REVIEW 3 major objections 5 minor 42 references
Born rule survives its first collider test, bounded to ε < 0.042
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · glm-5.2
2026-07-09 22:33 UTC pith:O2HJUIUN
load-bearing objection First collider bound on Born-rule violations — real but thin, limited by 1986 binning the 3 major comments →
First constraint on Born-rule violations at high-energy colliders
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The paper establishes the first experimental upper limit on Born-rule violations at high-energy colliders: ε < 0.042 at 95% confidence, where ε parameterizes a Gaussian angular smearing of the Bhabha scattering differential cross section. This bound, derived from 22 bins of PEP data at √s = 29 GeV, excludes smearing widths whose full-width at half-maximum exceeds twice the experimental bin width, placing a constraint at the threshold of detectability rather than deep in an unobservable regime.
What carries the argument
The central mechanism is the smeared cross section (Eq. 4): the standard QED differential cross section dσ/dx (with x = cos θ) is convolved with a normalized Gaussian δ_ε(x' − x) of width ε, integrated over a range parameter a = 0.4 to avoid edge effects. This smeared prediction is then compared bin-by-bin to the HRS/PEP data via a profile likelihood scan over ε, with a Gaussian-constrained nuisance parameter A (combining luminosity and radiative-correction uncertainties, σ_A = 0.0117). Confidence intervals use Wilks' theorem on the Δχ² profile. The robustness of the integration range was checked by varying a from 0.25 to 0.40 with no change in results to four decimals.
Load-bearing premise
The entire analysis rests on modeling Born-rule violations as a Gaussian angular smearing of the cross section. This is a phenomenological choice, not derived from an underlying theory, so the bound ε < 0.042 only constrains violations that happen to take this specific functional form.
What would settle it
If a future experiment with finer angular bins and higher statistics observed a differential cross section whose angular shape departed from the standard QED prediction in a manner consistent with a Gaussian smearing of width ε > 0.042, this bound would be falsified.
If this is right
- Modern high-luminosity experiments like BESIII, with event counts exceeding 10⁸, could in principle reduce the bin width—and thus the probeable smearing scale—by orders of magnitude, but only if detector angular resolution improves correspondingly.
- Current detector angular resolutions (ATLAS ~0.5–1 mrad, CMS ~0.5 mrad, FCC-ee target ~0.1 mrad) are less than two orders of magnitude better than the 6.5 mrad HRS resolution used here, capping realistic near-term improvement.
- The phenomenological Gaussian-smearing ansatz could be applied to other scattering processes and energies, potentially yielding complementary constraints if datasets with finer and more uniform angular binning become available.
- The analysis framework is model-independent within the smearing ansatz, so it can be directly re-applied to future data without requiring a specific underlying theory of Born-rule violation.
Where Pith is reading between the lines
- If Born-rule violations exist but manifest as energy-dependent or process-dependent smearing rather than a universal Gaussian, this bound would not constrain them—a null result here does not rule out all forms of Born-rule violation.
- The fact that the best-fit ε = 0.024 is non-zero and corresponds to roughly half the bin width suggests the fit is capturing binning artifacts rather than a physical signal, but a dedicated unbinned analysis could provide a cleaner test.
- The gap between detector resolution (δx ≈ 0.0065) and bin width (Δx = 0.05) implies that the current bound is statistics-limited by the analysis choice of binning, not by detector capability—a reanalysis of the same raw data with finer bins could potentially tighten the bound.
- If a future theory of Born-rule violation predicts a specific non-Gaussian smearing kernel, the framework would need to be generalized beyond the Gaussian ansatz to constrain that theory.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript presents what the authors claim is the first experimental constraint on Born-rule violations at high-energy colliders. The approach is phenomenological: Born-rule violations are modeled as a Gaussian angular smearing of the differential scattering cross section, parameterized by a width ε (Eq. 2, 4). This smeared cross section is fit to 22 angular bins of large-angle Bhabha scattering data from the HRS experiment at PEP (Ref. [5], Table XII, √s = 29 GeV). A profile likelihood scan over ε, with a normalization nuisance parameter A constrained by luminosity and systematic uncertainties, yields a best-fit ε = 0.024 and a 95% confidence upper bound of ε < 0.042. The authors discuss future prospects for improvement, noting that the bound is currently limited by the experimental bin width rather than detector angular resolution.
