Search for strangelets in Pb + Pb collisions at 158 A GeV/c

The NA52 experiment at CERN has investigated lead-lead collisions at 158 A GeV/ c and searched for long-lived strange quark matter droplets, so-called strangelets, with a unique signature of a high mass-to-charge ratio. This ratio was measured in a focusing spectrometer equipped with a time-of-flight system. A total of 3 x 10(11) Pb + Pb interactions at positive and 10(13) at negative spectrometer polarities have been recorded. No strangelet has been observed, which sets experimental upper limits (90% CL) for the strangelet production at 3 x 10(-9) per interaction for positively charged and at 2 x 10(-10) per interaction for negatively charged strangelets.