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A search for new interactions at Belle II using leptons

Project description

Pushing physics beyond the Standard Model

The Standard Model of particle physics describes the fundamental interactions and components of matter. It predicts that leptons of different generations interact in the same way. However, several recent experiments in the quark and lepton flavour sectors have shown inconsistencies regarding what we hold to be true about the Standard Model. Referred to as flavour anomalies, these deviations seem to violate the lepton flavour universality and could be the link between ordinary and dark matter. The EU-funded InterLeptons project will investigate this using data of the Belle II experiment at the Super-KEKB laboratory in Japan. Advanced techniques and deep learning tools will analyse events surrounding leptons and large missing energy in the final states to identify signals of the Belle II experiment, bringing physics one step closer to surpassing the Standard Model.


Several measurements in the quark and in the lepton flavor sectors have shown anomalies with respect to the standard model expectations and are now referred to as flavor anomalies. The Belle II experiment at the Super-KEKB laboratory in Japan is collecting data by colliding beams of electrons and positrons. The aim of this proposal is to look for physics beyond the standard model at the Belle II experiment by a) searching for the direct production of new light particles, and b) looking for deviations from theoretical predictions when performing precision tests of the standard model. The team will analyse events with leptons and large missing energy in the final states and implement the most advanced analysis techniques including, for the first time, deep learning tools in the identification of signals at the Belle II experiment. First, we will search for invisible decays of a dark Z' boson, a hypothetical particle that might also explain the anomaly reported in the anomalous magnetic moment of the muon. Second, we will test with per mille precision lepton flavor universality by studying leptonic decays of the tau lepton and use the results to constrain new physics models such as those containing a lepton flavor violating Z' boson. Finally, we will search for new physics via lepton flavor violating decays of bottomonium resonances produced in initial state radiation events that, thanks also to an effective field theory approach, will allow us to interpret the search in terms of new physics mass scale and coupling constant, with an approach complementary to that of the LHC.

Host institution

Net EU contribution
€ 1 486 137,00
1010 Wien

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Ostösterreich Wien Wien
Activity type
Research Organisations
Total cost
€ 1 486 137,00

Beneficiaries (1)