Vacuum Cherenkov Radiation for Nonminimal Isotropic Lorentz Violation

Abstract

In this work, we study the effects of vacuum Cherenkov radiation caused by nonminimal dimension-5 Lorentz-violating (LV) operators in the fermion sector. Explicitly, we focus on two independent isotropic pieces of each set of nonminimal coefficients. Under the assumption that vacuum Cherenkov radiation is an expected phenomenon, experimental data of ultra-high-energy cosmic rays (UHECRs) allow us to put stringent bounds on isotropic coefficients in quarks.

Figures (3)

• Figure 1: Tree-level Feynman diagram for vacuum Cherenkov radiation. There is an incoming fermion with momentum $\mathbf{q}$ and the outgoing photon and fermion with momenta $\mathbf{k}$ and $\mathbf{p}=\mathbf{q}-\mathbf{k}$, respectively.
• Figure 2: Double-logarithmic plot of the decay rates $\Gamma/\alpha$ with the fine-structure constant $\alpha=e^2/(4\pi)$ as functions of the initial-fermion momentum $q$ for $m_{\psi}=\unit[1.00]{GeV}$ as well as the isotropic coefficients $\mathring{m}_0=\unit[10^{-10}]{GeV^{-1}}$ and $\mathring{m}_2=\unit[10^{-10}]{GeV^{-1}}$, respectively. Both curves lie on top of each other.
• Figure 3: The same as Fig. \ref{['fig2']} for the isotropic coefficients $\mathring{a}_0=\unit[10^{-10}]{GeV^{-1}}$ and $\mathring{a}_2=\unit[10^{-10}]{GeV^{-1}}$, respectively. One curve lies on top of the other.