Quark Flavour

Physics Analysis

Analysis activities led by the Manchester group include precise measurements of standard model observables such as neutral meson oscillations, determination of CP violation parameters in beauty and charm mesons, and measurements of semileptonic and rare processes involving beauty and charm hadron decays. The group’s work has been instrumental in the 2019 landmark discovery of CP violation in charm decays. Our CP violation studies with beauty hadrons focus on three areas: searches for CP violation in baryons, measurements of semileptonic CP asymmetries, and CP violation measurements of B hadron decays to final states involving charm hadrons. Many of these are sensitive to the CKM angle gamma, but we also exploit these final states to determine other parameters. Some of the measurements within our group are performed exploiting synergies with the BESIII experiment.
Another area of significant interest within the group are measurements using semi-leptonic decays of charm and B hadrons, which primarily focus on tests of lepton universality, a fundamental principle of the Standard Model that has seen increasing tensions in a number of recent measurements. Among rare decays our general focus is on lepton-flavour violating processes, which we study in tau lepton decays as well as in B and charm hadron decays to a mixture of electrons and muons. A recent study of charm decays led to over 20 world-best limits.

Detector

Manchester has made a number of contributions to the original (2010-2018) and upgraded (2022-) Pixel Vertex Locator (VELO) detector design, commisioning and operation. Our group has carried out the assembly of the individual modules of the Pixel Vertex Locator, the highest precision detector at the LHC. The modules are based on 55 by 55 micron pitch silicon pixel sensors. They use an innovative micro-channel cooling system using liquid CO2. Commisioning and operations activities include monitoring the data quality, studies of radiation damage effects and studies of the data reconstruction and simulation performance.

R&D activities for future upgrades within the group include a new semiconductor detector to be used in the innermost regions of the tracking stations following the LHCb dipole magnet, and a novel vertex detector that in addition to high position resolution can also deliver precise timing information. This requires an ambitious R&D project to deliver a system that can cope with a factor ten more particles compared to the LHCb Pixel VELO.

Software and computing

Our group drives innovation of analysis methods. We have been the first to exploit Graphical Processing Units (GPUs) in an LHCb analysis and have pioneered a fast simulation method that is now responsible for most simulated events in LHCb. In addition, we have had leading involvement in LHCb’s Real-Time Analysis from the outset and remain committed to driving novel analysis approaches. We also have a leading role in the implementation of LHCb’s real-time trigger, alignment and calibration system, which is a novel approach that permits the acquisition of ready-for-analysis data straight out of the detector, as well as in the data processing and analysis project.