Start seminar by Roman Sultanov and William Lejon: The charm of baryon decays

Abstract: Why does our visible universe consist of so much matter, but almost no antimatter? How does the strong interaction form massive hadrons from the almost massless quarks? These two questions may seem disparate, but are connected through a common diagnostic tool: strange hyperons, and baryons containing charm quarks. While hyperons have been extensively studied by the Uppsala BESIII group, we now focus on the heavier charm baryons. The Belle II experiment at the B-factory SuperKEKB in Tsukuba, Japan produces equal amounts of heavy baryons and antibaryons in controlled, parameterizable processes. Furthermore, the versatile and almost hermetic Belle II detector enables the reconstruction of almost all produced particles; charged as well as neutral. This makes Belle II a unique tool to study the rich decay patterns of charm baryons and antibaryons. However, the multi-step and multi-body decays require sophisticated analysis methods which account for the complex interplay between electromagnetic, weak and strong interactions, in particular intermediate resonances. In addition, charm baryons and their decay products give rise to complicated detector signatures, involving charged as well as neutral particles, and often several displaced vertices. In this start seminar, we will address both the underlying questions, give a flavour of the complexity of charm baryon decays, and discuss novel methods to reconstruct the decay chains of charm baryon decays in the Belle II detector.