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

2026-07-22

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.

Switzerland

2026-02-15