Nuclear matter in neutron stars
investigated by experiments and
astronomical observations
実験と観測で解き明かす
中性子星の核物質
A research project
applying a Grant-in-Aid to create
a new science area (~15M USD)
科研費新学術領域 （15億円） 申請中
H. Tamura
Department of Physics, Tohoku Unviersity
1. Motivation
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
-1
0
３-dimensional nuclear chart
by M. Kaneta inspired by HYP06 conference poster
Maximum mass of n stars and
hyperon mixing
NN＋NNN
NN＋NNN
NN＋NNN
+ YN + YY
NN＋NNN
+ YN + YY
Radius
central density
Z.H. Li and H.-J. Schulze, PRC78(2008) 028801
1.44M
n-star mass seems to be explained by hyperon mixing.
(but slightly too light)
Heavy neutron star?
Shapiro delay
Heavy neutron star?
Nature 467 (2010) 1081
J1614-2230
(1.97 ± 0.04)Msun
To obtain robust error estimates,
we used a Markov chain Monte
Carlo (MCMC) approach to explore
the post-fit χ space and derive
posterior probability distributions for
all timing model parameters
Hyperon mixing in neutron stars
Hyperon (and kaon) fractions are sensitive to
hyperon (kaon) potentials (YN, YY, KbarN interactions）
We need:
XN force (both I = 1 and 0), LL force
SN force (I =3/2 (S-n) is particularly important)
KbarN force (both I=1 and 0)
LN-SN and LNN force, LN p-wave force, …
n-star
nuclear density n-star
exp.
UL= -30 MeV
存在比率
nuclear density
Nu ~ Nd ~ Ns
assumption
exp.
UL= -30 MeV
~exp
assumption
EOS constraints from astronomical
observations
Thermonuclear Burst
in X-ray Binaries
4U 1608-248
EXO 1745-248
4U 1820-30
Probability of
EOS P(e)
Ozel et al., arXiv: 1002.3153 [astro-ph.HE]
?
A. W. Steiner, et al., arXiv:1005.0811
Radius assuming isotropic black-body (flux + temperature)
and Eddington flux
Better understanding of nuclear matter in nuclear physics
More and reliable data for radius from X ray observations
=> EOS can be determined.
2. Our Project
ASTRO-H
EOS covering
wide range of r, p/n
asymmetry, strangeness
D: theory
World-best
two accelerators
and
astronomical satellite
RIBF
neutron star
C: astronomical
X-ray observation
⇒radius and
mass
J-PARC
A: strangeness
nuclear physics
r < 2r0
r
r > 2r0
B: neutron-rich nuclei
Ultra-cold atomic gas
⇒ asymmetric
nuclear matter and
thin neutron matter
⇒ Interactions between
strange particles
Neutron star matter and our research subjects
D01: Theoretical studies on neutron stars and nuclear matter
Ohnishi (YITP)
[fm-3]
A02: Multi-strange baryon-baryon interactions
Takahashi (KEK)
A01: Strangeness in neutron-rich matter
Tamura (Tohoku)
B02: High-density neutron-rich
nuclear matter Murakami (Kyoto)
B01①: Collective motions of
neutron-rich nuclei
B01②: di-neutron correlation
Baryon density
B01③: Ultra-cold Fermi
gas systems
n, p,
L, X,..
?
n nuclei + n
B01: neutron-rich
medium/low density
nuclear matter
Nakamura (TIT)
C01: Neutron stars studied by observation
of cosmic X rays and g rays Takahashi (JAXA)
Fraction
研究組織
X00 実験と観測で解き明かす中性子星の核物質
Nuclear matter in neutron stars investigated by
experiments and astronomical observations
田村 裕和（東北大）
H. Tamura (Tohoku)
A01 中性子過剰核物質中のストレンジネス
Strangeness in neutron-rich nuclear matter
田村 裕和（東北大）
H. Tamura (Tohoku)
A02 多重ストレンジネスのバリオン間相互作用
Multi-strangeness baron-baryon interactions
高橋俊行(KEK)
T. Takahashi (KEK)
B01 中性子過剰な低密度核物質の物性
Properties of low/medium density neutron-rich
nuclear matter
中村隆司(東工大）
T. Nakamura (TIT)
B02 高密度中性子過剰核物質の状態方程式
EOS of high-density neutron-rich nuclear matter
村上哲也（京大）
T. Murakami (Kyoto)
C01 宇宙Ｘ線・ガンマ線観測による中性子星研究の新展開 高橋忠幸(JAXA)
New development of neutron star studies by cosmic T. Takahashi (JAXA)
X-ray and g-ray observations
D01 中性子星と核物質の理論研究
Theoretical studies on neutron stars and
nuclear matter
大西 明(京大基研)
A. Ohnishi (YITP, Kyoto)
A: Strange nuclear matter at J-PARC
A0１: Strangeness in neutron-rich matter
New!!
Tamura (Tohoku)
S+p, S-p scattering exp. Miwa,…
-> SN interactions（in particular, S+p = S-n interaction)
下線は分担者
Spectroscopy of n-rich L hypernuclei (E10) Sakaguchi,...
g-spectroscopy of hypernuclei (E13) Tamura, Koike,..
-> LN, LN-SN (LNN) interaction in n-rich matter
K- nuclear bound states （E15) Outa, Iwasaki,..
-> KbarN interaction
T. Takahashi (KEK)
A02: Multi-strangeness baryon-baryon interactions
X hypernuclear spectroscopy （E05) Nagae,…
X atomic X-rays (E03) Tanida,…
LL hypernuclei and X atomic X-rays （E07) Nakazawa,…
New!!
S= -2 resonance Sato, Imai,...
-> LL, XN, XN-SN interactions, H dibaryon-like state
e ( r ,  ) = e ( r ,0) + Esym 2 + ...
e ( r ,  ) =matter
e ( r ,0) + E at
 +RIBF
...
B: EOS of neutron-rich
r -r
N -Z
2
sym
=
n
p
2=
rn - r p N - Z
=
=
r
A
e ( r ,  ) = e ( r ,0) + Ersym + ...A
r n - r p N - 1Z  2 E
p0 1  2 E
K 0 p0
2





E
=
=
a
+
r
r
+
r
r
+
...


