Ditauonium spectroscopy

TL;DR

This paper provides a detailed theoretical analysis of ditauonium, an exotic tau-lepton bound state, including energy levels, decay modes, and higher-order QED effects up to NNLO accuracy, with predictions for various decay channels.

Contribution

It offers the first comprehensive calculation of ditauonium properties, incorporating advanced QED corrections and rare decay channels, expanding understanding of this exotic atom.

Findings

Calculated energy levels and decay widths of ditauonium.

Predicted rates for rare decay channels such as Dalitz and radiative decays.

Quantified higher-order QED effects up to NNLO accuracy.

Abstract

We examine the properties of ditauonium, an exotic atom consisting of a pair of opposite-sign $\tau$ leptons bound together by the quantum electrodynamics (QED) interaction in a hydrogen-like state. The energy levels, decay modes and associated partial widths, as well as total widths and lifetimes of the ortho- and para-ditauonium states are calculated. Higher-order QED effects -- including Lamb shifts, hyperfine splitting structure, and partial decay widths corrections -- are incorporated up to approximately next-to-next-to-leading-order (NNLO) accuracy. Beyond the dominant diphoton and difermion decays, the rates of rare decay channels -- including Dalitz, radiative, triple-photon, double-Dalitz, four-fermion, and neutrinos final states -- are determined.