The treatment and rejection of two "strange" candidate events in the SLIM experiment

During the analysis of the CR39 Nuclear Track Detectors (NTDs) of the SLIM experiment exposed at the high altitude lab of Chacaltaya (Bolivia) we observed a sequence of puzzling etch-pits. We made a detailed investigation of all the CR39 and Makrofol detectors in the same stack and in all the stacks around the candidate event. We found a second puzzling sequence of etch-pits (plus some single etch-pits). The analysis of this configuration was important because we were searching for rare particles (Magnetic Monopoles, Nuclearites, Q-balls) in the cosmic radiation. Thus we analyzed in detail the evolution with increasing etching time of the etch-pits. We concluded that the two sequences of the etch-pits (and some other background etch-pits) may have originated from a rare manufacture malfunctioning which involved 1 m^2 of produced CR39.