RECEPT researchers used LHCb data to measure lepton universality between electrons and muons in decays of particles containing a “beauty” quark, called beauty mesons. Previous results from both LHCb and other experiments indicated potential deviations from the Standard Model of particle physics in these processes. In order to pave the way for these lepton universality tests, RECEPT researchers developed a method for measuring the efficiency of detecting single electrons in LHCb data, similarly to techniques which already existed for muons. The RECEPT team subsequently performed the world's most precise measurement of electron-muon universality in processes where beauty mesons decay to pairs of leptons and a meson containing a strange quark. Experimental techniques developed by the RECEPT team and our international collaborators meant that this measurement was significantly more sensitive, all other things being equal, compared to previous LHCb measurements of the same quantities. Unfortunately our analysis also uncovered the presence of additional backgrounds, caused by processes in which hadrons mimic electrons in the LHCb detector, which had been neglected in previous LHCb analyses of this kind. Once these backgrounds were properly taken into account by our analysis, the results were in very good agreement with the predictions of the Standard Model, as shown in the included figure.
RECEPT’s researchers also play a crucial role in the upgrade of LHCb, which will increase the data volume 100 times, allowing much more precise SM tests and searches for new particles and forces. In order to take full advantage of this, LHCb will have to process around 30 million collisions per second, corresponding to around 4 Terabytes of data per second, not only tagging individual LHC collisions as "interesting" but finding the trajectories of particles produced in such collisions and inferring their fundamental physical properties in real time. Such a data volume is equivalent to over one percent of today's global internet traffic, and must be processed in a data centre located close to LHCb, using only around 3000 computer servers. The RECEPT team has developed high-performance algorithms for both CPU and GPU computing architectures which have been shown to be able to meet this challenge. A particular highlight has been the development of "Allen", a complete framework for high-throughput processing on GPUs, which was adopted by the LHCb collaboration in 2020 and put into production by the RECEPT team and our international collaborators in time for the restart of LHCb datataking in 2022. During 2022 and 2023 RECEPT researchers were able to show that the first-level real-time processing of the LHCb experiment, now implemented using Allen on around 400 GPU cards, worked as planned. This is illustrated by the figure showing pairs of particles containing strange quarks, called K-short mesons, reconstructed in real time by the Allen GPU system in 2022 LHCb datataking.
