Speaker
Description
In this talk I will present ongoing work towards a more precise and unified description of heavy-flavour decays in Sherpa, combining modern form-factor parameterisations with QED radiative corrections.
On the hadronic side, I am implementing Boyd-Grinstein-Lebed (BGL) form factors for a set of benchmark channels: heavy-to-light pseudoscalar and vector decays ($B \to \pi, K, \rho, K^\ast$), heavy-to-heavy modes ($B \to D^{(\ast)}$), and selected baryonic decays such as $\Lambda_b \to \Lambda^{(\ast)}\ell\ell$. The aim is to provide a consistent, model-independent treatment across meson and baryon channels, using analyticity- and unitarity-based constraints in the BGL framework.
On the radiative side, I will switch on Yennie-Frautschi-Suura (YFS) resummation in these decays to quantify the impact of QED final-state radiation on key observables: dilepton invariant-mass spectra, angular distributions, and form-factor-sensitive kinematic variables. I will show first comparisons between "bare" and lepton-dressed definitions and discuss how QED effects propagate into quantities relevant for flavour fits.
Finally, I will outline planned extensions of the QED machinery in Sherpa, including more flexible treatments of radiation off hadronic currents and possible structure-dependent corrections, and comment on how this programme can interface with lattice inputs and experimental analyses at LHCb and Belle~II.