E
=
=
a
+
r
r
+
=
=sym
4
0
0
2
2
sym
4 2
0
2
2
2


2


r
18
r
18
r
r
A
0
0
0
 =0
 =0
p0 dipole resonance
K 0
1 2E
2
Pigmy




Esym =
=
a
+
r
r
+
r
r
+ ...
4
0
0
2
2
2
Neutron
2   =0
rof0 n-skin nuclei18r 0
matter
unknown
?
?
?
??
Nakamura (TIT)
n-skin Core
r <~ r0
Monopole (E0) giant resonance
(breathing mode) of n-rich nuclei
Di-neutron correlation, 4-n states
N-rich nucleus-nucleus collisions
52Ca+48Ca, 132Sn+124Sn, …
r0
Ultra-cold Fermi gas systems Horikoshi (Tokyo)
-> Properties of low density neutron matter
< r < 2r0
Murakami (Kyoto)
r << r0
C: X-ray observations
 Observables for radius
T. Takahashi (JAXA)
• kHz QPO (quasi periodic oscillation)
Periodic X ray burst from a nuclear fusion spot orbiting
near the surface of the n star
Several data samples exist.
• Red shift (~30%) of absorption lines from the surface of
the n star
Only a few data samples exist.
 ASTRO-H: 2014~
~10 good samples of kHz QPO and red shift for radius expected.
 Better X-ray detectors should be developed for future
Present constraints
to mass-radius relation
D01: Theory group (slide by Ohnishi)
計画班研究代表者
大西 明(基研、班長):中性子星と核物質の理論研究
分担研究者
松尾正之(新潟大):中性子対相関とダイニュートロン
原田 融（大阪電通大)：ハイパー核の生成と構造
中田 仁（千葉大)：n-rich 物質の状態方程式
飯田 圭（高知大): 中性子星の諸現象
巽 敏隆（京大): 高密度物質における非一様凝縮
小野 章(東北大): 重イオン衝突から探る対称エネルギー
土手昭伸（KEK): K中間子を含む原子核と核物質
木村真明(北大): 中性子過剰ハイパー核の構造
連携研究者:
国広(京大)、西崎(岩手大)、親松(愛知淑徳大)、丸山(敏)(JAEA)、
阿武木(東京理科大)、大橋（慶應大）、柴崎（立教大）
D01: Theory group (slide by Ohnishi)
中性子対相関と低密度中性子物質（松尾、中田、木村、(阿部(喬)、関)、...）
中性子物質におけるギャップの第一原理計算 Abe, Seki, 2009
密度による相互作用の強度変化→BEC-BCS cross over
中性子過剰核におけるダイニュートロン相関
対称エネルギーの密度依存性 (中田、小野、飯田、...)
r0 での対称核物質では圧力０→
対称エネルギーが中性子星を支える
有限レンジ相互作用（M3Y）を用いたHF
GMR、重イオン衝突から対称エネルギーへ
ストレンジネス混合（原田、土手、木村、大西、...)
ハイペロン-核相互作用 → ΛからΣ、Ξへ(Hypernuclear Sym. E. ?)
構成要素としての中間子（K, π, ..)
M=1.67 Msun を支える３体力
クォーク物質（巽、飯田、国広、阿武木、...)
非一様カイラル凝縮(~ π 凝縮)の再発見
超新星爆発での相転移の影響 → Quarkyonic物質、カラー超伝導、
 X線観測と中性子星物質状態方程式 （飯田、大西、中田、巽、...)
TOV方程式を使うと、M(R) versus P(ε) は１対１対応
半径と質量の同時測定 →状態方程式へ( Baym et al., Lattimer et al.)
→国内での研究者はほぼいないので、ここで組織して共同研究を開始！（観測＋理
論）
パスタ原子核（飯田、親松、丸山、....)
How to use money + shared use
A01: Detector system for YN scattering exp. (fiber trackers)
Development of high-rate beam line trackers
Fast readout system for Hyperball-J
A02: Emulsion, emulsion scanning system
DSSD for LL nuclei and X X-rays
Decay particle detector (TPC) for S=-2 resonance
B01: A new generation neutron counters => A01 kaonic nucleus, …
g-ray calorimeter (LaBr crystal array etc.) => A01 hypernuclear g rays
Laser cooling system for cold atoms
B02: TPC in SAMURAI
CsI forward calorimeter
+NEBULA
SAMURAI
C01: Development of new X/g-ray detectors
(Compton camera w/ Ge, CdTe, Si..)
=> can be tested in J-PARC/RIBF
D01: PD’s
Workshops
(NEutron Detection
System for Breakup
of Unstable Nuclei
with Large
Acceptance)
3. Summary
 Combined with nuclear physics experiments and
astronomical observations, nuclear matter EOS in
neutron stars will be able to be determined.
 The proposed project combines researches on
A: Strangeness nuclear physics experiments at J-PARC
B: Neutron-rich nuclear experiments at RIBF
+ Ultra-cold Fermi atoms by laser cooling
C: X-ray observations by ASTRO-H satellite
D: Theoretical studies
in order to determine THE EOS covering wide ranges of
density, asymmetry, and including strangeness.
 We are applying a grant (15M USD for 5 years in total)
to MEXT.