Vector currents of integer-spin Majorana particles

TL;DR

This paper provides a comprehensive covariant analysis of vector currents involving massive integer-spin particles, especially Majorana bosons, including their couplings, symmetry constraints, decay processes, and angular correlations.

Contribution

It introduces a full analytic framework for vector currents of arbitrary integer-spin Majorana particles, incorporating symmetry constraints and decay analysis in a covariant formalism.

Findings

Derived analytic expressions for decay angular correlations.

Identified constraints on couplings due to CP and Majorana conditions.

Numerical exploration of spin scenarios for vertex structure probing.

Abstract

A general and comprehensive analysis for the vector currents of two massive particles, $X_2$ and $X_1$, with arbitrary integer-spin values is given. Our special focus is on the case when two particles are charge self-conjugate, i.e. Majorana bosons. The general structure of their couplings to an on-shell or off-shell vector boson $V$ is described in a manifestly covariant way and then the constraints on the triple vertex due to discrete CP symmetry and the Majorana condition of two particles being Majorana are worked out. The validity of our full analytic investigation is checked by studying the two-body decay, $X_2\to V X_1$, with an on-shell or off-shell $V$ boson in the helicity formalism complementary to the covariant formulation. Threshold effects of the two-lepton invariant-mass and polar-angle correlations in the two sequential two-body decays, $X_2\to V X_1$ and $V\to \ell^-\ell^+$ with $\ell=e$ or $\mu$, are derived analytically in a compact form by use of the Wick helicity rotation and they are investigated numerically in a few specific spin-combination scenarios for probing the spin and dynamical structure of the $X_2X_1V$ vertex.