Jun. 27, 2013 ＠ Baryons2013, Glasgow

Motoi Tachibana (Saga Univ.)

Dark matter capture in neutron stars with exotic phases

A modern physics perspective

“UROBOROS” = unity of matters & universe

Galaxy

Stars

Sun

Earth

MountainHuman

Atom

Nuclei

Particles

Universe

DNA

astrophysics

cosmology

nuclearparticlephysics

chemistrybiology

Interesting connectionbetween

matters and universe

Dark Matter and Neutron StarsHarmony of particle, astro-, and condensed matter physics

What/Why dark matter (DM)?Undoubtedly exists, but properties unknownJust weakly-interacting with other particlesProposed by Zwicky as missing mass (1934)

arXiv:1210.0682

What/Why neutron star (NS)?Landau’s gigantic nucleus

Good market selling ultimate environmentsProposed by Baade and Zwicky

as a remnant after supernova explosion (1934)

Why their connections?Possibly constraining WIMP-DM properties via NS

For a typical neutron star,

Way below the CDMS limit!

NS may constrain the DM properties

CDMSII, 1304.4279

Constraining the dark matter mass and its scattering cross section through the impacts on neutron stars

• Mass-radius relation with the DM EOS• Cooling in the presence of dark matter　　　 　　　　　　　：

cf) This is not so a new idea. People have considered the DM capture by Sun and the Earth since 80’s. [W. Press and D. Spergel (1984) etc]

• (Asymmetric) dark matter capture in NS and black hole formation to collapse neutron stars

DM capture in NS

*based on paper by McDermott-Yu-Zurek (2012)

*

(1)Accretion of DM

(2)Thermalization of DM (energy loss)

(3)BH formation and destruction of host NS

(1) DM capture rateThe accretion rate (A. Gould, 1987)

neutron-DM elastic cross section

Capture efficiency factor ξ

(i) If momentum transfer δp is less than p , only neutrons with momentum larger than p -δp can participate in

(ii) If not, all neutrons can join

F

F

In NS, neutrons are highly degenerated

(2) Thermalization of DM

Thermalization time scale:

If δp is less than p , then

After the capture, DMs lose energy via scatteringwith neutrons and get thermalized with the star

F

(3) Self–gravitation & BH formationIf the DM density gets larger than the baryon density within thermal radius, DM particles be self-gravitating.This is the on-set of the gravitational collapse and black-hole formation (the Chandrasekhar limit)

To avoid destruction of NS,

Observational constraints

For the case of the pulsar B1620-26:

So far people have been mainly studyingthe issue from particle physics side.

However, as I told you, hadrons in NS arein EXTREME, and exotic phases could appear.

An idea

(e.g.) neutron superfluidity Bose condensation of mesons superconductivity of quarks

What if those effects are incorporated?

Possible effects① Modification of capture efficiency via energy gap

② Modification of low-energy effective theory

We are on the way of the calculations

(e.g.) neutron superfluidity dominant d.o.f. is a superfluid phonon.

Cirigliano, Reddy, Sharma (2011)

(e.g.) color-flavor-locked(CFL) quark matter

larger suppression

On-going project w/ M. Ruggieri

SummaryConstraining dark matter properties via neutron star--dark matter capture in neutron stars—

Accretion, thermalization and on-set of BH formation

Models for DM, but not considering NS seriously

Proposal of medium effects for hadrons in NS--modified vacuum structures and collective modes--

Thank you