Λ b →Λ ℓ + ℓ - form factors, differential branching fraction, and angular observables from lattice QCD with relativistic b quarks

By William Detmold, S. Meinel. 2016

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Using ($2+1$)-flavor lattice QCD, we compute the 10 form factors describing the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}$ matrix elements of the $b\ensuremath{\rightarrow}s$ vector, axial vector, and tensor currents. The calculation is based on gauge field ensembles generated by the RBC and UKQCD Collaborations with a domain-wall action for the $u$, $d$, and $s$ quarks and the Iwasaki gauge action. The $b$ quark is implemented using an anisotropic clover action, tuned nonperturbatively to the physical point, and the currents are renormalized with a mostly nonperturbative method. We perform simultaneous chiral, continuum, and kinematic extrapolations of the form factors through modified $z$ expansions. Using our form factor results, we obtain precise predictions for the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}(\ensuremath{\rightarrow}{p}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}){\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ differential branching fraction and angular observables in the Standard Model.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d1a77c1591cc45a2985e18074306589a971d02df