Discovery of the anti-alpha particle at STAR

Charles Steinhardt
Hank Crawford (LBNL)


I report on the discovery of the antimatter 4He nucleus, the antialpha (4He or 4 ) consisting of 2 antiprotons (p), and 2 antineutrons (n). The STAR experi5 ment at RHIC examined 109 interactions produced by colliding beams of gold 6 nuclei at a center-of-mass energy of 200 GeV per nucleon pair. Our analysis 7 yields 18 clean 4He particles. I discuss this in light of the recent AMS experi8 ment now operating on the International Space Station and the prospects for 9 further exotic particle searches at STAR and the LHC..