Download - Jun. 27, 2013 @ Baryons2013, Glasgow
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Jun. 27, 2013 @ Baryons2013, Glasgow
Motoi Tachibana (Saga Univ.)
Dark matter capture in neutron stars with exotic phases
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A modern physics perspective
“UROBOROS” = unity of matters & universe
Galaxy
Stars
Sun
Earth
MountainHuman
Atom
Nuclei
Particles
Universe
DNA
astrophysics
cosmology
nuclearparticlephysics
chemistrybiology
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Interesting connectionbetween
matters and universe
Dark Matter and Neutron StarsHarmony of particle, astro-, and condensed matter physics
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What/Why dark matter (DM)?Undoubtedly exists, but properties unknownJust weakly-interacting with other particlesProposed by Zwicky as missing mass (1934)
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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)
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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
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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
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DM capture in NS
*based on paper by McDermott-Yu-Zurek (2012)
*
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(1)Accretion of DM
(2)Thermalization of DM (energy loss)
(3)BH formation and destruction of host NS
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(1) DM capture rateThe accretion rate (A. Gould, 1987)
neutron-DM elastic cross section
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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
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(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
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(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,
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Observational constraints
For the case of the pulsar B1620-26:
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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?
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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
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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--
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Thank you