Study of the decays Xi0_c -> Xi- pi+ pi0 and Xi+_c -> Xi0 pi+ pi+ pi- in the Belle II data

Abstract

The study of charmed baryons remains an active field of research. Although all the predicted ground states of singly charmed baryons have been measured, the spectroscopy of the doubly and triply charmed baryons states remains incomplete. Furthermore even among the measured ground states, a number of quantum numbers have not yet been conclusively determined.In this thesis, the relative branching ratios of two rarer decay modes of the two charm baryons Ξc+ and Ξc0 are measured, using data collected by the Belle II experiment at the SuperKEKB e+e- collider.In particular, data from the experiment 18 data taking period was used which had around 89.176 fb−1 of integrated luminosity taken at the Υ(4S) resonance.The decay channels studied were Ξc+ → Ξ0π+π+π− and Ξc0 → Ξ−π+π0 which were compared to the normalization modes Ξc+ → Ξ−π+π+ and Ξc0 → Ξ−π+.With the help of a Monte Carlo simulation, optimal selections and the resulting signal shape were studied and then applied to the Belle II data.The resulting relative branching ratios were determined to be 0.726 ± 0.140 (stat) ± 0.103 (sys) for the Ξc+ mode and 1.435 ± 0.106 (stat) ± 0.078 (sys) for the Ξc0 mode.The result for the Ξc+ mode differs by 1.9σ from the measurement available from the Particle Data Group taken at CLEO, which lies at 1.74 ± 0.42 (stat) ± 0.27 (sys), while the relative branching ratio for the Ξc0 represents the first measurement for this decay.