The Electroweak Sphaleron Revisited: II. Study of Decay Dynamics

TL;DR

This paper analyzes electroweak sphaleron decay dynamics using analytical and numerical methods, revealing dominant gauge boson production and characteristic spectra, with implications for baryon number violation and collider signatures.

Contribution

It provides a detailed stability analysis and decay characterization of the electroweak sphaleron with realistic Standard Model parameters, including particle spectra and decay products.

Findings

Decay dominated by transverse gauge bosons (~80%)

Average decay yields 49 W bosons and 4 Higgs bosons

Particle spectra peak at momenta around 1-1.5 m_W

Abstract

We present a comprehensive analysis of electroweak sphaleron decay dynamics, employing both analytical techniques and high-resolution numerical simulations. Using a spherically symmetric ansatz, we reformulate the system as a $(1+1)$-dimensional problem and analyze its stability properties with current Standard Model parameters ($m_H = 125.1$ GeV, $m_W = 80.4$ GeV). We identify precisely one unstable mode with eigenvalue $\omega_{-}^2 \simeq -2.7m_W^2$ and numerically evolve the full non-linear field equations under various initial conditions. Through spectral decomposition, we quantify the particle production resulting from the sphaleron decay. Our results demonstrate that the decay process is dominated by transverse gauge bosons, which constitute approximately 80% of the total energy and multiplicity, while Higgs bosons account for only 7-8%. On average, the sphaleron decays into 49 $W$ bosons and 4 Higgs bosons. The particle spectra consistently peak at momenta $k \sim 1 - 1.5 \, m_W$, reflecting the characteristic size of the sphaleron. Remarkably, these properties remain robust across different decay scenarios, suggesting that the fundamental structure of the sphaleron, rather than specific triggering mechanisms, determines the decay outcomes. These findings provide distinctive experimental signatures of non-perturbative topological transitions in the electroweak theory, with significant implications for baryon number violation in the early universe and potentially for high-energy collider physics.