Significance. The paper addresses a genuinely novel question: whether the Born probability rule can be tested in the high-energy collider regime. The statistical methodology is standard and transparent (profile likelihood, Wilks' theorem, Gaussian nuisance parameter), the fit quality is good (χ²/ndof ≈ 1.06), and the authors are commendably honest about the limitations of their result, including the fact that the best-fit ε is comparable to the bin width and likely a binning artifact. The use of a single-energy dataset with publicly available bin-by-bin corrections is a reasonable starting point. The bound ε < 0.042 is a concrete, falsifiable result, though its physical reach is modest. The discussion of future detector improvements (ATLAS, CMS, FCC-ee) provides useful context.
major comments (3)
- The central tension in the paper is that the bound ε < 0.042 is almost entirely determined by the experimental bin width Δx = 0.05, rather than by the statistical power of the data or the underlying physics. The authors themselves acknowledge (page 4) that the best-fit ε = 0.024 has a FWHM ≈ 0.058 that 'closely matches the bin width Δx = 0.05' and that this is expected from bin averaging. The 95% upper limit (FWHM ≈ 0.10 ≈ 2Δx) is then the scale at which smearing becomes visibly inconsistent with the data. This means the constraint is essentially 'ε must be smaller than ~2Δx,' which is a statement about experimental resolution rather than about Born-rule violations per se. The authors should more clearly distinguish what is genuinely constrained by the data (i.e., that no anomalous smearing beyond the binning scale is present) from what is merely a restatement of the binning choice. The
- The physical motivation for the Gaussian smearing ansatz (Eq. 2, 4) is thin. The authors cite the de Broglie-Bohm pilot-wave framework and node regularization as a possible origin (page 1–2), but the connection from that theoretical motivation to a Gaussian smearing of the angular cross section in x = cos θ is not derived. The bound is therefore only meaningful for violations that take this specific functional form. A Born-rule violation with a different signature (non-Gaussian, energy-dependent, normalization-only, or affecting specific angular structures) would not be constrained. The authors acknowledge this is phenomenological, but the abstract and conclusion could be read as overclaiming a 'constraint on Born-rule violations' when the constraint is on a specific model of violations. The authors should qualify the central claim accordingly.
- The choice of a Gaussian smearing in x = cos θ (rather than in θ, or in a different angular variable) is presented without justification. Different choices of smearing variable would generally yield different bounds on the corresponding width parameter. The authors should briefly justify why x = cos θ is the natural variable for the pilot-wave motivation cited, or at minimum acknowledge that the bound is variable-dependent.
minor comments (5)
- Eq. (3): the electroweak amplitude definitions use notation that could be clearer — for instance, the coupling notation g_V, g_A is standard but their numerical values are not stated, making it difficult for a reader to reproduce the prediction without consulting Ref. [5].
- Fig. 2: the y-axis label 'Δχ²' is clear, but the horizontal line indicating the 95% confidence level is not explicitly drawn or labeled on the figure, making it slightly harder to read off the bound visually.
- Page 4: the statement 'This is nearly half the experimental angular bin width, Δx/2 = 0.025' is correct but could be misread; clarifying that ε = 0.024 is the best-fit smearing width (not the FWHM) would help.
- The robustness check with a = 0.25, 0.3, 0.35, 0.4 (page 3) is mentioned but the results are only summarized qualitatively. A small table or explicit statement of the best-fit ε and upper bound for each value of a would strengthen this claim.
- Reference [13] is listed as a 2026 Oxford Research Encyclopedia entry; the authors should verify this is publicly available at the time of submission or mark it as forthcoming.
