Jun. 27, 2013 @ Baryons2013, Glasgow
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Transcript of Jun. 27, 2013 @ Baryons2013, Glasgow
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