The search for lepton flavour violation in very rare decays of heavy mesons and the prototyping of the TORCH sub-detector

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This student will work on searches for new physics in heavy flavour observables and on the development of the TORCH project. TORCH (Time Of internally Reflected CHerenkov light) is a novel Time-of-Flight detector to identify charged particles. The application is for an upgrade of the LHCb experiment, where it would supplement the particle identification at low momentum. In order to reach three sigma separation between pions and kaons up to 10 GeV/c over a nominal flight path of 10m, a time resolution of ~15ps per track is required, given ~30 photons per track. The student will work on a prototype half-sized TORCH module of area 66x125x1cm^3. He will take data at the PS testbeam at CERN and then analyse the complex photon patterns to separate pions and protons, striving to reach the required timing accuracy of 70ps per photon and a spatial resolution of around a 100 microns. He will test in the laboratory industry-fabricated micro-channel plate detectors (MCP-PMTs) which use a novel charge division technique, read out by customised electronics which have been developed in Oxford. This project is unique opportunity for the D.Phil student as it is leads the concept of dealing with high luminosities through the use of sub-nanosecond timing information in event reconstruction.The physics topics for this student will concentrate on rare decays used to probe for new physics effects in the light of the intriguing evidence of unexplained effects from LHCb in final states involving leptons. Several decay modes are currently being considered and an important part of the first year project will be to evaluate the viability of these avenues. The novel focus will be on final states involving a mixture of hadrons and leptons in flavour configurations that are highly suppressed, or forbidden in the SM. A key idea will be using final states with two lepton of different flavour for which no mechanism exists in the the SM but is a hallmark of leptoquark models, for example. The work will evaluate the potential sensitivity to these signatures in LHCb, and the LHCb upgrade. Consideration will also be given to lepton flavour violation without hadrons by looking for the mu-tau final state from B, J/psi or Upsilon decays. Finally, and along the same theme, the student will conduct a search for electroweak penguins in Bc decays. Following our group's discovery of large non-tree amplitudes contributing to hadronic decays of the Bc meson, it is of interest to search for enhanced electroweak penguins.