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 3×1011 Pb + Pb interactions at positive and 1013 at negative spectrometer polarities have been recorded. No strangelet has been observed, which sets experimental upper limits (90% CL) for the strangelet production at 3×10-9 per interaction for positively charged and at 2×10-10 per interaction for negatively charged strangelets.