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Motoi Tachibana (Saga Univ.) Dark matter capture in compact stars -stellar constraints on dark matter- Oct. 20, 2014 ＠ QCS2014, KIAA, Beijin Dark matter capture in neutron stars with exotic phases

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What/Why dark matter (DM) ? Undoubtedly exists, but properties unknown Interacting with other particles very weakly Proposed by Zwicky as missing mass (1934)

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What/Why neutron star (NS) ? Landau’s gigantic nucleus Good market selling ultimate environments Proposed by Baade and Zwicky as a remnant after supernova explosion (1934)

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Why the connection between DM and NS?

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Possibly constraining WIMP-DM properties via NS For a typical neutron star, Way below the CDMS limit! CDMSII, 1304.4279

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Impacts of dark matter on NS NS mass-radius relation with dark matter EOS NS heating via dark matter annihilation NS seismology ： 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) Dark matter capture in NS and formation of black-hole to collapse host neutron stars cosmion

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Cooling curves of Neutron Star t T C. Kouvaris (‘10)

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DM capture in NS *based on paper by McDermott-Yu-Zurek (2012) *

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(1)Accretion of DM (1)Thermalization of DM (energy loss) (2)BH formation and destruction of host NS condition of self-gravitation

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Capture rate due to DM-neutron scattering Self-capture rate due to DM-DM scattering DM self-annihilation rate Capturable number of DMs in NS

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(A) (no self-capture) Reaches the steady state value, within time.

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(B) (no self-annihilation) Linearly grows until, and then exponentially grows until the geometric limit is reached.

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(C) (no self-capture/annihilation) Just linearly grows and is the growth rate. Realized when DM carries a conserved charge, analogous to baryon number? Below we consider the case (C)

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DM capture rate The 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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Thermalization of DM After the capture, DMs lose energy via scattering with neutrons and eventually get thermalized DM mass ≦ 1GeV, DM mass ≧ 1GeV,

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Then, the DM gets self-gravitating once the total number of DM particles is larger than a critical one If this condition is met, for the wide range of the DM mass, gravitational collapse takes place, i.e., N self exceeds the Chandrasekhar limit.

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Condition

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Observational constraints For the case of the pulsar B1620-26: McDermott-Yu-Zurek (2012)

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But… Neutron star is Landau’s gigantic nucleus!

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So far people have been mainly studying the issue from particle physics side. However, hadrons in NS are in EXTREME, and exotic matter states could appear. (e.g.) neutron superfluidity meson condensation superconductivity of quarks What if those effects are incorporated?

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Possible effects ① Modification of capture efficiency via energy gap ② Modification of low-energy effective theory We are still struggling… (e.g.) neutron superfluidity dominant d.o.f. is a superfluid phonon. (e.g.) color-flavor-locked (CFL) quark matter sizable effect? M. Ruggieri and M.T. (2013)

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Bertoni, Nelson and Reddy, Phys. Rev. D88 (2013)

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Asymmetric Complex scalar M_DM ~ 1 keV – 5 GeV Couples to regular matter via heavy vector boson Pauli blocking Kinematic constraints Superfluidity/Superconductivity Significantly affects thermalization time!

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Summary Stellar constraints on dark matter properties 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-- Study of dark matter from neutron stars!

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