DEVELOPING a NEXT GENERATION TRACKER and STUDYING CHARM PHYSICS at LHCb (2019)
Co-supervisors: PPD: F. Wilson, Manchester - C. Parkes
The LHCb Collaboration is planning a new quark flavour physics experiment for the HL-LHC, an Upgrade II. You will work on the development of novel radiation hard CMOS detectors for the tracking detectors of LHCb but with the potential for application to a range of other experiments. You will undertake testing of prototype detectors along with simulation and layout and performance optimisation studies. You will also work on the study of charm quark physics using the unprecedentedly large data sample collected by LHCb from 2011-2018, potentially in the area of rare decays which are suppressed or forbidden in the standard model but can occur in new physics scenarios or undertake one of the first searches for matter anti-matter differences in charm baryon decays.
BEAUTY MESONS as a PROBE of NEW PHYSICS (2020)
Co-supervisors: PPD: S. Ricciardi, University of Edinburgh - Prof F. Muheim
For this studentship special conditions are available. International students are eligible for this studentship, which will cover all fees, stipend, and other related costs of the PhD.
The LHCb experiment recently (Oct 2020) announced the first observation of time-dependent CP violation in the strange-beauty (Bs0 ) meson, through decays into a pair of kaons, Bs0 -> K+K. This result achieved a further milestone in the field of CP violation. The asymmetry between matter and antimatter requires that CP violation exists between particles and antiparticles, but the Standard Model (SM) prediction for this effect falls short by nine orders of magnitude. New physics beyond the SM must exist and can be probed with beauty mesons. This opens up exciting prospects of additional studies in B0 and Bs0 mesons, both in the Run 1-2 data sample already collected by the LHCb experiment, and in the upcoming Run 3 period in which the LHCb experiment
will use an almost entirely new detector.
In this project, the student will study the B0 and Bs0 meson systems in decays which are sensitive to the same underlying CP-violating processes, and provide key measurements to test the standard model of particle physics. Building on the well-established expertise and tools developed by the Edinburgh group, the student will reconstruct and study the time dependence of B -> J/Psi X decays. This will open up, for example, the possibility to measure the lifetime difference between B0 meson mass eigenstates (d), an important outstanding measurement from LHCb which is sensitive to new physics in B0 decays. The student will primarily focus on analysing Run 2 data, and in particular, will help to develop new favour tagging tools which can significantly boost the sensitivity of a wide range of CP violation measurements. Improving the tagging power by a factor of 2, which is feasible through a total event tagger and the use of multivariate machinery, would be the equivalent of doubling the data sample, giving a large gain in precision. The student will also work on preparing for the Run 3 data collection period and use their experience from the Run 2 data analysis and tagging algorithms to validate the early Run 3 data.
The student will also work on detector hardware for future LHCb upgrades. Excellent discrimination among pion, kaons and protons, referred to as particle identication (PID), is essential for flavour tagging. The PID provided by the Ring Imaging Cherenkov (RICH) system has been central to the success of LHCb. The student will contribute first to the commissioning of the newly installed RICH photon detectors and then to RICH operation during the upcoming Run 3 data. To operate at higher luminosities, however, the RICH system needs to be redesigned. A significant R&D programme is needed to produce a photon detector with sufficient timing capabilities, able to operate with low noise in the harsh radiation environment and with sufficiently fine granularity to cope with the expected occupancy. Silicon Photo Multipliers (SiPMs) are the baseline choice for the future detector upgrade. Recent progress in SiPMs technology motivates a vigorous R&D programme, starting in 2021, to develop efficient and fast single-photon capable devices. The student will contribute to the characterization of SiPMs at RAL, where a dedicated lab is being set up to lead the UK R&D on the use of SiPMs in LHCb.
This project offers a combination of crucial detector development activities and an analysis programme which could lead to several high-impact publications. Both aspects are ideally suited to the experience and interests of the RAL and Edinburgh LHCb groups.
DEVELOPMENT of RICH DETECTORS for LHCb PHASE2 UPGRADE (2020)
Co-supervisors: PPD: S. Easo, Cambridge - S. Wotton
LHCb has two RICH detectors for identifying hadronic particles created in p-p collisions at the LHC. These detectors are being upgraded to collect data at a readout rate of 40 MHz and to cope with a fivefold increase in occupancies expected from the beam conditions in LHCb during the HL-LHC time period.
The first phase of this upgrade is being completed and the new detector system will be commissioned for RUN3 during the next couple of years. This will use MaPMTs as photon detectors. Simulations have shown that signal-time gating can reduce the backgrounds and improve particle identification performance. Hence the readout is expected to have a signal time-gating at the level of a few nanoseconds, and this will be an unprecedented feature of the LHCb readout.
The R&D for a second major upgrade has started. Simulations show that the RICH designed for the phase 1 upgrade will have occupancies exceeding 100% in phase 2 upgrade beam conditions. In order to avoid this, one needs to record both the time and space coordinates of single photons with much better precision than what is foreseen for RUN3. This will include testing new radiators, improving the optical configuration and developing novel photon detectors with fast timing at the level of about 100 picoseconds. This has been motivated by recent advances in SiPM technology. Such photon detectors may need to be operated at cryogenic temperatures for detecting single photons. This development will also require upgraded versions of readout chips such as the 'CLARO' or 'TimePix4', along with advances in the digital readout system.
The project plan for the student would be to expand on the simulation studies and validate the results using tests on prototypes. The student will be expected to have an aptitude for software development using C++ and will be working on the hardware for a modern data acquisition system. The laboratory facilities for performing various tests are expected to be available at CERN and there is already a setup at CERN dedicated to the verification of the readout timing for RUN3. Further validations will be done using beam tests on prototypes at a later stage. The student will be integrated with a small team working at CERN and Cambridge on this project.
