A hypothetical heavy charged lepton is massive enough that all of the following…

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Particles, interactions and experiment · Particles, interactions and experiment

Symmetry and Flavour, Ch Heavy flavour: charm and beauty decays and the magnitudes of the CKM elements

Problem

A hypothetical heavy charged lepton L−L^- is massive enough that all of the following channels are open and, in the spectator-model spirit used for the τ\tau lepton, equally likely: L−→νLe−νˉeL^- \to \nu_L e^-\bar\nu_e, L−→νLμ−νˉμL^-\to\nu_L\mu^-\bar\nu_\mu, L−→νLτ−νˉτL^-\to\nu_L\tau^-\bar\nu_\tau, and L−→νL uˉdL^-\to\nu_L\, \bar u d in each of three colours. ((a)) Count the equally likely channels. ((b)) Estimate B(L−→νLμ−νˉμ)\mathcal{B}(L^-\to\nu_L\mu^-\bar\nu_\mu).

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