Kinematic Edges with Flavor Oscillation and Non-Zero Widths

TL;DR

This paper explores how flavor oscillation and particle widths affect kinematic edges in cascade decays, providing formulas and analysis relevant for identifying new particles in physics experiments.

Contribution

It introduces explicit formulas for decay rates that incorporate both flavor oscillation and non-zero widths, highlighting their combined effects in certain mass regimes.

Findings

Oscillation and width effects are significant when mass differences are comparable to widths.

Derived explicit formulas for scalar and fermion intermediate particles.

Analyzed how these effects influence observable decay spectra.

Abstract

Kinematic edges in cascade decays provide a probe of the masses of new particles. In some new physics scenarios the decay chain involves intermediate particles of different flavors that can mix and oscillate. We discuss the implication of such oscillation, and in particular its interplay with the non-zero widths of the particles. We derive explicit formulae for differential decay rates involving both non-zero widths and oscillation, and show that in the case where the mass difference between the intermediate particle is of the order of their widths, both oscillation and width effects are important. An examination of the physical observables contained in these differential decay rates is provided. We calculate differential decay rates for cases in which the intermediate particles are either scalars or fermions.