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Model-independent angular analysis of semileptonic B meson decays involving tau leptons

Project description

Measurements of key parameters during tau lepton decay could point to new physics

The Standard Model of particle physics, developed in the 1970s and having changed little since then, posits that the universe is made of 12 elementary matter particles, six quarks and six leptons. The best-known lepton is the electron, negatively charged and with a very small mass. There are two more negatively charged leptons, the muon and the tau, with much larger masses than the electrons, and three neutral neutrinos. A key assumption of the Standard Model is that the interactions of charged leptons differ due to their mass variability. Recent studies of B meson decays involving the tau lepton challenge that notion. The EU-funded B2DTauNu project is conducting pioneering measurements of important properties of semileptonic B meson decays involving tau leptons from experimental data. The results could pave the way for enhanced high-precision measurements in the future, with implications for the Standard Model and our understanding of the universe.

Objective

The project will characterise the physics of semileptonic b -> c tau nu quark transitions, by studying the angular properties of B -> D(*) tau nu meson decays. The branching fractions of B -> D(*) tau nu decays are measured to be larger than expected relative to their B -> D(*) mu nu counterparts, offering an intriguing hint of beyond the Standard Model (SM) physics in the form of lepton universality violation. Due to the spin structure of B -> D(*) tau nu decays, the full decay rate is described by a sum of twelve angular terms each with a corresponding coefficient. The values of these coefficients can be altered by New Physics (NP) operators such as charged Higgs bosons, Z' bosons, or leptoquarks, and measuring their values thus provides a powerful probe to search for deviations from the SM.
The project will use LHCb Run 1 and 2 data to measure the B -> D(*) tau nu angular coefficients and signal yields in a model-independent manner, making use of novel binned template fit methods that fully account for resolution effects caused by the missing neutrino information. The measurements made will be a ground-breaking proof-of-principal, paving the way for high-precision angular coefficient measurements in future.

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Topic(s)

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Funding Scheme

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

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Call for proposal

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

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Coordinator

ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE
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.

€ 203 149,44
Address
BATIMENT CE 3316 STATION 1
1015 LAUSANNE
Switzerland

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Region
Schweiz/Suisse/Svizzera Région lémanique Vaud
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.

€ 203 149,44
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