Abstract: | We present the first IceCube search for a signal of dark matter annihilations
in the Milky Way using all-flavour neutrino-induced particle cascades. The
analysis focuses on the DeepCore sub-detector of IceCube, and uses the
surrounding IceCube strings as a veto region in order to select starting events
in the DeepCore volume. We use 329 live-days of data from IceCube operating in
its 86-string configuration during 2011-2012. No neutrino excess is found, the
final result being compatible with the background-only hypothesis. From this
null result, we derive upper limits on the velocity-averaged self-annihilation
cross-section, < sigma_A v >, for dark matter candidate masses ranging from 30
GeV up to 10 TeV, assuming both a cuspy and a flat-cored dark matter halo
profile. For dark matter masses between 200 GeV and 10 TeV, the results improve
on all previous IceCube results on < sigma_A v >, reaching a level of 10^{-23}
cm^3 s^-1, depending on the annihilation channel assumed, for a cusped NFW
profile. The analysis demonstrates that all-flavour searches are competitive
with muon channel searches despite the intrinsically worse angular resolution
of cascades compared to muon tracks in IceCube. |