Martín Novoa-Brunet — Page 2

arXiv2020

Angular analysis of the rare decay $Λ_b\to Λ(1520)(\to NK)\ell^+\ell^-$

We study the differential decay rate for the rare decay $Λ_b\to Λ(1520)(\to NK)\ell^+\ell^-$ where $\ell$ is a light lepton, as this decay mode can provide new and complementary constraints on the Wilson coefficients in $b\to s\ell^+\ell^-$ transitions compared to other modes. We provide a determination of the complete angular distribution, assuming unpolarised $Λ_b$ baryons and neglecting the lepton mass. The resulting angular observables are expressed in terms of helicity amplitudes involving hadronic form factors within the Standard Model and New physics models with chirality-flipped operators. We study these observables at low and large $Λ$ recoils, using effective theories to determine relations among the hadronic form factors involved. As there is currently no determination of the form factors available from lattice simulations or light-cone sum rules, we perform a first illustration of the sensitivity of some observables to New Physics contributions using hadronic inputs from quark models.

hep-ph↗

arXiv2020

Implications of $b\to sμμ$ Anomalies for Future Measurements of $B \to K^{(*)} ν\bar ν$ and $K\to πν\bar ν$

We investigate the consequences of deviations from the Standard Model observed in $b\to sμμ$ transitions for flavour-changing neutral-current processes involving down-type quarks and neutrinos. We derive the relevant Wilson coefficients within an effective field theory approach respecting the SM gauge symmetry, including right-handed currents, a flavour structure based on approximate $U(2)$ symmetry, and assuming only SM-like light neutrinos. We discuss correlations among $B \to K^{(*)} ν\bar ν$ and $K\to πν\bar ν$ branching ratios in the case of linear Minimal Flavour Violation and in a more general framework, highlighting in each case the role played by various New Physics scenarios proposed to explain $b\to sμμ$ deviations.

hep-ph↗