2022/10/19 by Ekata Nandy, Subhasis Chattopadhyay, S. Chattopadhyay
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.1140/epja/s10050-022-00856-x
A deconfined medium of quarks and gluon, called the Quark-Gluon Plasma (QGP) is produced when heavy-nuclei are collided at relativistic energies. The QGP formation is often characterized by a phenomenon called strangeness enhancement where, the relative production of strange-to-non-strange particles are enhanced in central collisions compared to peripheral or proton-proton interactions. Besides the enhancement in K/π ratios, a non-monotonic energy dependence was also reported for Λ to p ratios at CERN SPS, attributed to a signature for the strangeness enhancement as well. As anti-particles are produced directly from the reaction, the Λ/p ratios are considered as a cleaner probe for the strangeness enhancement. However, at this energy range hadronic interactions have a dominant role to play and, importantly for Λ and p, processes like baryon-anti-baryon (\mathrmBB) annihilation can have a significant impact. In this work, we use a hadronic transport model UrQMD, to investigate the role of baryon-anti-baryon (\mathrmBB) annihilation on Λ, Λ hyperon production and its effect on Λ/p ratios. The UrQMD calculations that include \mathrmBB annihilation can produce the trend of average transverse mass spectra for Λ and Λ, as well as, the characteristic enhancement in Λ/p ratios in data as a function of centrality and collision energy. Furthermore, Λ/p ratios extracted from the feed-down corrected SPS data are seen to be in good agreement with UrQMD model calculations with \mathrmBB annihilation. This suggests that Λ/p enhancement is not necessarily because of strangeness enhancement and \mathrmBB annihilation has a significant role to play.