The axion-photon interaction and gamma ray signals of dark matter

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The axion-photon interaction and gamma ray signals of dark matter Juan Barranco Monarca DCI Universidad de Guanajuato In collaboration with A.Bernal, D.

1 The axion-photon interaction and gamma ray signals of dark matter Juan Barranco Monarca DCI Universidad de Guanajuato In collaboration with A.Bernal, D. Delepine and A. Carrillo Essential Cosmology for the Next Generation. Los Cabos San Lucas, México 2014 The axion-photon interaction and gamma ray signals of dark matter p. 1

2 Two fantastic news! Higgs discovery. 1. Confirms the Standard Model of elementary particles. 2. First élementary scalar particle found in nature Is there somenthing else? Any other fundamental scalar? The axion-photon interaction and gamma ray signals of dark matter p. 2

3 Axion The strong CP problem. Axion was originally proposed to solve strong CP problem There is a remnant γ a interaction L = 1 2 ( µ φ µ φ m 2 φ 2 ) 1 4 φ M F µν F µν 1 4 F µνf µν The axion-photon interaction and gamma ray signals of dark matter p. 3

4 Self-gravitating axion Axion properties GeV f a GeV 10 5 ev m 10 3 ev At late times in the evolution of the universe, the energy density potential of the axion is which can be expanded as V(φ) = m 2 f 2 a [ ( )] φ 1 cos,, f a V(φ) 1 2 m2 φ 2 1 4! m2φ4 f 2 a + 1 6! m2φ6 f 4 a... with the identification λ = m 2 /6f 2 a : Hence, we can estimate (incorrectly) M max λm 10 4 M! F.E. Shunck and W. Mielke. Class. Quantum Grav. 20 (2003) The axion-photon interaction and gamma ray signals of dark matter p. 4

5 Axion star R = f a σ, r = m p m m f a 4π x, α = 4πf2 a m 2 pm, A(x) = 1 a(x) a + a(1+a) x σ + +(1 a) 2 x [( 1 )m B +1 2 σ 2 mσ4 4 ] +α σ 2 (1 a) + σ6 72 ] +α σ 2 (1 a) σ6 72 B + ab [( ) 1 x (1 a)bx B 1 m 2 σ 2 + mσ4 4 ( 2 x + B 2B + a ) [( 1 σ +(1 a) )m 2(1 a) B 1 2 σ + mσ3 3 σ5 24 ] = 0, = 0, = 0 The axion-photon interaction and gamma ray signals of dark matter p. 5

6 Axion star σ(x) σ(0)=5x10-4 σ(0)=3x10-4 σ(0)=1x10-4 a(x) 0-1e-14-2e-14-3e-14-4e-14-5e-14-6e-14-7e x σ(0) Mass (Kg) R 99 (meters) density ρ (Kg/m 3 ) , ,83 6, , ,86 2, , ,54 3, [J. Barranco, A. Bernal, PRD83, (2011)] The axion-photon interaction and gamma ray signals of dark matter p. 6

7 Galactic halo as a collisionless ensemble of DM machos 8e-21 5e-15 M [Solar masses] 6e-21 4e-21 2e-21 4e-15 3e-15 2e-15 1e e+11 4e+11 6e+11 ρ(0)[kg/m 3 ] 0 0 3e+10 6e+10 9e+10 ρ(0)[kg/m 3 ] [J. Barranco, A. Carrillo, D. Delepine, PRD87 (2013) ] The axion-photon interaction and gamma ray signals of dark matter p. 7

8 Galactic halo as an ensemble of DM mini-machos log10 t/ys Mini MACHOS Forbidden because of MACHO Microlensing Rich Cluster Mo Large Galaxy Mo Dwarf Galaxy 10 8 Mo Forbidden because of dynamical instability Forbidden because of arguments on massive BHs 10 t = 13.7 Gyr 5 Forbidden because of gravothermal instability log 10 m/m o X. Hernandez, T. Matos, R. A. Sussman and Y. Verbin, Scalar field mini-machos: A new explanation for galactic dark matter, Phys. Rev. D 70, (2004) Axions may form such scalar field mini-machos. M axion star < M J. Barranco, A. Bernal, Phys. Rev. D 83 (2011) The axion-photon interaction and gamma ray signals of dark matter p. 8

