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Testing leptOn Flavour Universality in excited strange mesons

Project description

A novel test of the Standard Model could negate lepton universality

The Standard Model of particle physics developed in the 1970s is anything but 'standard'. It describes what everything in our universe is made of and what holds it together – the elementary matter particles and the force particles mediating their interactions. While it is our most complete description, it still does not describe everything and is continuously updated as new information becomes available. Matter particles consist of six quarks and six leptons. Recent experiments suggest that not all leptons have the same couplings to forces, referred to as 'lepton universality', as was previously believed. The EU-funded TOFU project is developing a protocol for the Large Hadron Collider beauty experiment using particle decays with products that are easier to distinguish with certainty. If these experiments support the previous ones, the Standard Model will get its latest update.

Objective

Our understanding of all known particles and their interactions is successfully described in the Standard Model (SM). It is, however, known to be incomplete since it does not explain e.g. dark matter, or the matter-antimatter asymmetry in the universe. Recently, several experiments found hints of physics beyond the SM, which must be further investigated.

A key assumption of the SM is that leptons (electrons and their heavier siblings, muons and taus) have the exact same couplings to forces, called lepton universality. When testing this assumption using decays of so-called B mesons, three independent experiments found increased values for their decay rate to a D meson and tau lepton, compared to a D meson and a muon. This could be explained by the existence of new particles, such as leptoquarks, which couple more strongly to leptons with a higher mass.

This proposal concerns a similar measurement using strange B mesons (Bs), which decay into strange D mesons (Ds). The D mesons that were measured before are extremely difficult to distinguish from their so-called resonance states, which are excitations of the D meson. Misidentifying these could wrongly increase the rate of tau decays of all three experiments. Ds mesons, on the other hand, have a different structure of resonances, and fewer exist that can mimic the signal. Additionally, these can be constrained using their well-defined kinematics. As such, an observation of non-universality in the Bs meson decays would provide conclusive evidence for the existence of physics beyond the SM.

In 2021, the LHCb experiment will recommence data-taking with a completely new detector and reconstruction software. Dr. Klaver plays a key role in studying the impact of misaligned or misplaced detectors and detector defects of the upgrade detector. This proposal describes how a validation framework is to be set up to aid the commissioning of the new experiment. This secures future tests of lepton universality with high precision.

Fields of science (EuroSciVoc)

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Funding Scheme

MSCA-IF - Marie Skłodowska-Curie Individual Fellowships (IF)

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Call for proposal

(opens in new window) H2020-MSCA-IF-2019

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Coordinator

STICHTING NEDERLANDSE WETENSCHAPPELIJK ONDERZOEK INSTITUTEN
Net EU contribution
€ 175 572,48
Total cost
€ 175 572,48