Abstract
A massive real scalar dark matter particle $S$ can couple to Standard Model leptons or quarks through a vector-like fermionic mediator $\psi$, a scenario known as the Vector-like portal. Due to helicity suppression of the annihilation cross section into a pair of SM fermions, it has been shown in previous works that radiative corrections, either at one-loop or through radiation of gauge bosons, may play a significant role both in determining the relic abundance and for indirect detection. All previous works considered the limit of massless final state quarks or leptons. In this work, we focus on a technical issue, which is to reliably determine the annihilation cross sections taking into account finite fermion masses. Following previous works in the framework of simplified supersymmetric dark matter scenarios, and building on an analogy with Higgs decay into fermions, we address the issue of infrared and collinear divergences that plagues the cross section by adopting an effective operator description, which captures most of the relevant physics and give explicit expressions for the annihilation cross sections. We then develop several approximations for the differential and total cross sections, which simplify greatly their expressions, and which can then be used in various phenomenological studies of similar models. Finally, we describe our method to compute the final gamma-ray spectrum, including hadronisation of the heavy fermions, and provide some illustrative spectra for specific dark matter candidates.
Highlights
Dark matter (DM) amounts to about 27% of the energy budget of our Universe, and, yet, little is known about its precise nature
Due to helicity suppression of the annihilation cross section into a pair of Standard Model fermions, it has been shown in previous works that radiative corrections, either at one loop or through radiation of gauge bosons, may play a significant role both in determining the relic abundance and for indirect detection
Following previous works in the framework of simplified supersymmetric dark matter scenarios, and building on an analogy with Higgs decay into fermions, we address the issue of infrared and collinear divergences that plagues the cross section by adopting an effective operator description, which captures most of the relevant physics, and we give explicit expressions for the annihilation cross sections
Summary
Dark matter (DM) amounts to about 27% of the energy budget of our Universe, and, yet, little is known about its precise nature. That annihilation of a binolike candidate is p-wave in the chiral limit [8] while that of the real scalar S is d-wave [2,9] In both cases, the helicity suppression is lifted by radiative corrections [10,11]. In the case of coupling to leptons, radiative processes, either in the form of internal bremsstrahlung or annihilation at one loop into, say, two gamma rays, may lead to striking spectral features Such spectral features are of interest for indirect searches for WIMPs In the case of coupling to (light) quarks, radiative processes involving gluons on top of gammas may be relevant at the time of thermal freeze-out, impacting both the effective annihilation cross section and indirect signatures; see, e.g., Refs.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
