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  • Open Access

Toward a test of the Born rule in high-energy collisions

Antony Valentini*

Mira Varma†

  • Abdus Salam Centre for Theoretical Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom

  • *Contact author: a.valentini@imperial.ac.uk
  • †Contact author: mira.varma@yale.edu
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Phys. Rev. D 112, 112024 – Published 30 December, 2025

DOI: https://doi.org/10.1103/4llk-pt1j

Abstract

We consider how the Born rule, a fundamental principle of quantum mechanics, can be tested for particles created on the shortest timescales (∼10−25  s) currently accessible at high-energy colliders. We focus on targeted tests of the Born rule for spin or polarization probabilities, which offer a particularly clean experimental signal, and which can be described by a simple hidden-variables model of two-state systems proposed by Bell. These probabilities test a remarkable feature of the quantum formalism, whereby expectation values for incompatible experiments are linearly related. Born-rule violations can be parametrized by nonlinear expectation values for quantum measurements of spin or polarization, together with anomalies in ensemble averages, which may then be constrained by experiments. Notable experiments considered here include the recent detection of single photons from top-quark decay, and the indirect measurement of tau-lepton polarization. Repurposing these experiments as tests of the Born rule, however, presents several challenges, which are discussed in this paper.

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Phys. Rev. D 112, 112024– Published 30 December, 2025
  • Received 20 June 2025
  • Accepted 5 December 2025
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