
We study the scenario of fermionic dark matter that annihilates to standard model fermions through an s-channel axial vector mediator. We point out that the well-known chirality suppression of the annihilation cross section can be alleviated by s-channel internal Higgsstrahlung. The shapes of the cosmic ray spectra are identical to that of t-channel internal Higgsstrahlung in the limit of a heavy mediating particle. Unlike the general case of t-channel bremsstrahlung, s-channel Higgsstrahlung can be the dominant annihilation process even for Dirac dark matter. Since the s-channel mediator can be a standard model singlet, collider searches for the mediator are easily circumvented.
7 pages, 4 figures
High Energy Astrophysical Phenomena (astro-ph.HE), Nuclear and High Energy Physics, High Energy Physics - Phenomenology, High Energy Physics - Experiment (hep-ex), High Energy Physics - Phenomenology (hep-ph), Physics, QC1-999, FOS: Physical sciences, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
High Energy Astrophysical Phenomena (astro-ph.HE), Nuclear and High Energy Physics, High Energy Physics - Phenomenology, High Energy Physics - Experiment (hep-ex), High Energy Physics - Phenomenology (hep-ph), Physics, QC1-999, FOS: Physical sciences, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
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