Phenomenology of Λ b → Λ c τ ν ¯ τ Λb→ Λcτ ν̄τ using lattice QCD calculations

In a recent paper we studied the effect of new-physics operators with different Lorentz structures on the semileptonic Λb→ Λcτ ν̄τ decay. This decay is of interest in light of the R(D (*)) puzzle in the semileptonic B̄→ D( )τ ν̄τ decays. In this work we add tensor operators to extend our previous results and consider both model-independent new physics (NP) and specific classes of models proposed to address the R(D (*)) puzzle. We show that a measurement of $$ R({Λ}_c)={B}[{Λ}_b→ {Λ}_cτ {ν̄}τ]/{B}[{Λ}_b→ {Λ}_c {ν̄}_{}] $$ can strongly constrain the NP parameters of models discussed for the R(D (*)) puzzle. We use form factors from lattice QCD to calculate all $$ {Λ}_b→ {Λ}_cτ {ν̄}τ $$ observables. The Λ b → Λ c tensor form factors had not previously been determined in lattice QCD, and we present new lattice results for these form factors here.