Remarks on bosonic super-WIMP search experiments

Abstract

Bosonic super--weakly interacting massive particles (WIMPs), including pseudoscalar and vector particles, are dark-matter candidates. To date, many underground experiments searches for super-WIMPs have been performed in the mass range of a few $\mathrm{keV}/{c}^{2}$ to $1\text{ }\text{ }\mathrm{MeV}/{c}^{2}$. All these searches utilize the absorption process of a super-WIMP by a target atom in the detector, which is similar to the photoelectric effect. We consider another process---namely, a Compton-like process. As an example, we compare the cross section of a germanium atom for the absorption process with that of a Compton-like process. Our findings indicate that the cross section for the Compton-like process becomes dominant relative to that for the absorption process for mass above approximately $150\text{ }\text{ }\mathrm{keV}/{c}^{2}$ for both pseudoscalar and vector super-WIMPs. In particular, the cross section for the Compton-like process for a vector super-WIMP becomes increasingly greater than that for the absorption process by 1 to 2 orders of magnitude in the $400\text{ }\text{ }\mathrm{keV}/{c}^{2}$ to $1\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ mass range, respectively. By including the Compton-like process, which has not been used in any other super-WIMP search experiments, the experimental upper limits can be improved.