LHCbDFEI · Design of a Deep Full Event Interpretation for LHCb and application in semitauonic B decays
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2020-10-01 → 2022-09-30
- EU contribution
- €171,473
- Participants
- 1
- Scheme
- MSCA-IF
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Results in brief
Design of a Deep Full Event Interpretation for LHCb and application in semitauonic B decays
LHCb is a particle physics experiment specialised in the study of properties and decays of heavy particles containing beauty and charm quarks, created in proton–proton collisions at the LHC. In Run 3, LHCb will collect physics events at higher rates thanks to newly installed detectors and a revolutionary software trigger that will enable LHCb to rapidly process signal data. The increase in physics reach brought by this upgrade comes at the cost of having to discriminate the interesting particles in the event from the rest at trigger time, since the amount of data produced would be too big to be stored. The higher collision rates also bring a much larger particle-combinatorics challenge than before, which motivates the development of new trigger approaches and algorithms. The current challenges will become dramatic for the foreseen Upgrade II of LHCb, in which the expected number of proton-proton collisions per event will experience an extra ten-fold increase. The EU-funded LHCbDFEI project has led to the design and development of the prototype for a new trigger algorithm, that performs a Deep-learning based Full Event Interpretation (DFEI) for the first time in LHCb. The DFEI algorithm provides an inclusive, automatic and accurate multi-signal selection per event, which potentially maximises the trigger efficiency that can be achieved. This has been made possible by systematically leveraging the correlations amongst all the reconstructed particles per event, thanks to the use of Graph Neural Networks. As a secondary complementary goal of the project, the analysis of LHCb data was done towards the measurement of quantum amplitudes of beauty-hadron decays with a tau lepton, that has important consequences for tests of the Standard Model of particle physics.
Data: CORDIS, © European Union
Project objective
The LHCb experiment has shown an excellent performance in precision measurements of beauty- and charm-hadron decays during the LHC runs 1 and 2. Now, it is undertaking its first major upgrade, to face the challenges of a large increase in instantaneous luminosity, that implies augmented event complexity and background levels. This impacts the trigger, which needs to quickly and efficiently identify signals, while facing limits on the disk storage capacity. The proposed project aims at fighting these limitations in a new way for LHCb: performing a Deep Full Event Interpretation (DFEI) during trigger, where a deep neural network processes the low-level information from the detector and infers the heavy-hadron decays that occurred in the event. This allows to quickly identify different types of background and provides enhanced information on the mother particles. As a first application of DFEI, the first angular analysis of semitauonic decays at LHCb is proposed. Semitauonic decays are partially reconstructed in LHCb, due to the presence of neutrinos in the final state. This leads to high levels of backgrounds, hard to separate from the signal, which makes them a perfect validation bench for the power of DFEI. From a physics perspective, the recently-observed flavour anomalies defy the concept of Lepton Universality of the Standard Model (SM), and point towards potential beyond-the-SM effects in semitauonic B decays. The complementary aim of this project is to perform the first LHCb angular analysis of both B0 -> D+ tau- nu and B0 -> D*+ tau- nu decays, where D*+ -> D+ pi0 and tau- -> mu- nu nu. This analysis will provide crucial information to discriminate between different new models proposed to explain the anomalies. The ambitious projects in this proposal are solidly based on my experience with semitauonic decays, angular analyses and the creation of new software tools, as well as the broad experience of the host group in event reconstruction and data analysis.
Original text from CORDIS.
Participants
- UNIVERSITA' DEGLI STUDI DI MILANO-BICOCCA · MilanoCoordinatorItaly
Links
Data: CORDIS, © European Union