Title: Strange Quark Matter in Lunar Soil


Strange Quark Matter (SQM) is a proposed state of hadronic matter made up of roughly one-third each of up, down, and strange quarks in a single hadronic bag. For the last three decades, a wide range of experimental searches for strangelets (small lumps of SQM with baryon number less than $106$) have been conducted but all failed to give a definite answer to the existence of SQM. We report results from a search for strangelets in a lunar soil sample, in which the predicted strangelet concentration is about 104 times higher than that on the Earth. The search used the tandem Van-de-Graaff accelerator at Yale as an ultra-sensitive mass spectrometer. We have searched over a range in mass from A=42 to A=70 amu for nuclear charges 5, 6, 8, 9, and 11. No strangelets were found in the experiment. For strangelets with nuclear charge 8, a concentration in lunar soil higher than 10^{-16} per normal atom is excluded at the 95% confidence level. The implied limits on the strangelet flux in cosmic rays are the most sensitive to date for the covered range and are relevant to both recent theoretical flux predictions and a strangelet candidate event found by the AMS-01 experiment.