Speaker: Aihong Tang (BNL)


Title: Observation of antimatter helium-4 nucleus

Abstract:
The antimatter Helium-4 nucleus (anti-alpha) has not been observed previously although
the alpha particle was identified a century ago by Rutherford. High-energy nuclear collisions
recreate energy density similar to that of the universe microseconds after the Big Bang,
and in both cases, matter and antimatter are created with comparable abundances.
However, the relatively short-lived expansion in nuclear collisions makes it possible for
antimatter to decouple quickly from matter. This makes a high-energy accelerator facility the
ideal environment for producing and studying antimatter. In this talk, we report 18 anti-helium 4
discovered by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC).
The measured invariant differential cross section is consistent with expectation from
thermodynamics and coalescent nucleosynthesis models, which has implications for future
production of even heavier antimatter nuclei, as well as for experimental searches for new
phenomena in the cosmos. Future directions of rare/exotic matter searches from STAR
will also be discussed.