Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays

In the semileptonic decays of heavy mesons and baryons, lepton-mass dependence factors out in quadratic ${\mathrm{cos}}^{2}\ensuremath{\theta}$ coefficient differential $\mathrm{cos}\ensuremath{\theta}$ distribution. We call corresponding normalized convexity parameter. This observation opens path to a test lepton universality meson baryon that is independent form-factor effects. By projecting rate coefficient, dividing lepton-mass-dependent factor, restricting phase space integration $\ensuremath{\tau}$ space, one can define optimized partial rates which, Standard Model, are same for all three $(e,\ensuremath{\mu},\ensuremath{\tau})$ modes given decay process. discuss how identity spoiled by new physics such as ${\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{(*)+}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ ${B}_{c}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}({\ensuremath{\eta}}_{c}){\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ each $\ensuremath{\ell}=e$, $\ensuremath{\mu}$, $\ensuremath{\tau}$.