HEIndividual fellowship2023–2025

RAD TORCH · Rare decays of heavy mesons to resonant channels

Horizon Europe — Marie Skłodowska-Curie Actions

Duration: 2023-11-01 → 2025-10-31
EU contribution: €210,789
Participants: 1
Scheme: HORIZON-TMA-MSCA-PF-EF

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Results in brief

Rare decays of heavy mesons to resonant channels

Measurements of rare decays of kaons, pions and heavy mesons have become powerful tools to search for new physics beyond the Standard Model. To fully exploit these measurements, experiments such as LHCb require precise theoretical predictions of the underlying strong-interaction effects. These can only be computed using large-scale numerical simulations of Quantum Chromodynamics (QCD) on a space–time lattice. The objective of this project was to develop and apply advanced lattice-QCD methods to study processes that involve unstable, strongly interacting particles in the final state. The project focused on the resonant form factors that determine rare decays such as B→K*ℓ+ℓ−. These quantities are key inputs for interpreting experimental searches for new physics in the flavour sector. By improving both the methodology and the computational tools, the project aimed to contribute to the long-term precision programme of flavour physics in Europe.

Data: CORDIS, © European Union

Project objective

Reliable and precise Standard Model predictions are becoming increasingly important in searches for new physics as the gap closes between experiment and theory. At CERN I will perform the first physical-quark-mass calculation of resonant form factors, including B → K*. This will allow future analyses of the LHCb data set to give significantly stronger probes of flavour non-universality and pave the way to discover new physics from the current 2.5σ tension in the R(K*) ratio of branching fractions observed at LHCb.Access to those form factors can be gained by studying rare decay processes like B→K* ℓ+ ℓ− . These processes, which involve neutral-current b→s quark transitions, are forbidden at tree level in the Standard Model. The resonant final state poses a particular challenge on the lattice due to its Euclidean formalism, which requires a careful study of the finite volume spectrum which can be related to pion-kaon asymptotic scattering states. The computational strategy is the distillation technique, which projects computationally expensive propagators into a subspace to be re-used efficiently. I have written high-performance-computing (HPC) code for distillation as part of the lattice QCD softwares Grid and Hadrons. This is free, open-source and runs in data production on various computing architectures, including GPU-based ones.The other main challenge of the computation of B → K* form factors is the treatment of the heavy-quark on the lattice. My work on B-meson mixing has demonstrated the viability of using a fully relativistic action for the heavy quark with fully controlled systematic errors. The combination of the careful treatment of the resonant effects and the innovative approach to incorporate the heavy quark will be essential to advance the precision physics goals in the B-sector, as well as provide the platform to study other related processes like Kγ → Kπ from QCD.

Original text from CORDIS.

Participants

ORGANISATION EUROPEENNE POUR LA RECHERCHE NUCLEAIRE · GENEVE 23CoordinatorSwitzerland

RAD TORCH · Rare decays of heavy mesons to resonant channels

Results in brief

Rare decays of heavy mesons to resonant channels

Project objective

Participants

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