Circularity Check
No significant circularity: the bound is obtained by fitting a phenomenological parameter to external experimental data.
full rationale
The paper's central result — the upper bound ε < 0.042 at 95% CL — is obtained by fitting a phenomenological smearing model (Eq. 4, with free parameter ε) to external experimental data (HRS/PEP, Ref. [5], Table XII). The Standard Model cross section (Eq. 3) uses standard QED/electroweak parameters from the literature. The smearing ansatz (Eq. 2, 4) is the authors' construct but introduces ε as a genuinely free parameter that is independently constrained by the data via a profiled likelihood scan. No step in the derivation chain reduces to its own inputs by construction: ε is not defined in terms of the bound, and the bound is not a renamed fit input. The self-citations to Valentini's prior work (refs [2], [4], [11–13]) provide physical motivation for why Born-rule violations might exist, but the central result does not depend on them — the fit stands alone as a phenomenological parameter estimation against external data. The skeptic's concern that the bound is numerically close to 2Δx (twice the bin width) is a question about physical significance and experimental resolution, not about circularity of the derivation. The bound is a genuine output of the statistical analysis, not a tautological restatement of the binning choice.
Axiom & Free-Parameter Ledger
free parameters (3)
- ε (smearing width) =
best-fit 0.024, upper bound 0.042
- A (normalization nuisance parameter) =
best-fit 0.99
- a (integration range parameter) =
0.4
axioms (3)
- ad hoc to paper Born-rule violations at high energies can be modeled as a Gaussian angular smearing of the differential cross section (Eq. 2, 4).
- domain assumption Standard QED/electroweak prediction for Bhabha scattering (Eq. 3) is correct at O(α²) at √s = 29 GeV.
- standard math Wilks' theorem applies for constructing confidence intervals from the profile likelihood.
invented entities (1)
-
Gaussian smearing function δ_ε(x' − x)
no independent evidence
read the original abstract
We obtain an experimental constraint on possible Born-rule violations at high-energy colliders. We model Born-rule violations with differential scattering cross sections $d\sigma/d\Omega$ subject to an angular smearing by a narrow Gaussian of width $\varepsilon$ (with respect to $x=\cos\theta$ for scattering angle $\theta$). For large-angle Bhabha ($e^{+}e^{-} \rightarrow e^{+}e^{-}$) scattering, at a centre-of-mass energy $\sqrt{s}=29\, \mathrm{GeV}$, data from the PEP collider at SLAC allow us to set an upper bound of $\varepsilon<0.042$ at $95\%$ confidence. This corresponds to a Gaussian smearing over an angular range of twice the experimental bin width, and hence provides a physically meaningful limit on deviations from the Born rule. Future prospects for improving this limit are discussed.
Figures
Reference graph
Works this paper leans on
-
[1]
A. J. Barr et al., Quantum entanglement and Bell in- equality violation at colliders, Prog. Part. Nucl. Phys. 139, 104134 (2024)
work page 2024
-
[2]
Pilot-wave theory and the search for new physics
A. Valentini, Pilot-wave theory and the search for new physics, Ann. Fond. Louis de Broglie48, 329 (2024); arXiv:2411.10782
work page internal anchor Pith review Pith/arXiv arXiv 2024
- [3]
-
[4]
A. Valentini and M. Varma, Toward a test of the Born rule in high-energy collisions, Phys. Rev. D112, 112024 (2025)
work page 2025
-
[5]
Derrick et al., Experimental study of the reactions e+e− →e +e− ande +e− →γγat 29 GeV, Phys
M. Derrick et al., Experimental study of the reactions e+e− →e +e− ande +e− →γγat 29 GeV, Phys. Rev. D 34, 3286 (1986)
work page 1986
-
[6]
L. de Broglie, La nouvelle dynamique des quanta, in: ´Electrons et Photons: Rapports et Discussions du Cin- qui` eme Conseil de Physique(Gauthier-Villars, Paris, 1928). [English translation in ref. [7].]
