A Nondiagonal Pair of Majorana Particles at $e^+e^-$ Colliders

TL;DR

This paper develops a model-independent framework to analyze the production and decay of non-diagonal pairs of Majorana particles at $e^+e^-$ colliders, focusing on their spin, polarization, and CP symmetry effects.

Contribution

It introduces a helicity formalism and Wick helicity rotation approach to characterize Majorana pair production and decay, including CP and Majorana conditions, with an application to the MSSM.

Findings

Provides detailed amplitude and distribution implications of CP and Majorana conditions.

Demonstrates the formalism with a specific MSSM example.

Enhances understanding of Majorana particle signatures at colliders.

Abstract

We perform a comprehensive and model-independent analysis for characterizing the spin and dynamical structure of the production of a non-diagonal pair of Majorana particles with different masses and arbitrary spins, $e^-e^+\to X_2 X_1$, followed by a sequential two-body decay, $X_2\to Z X_1$, of the heavier particle $X_2$ into a $Z$ gauge boson and the lighter particle $X_1$ escaping undetected at high-energy $e^+e^-$ colliders. Standard leptonic $Z$-boson decays, $Z\to \ell^-\ell^+$ with $\ell=e$ or $\mu$, are employed for precisely diagnosing the $Z$ polarization influenced by the production and decay processes. Based on helicity formalism and Wick helicity rotation for describing the correlated production-decay amplitudes and distributions, we work out the implications on the amplitudes and distributions of discrete CP symmetry and the Majorana condition that two particles are their own anti-particles. For the sake of a concrete illustration, an example of this type in the minimal supersymmetric Standard Model is investigated in detail.