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Self-annihilation of the neutralino dark matter into two photons or a Z and a photon in the MSSM
We revisit the one-loop calculation of the annihilation of a pair of the
lightest neutralinos into a pair of photons, a pair of gluons and also a Z
photon final state. For the latter we have identified a new contribution that
may not always be negligible. For all three processes we have conducted a tuned
comparison with previous calculations for some characteristic scenarios. The
approach to the very heavy higgsino and wino is studied and we argue how the
full one-loop calculation should be matched into a more complete treatment that
was presented recently for these extreme regimes. We also give a short
description of the code that we exploited for the automatic calculation of
one-loop cross sections in the MSSM that could apply both for observables at
the colliders and for astrophysics or relic density calculations. In particular
the automatic treatment of zero Gram determinants which appear in the latter
applications is outlined. We also point out how generalised non-linear gauge
fixing constraints can be exploited.Comment: 20 pages, 5 figure
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