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Challenging the Standard Model with suppressed b to d l+l- decays

Project description

Discovering new physics in rare b quark decays

Rare particle decays boost evidence for new physics beyond the Standard Model. Although it has predicted the outcome of countless experiments in particle physics with remarkable accuracy, it cannot account for the observed b quark decays into an s quark and two leptons (b to sll transition). The ERC-funded CLIMB project will study the b quark decays into a d quark and two leptons (b to dll transition), which are far more poorly known. Specifically, researchers will investigate whether the deviations observed in the b to sll transition also occur in the b to dll transition. Furthermore, they will probe the existence of a new form of matter-antimatter asymmetry in the b to dll transition.

Objective

The Standard Model (SM) of particle physics is one of the most complete theories in science with a hugely successful predicting power. However, it is unable to explain critical observed phenomena, such as the dominance of matter over antimatter in the universe, and thus needs to be extended. Rare decays of b quarks to an s quark and two leptons (b to sll) are very sensitive to the existence of New Physics (NP). Recent measurements of their properties show intriguing deviations with respect to SM predictions that could be the first clear hint of NP in decades. In this project, I will explore the related and even more suppressed b-quark decays to a d quark and two leptons (b to dll), which are so far poorly known and will shed light on the type on NP that could explain the observed discrepancies. For this purpose, my team will develop innovative analysis tools and exploit the uniquely large sample of b hadrons from the LHCb experiment.

The CLIMB project will address two specific questions: are the deviations observed in b to sll decays also present in b to dll transitions? Are there new sources of matter-antimatter asymmetry beyond the SM in b to dll processes?
The first will be addressed by measuring differential decay probabilities and lepton universality ratios in b to dll decays for the first time.
In the SM, these transitions are related by the quark-mixing matrix, the hierarchy of which is not fully understood. NP models aim to provide an explanation for the structure observed in nature. Knowing the properties of b to dll decays precisely is a critical input in this endeavour.
The second question will be answered by measuring matter-antimatter asymmetries in b to dll decays with unprecedented precision, providing very strong constraints to NP models predicting an enhanced quantity. The main challenge of this programme lies in the study of very suppressed decays. Innovative reconstruction and selection techniques will be developed to access them.

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(opens in new window) ERC-2022-STG

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Host institution

UNIVERSITAT DE BARCELONA
Net EU contribution

Net EU financial contribution. The sum of money that the participant receives, deducted by the EU contribution to its linked third party. It considers the distribution of the EU financial contribution between direct beneficiaries of the project and other types of participants, like third-party participants.

€ 1 622 273,00
Address
GRAN VIA DE LES CORTS CATALANES 585
08007 BARCELONA
Spain

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Region
Este Cataluña Barcelona
Activity type
Higher or Secondary Education Establishments
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Total cost

The total costs incurred by this organisation to participate in the project, including direct and indirect costs. This amount is a subset of the overall project budget.

€ 1 622 273,00

Beneficiaries (1)

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