Discovery prospects of a singly-charged scalar at $\mu$TRISTAN

TL;DR

This paper explores the potential to discover a singly-charged scalar in a muon collider, leveraging lepton flavor violation signals that are free from Standard Model backgrounds, within the context of the Type-II seesaw neutrino mass model.

Contribution

It proposes a novel method to detect a singly-charged scalar at a muon collider using LFV processes and distinguishes neutrino mass hierarchies based on lepton flavor distributions.

Findings

LFV processes at $ ext{μ}$TRISTAN can reveal the singly-charged scalar.

The method can differentiate between Normal and Inverted neutrino mass hierarchies.

LFV signals are background-free in this collider setup.

Abstract

In this article, we study the associated production of a singly-charged ($\Delta^+$) scalar along with a $W^+$ boson in the newly proposed $\mu^+\mu^+$ collider (also known as $\mu$TRISTAN) at $\sqrt{s} = 2~$ TeV. Such a singly-charged scalar is naturally accommodated in an extremely well-motivated neutrino mass model, namely, the Type-II seesaw model. This model, beside providing a viable explanation of neutrino mass generation, also allows for lepton flavor violating (LFV) processes. Since LFV processes are not allowed in the Standard Model (SM), we focus on the discovery prospect of the singly-charged scalar in the Type-II seesaw model at $\mu$TRISTAN through a LFV process, owing to the advantage of this process being free of any SM background. Additionally, this article also proposes a method to indicate if the underlying theory follows a Normal or an Inverted hierarchy depending on the distribution of lepton flavors in the final state.