9 Galactic halo as an ensemble of DM mini-machos log10 t/ys Mini MACHOS t = 13.7 Gyr Forbidden because of MACHO Microlensing Rich Cluster Mo Large Galaxy Mo Dwarf Galaxy 10 8 Mo log 10 m/m o Forbidden because of dynamical instability Forbidden because of arguments on massive BHs Forbidden because of gravothermal instability X. Hernandez, T. Matos, R. A. Sussman and Y. Verbin, Scalar field mini-machos: A new explanation for galactic dark matter, Phys. Rev. D 70, (2004) Axions may form such scalar field mini-machos. M axion star < M J. Barranco, A. Bernal, Phys. Rev. D 83 (2011) Clumpy neutralino dark matter M neutralino star 10 7 M. J. Ren, X. Li, H. Shen, Commun.Theor.Phys. 49 (2008) Formation of dark matter clumps: Axion minicluster:the evolution of the axion field at the QCD transition epoch may produce gravitationally bound miniclusters of axions Such minicluster, due to collisional 2a 2a process, it may relax to a selfgravitating system. [Kolb and Tkachev PRL 71 (1993) ] Neutralino clumps: At the phase transition from a quark-gluon plasma to a hadron gas, the spectrum of density perturbations may develop peaks and dips produced by the growth of hadronic bubbles. Kinematically decoupled CDM falls into the gravitational potential wells provided from those peaks leading the formation of dark matter clumps with masses < M. [Schmid PRD 59 (1999) ] The axion-photon interaction and gamma ray signals of dark matter p. 8

10 Possible γ signal? Consider the galactic halo as an ensemble of axion stars Axion stars/pc Moore Navarro-Frenk-White Kratsov Isothermal r [Kpc] Remember L = 1 2 ( µ a µ a m 2 a 2 ) 1 4 a M F µν F µν 1 4 F µνf µν It is possible axion transform to photons in presence of an external magnetic field! The axion-photon interaction and gamma ray signals of dark matter p. 9

11 Possible γ signal? Strong magnetic fields NS > 10 8 Gauss NS in the galaxy Does axion stars collision with Neutron Stars produce a visible effect? Start with Obtain modified Gauss law: L aγγ = cα f PQ π a E B E = cα (ab) f PQ π Energy dissipated in the magnetized conducting media, with averange σ electric conductivity (Ohm s law) W = ABS σe 2 ad 3 x = 4c erg/s σ 10 26/s M 10 4 M B 2 (10 8 G) 2 YES! there could be a signal The axion-photon interaction and gamma ray signals of dark matter p. 10

12 Possible γ signal? The number of collisions per pc 3 per second will be R c = n AS (r) ρ NS (r) S v, n AS is the number of AS per pc 3, ρ NS is the probability to find a Neutron Star at that point Collisions per year Moore Navarro-Frenk-White Kratsov Isothermal Salucci et al r [Kpc] The axion-photon interaction and gamma ray signals of dark matter p. 11

13 HE Gamma rays from the Sun? Remember the Lagrangian L = 1 2 ( µ φ µ φ m 2 φ 2 ) 1 4 φ M F µν F µν 1 4 F µνf µν If the magnetic field changes on length scales larger than the wavelength of the particles, the equation of motion will be i z Ψ = (ω +M)Ψ; Ψ = (A x,a y,φ) p 0 Mx M = 0 p My. Mx My m Mi = B ( i 2M = Bi 1, G m p = m2 2ω = 2, ( m 10 3 ev = ω2 p 2ω = 3, ( )( 10 5 ) GeV n e M ) ( ) 1GeV ω )( 1GeV cm 3 ω cm 1 cm 1 ) cm 1 The axion-photon interaction and gamma ray signals of dark matter p. 12

14 HE Gamma rays from the sun? P = 4B 2 ω 2 M 2 (ω 2 p m 2 ) 2 +4B 2 ω 2 sin2 ( π z ) l osc l osc = 4πωM M 2 (ωp 2 m 2 ) 2 +4B 2 ω 2 The axion-photon interaction and gamma ray signals of dark matter p. 13

15 HE Gamma rays from the sun? The axion-photon interaction and gamma ray signals of dark matter p. 14

16 Conclusions Axions are good candidates for DM They may form mini-clumps i.e. axion stars Galaxies may be a collisionless ensemble of such axion stars The axion-photon conversion is an interesting tool for indirect detection of axion The axion-photon interaction and gamma ray signals of dark matter p. 15

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