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Collider Bounds on Pseudoscalars Coupling to Gauge Bosons

Matthew Kleban, Raul Rabadan

TL;DR

The paper investigates collider-based bounds on light pseudoscalars coupling to gauge bosons, addressing couplings to gluons and photons. It leverages missing-energy signatures from hadron colliders ($pp/p\bar{p}\to \text{jet}+\slashed{E}_T$) and electron-positron colliders ($e^+e^-\to \gamma+\slashed{E}_T$) to extract 95% CL limits, highlighting the energy-independence of the pseudoscalar production amplitude at high $s$ due to the dimensionful coupling. Key results include a Tevatron bound of $f>35$ GeV for the gluon coupling and LEP bounds of $g<1.5\times10^{-4}$ GeV$^{-1}$ for $m_\phi<65$ MeV, with the LHC and future $e^+e^-$ machines extending sensitivity to $f\sim O(1{,}000)$ GeV and $g\sim O(10^{-6})$ GeV$^{-1}$ for sub-GeV masses, respectively. These collider constraints probe regions relevant to the PVLAS hints and demonstrate a direct, collider-based test of light pseudoscalars that complements astrophysical bounds.

Abstract

We bound the coupling of pseudo-scalar particles to Tr G^G_{QCD} using (the lack of) monojet plus missing E_T events at the Tevatron, and estimate the bounds obtainable from LHC. In addition, we revisit the bounds on the coupling to F^F_{EM} from e^+e^- collider events with single photon and missing E_T final states. This is especially interesting in light of the recent experimental results from the PVLAS collaboration, which we believe can be tested by data which will be available in the near future.

Collider Bounds on Pseudoscalars Coupling to Gauge Bosons

TL;DR

The paper investigates collider-based bounds on light pseudoscalars coupling to gauge bosons, addressing couplings to gluons and photons. It leverages missing-energy signatures from hadron colliders () and electron-positron colliders () to extract 95% CL limits, highlighting the energy-independence of the pseudoscalar production amplitude at high due to the dimensionful coupling. Key results include a Tevatron bound of GeV for the gluon coupling and LEP bounds of GeV for MeV, with the LHC and future machines extending sensitivity to GeV and GeV for sub-GeV masses, respectively. These collider constraints probe regions relevant to the PVLAS hints and demonstrate a direct, collider-based test of light pseudoscalars that complements astrophysical bounds.

Abstract

We bound the coupling of pseudo-scalar particles to Tr G^G_{QCD} using (the lack of) monojet plus missing E_T events at the Tevatron, and estimate the bounds obtainable from LHC. In addition, we revisit the bounds on the coupling to F^F_{EM} from e^+e^- collider events with single photon and missing E_T final states. This is especially interesting in light of the recent experimental results from the PVLAS collaboration, which we believe can be tested by data which will be available in the near future.

Paper Structure

This paper contains 4 sections, 17 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Summary of Results
  3. Bounds from hadron colliders
  4. Bounds from $e^+ e^-$ colliders

Figures (4)

  • Figure 1: 95 % confidence bounds on pseudoscalar-gluon couplings versus pseudoscalar mass obtainable for hadron colliders. The testable regions for each experiment are below the line.
  • Figure 2: Bounds on pseudoscalar-photon coupling versus pseudoscalar mass for $e+e^-$ colliders, the preferred region for the PVLAS results, and the band covered by typical QCD axion models. The area above the lines could be tested with an analysis of collider data.
  • Figure 3: Feynman diagrams for the process $p\bar{p} \rightarrow \phi + {\rm jet}$.
  • Figure 4: Feynman diagram of the process $e^+ e^- \rightarrow \gamma \phi$.