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Electroweak bremsstrahlung in bino-like dark matter annihilations

We investigate the effects of electroweak bremsstrahlung on bino-like neutralino dark matter pair annihilations in the minimal supersymmetric standard model (MSSM). We calculate the nonrelativistic pair annihilation cross sections via $W$-strahlung from leptonic final states, $χχ$ $\to$ $W\ell\barν$, and compare them with the contributions of the relevant two-body final states. We explore the case that sleptons lie below the TeV scale, while squarks are extremely heavy. It is found that the electroweak bremsstrahlung can give a dominant contribution to the cross section for some parameter regions which include slepton coannihilation regions with the observed relic abundance. We also evaluate the neutrino spectra at injection in the Sun. It is shown that energetic neutrinos via weak bremsstrahlung processes can be dominant over contributions of the two-body final states.