Doubly-charged scalar in four-body decays of neutral flavored mesons

TL;DR

This paper investigates four-body decay processes of neutral flavored mesons mediated by a hypothetical doubly-charged scalar, calculating branching ratios and setting limits based on experimental data, thus exploring lepton number violation in meson decays.

Contribution

It introduces a detailed calculation of branching ratios for meson decays involving a doubly-charged scalar and derives experimental constraints on model parameters.

Findings

Branching ratios range from 10^{-13} to 10^{-10} GeV^4 for different mesons.

Upper limits on scalar coupling parameters are established from D^0 decay data.

Provides theoretical predictions for lepton number violating meson decays.

Abstract

In this paper, we study the four-body decay processes of neutral flavored mesons, including $\bar K^0$, $D^0$, $\bar B^0$, and $\bar B_s^0$. These processes, which induced by a hypothetical doubly-charged scalar particle, violate the lepton number. The quantity $Br\times\left(\frac{s_\Delta h_{ij}}{m_\Delta^2}\right)^{-2}$ of different channels are calculated, where $s_\Delta$, $h_{ij}$, and $M_\Delta$ are parameters related to the doubly-charged scalar. For $\bar K^0\rightarrow h_1^+h_2^+l_1^-l_2^-$, $D^0\rightarrow h_1^-h_2^-l_1^+l_2^+$, and $\bar B_{d,s}^0\rightarrow h_1^+h_2^+l_1^-l_2^-$, it is of the order of $10^{-13}\sim 10^{-11}$ ${\rm GeV^4}$, $10^{-17}\sim 10^{-10}$ ${\rm GeV^4}$, and $10^{-17}\sim 10^{-10}$ ${\rm GeV^4}$, respectively. Based on the experimental results for the $D^0\rightarrow h_1^-h_2^-l_1^+l_2^+$ channels, we also set the upper limit for $\frac{s_\Delta h_{ij}}{M_\Delta^2}$.