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Electromagnetic signatures of dark photon superradiance

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Andrea Caputo, Samuel J. Witte, Diego Blas, Paolo Pani

Original languageEnglish
Article number043006
JournalPhysical Review D
Issue number4
Published15 Aug 2021

Bibliographical note

Funding Information: We thank Aditya Parikh, Georg Raffelt, Toni Riotto, and Giuseppe Rossi for useful discussions. We also thank Edoardo Vitagliano and Enrico Cannizzaro for discussions and comments on the manuscript. A. C. acknowledges support from the Israel Science Foundation (Grant No. 1302/19), the US-Israeli BSF (Grant No. 2018236) and the German Israeli GIF (Grant No. I-2524-303.7). A.C acknowledges also hospitality and support from the Max Planck Institute for Physics of Munich. S. J. W. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 864035—UnDark). P. P. acknowledges financial support provided under the European Union’s H2020 ERC, Starting Grant Agreement No. DarkGRA–757480. We also acknowledge support under the MIUR PRIN and FARE programmes (GW-NEXT, CUP: B84I20000100001), and from the Amaldi Research Center funded by the MIUR program “Dipartimento di Eccellenza” (CUP: B81I18001170001). Funding Information: Israel Science Foundation United States-Israel Binational Science Foundation German-Israeli Foundation for Scientific Research and Development Max Planck Institute for Physics European Research Council Horizon 2020 Framework Programme Ministero dell?Istruzione, dell?Universit? e della Ricerca PRIN Amaldi Research Center Publisher Copyright: © 2021 Published by the American Physical Society Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors


Black hole superradiance is a powerful tool in the search for ultralight bosons. Constraints on the existence of such particles have been derived from the observation of highly spinning black holes, absence of continuous gravitational-wave signals, and of the associated stochastic background. However, these constraints are only strictly speaking valid in the limit where the boson’s interactions can be neglected. In this work we investigate the extent to which the superradiant growth of an ultra-light dark photon can be quenched via scattering processes with ambient electrons. For dark photon masses , and for reasonable values of the ambient electron number density, we find superradiance can be quenched prior to extracting a significant fraction of the black-hole spin. For sufficiently large and small electron number densities, the in-medium suppression of the kinetic mixing can be efficiently removed, and quenching occurs for mixings ; at low masses, however, in-medium effects strongly inhibit otherwise efficient scattering processes from dissipating energy. Intriguingly, this quenching leads to a time- and energy-oscillating electromagnetic signature, with luminosities potentially extending up to , suggesting that such events should be detectable with existing telescopes. As a by-product we also show that superradiance cannot be used to constrain a small mass for the Standard Model photon.

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