Excitation of the Glashow resonance without neutrino beams

Abstract

The $s$-channel process $\bar\nu_ee^-\rightarrow W^-$ (on-shell) is now referred to as the Glashow resonance and being searched for at kilometer-scale neutrino ice/water detectors like IceCube, Baikal-GVD or KM3NeT. After over a decade of observations, IceCube has recorded only a few neutrino events with energies of interest such that an independent confirmation of the existence of this resonant interaction would be of great importance for testing the Standard Model. One might therefore ask: are there reactions with the Glashow resonance that would not necessitate having initial (anti)neutrino beams? This article suggests a surprisingly affirmative answer to the question $-$ namely, that the process may proceed in electron-positron collisions at accelerator energies, occurring as $e^+e^-\rightarrow W^-\rho(770)^+$. Although the resonance appears somewhat disguised, the underlying physics is transparent, quite resembling the well known radiative return: emission of $\rho^+$ from the initial state converts the incident $e^+$ into $\bar\nu_e$. Likewise, the CP conjugate channel, $\nu_e e^+\rightarrow W^+$, takes the form $e^+e^-\rightarrow W^+\rho(770)^-$. Similar reactions with muons and other hadrons are also possible. From this viewpoint, future high-luminosity lepton colliders seem to be promising for excitation of the Glashow resonance in laboratory conditions.