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Models of dark matter with ~ GeV scale force mediators provide attractiveexplanations of many high energy anomalies, including PAMELA, ATIC, and theWMAP haze. At the same time, by exploiting the ~ MeV scale excited states thatare automatically present in such theories, these models naturally explain theDAMA/LIBRA and INTEGRAL signals through the inelastic dark matter (iDM) andexciting dark matter (XDM) scenarios, respectively. Interestingly, with onlyweak kinetic mixing to hypercharge to mediate decays, the lifetime of excitedstates with delta < 2 m_e is longer than the age of the universe. Thefractional relic abundance of these excited states depends on the temperatureof kinetic decoupling, but can be appreciable. There could easily be othermechanisms for rapid decay, but the consequences of such long-lived states areintriguing. We find that CDMS constrains the fractional relic population of~100 keV states to be <~ 10^-2, for a 1 TeV WIMP with sigma_n = 10^-40 cm^2.Upcoming searches at CDMS, as well as xenon, silicon, and argon targets, canpush this limit significantly lower. We also consider the possibility that theDAMA excitation occurs from a metastable state into the XDM state, which decaysvia e+e- emission, which allows lighter states to explain the INTEGRAL signaldue to the small kinetic energies required. Such models yield dramatic signalsfrom down-scattering, with spectra peaking at high energies, sometimes as highas ~1 MeV, well outside the usual search windows. Such signals would be visibleat future Ar and Si experiments, and may be visible at Ge and Xe experiments.We also consider other XDM models involving ~ 500 keV metastable states, andfind they can allow lighter WIMPs to explain INTEGRAL as well.

PAMELA, DAMA, INTEGRAL and Signatures of Metastable Excited WIMPs