Standard Model predictions for B → Kl +l- , B- → Kl1-l2+ and B → Kν(ν)over-bar over line using form factors from Nf=2+1+1 lattice QCD

We use HPQCD's recent lattice QCD determination of B -> K scalar, vector and tensor form factors to determine Standard Model differential branching fractions for B -> Kl (+)l(-) , B- -> Kl(1)(-)l(2)(+) and B -> K nu(nu) over bar over bar . These form factors are calculated across the full q(2) range of the decay and have smaller uncertainties than previous work, particularly at low q(2). For B -> Kl(+)l(-) we find the Standard Model branching fraction in the q(2) region below the squared J/psi mass to exceed the LHCb results, with tensions as high as 4.7 sigma for B+ -> K+mu(+)mu(-). For the high q(2) region we see 3 sigma tensions. The tensions are much reduced by applying shifts to Wilson coefficients C-9 and C-10 in the effective weak Hamiltonian, moving them away from their Standard Model values consistent with those indicated by other B phenomenology. We also update results for lepton-flavor ratios R-e(mu) and R-mu(tau) and the flat term, FeH in the differential branching fraction for l is an element of{e; mu;tau}. Our results for the form-factor dependent contributions needed for searches for lepton-flavor violating decays B -> Kl(1)(-)l(2)(+) achieve uncertainties of 7%. We also compute the branching fraction B(B -> K nu(nu) over bar) with an uncertainty below 10%, for comparison with future experimental results.

Automated summary

Using HPQCD's recent lattice QCD determination of B -> K scalar, vector and tensor form factors, we calculate the Standard Model differential branching fractions for B -> Kl(+)/l(-), B- -> Kl(1)(-)/l(2)(+) and B -> K nu(nu) over bar over bar. Our results have smaller uncertainties than previous work, especially at low q(2). We find tensions between our results and the LHCb results in the low q(2) region, but these tensions can be reduced by adjusting the Wilson coefficients of the effective weak Hamiltonian.