeV
primary beam
g spectroscopy
S hypernuclei
YN scattering
Q+ nucleus
K0.8 (when?)

29. An Example of Setup (E13) K- SKS spectrometer(SksMinus) p- 1.4 GeV/c
SKS superconducting magnet 　
1.4 GeV/c
Hyperball-J K-
1.5 GeV/c
K1.8 beamline spectrometer

30. SKS spectrometer SksPlus for (K-,K+) Modified SKS magnet 1.4 GeV/c
Disassembled Jan.15-30
Under modification of cooling system
Assemble at J-PARC site (2008 Sep.-Oct.)
1.4 GeV/c
SksPlus for (K-,K+)
Additional magnet produced
using an old iron yoke

31. Faster emulsion scanning system
Double-sided Si Strip Detector
Almost same
as PS-E373
Setup of E07
KURAMA spectrometer
(existing)
# Beam : K- (1.7GeV/c),
　　　3 x 105 K-/spill with K-/p- > 6
at K1.8 beam-line (~20% of 9mA)
# Trigger : (K-, K+)
=> 104 X- stopping events
(more than 10 times higher statistics than E373)
Hyperball-J
Faster emulsion scanning system

32. 5. Other plans High resolution (~0.2 MeV) (p±,K+) spectroscopy
for (n-rich) L, S hypernuclei (Noumi)
Weak decay of L hypernuclei (Bhang)
g spectroscopy of heavy L hypernuclei and n-rich L hypernuclei (Tamura)
Light S hypernuclear systems (Tamura)
SN, LN, (XN) scattering experiments (Ieiri, Miwa)

33. 6. Summary
Hypernuclear physics is one of the most important physics subjects at the J-PARC Hadron Hall.
g spectroscopy of hypernuclei using Hyperball-J will further investigate LN interactions. Nuclear medium effect can be also studied from in-medium gL.
n-rich L hypernuclei to be studied at J-PARC will extend the hypernuclear chart and clarify the LN-SN mixing.
X hypernuclear data will provide the strength of XN interaction for the first time.
Many LL hypernuclear samples will be found, establishing the LL interaction, and revealing a possible LL correlation.