Study of strange matter in STAR with express analysis

¹ Goethe University, Frankfurt am Main, Germany
² FIAS, Frankfurt Institute for Advanced Studies, Frankfurt am Main, Germany
³ HFHF, Helmholtz Research Academy Hesse, Frankfurt am Main, Germany
⁴ GSI, Helmholtz Center for Heavy Ion Research, Darmstadt, Germany

^* e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 9 November 2022

Abstract

The STAR experiment provides a perfect machinery for studying strange matter for more than two decades. Recently, we developed the express procedure, which allows online monitoring of the collected physics data. The high quality of express calibration and reconstruction provides a unique possibility to run the express production and observe almost in real time strange particles including mesons, hyperons, resonances and even hypernuclei.

The STAR Beam Energy Scan II program, including fixed target Au+Au collisions taken in 2018–2021, is particularly suited to study hypernuclei. Light hypernuclei are expected to be abundantly produced in low energy heavy-ion collisions. Measurements of hypernuclei production and their properties will provide information on the hyperon-nucleon interactions, which are essential ingredients for understanding nuclear matter equation of state at high net-baryon densities, such as inside neutron stars.

With the heavy fragment trigger introduced for the 2021 data taking, we were able to run the express production at the STAR High Level Trigger farm. The collected data were suffcient to observe the decay process of _Λ⁵He →⁴Hepπ⁻ with more than 11σ significance, measure binding energy as a function of hypernuclei mass, and study hypernuclei decay properties with the Dalitz plot technique.