Note on a 'hint' for an annual modulation signature of a 60 GeV WIMP

Abstract

In a recent presentation at the TAUP97 conference about the analysis of data from a NaI(Tl) 100 kg underground detector run at the Gran Sasso Laboratory by the DAMA/NaI group, the speaker concluded there was a hint for a WIMP of mass 60 GeV with a cross section on proton of 10-5 pb (Spin Independent coupling) (see also ROM2F/97/33). Even if no claim of any definite signal is made, such a statement is strong enough to deserve a critical look. The present note puts forward a few arguments which point towards a largely overestimated statistical significance of the effect, an inconsistency in the energy distribution and several experimental effects which could easily mimic the observed excess. The conclusion is that, in no way, the presented result can be considered as a hint of a WIMP annual modulation.