The light meson guide to New Physics: Latest searches of rare decays using LHCb data

This thesis presents the first-ever study of the decay of a neutral kaon into four muons. Using data collected by the LHCb experiment between 2016 and 2018, no signal was found, and stringent upper limits on the branching fractions of both the short- and long-lived modes were set. They represent the...

Descripción completa

Detalles Bibliográficos
Autor: Fernández Gómez, Miguel
Tipo de recurso: tesis doctoral
Fecha de publicación:2025
País:España
Institución:Universidad de Santiago de Compostela (USC)
Repositorio:Minerva. Repositorio Institucional de la Universidad de Santiago de Compostela
Idioma:inglés
OAI Identifier:oai:minerva.usc.gal:10347/42950
Acceso en línea:https://hdl.handle.net/10347/42950
Access Level:acceso abierto
Palabra clave:mesons
kaon
LHCb
muons
particle physics
220807 Física de partículas
Descripción
Sumario:This thesis presents the first-ever study of the decay of a neutral kaon into four muons. Using data collected by the LHCb experiment between 2016 and 2018, no signal was found, and stringent upper limits on the branching fractions of both the short- and long-lived modes were set. They represent the first time either decay was experimentally studied, and to date, they are, respectively, the tightest upper limit and the first long-kaon result for an LHC experiment. Additionally, the study of four decays of eta and eta prime mesons are presented. The thesis introduces the first-ever study of the eta prime decaying into a pair of muons, as well as significant improvements on the precision of the branching fractions of the di-muon decay of the eta. Significant improvements on the branching fraction measurement of the eta prime meson decaying into two muons are presented, as well as a new study of the eta meson decaying into two pions and two muons.