Unitarity bounds with subthreshold and anomalous cuts for b -hadron decays
Year: 2025
Type: article
Abstract: We derive a generalization of the Boyd-Grinstein-Lebed (BGL) parametrization. Most form factors (FFs) in b -hadron decays exhibit additional branch cuts—namely subthreshold and anomalous branch cuts—beyond the “standard” unitarity cut. These additional cuts cannot be adequately accounted for by the BGL parametrization. For instance, these cuts arise in the FFs for B → D ( * ) , B → K ( * ) , and Λ b → Λ processes, which are particularly relevant from a phenomenological standpoint. We demonstrate how to parametrize such FFs and derive unitarity bounds in the presence of subthreshold and/or anomalous branch cuts. Our work paves the way for a wide range of new FF analyses based solely on first principles, thereby minimizing systematic uncertainties.
Authors: Abinand Gopal, Nico Gubernari
Institutions: University of California, Davis, University of Cambridge
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4407320573