First analysis of a decay with neutrons at the LHC

An investigation at the LHCb detector is conducted focused on the first analysis of a decay mode with neutrons. This is attempted by probing neutrons in the final state of the purely baryonic decay (PBD). Due to the experimental difficulty arising from the neutron not interacting with the silicon tracking system there are two proposed analysis routes to consider and ideally compare.

The decay may be modelled and analysed as a semileptonic decay with the neutron considered "missing momentum" similar to a semileptonic neutrino. Further to this a more involved analysis is attempted to study the behaviour of neutrons in the hadronic calorimeter making use of the legacy detector and software stack. This study is formulated with the goal of reconstructing neutrons by disentangling them from other hadrons in the calorimeter, in effect identifying them. It is also paramount to study sources of background.

This project constitutes the first attempted study of this decay mode, which is a significant observation pertaining to the b sector as the decay offers a predicted branching fraction of 10-4. This is at least an order of magnitude greater than typical A_b decays into charmonia which have branching fractions usually of 10-6 10-5. More generally this PhD targets the first study of purely baryonic decays with neutrons in the final state.

PBDs constitute a region of particle physics in which knowledge is currently limited as experimentally only one PBD is known. Therefore, this project offers a novel and unique window into baryonic phenomenology.