work page 1928
-
[7]
G. Bacciagaluppi and A. Valentini,Quantum Theory at the Crossroads: Reconsidering the 1927 Solvay Confer- ence(Cambridge University Press, 2009); arXiv:quant- ph/0609184
-
[8]
Bohm, A suggested interpretation of the quantum the- ory in terms of ‘hidden’ variables
D. Bohm, A suggested interpretation of the quantum the- ory in terms of ‘hidden’ variables. I, Phys. Rev.85, 166 (1952)
work page 1952
-
[9]
Bohm, A suggested interpretation of the quantum the- ory in terms of ‘hidden’ variables
D. Bohm, A suggested interpretation of the quantum the- ory in terms of ‘hidden’ variables. II, Phys. Rev.85, 180 (1952)
work page 1952
-
[10]
P. R. Holland,The Quantum Theory of Motion: an Ac- count of the de Broglie-Bohm Causal Interpretation of Quantum Mechanics(Cambridge University Press, Cam- bridge, 1993)
work page 1993
-
[11]
De Broglie-Bohm Quantum Mechanics
A. Valentini, De Broglie-Bohm quantum mechanics, in: Encyclopedia of Mathematical Physics (Second Edition), volume 2, eds. R. Szabo and M. Bojowald (Academic Press, Amsterdam, 2025); arXiv:2409.01294
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[12]
A. Valentini,Beyond the Quantum: A Quest for the Ori- gin and Hidden Meaning of Quantum Mechanics(Oxford University Press, Oxford, 2025)
work page 2025
-
[13]
A. Valentini, De Broglie-Bohm pilot-wave theory, in:Ox- ford Research Encyclopedia of Physics(Oxford Univer- sity Press, Oxford, 2026); https://oxfordre.com/physics
work page 2026
-
[14]
Valentini, Signal-locality, uncertainty, and the sub- quantumH-theorem
A. Valentini, Signal-locality, uncertainty, and the sub- quantumH-theorem. I, Phys. Lett. A156, 5 (1991)
work page 1991
-
[15]
A. Valentini and H. Westman, Dynamical origin of quan- tum probabilities, Proc. Roy. Soc. A461, 253 (2005)
work page 2005
-
[16]
M. D. Towler, N. J. Russell, and A. Valentini, Time scales for dynamical relaxation to the Born rule, Proc. Roy. Soc. A468, 990 (2012)
work page 2012
-
[17]
E. Abraham, S. Colin and A. Valentini, Long-time relax- ation in pilot-wave theory, J. Phys. A: Math. Theor.47, 395306 (2014)
work page 2014
-
[18]
A. Valentini, Foundations of statistical mechanics and the status of the Born rule in de Broglie-Bohm pilot-wave theory, in:Statistical Mechanics and Scientific Explana- tion: Determinism, Indeterminism and Laws of Nature, ed. V. Allori (World Scientific, 2020); arXiv:1906.10761
work page internal anchor Pith review Pith/arXiv arXiv 2020
-
[19]
Valentini, Signal-locality, uncertainty, and the sub- quantumH-theorem
A. Valentini, Signal-locality, uncertainty, and the sub- quantumH-theorem. II, Phys. Lett. A158, 1 (1991)
work page 1991
-
[20]
A. Valentini, On the pilot-wave theory of classical, quan- tum and subquantum physics, PhD thesis, Interna- tional School for Advanced Studies, Trieste, Italy (1992); http://hdl.handle.net/20.500.11767/4334
work page 1992
-
[21]
A. Valentini, Pilot-wave theory of fields, gravitation and cosmology, in:Bohmian Mechanics and Quantum The- ory: an Appraisal, eds. J. T. Cushing et al. (Kluwer, Dordrecht, 1996)
work page 1996
-
[22]
Valentini, Subquantum information and computa- tion, Pramana–J
A. Valentini, Subquantum information and computa- tion, Pramana–J. Phys.59, 269 (2002); arXiv:quant- ph/0203049. 6
-
[23]
A. Valentini, Beyond the quantum, Phys. World22N11, 32 (2009); arXiv:1001.2758
work page internal anchor Pith review Pith/arXiv arXiv 2009
-
[24]
