Hypernuclear Physics
at J-PARC
Dept. of Physics, Tohoku University
H. Tamura
1. Introduction
Contents
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
1. Introduction
World of matter made of u, d, s quarks
Nu ~ Nd ~ Ns
Strangeness in neutron stars ( r > 3 - 4 r0 )
Strangeness
“Stable” Strange hadronic matter (A → ∞)
Higher
density
LL, X Hypernuclei
Z
-2
L, S Hypernuclei
n-rich nuclei
N
-1
Lower density
0
３-dimensional nuclear chart
by M. Kaneta inspired by HYP06 conference poster
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
What we know about YN, YY interactions

LN
Established
Suggested
Unknown
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.
PRC 64 (2001) 044302
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??
Isospin dependence???

<-
12C
(K-,K+) spectrum
J-PARC
will answer
LL
Weakly attractive
<- 6LLHe
-> UL = - 30 MeV (c.f. UN = -50 MeV)
LL-XN-SS
coupling force ???

LS, SS, XL, XS, XX
Unknown at all ???
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?),
帆座超新星残骸
LN p-wave force, NNN and YNN force, …
r0
存在比率
かに座超新星残骸
n star
2.
S=-1
Present Status of
L Hypernuclear Spectroscopy
(2006)
Updated from: O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys. 57 (2006) 564.
2.1
S=-1
g spectroscopy
of L hypernuclei
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) 054315
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
-
V
D
SL
Dalitz and Gal, Ann. Phys. 116 (1978) 167
Millener et al., Phys. Rev. C31 (1985) 499
SN
T
p-shell: 5 radial integrals for sL pN w.f.
Well know
from UL = - 30 MeV
D =V s(r) |u (r)|2 r2dr, r = r sL- r
pN
Determination of the spin-dependent
force parameters
PRC 73 (’06) 012501
D , SL, T: consistent
DE = 1.29D + 2.17SL - 2.38T
DE = -0.04D + 2.46SL+ 0.99T
3/2+
2+
1-
1/2-
1-
43 keV
7/2+
3+
3/2-
5/2+
471 keV
5/2+
-310 keV
DE = 0.70SN
3/2+
1+
692 keV
0+
1/2+
6Li
DE = 1.44 D + 0.05SL- 0.27T
7
D = 0.4 MeV
LLi
SN = - 0.4 MeV
PRL 86 (’00) 5963
1/2+
8Be
15O
9
LBe
SL = - 0.01 MeV
PRL 88 (’02) 082501
0-
26 keV
DE = - 0.38 D + 1.38SL+ 7.85T
16 O
L
T = 0.03 MeV
PRL 93 (2004) 232501
-> Test and improve baryon-baryon interaction models
(meson exchange/ quark models)
E13 (Tamura et al.)
g-ray spectroscopy of light L hypernuclei
r (sL-dN) > r (sL-pN)
(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
sensitive to interaction range
and breaking
exchanging meson
mass
symmetry
(Ln≠Lp?)

Charge

Radial dependence (Interaction range)
4
LHe,
10
LB,
11
LB,
19
LF
 gL in a nucleus from spin-flip B(M1)
7
(K-,p- )
??
LLi
BL(MeV)
Very large CSB !?
Not theoretically understood.
g factor of L in nucleus
mq=
mL in nucleus -> medium effect of baryons
eh
2mqc
mq : Const.
quark mass
 Direct measurement extremely difficult
(tL ~ 0.1-- 0.2 ns)
reduction of mass
-> enhancement of m??
 B(M1) of L-spin-flip M1 transition -> gL
gL
Jc
core nucleus
Jc +1/2
gc
ψL↑ψc
"hypernuc
fine struct
M1
Jc -1/2
L
ψL↓ψc
in s-orbit
s-orbit
hypernucleus
~100% Doppler Shift Attenuation Method : applied to “hypernuclear shrinkage”
in 7LLi from B(E2) : PRL 86 (’01)1982
-> Precise B(M1) measurement (~5%) of 7LLi at J-PARC
2.2
S=-1
n-rich hypernuclei
Search for n-rich hypernuclei
by (Stopped K-, p+)
9
LHe
6
12
LH
LBe
7
16
LH
LC
Only upper limit
Background from Sigma decay
Neutron-rich hypernucleus
(KEK E521, K6+SKS)
Physics Interest
 L-S coherent coupling
-> more bound?
p- p p -> L n K+
10B
(p-, K+) 10LLi
pp~1.2 GeV/c
L-S coherent coupling
11.1±1.9 nb/sr
Akaishi et al.,
PRL 84 (2000) 3539
Almost no
background
 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)
Saha et al., PRL 94 (2005) 052502
First data on n-rich hypernucleus
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
SCX: (e,e’K+), (K-,p0), (p-,K0) reaction
L-hypernuclei
DCX: (K-,p), (p-,K+) reaction
ordinary nuclei
this study
5H
n
n
p
n
n
unbound
p
n L
n
n n
6
LH
Akaishi:
Glue-like role of L
(BL=4.4 MeV)

