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Excitation of the Glashow resonance without neutrino beams

I. Alikhanov

Abstract

The $s$-channel process $\barν_ee^-\rightarrow W^-$ (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 $e^+e^-\rightarrow W^-ρ(770)^+$. Although the resonance appears somewhat disguised, the underlying physics is transparent, quite resembling the well known radiative return: emission of $ρ^+$ from the initial state converts the incident $e^+$ into $\barν_e$. Likewise, the CP conjugate channel, $ν_e e^+\rightarrow W^+$, takes the form $e^+e^-\rightarrow W^+ρ(770)^-$. 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.

Excitation of the Glashow resonance without neutrino beams

Abstract

The -channel process (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 . Although the resonance appears somewhat disguised, the underlying physics is transparent, quite resembling the well known radiative return: emission of from the initial state converts the incident into . Likewise, the CP conjugate channel, , takes the form . 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.

Paper Structure

This paper contains 7 sections, 9 equations, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Initial state photon emission
  3. Initial state meson emission
  4. CP symmetry and lepton universality
  5. Nonresonant background
  6. Numerical results
  7. Conclusions

Figures (3)

  • Figure 1: Diagrams illustrating: (a) the QED photon coupling to the positron current; (b) annihilation of the $e^+e^-$ pair into $Z$ boson accompanied by ISR, $e^+e^-\rightarrow Z\gamma$; (c) the effective coupling of $\rho^+$ meson to the electroweak charged current; (d) annihilation of the $\bar{\nu}_ee^-$ pair into $W^-$ boson accompanied by initial state $\rho^+$ emission, $e^+e^-\rightarrow W^-\rho^+$. The arrows sketch the spatial momentum flows.
  • Figure 2: Diagrams illustrating: (a) excitation of the CP conjugate of the Glashow resonance accompanied by initial state $\rho^-$ meson emission, $e^+e^-{\rightarrow}\,W^+\rho^-$; (b) excitation of the muonic counterpart of the Glashow resonance accompanied by initial state $\rho^+$ meson emission, $\mu^+\mu^-\rightarrow W^-\rho^+$. The arrows sketch the spatial momentum flows.
  • Figure 3: Leading-order Feynman diagrams for nonresonant background: (a) with $s$-channel $\gamma$ exchange; (b) with $s$-channel $Z$ boson exchange. The arrows sketch the spatial momentum flows.