Test of lepton flavour universality in rare beauty-quark decays using the LHCb detector
File(s)
Author(s)
Herd, James
Type
Thesis
Abstract
Among the fundamental particles that comprise the Standard Model, the three charged leptons -- the electron, muon, and tau -- are identical except for their interactions with the Higgs boson, which determines their differing masses. This symmetry, known as lepton flavour universality, leads to the prediction that the ratio of branching fractions for the decays 𝐵+ → 𝐾+𝜇+ 𝜇− and 𝐵+ → 𝐾+ 𝑒 + 𝑒 − should be unity, with a theory uncertainty at the sub-percent level. This thesis presents the most precise measurement of the ratio of these branching fractions, denoted as 𝑅 𝐾 , in the dilepton invariant mass squared (𝑞 2 ) region above the 𝜓(2𝑆) resonance. It represents the first measurement involving such decays in the 𝑞2 region above the 𝜓(2𝑆) resonance using data from a hadron collider.
Version
Open Access
Date Issued
2025-04-20
Date Awarded
01/10/2025
License URL
Advisor
Patel, Mitesh
Publisher Department
Department of Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)