Nathan Jurik (Oxford)

Observation of new pentaquark candidates

Abstract: In 2015 LHCb reported a surprising observation of two pentaquark candidates using decays of the Λ_b baryon to the J/ψpK-final state. These candidates can clearly be seen as intermediate resonances decaying to J/ψp, and were characterised with an amplitude analysis followed by a model-independent study to rule out more mundane explanations. With the addition of Run 2 data and a re-optimisation of the candidate selection, the increase in statistics has revealed more surprises in this decay mode: a new, narrow peak has appeared in the J/ψp system, and one of the previous peaks has been resolved into two separate structures. In this talk, the new results will be presented along with a discussion of their implications and outlook for future studies.