Photon-photon dispersion of TeV gamma rays and its role for photon-ALP conversion

Dobrynina, Alexandra; Kartavtsev, Alexander; Raffelt, Georg G.

doi:10.1103/physrevd.91.083003

Cited by 75 publications

(68 citation statements)

References 63 publications

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“…Such resonances can occur in the often-studied case of axion-photon oscillations [32] at high energies, where one typically assumes axions and photons to be nearly degenerate, i.e., it is assumed that ∆ b ω m 2 a and ∆ b ω |n 2 − 1|ω 2 . Actually at the highest astrophysically relevant energies in the 10 TeV range, intergalactic magnetic fields provide this condition as the cosmic microwave background then produces a non-negligible refractive index [33].…”

Section: B)mentioning

confidence: 99%

Dielectric haloscopes: sensitivity to the axion dark matter velocity

Millar¹,

Redondo²,

Steffen³

2017

J. Cosmol. Astropart. Phys.

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Abstract. We study the effect of the axion dark matter velocity in the recently proposed dielectric haloscopes, a promising avenue to search for well-motivated high mass (40−400 µeV) axions. We describe non-zero velocity effects for axion-photon mixing in a magnetic field and for the phenomenon of photon emission from interfaces between different dielectric media. As velocity effects are only important when the haloscope is larger than about 20% of the axion de Broglie wavelength, for the planned MADMAX experiment with 80 dielectric disks the velocity dependence can safely be neglected. However, an augmented MADMAX or a second generation experiment would be directionally sensitive to the axion velocity, and thus a sensitive measure of axion astrophysics.

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Section: B)mentioning

confidence: 99%

Dielectric haloscopes: sensitivity to the axion dark matter velocity

Millar¹,

Redondo²,

Steffen³

2017

J. Cosmol. Astropart. Phys.

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“…Recently it has been realized that also background photons can contribute to the photon polarization. At this regard a guaranteed contribution is provided by the CMB radiation, leading to ∆ CMB ∝ ρ CMB [47]. We will show how this term would play a crucial role for the development of the conversions at high energies.…”

Section: Fig 2 Photon Transfer Functionmentioning

confidence: 87%

“…The effect of the ∆ CMB term -We briefly comment on the role of ∆ CMB term on the ALP-photon conversions at high energies. This term due to VHE photon refraction on CMB photons been recently calculated in [47]. From Eqs.…”

Section: 55mentioning

confidence: 97%

“…Left panels refer to the "cell" model, while right panels represent the more realistic model of our cosmological simulation. In both the cases we have chosen as average value of the magnetic field BT = 1.6 × 10 −9 G. culated in [47]. This term would be dominated by the energy density of cosmic microwave background photons.…”

Section: Fig 2 Photon Transfer Functionmentioning

confidence: 99%

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Enhancing the Spectral Hardening of Cosmic TeV Photons by Mixing with Axionlike Particles in the Magnetized Cosmic Web

et al. 2017

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Large-scale extragalactic magnetic fields may induce conversions between very-high-energy photons and axionlike particles (ALPs), thereby shielding the photons from absorption on the extragalactic background light. However, in simplified "cell" models, used so far to represent extragalactic magnetic fields, this mechanism would be strongly suppressed by current astrophysical bounds. Here we consider a recent model of extragalactic magnetic fields obtained from large-scale cosmological simulations. Such simulated magnetic fields would have large enhancement in the filaments of matter. As a result, photon-ALP conversions would produce a significant spectral hardening for cosmic TeV photons. This effect would be probed with the upcoming Cherenkov Telescope Array detector. This possible detection would give a unique chance to perform a tomography of the magnetized cosmic web with ALPs.Introduction-Axionlike particles (ALPs) are ultralight pseudoscalar bosons a with a two-photon vertex aγγ, predicted by several extensions of the Standard Model (see [1] for a recent review). In the presence of an external magnetic field, the aγγ coupling leads to the phenomenon of photon-ALP mixing [2]. This effect allows for the possibility of direct searches of ALPs in laboratory experiments. In this respect a rich, diverse experimental program is being carried out, exploiting different sources and approaches [3][4][5]. See [6] for a review.Because the aγγ coupling, ultralight ALPs can also play an important role in astrophysical observations. In particular, an intriguing hint for ALPs has been recently suggested by very-high-energy (VHE) γ-ray experiments. In this respect, recent observations of cosmologically distant γ-ray sources by ground-based γ-ray Imaging Atmospheric Cherenkov Telescopes have revealed a surprising degree of transparency of the Universe to VHE photons [7,8], where one would have expected a significant absorption of VHE photons by pair-production processes (γ VHE + γ EBL → e + e − ) on the extragalactic background light (EBL). Even though this problem has been also analyzed using more conventional physics (see, e.g., [9,10]), photon-ALP oscillations in large-scale magnetic fields provide a natural mechanism to drastically reduce the photon absorption [11][12][13][14][15][16][17][18]. In order to have efficient conversions one should achieve the strong-mixing regime which is realized above a critical energy given by [19]

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“…for the derivation presented in reference [60]. However, forward scattering on CMB photons recently identified in reference [63] ensures that the oscillation length decreases as the energy increases and prevents the mixing from becoming maximal for TeV gamma rays. In this section we demonstrate that the approach of reference [60] can nevertheless be extended to the case of arbitrary mixing angles as long as the oscillation length remains large compared to the width of the transition region between the domains.…”

Section: Statistical Approach To Photon-alp Propagationmentioning

confidence: 99%

Extragalactic photon-ALP conversion at CTA energies

Kartavtsev

Raffelt

Vogel

2017

J. Cosmol. Astropart. Phys.

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Abstract. Magnetic fields in extragalactic space between galaxy clusters may induce conversions between photons and axion-like particles (ALPs), thereby shielding the photons from absorption on the extragalactic background light. For TeV gamma rays, the oscillation length (l osc ) of the photon-ALP system becomes inevitably of the same order as the coherence length of the magnetic field l and the length over which the field changes significantly (transition length l t ) due to refraction on background photons. We derive exact statistical evolution equations for the mean and variance of the photon and ALP transfer functions in the non-adiabatic regime (l osc ∼ l l t ). We also make analytical predictions for the transfer functions in the quasi-adiabatic regime (l osc l, l t ). Our results are important in light of the upcoming Cherenkov Telescope Array (CTA), and may also be applied to models with non-zero ALP masses.

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Photon-photon dispersion of TeV gamma rays and its role for photon-ALP conversion

Cited by 75 publications

References 63 publications

Dielectric haloscopes: sensitivity to the axion dark matter velocity

Dielectric haloscopes: sensitivity to the axion dark matter velocity

Enhancing the Spectral Hardening of Cosmic TeV Photons by Mixing with Axionlike Particles in the Magnetized Cosmic Web

Extragalactic photon-ALP conversion at CTA energies

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