Paper detail

Could a reported 2007 analysis of Super-Kamiokande data have missed a detectable supernova signal from Andromeda?

According to a 2007 paper there was no evidence for a neutrino burst of two or more events in Super-Kamiokande (SK) during the entire period of data-taking from 1996 to 2005 from Andromeda or anywhere else. There is, however a scenario under which a detectable signal could have been missed given the search method employed by the analysis, and it would have been found using an alternate method. The alternate method depends on the hypothesis that two of the neutrino mass eigenstates have masses 4.0 eV and 21.4 eV which was inferred from an analysis of the SN 1987A data. Although one might argue that the hypothesis of such large neutrino masses is remote, there is a way they could be compatible with observed constraints on neutrino masses involving a third tachyonic ($m^2<0$) eigenstate, plus three sterile neutrinos. Given the importance of a positive supernova search result, and the ease of conducting it using existing SK data, there would seem to be little reason not to do it.