Measurement of the angular coefficients in B to D mu nu decays

Rizwaan Mohammed will have three distinct parts to their work, in addition to full participation in the Oxford graduate course during the first six months of the studentship.
The first part of the studentship will be establish, with the support of a departmental electrical design engineer a test bench for a new ultra-fast time discriminator called picoTDC. A prototype chip will be available in early 2020. An older chip call (HPTDC) is available immediately to initialise the test bench and gain some experience using LabView to gather low-level data from the chip. Once the picoTDC is delivered, characterisation studies should be complete before the 1st year viva. Afterward, the student will help construct a fast timing reference system for use in a CERN test beam. A departmental and mechanical engineer will assist this project, producing bespoke electronic boards and mechanics. The student should take intellectual responsibility for understanding the components' function, commissioning of the complete system in Oxford and providing user documentation.
The second part will be an angular analysis of the semileptonic decay, B->D*munu using a recently proposed method based on angular variables. This work will use fitting tools that have been developed by the Oxford group for a similar analysis of B->D*taunu decays; the tau mode is studied by another Oxford D.Phil. Both analyses will rely on template fitting built on TensorFlow for fast execution of fitting in multiple dimensions. Both analyses will measure a set of 11 angular coefficients in a model independent manner, as well as a model-dependant overall yield. All parameters are predicted by the Standard Model. The similarly of the analysis implementation will be key to minimising doubts and systematics. This work will use the whole Run 1+Run 2 LHCb datasets (2011-2018). The student will work closely with a post-doc at Oxford as well as a student at Manchester University who is developing the selection of B->D*munu, though not with the Oxford method in mind. The analysis should complete within 2.5 years with 50% effort, targeting the winter conference season of 2022.
The third part of the project will bring the student's timing reference system to CERN for operation in a test beam that will operate prototype silicon detectors (called "Timepix4") in 2021 and 2022. These pixel detectors are a stepping-stone to a technological solution for Upgrade II of LHCb. The big-picture purpose of the test beam will be to demonstrate with what precision a "telescope" of 4-8 Timepix4 chips can measure the passage of a particle. At least 50ps is expected with a goal of demonstrating 20ps with respect to the reference time provided by the Oxford system. The student will participate in the test beam activities with around 15 international collaborators. The principal contribution will be the integration of the Oxford system into the telescope data acquisition, and performing the calibration.
A long-term attachment (LTA) at CERN is foreseen for the test beams. This would be from July 2021 until September 2022. The student may extend this by three months. Short term travel funds will be split roughly equally between conferences and trips to Geneva in the second year. Two conferences are envisaged, one presenting physics results and the second to an instrumentation conference. The first year report (June 2020) could report on the picoTDC characterisation and design of the fast timing system and the confirmation report (January 2022) will summarise the semileptonic analysis. The final thesis should contain both hardware and physics analysis aspects of the DPhil. with a submission soon after the end of Hilary term 2023.