Valentini, Signal-locality in hidden-variables theories, Phys
A. Valentini, Signal-locality in hidden-variables theories, Phys. Lett. A297, 273 (2002)
work page 2002
-
[25]
Valentini, Universal signature of non-quantum sys- tems, Phys
A. Valentini, Universal signature of non-quantum sys- tems, Phys. Lett. A332, 187 (2004)
work page 2004
-
[26]
Valentini, Astrophysical and cosmological tests of quantum theory, J
A. Valentini, Astrophysical and cosmological tests of quantum theory, J. Phys. A: Math. Theor.40, 3285 (2007)
work page 2007
-
[27]
Valentini, Inflationary cosmology as a probe of pri- mordial quantum mechanics, Phys
A. Valentini, Inflationary cosmology as a probe of pri- mordial quantum mechanics, Phys. Rev. D82, 063513 (2010)
work page 2010
-
[28]
S. Colin and A. Valentini, Mechanism for the suppres- sion of quantum noise at large scales on expanding space, Phys. Rev. D88, 103515 (2013)
work page 2013
-
[29]
S. Colin and A. Valentini, Primordial quantum nonequi- librium and large-scale cosmic anomalies, Phys. Rev. D 92, 043520 (2015)
work page 2015
-
[30]
S. Vitenti, P. Peter and A. Valentini, Modeling the large- scale power deficit with smooth and discontinuous pri- mordial spectra, Phys. Rev. D100, 043506 (2019)
work page 2019
-
[31]
Valentini, Beyond the Born rule in quantum gravity, Found
A. Valentini, Beyond the Born rule in quantum gravity, Found. Phys.53, 6 (2023)
work page 2023
-
[32]
N. Ahmadiet al., QUICK3—Design of a satellite-based quantum light source for quantum communication and extended physical theory tests in space, Adv. Quantum Technol.7, 2300343 (2024)
work page 2024
-
[33]
Entanglement distribution in Bhabha scattering with entangled spectator particle
M. Blasone, G. Lambiase and B. Micciola, Entanglement distribution in Bhabha scattering with entangled specta- tor particle, arXiv:2401.10715
work page internal anchor Pith review Pith/arXiv arXiv
-
[34]
L. Gao, A. Ruzi, Q. Li, C. Zhou and Q. Li, Testing entan- glement between free-traveling electron-positron pairs, Phys. Rev. D111, 116018 (2025)
work page 2025
-
[35]
S. Schael et al. (ALEPH Collaboration), Fermion pair production ine +e− collisions at 189-209-GeV and con- straints on physics beyond the Standard Model, Eur. Phys. J. C49, 411 (2007)
work page 2007
-
[36]
J. Abdallah et al. (DELPHI Collaboration), Measure- ment and interpretation of fermion-pair production at LEP energies above theZresonance, Eur. Phys. J. C 45, 589 (2006)
work page 2006
-
[37]
W. Braunschweig et al. (TASSO Collaboration), A study of Bhabha scattering at PETRA energies, Z. Phys. C37, 171 (1988)
work page 1988
-
[38]
M. Ablikim et al. (BESIII Collaboration), Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024, Chin. Phys. C48, 123001 (2024)
work page 2021
-
[39]
Z. Drasal and W. Riegler, An extension of the Gluckstern formulae for multiple scattering: analytic expressions for track parameter resolution using optimum weights, Nucl. Instrum. Meth. A910, 127 (2018)
work page 2018
- [40]
-
[41]
S. Chatrchyan et al. (CMS Collaboration), Alignment of the CMS silicon tracker during commissioning with cos- mic rays, JINST5, T03009 (2010)
work page 2010
-
[42]
Polarization and Centre-of-mass Energy Calibration at FCC-ee
A. Blondel et al., Polarization and centre-of-mass energy calibration at FCC-ee, arXiv:1909.12245
work page internal anchor Pith review Pith/arXiv arXiv 1909
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.