Abstract

An efficient algorithm is developed for compactly weaving all the Lorentz covariant three-point vertices in relation to the decay of a massive particle $X$ of mass $m_X$ and spin $J$ into two particles $ M_{1,2}$ with equal mass $m$ and spin $s$. The closely-related equivalence between the helicity formalism and the covariant formulation is utilized so as to identify the basic building blocks for constructing the covariant three-point vertex corresponding to each helicity combination explicitly. The massless case with $m=0$ is worked out straightforwardly and the (anti)symmetrization of the three-point vertex required by spin statistics of identical particles is made systematically. It is shown that the off-shell electromagnetic photon coupling to the states $M_1$ and $M_2$ can be accommodated in this framework. The power of the algorithm is demonstrated with a few typical examples with specific $J$ and $s$ values.

Highlights

  • The Standard Model (SM) [1,2,3,4] of particle physics has been firmly established by the discovery of the spin-0 resonance of about 125 GeV mass at the Large Hadron

  • Even though a lot of high-energy experiments have searched for new phenomena beyond the SM (BSM) and they have tested the SM with great precision for decades, none of any BSM

  • We show that the massless (m 1⁄4 0) case treated previously [30] can be worked out straightforwardly and thesymmetrization of the vertex required by the spin statistics of identical particles [43] can be made systematically

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Summary

INTRODUCTION

The Standard Model (SM) [1,2,3,4] of particle physics has been firmly established by the discovery of the spin-0 resonance of about 125 GeV mass at the Large Hadron. We adopt the conventional description of the integer and half-integer wave tensors [33,34,35,36,37,38,39] and we effectively utilize the closely related equivalence between the helicity formalism in the Jacob-Wick (JW) convention [40,41] and the standard covariant formulation Their one-to-one correspondence enables us to identify every basic building block for constructing the covariant three-point vertex corresponding to each helicity combination explicitly.. Another convenient procedure for describing the three-point vertex of on-shell massive particles of any spin is to use a spinor formalism developed in Ref. [42]

CHARACTERIZATION IN THE HELICITY
SPIN-J AND SPIN-s WAVE TENSORS
BASIC COVARIANT THREE-POINT
WEAVING THE COVARIANT THREE-POINT
Bosonic three-point vertices
Fermionic three-point vertices
General form of three-point vertices
Massless case
Identical particle relation
Off-shell electromagnetic gauge-invariant vertices
VARIOUS SPECIFIC EXAMPLES
Specific decay modes
CONCLUSIONS

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