Hyperon-mixed Neutron-star matter in
Dirac-Brueckner-Hartree-Fock approach
Department of Physics, Faculty of Science and Technology
Tokyo University of Science

Tetsuya Katayama
J-PARC hadron physics in 2014,
Nov. 30 – Dec. 2, 2014 Ibaraki Quantum Beam Research CenterTable of Contents• Difference between the MFT andthe DBHF approach• Model (DBHF)• Numerical results– Symmetric nuclear matter– Neutron-star matter without hyperons– Neutron-star matter with hyperons• Summary and future works

Models for isospin-asymmetric , dense matter
MFTA large amount of
NN scattering dataMeson-baryon
coupling constants

B/A (MeV)

B/A (MeV)

Nuclear matter
Properties

DBHF
Realistic
NN interactions

DBHF can mostly reproduce thenuclear matter properties
without any readjustment of thecoupling constants.

Extrapolation to extremely isospin-asymmetricand dense matternB (MeV)nB (MeV)The reason for the great success of DBHF is the density dependence
mainly caused by many-body effects, the Pauli exclusion principle
and the short-range NN correlations.

RH(MFT) , RHF and RBHF
• Bethe-Salpeter equation：• Self-energy：• Dyson’s equation:

Conventional DBHF vs Our DBHF
The conventional DBHF approach requires two assumptions:
Conventional DBHF approach
1. The space components of the in-medium
baryon self-energy, , is ignored.
2. The relationship between the in-medium Tmatrix for NN scattering and the in-medium
nucleon self-energies is not clear.

1. We fully consider the.

Our DBHF approach

2. We also include the negative-energy states ofbaryon in the Bethe-Salpeter amplitude.

Numerical results

Binding energy per particle insymmetric nuclear matterBonn A, B and C potentials
NN potential is generated by the exchanges
ofand mesons.

withCase

(fm )

(MeV)

(MeV)

(MeV)

(MeV)

DBHF (A)

0.149

-10.5

204

28.8

78.6

DBHF (B)

0.130

-7.3

133

22.7

58.2

DBHF (C)

0.112

-5.2

87

18.0

42.2

DBHF *(A)

0.186

-15.1

402

36.8

117.0

•
•
•
•

：binding energy：incompressibility：symmetry energy：slope parameterNeutron stars without hyperons
We assume that
DBHF(A) and DBHF*(A)neutron-star matter is composed of …
Leptons

MesonsBaryons• Charge neutrality:• β-equilibrium in weak interaction:• Baryon number conservation:

Tolman-Oppenheimer-Volkoff (TOV) equation

ccccvv
v*v

Inclusion of hyperons

One-boson-exchange processes for thesystem.

We assume that neutron-star matter is composed of …
Leptons

NlY5
NlY8Mesons

Baryons

Calculation parameters for hyperons
Parameters for hyperons cannot be determined
without large ambiguities.
• Baryon-Baryon-meson coupling constants:
SU(6) symmetrye.g.

• Baryon-Baryon-sigma coupling constants:• Cutoff parameters in the form factor:

Particle fractions for NlY5 and NlY8NlY5NlY8The difference between the result in NlY5 and NlY8 is
expected to be very small.
We proceed to the next calculation, wheremesons are considered.

andBaryon-exchange andBaryon-transition processes

One-boson-exchange processes for thesystem.

We assume that neutron-star matter is composed of …
Leptons

NlY5KK*

MesonsBaryons

Particle fractions in cases ofMFT and NlY5KK*
MFT

NlY5KK*The results are similar to one another, except for theappearance ofin NlY5KK*.
HoweverEOSs in two cases make large difference.

Mass-radius relations for neutron stars
2.02M

◎

NlY5KK*MFTThe DBHF calculation involves
the strong density dependence of the in-medium baryonbaryon scattering amplitude.

Summary••

Using the improved DBHF approach, we haveinvestigated the nuclear matter properties,
and have applied the DBHF approach toneutron stars.
The hyperon-mixed neutron-star calculation
has predicted the maximum neutron-starmass of.

Future works•

More realistic parameter set for hyperons