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Studying the most basic constituents of matter, and how they interact with each other, is the primary challenge of particle physics. Our current understanding is embodied in a mathematical description called 'the Standard Model' (SM). This has been spectacularly successful, with many measurements confirming its predictions to extraordinary precision. CERN's latest particle accelerator, the Large Hadron Collider (LHC), smashes together two beams of protons at the highest energies and rates ever observed. The past three years have proven to be very productive for the LHC, with the discovery of the Higgs boson, responsible for giving masses to particles, and the observation of the very rare decay of the Bs particle into a pair of muons, occurring at a rate compatible with the predictions from the SM. Although both of these measurements provide further confirmation that the SM is a complete description of the physical world, we know that is not the case because it provides no explanation for the relationship between the different families of particles that are seen. It also doesn't explain the nature of the 'dark matter' that is inferred to exist from astronomical observations, or the observed dominance of matter over anti-matter in the universe. A number of new models have been proposed to overcome these problems, however further measurements of high precision are required in order to confirm or refute these models.
Searches for new particles produced in collisions, are typically performed either by looking for specific decays of the new particles, which tend to be too short-lived to observe directly, or by carefully studying the properties of the decays of known particles, which should be accurately described by the SM. In the latter case, processes which occur only very rarely are particularly interesting. Such rare decays typically involve a relatively light particle decaying into another particle through a 'quantum loop'. Within such a loop, intermediate particles, that are heavier than the amount of mass-energy available from the original particle, can be briefly created, as long as they are destroyed again very quickly. This makes the processes involved very rare but allows new heavy particles in the loop to influence the decay. These heavy particles can cause very large deviations from the SM predictions of various properties of the decays. Precision measurements of the rate at which these decays occur, and of the angular distribution of the decay products, can be used to search for new heavy particles. Certain decays of B hadrons are ideal to perform such searches. In its first three years of operation, the LHCb experiment has collected around 10^10 B hadron decays with an additional 10^11 expected to be collected. This is the largest sample of B-hadron decays ever collected. Isolating a few thousands of interesting signal events in this data, from the large amount that just happen to look like signal events will be extremely challenging. The goal of my research is to perform such a separation and to use the signal decays to search for physics beyond the SM by making measurements with unprecedented precision. Even if no deviation from the SM prediction is seen, these measurements will be able to exclude the existence of certain types of new particles or new physics models. Studying these decays is therefore an essential part of the LHC research program.
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LHCb Collaboration & et al., 7 Dec 2020, In: Physical Review D. 102, 11, 33 p., 112003.
Research output: Contribution to journal › Article (Academic Journal) › peer-reviewOpen AccessFile37 Downloads (Pure)
LHCb Collaboration & Magalhaes, P., 21 Jan 2020, In: Physical Review D. 101, 1, 46 p., 012006.
Research output: Contribution to journal › Article (Academic Journal) › peer-reviewOpen AccessFile47 Citations (Scopus)90 Downloads (Pure)
LHCb Collaboration, 22 Sep 2020, In: Physical Review D. 102, 051102(R)
Research output: Contribution to journal › Letter (Academic Journal) › peer-reviewOpen Access