Physicists will generally require a confidence level of 3 sigma (standards deviations) to suggest the existence of an event and 5 sigma (along with independent verification) to assert that the event is highly likely. Thus they are making no claim of certainly (yet).
Currently being announced live at a presentation from CERN in Switzerland, particle physicists express optimism that they have identified the likely mass of the Higgs Boson and also the typical decay paths.
A previous informal announcement claiming a discovery with an estimated mass of 115GeV has almost certainly been discredited.
The second presenter (Guido Tonelli) representing the CMS experiment at CERN was able to advise the audience that they found similar data - with a probably event around 124GeV, but currently with somewehat lower confidence levels and thus they were unwilling to make the same kinds of assertions that were heard from the ATLAS team.