Little task : The great unification theory says that there is a very little probability that the proton will disintegrate for meson pi0 and positron (e+) . In one of the experiments ,checking this theory, there were 3300 tons of water obserwed using very sensible gear , the gear can manage to detect even single case of disintegration . During one year of obserwations there weren't noticed any cases of disintegration. Questions : 1- What limitation for half-life period is implicated by this obserwations ? 2- In which value of half-life period ,in one year of obserwations , would be obserwed at least one case of disintegration with 95% probability ? Good luck !