3 research outputs found
Forbidden dark matter annihilation into leptons with full collision terms
The standard approach of calculating the relic density of thermally produced
dark matter based on the assumption of kinetic equilibrium is known to fail for
forbidden dark matter models since only the high momentum tail of the dark
matter phase space distribution function contributes significantly to dark
matter annihilations. Furthermore, it is known that the computationally less
expensive Fokker-Planck approximation for the collision term describing elastic
scattering processes between non-relativistic dark matter particles and the
Standard Model thermal bath breaks down if both scattering partners are close
in mass. This, however, is the defining feature of the forbidden dark matter
paradigm. In this paper, we therefore include the full elastic collision term
in the full momentum-dependent Boltzmann equation as well as in a set of fluid
equations that couple the evolution of the number density and dark matter
temperature for a simplified model featuring forbidden dark matter
annihilations into muon or tau leptons through a scalar mediator. On the
technical side, we perform all angular integrals in the full collision term
analytically and take into account the effect of dark matter self-interactions
on the relic density. The overall phenomenological outcome is that the updated
relic density calculation results in a significant reduction of the
experimentally allowed parameter space compared to the traditional approach,
which solves only for the abundance. In addition, almost the entire currently
viable parameter space can be probed with CMB-S4, next-generation beam-dump
experiments or at a future high-luminosity electron-position collider, except
for the resonant region where the mediator corresponds to approximately twice
the muon or tau mass.Comment: 23 pages, 6 figure
The dipole formalism for massive initial-state particles and its application to dark matter calculations
The dark matter abundance plays a crucial role in the determination of the
valid parameter space of models both in case of a discovery of dark matter and
in the context of exclusion limits. Reliable theoretical predictions of the
dark matter relic density require technically demanding precision calculations,
which were so far limited in their automation due to challenges in the
treatment of infrared divergences appearing in higher order calculations. In
particular, massive initial states need to be considered in early Universe
computations, so that the known dipole subtraction methods could not be
directly exploited. We therefore provide a full generalization of the dipole
subtraction method by Catani and Seymour to (SUSY)-QCD with massive initial
states. All dipole splitting functions and their integrated counterparts are
given explicitly for four different dimensional schemes. To showcase their
application, we apply our results to dark matter (co)-annihilation processes in
the context of the Minimal Supersymmetric (SUSY) Standard Model (MSSM). We also
demonstrate the accuracy of the dipole method by comparing our numerical
results with those obtained with the space space slicing method. Our analytical
results will facilitate future automation of dark matter abundance calculations
at next-to-leading order for both SUSY and non-SUSY models.Comment: 42 pages, 8 figures, 3 table
Precision predictions for dark matter with DM@NLO in the MSSM
International audienceWe present DM@NLO, a Fortran 77 based program with a C++ interface dedicated to precision calculations of dark matter (DM) (co)annihilation cross-sections and elastic dark matter-nucleon scattering amplitudes in the Minimal Supersymmetric (SUSY) Standard Model (MSSM) at next-to-leading order (NLO) in perturbative (SUSY) QCD. If the annihilating initial particles carry an electric or colour charge, the Sommerfeld enhanced cross section is included as well and can be matched to the NLO cross section. We review these calculations including technical details relevant for using the code. We illustrate their impact by applying DM@NLO to an example scenario in the constrained MSSM