Systematizing the effective theory of self-interacting dark matter
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Springer
Received: May Revised: August Accepted: September Published: October
12, 17, 20, 28,
2020 2020 2020 2020
Prateek Agrawal, Aditya Parikh and Matthew Reece Department of Physics, Harvard University, Cambridge, MA 02138, U.S.A.
E-mail: [email protected], [email protected], [email protected] Abstract: If dark matter has strong self-interactions, future astrophysical and cosmological observations, together with a clearer understanding of baryonic feedback effects, might be used to extract the velocity dependence of the dark matter scattering rate. To interpret such data, we should understand what predictions for this quantity are made by various models of the underlying particle nature of dark matter. In this paper, we systematically compute this function for fermionic dark matter with light bosonic mediators of vector, scalar, axial vector, and pseudoscalar type. We do this by matching to the nonrelativistic effective theory of self-interacting dark matter and then computing the spin-averaged viscosity cross section nonperturbatively by solving the Schr¨odinger equation, thus accounting for any possible Sommerfeld enhancement of the low-velocity cross section. In the pseudoscalar case, this requires a coupled-channel analysis of different angular momentum modes. We find, contrary to some earlier analyses, that nonrelativistic effects only provide a significant enhancement for the cases of light scalar and vector mediators. Scattering from light pseudoscalar and axial vector mediators is well described by tree-level quantum field theory. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM ArXiv ePrint: 2003.00021
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP10(2020)191
JHEP10(2020)191
Systematizing the effective theory of self-interacting dark matter
Contents 1 Introduction 1.1 Goals of this work and relation to the previous literature
1 2
2 SIDM and our examples
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4 Sommerfeld enhancement 4.1 Yukawa potential 4.2 Pseudoscalar mediator 4.2.1 Diagrammatic argument 4.3 Axial vector mediator 4.4 Results
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5 Conclusions
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A Angular momentum basis conversions ~ · rˆ operator A.1 S
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B Fermion/antifermion spin matrices and minus signs
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C Feynman diagrammatic argument for Sommerfeld enhancement
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1
Introduction
The majority of mass in our universe is in the form of dark matter, but the underlying nature of dark matter and its interactions remains elusive. Many attempts to understand the nature of dark matter rely on searching for its interactions with ordinary matter, through direct or indirect detection experiments or attempts to directly produce dark matter particles at colliders or fixed-target experiments. We may also be able to learn about the particle nature of dark matter if it has significant self-interactions, which can alter the astrophysical and cosmological signals of dark matter in ways that may be detectable [1, 2]. In recent years, many aspects of the astrophysics and cos
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