LNN coherent
coupling ( +1.4 MeV)
“Hyperheavy hydrogen”: deeply bound
3.1
S= -2
X-hypernuclei
E05 (Nagae et al.)
K- p -> X- K+
X-hypernuclear spectroscopy by (K-,K+)
First
spectroscopic study of
S=-2 systems in (K-,K+) reaction


First step to multi-strangeness
baryon systems
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
-> Take a similar spectrum
for (K-,K+) reaction
Previous data
on XN interaction
(BNL AGS E855)
PK=1.8 GeV/c
M=9.9 MeV/c2 (FWHM) for
p(K ,K+)
20 < E < 0 MeV
89±14 nb/sr  < 8°
42± 5 nb/sr  <14°
V = -14 MeV?
Expected 12C (K-,K+) 12XBe Spectrum
[counts/0.5MeV]
Emeas. = 3 MeVFWHM
pX
V= -20MeV
V= -14MeV
sX
Precision:
Peak Position: 0.1 - 0.3 MeV
Width: 0.2 - 1 MeV
-B [MeV]
3.2
S=-2
LL hypernuclei
(and X- atoms)
A golden event of LL Hypernuclei
Nagara event
The first well-identified
double L hypernucleus event
p
L
n
“Triple magic nucleus”
p(0s)2 n(0s)2L(0s)2
produced from
K- p -> X- K+ reaction
Mass -> DBLL =1.01±0.20 +0.18
- 0.11 MeV
Takahashi
KEK E377et al., PRL 87 (2001) 212502
Emulsion-counter hybrid method
~103 stopped X-
Interaction between L-L
is weekly attractive.
PRL 87 (2001) 212502
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
4. Experimental Apparatus
K1.8
Hadron Hall
SKS
K- nucleus bound states
K- atomic X rays
h, f nucleus
Handron Hall
X hypernuclei
LL hypernuclei
X-atomic X rays
g spectroscopy
n-rich L hypernuclei
Q search
w nucleus
K1.8 (Fall,2009~)
KL
K1.8BR (Dec.2008~)
Production
target (T1)
30 (→ 50) GeV
primary beam
Beam
Dump
K1.1 (when?)
K0.8 (when?)
g spectroscopy
S hypernuclei
YN scattering
Q nucleus
SKS
spectrometer
(SksMinus)
An Example
of Setup
(E13)
p-
SKS superconducting magnet
1.4 GeV/c
Hyperball-J
K-
1.5 GeV/c
K1.8 beamline
spectrometer
SKS spectrometer
Modified SKS magnet


1.4 GeV/c

Disassembled Jan.15-30
Under modification of cooling system
Assemble at J-PARC site (2008 Sep.-Oct.)
SksPlus for (K-,K+)
Additional
magnet produced
using an old iron yoke
Double-sided Si Strip Detector
Setup of E07
Almost same
as PS-E373
KURAMA spectrometer
(existing)
# Beam : K- (1.7GeV/c),
Hyperball-J
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)
Faster emulsion
scanning system
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)
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.