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Higgs Boson Spookiness: Probing Quantum Nonlocality with Spacetime-Resolved $H\rightarrowτ^+τ^-$ Decays

Lawrence Lee, John Lawless, Caroline Riggall

Abstract

We demonstrate that a future precision $ee$ Higgs factory would be able to perform a spacetime-resolved test of quantum nonlocality in Higgs boson decays. In simulated $ee\rightarrow ZH \rightarrow (μμ)(ττ)$ events at $\sqrt{s}=240$ GeV, we reconstruct $τ$ lepton decay vertices and measure spin correlations as a function of the spacetime interval between the two $τ$ decays. Such a measurement would be able to test Bell-inequality-violating correlations for spacelike-separated decays, enabling direct exclusion of superluminal, finite-speed entanglement signaling theories. With 0.75 ab$^{-1}$ of integrated luminosity, entanglement signal propagation speeds below $\approx2c$ can be excluded at 95$\%$ CL. Signals establishing any spin correlation can be excluded for speeds below $\approx9c$. This constitutes the first proposed spacetime-resolved measurement of electroweak quantum entanglement at a particle collider and demonstrates a unique capability of future Higgs factories.

Higgs Boson Spookiness: Probing Quantum Nonlocality with Spacetime-Resolved $H\rightarrowτ^+τ^-$ Decays

Abstract

We demonstrate that a future precision Higgs factory would be able to perform a spacetime-resolved test of quantum nonlocality in Higgs boson decays. In simulated events at GeV, we reconstruct lepton decay vertices and measure spin correlations as a function of the spacetime interval between the two decays. Such a measurement would be able to test Bell-inequality-violating correlations for spacelike-separated decays, enabling direct exclusion of superluminal, finite-speed entanglement signaling theories. With 0.75 ab of integrated luminosity, entanglement signal propagation speeds below can be excluded at 95 CL. Signals establishing any spin correlation can be excluded for speeds below . This constitutes the first proposed spacetime-resolved measurement of electroweak quantum entanglement at a particle collider and demonstrates a unique capability of future Higgs factories.

Paper Structure

This paper contains 6 sections, 2 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Complete $\tau\tau$ System Reconstruction
  3. Spin Entanglement Measurement in $H\rightarrow\tau\tau$
  4. Probing nonlocality in $H\rightarrow\tau\tau$
  5. Discussion
  6. Conclusion

Figures (3)

  • Figure 1: The angular correlation between the two polarimeter vectors is shown as measured in the Higgs rest frame. The SM expectation is shown in grey. Simulated points with realistic detector resolution are shown in black, and a cosine fit of this pseudo-data gives the red curve, in good agreement with the SM expectation.
  • Figure 2: The fitted cosine amplitude $B$ (top) and Horodecki parameter $m_{12}$ (bottom) are shown as a function of the speed needed to connect measurement events $v_{min}$. The SM value of $m_{12}=2$, $B=-0.5$ and the Bell threshold of $m_{12}=1$ are shown as horizontal lines, simulated events with $\mathcal{L}=0.75$ ab$^{-1}$ are shown as markers, and example superluminal, finite $v_\psi$ quantum signaling hypotheses are shown assuming ILD-like detector resolutions.
  • Figure 3: With an integrated luminosity of 0.75 ab$^{-1}$ (1.5 ab$^{-1}$), the potential rejection significance for this measurement for the $m_{12}=0$ and $m_{12}=1$ hypotheses is shown as a function of $v_\psi$ as solid (dotted) lines. Bell-threshold-level entanglement (red) can be rejected at 95% CL up to $v_\psi\approx2c$ ($5c$) and complete noncorrelation (blue) could be rejected up to $v_\psi\approx9c$ ($16c$).