# Searching for new physics in b → sℓ$$^+$$ℓ$$^-$$ transitions at the LHCb experiment

Pescatore, L. (2016). Searching for new physics in b → sℓ$$^+$$ℓ$$^-$$ transitions at the LHCb experiment. University of Birmingham. Ph.D.

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## Abstract

Flavour Changing Neutral Currents are transitions between different quarks with the same charge such as b → s processes. These are forbidden at tree level in the Standard Model (SM) but can happen through loop diagrams, which causes the branching ratio of this type of decays to be small, typically ~ 10$$^-$$$$^6$$ or less. Particles beyond the SM can contribute in the loops enhancing the branching fractions of these decays, which are therefore very sensitive new physics. In this work two analysis of semileptonic b → sℓ$$^+$$ℓ$$^-$$decays are presented. In the first, ∧$$^0$$$$_b$$ → ∧μ$$^+$$μ$$^-$$decays are analysed to measure their branching fraction as a function of the square of the dimuon invariant mass, q$$^2$$. An angular analysis of these decays is also performed for the first time. Secondly, B$$^0$$→ K$$^*$$$$^0$$ℓ$$^+$$ℓ$$^-$$ decays are analysed measuring the R$$_k$$$$_*$$$$_0$$ ratio between the muon, B$$^0$$ → K$$^*$$$$^0$$μ$$^+$$μ$$^-$$, and electron, B$$^0$$ → K$$^*$$$$^0$$e$$^+$$e$$^-$$, channels, which is interesting as it is largely free from uncertainties due to the knowledge of the hadronic matrix elements.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Supervisor(s):
Supervisor(s)EmailORCID
Watson, NigelUNSPECIFIEDUNSPECIFIED
Licence:
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Physics and Astronomy
Funders: None/not applicable
Subjects: Q Science > QC Physics
URI: http://etheses.bham.ac.uk/id/eprint/6739

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