{"id":"8e232097-8510-4edf-b560-9f43f082d747","arxiv_id":"2607.00200","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":5.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"New experimental upper bounds on axial-axial (V2) and axial-vector (V11) couplings between electron spins and nucleon spins at long ranges, improving prior limits.","lead":"This paper reports new upper bounds on long-range exotic spin-spin interactions between electrons and neutrons or protons, measured with a Hg-Cs comagnetometer on a rotating platform. The results tighten constraints on possible new bosons in Standard Model extensions by up to a factor of 17.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.3","headline":"Comagnetometer residual attribution after known-effect subtraction is the load-bearing assumption","rationale":"The reader's weakest_assumption matches the single point whose failure would falsify the numerical bounds; full-text access does not remove the dependence on that modeling assumption, so the UNVERDICTED status is retained.","tokens_in":1886,"tokens_out":324,"duration_ms":13558,"concrete_test":"Re-fit the rotation-angle time series (or the published residual spectra) while allowing an additional free parameter for a possible unmodeled sinusoidal term at the rotation frequency; if the 95% CL bound on the exotic coupling weakens by more than a factor of 3, the central claim is sensitive to the completeness of the known-effects model.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The headline bounds (|g_A^e g_A^n| ≤ 3.0×10^{-48} at infinite range for V2; |g_A^e g_V^n| ≤ 2.2×10^{-25} at λ≈10^3 km for V11) are obtained by attributing any post-rotation residual signal, after subtraction of magnetic and geometric contributions, exclusively to the exotic potentials. This requires that the model of the ^{199}Hg-^{133}Cs free-precession response on the rotation platform is complete to better than the reported sensitivity. Any unmodeled platform vibration, field gradient drift, or comagnetometer nonlinearity that correlates with orientation would directly loosen or invalidate the quoted limits and the claimed factor-of-17 improvement.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript reports new experimental upper bounds on long-range exotic spin-spin interactions between polarized electrons (in Earth) and neutrons/protons (in the sensor) using an optical ^{199}Hg-^{133}Cs free-precession comagnetometer mounted on a precision rotation platform. By rotating the apparatus and subtracting known magnetic and geometric contributions, the authors extract limits on the dimensionless couplings for the axial-axial potential V_2 (infinite range: |g_A^e g_A^n| ≤ 3.0 × 10^{-48}, |g_A^e g_A^p| ≤ 3.0 × 10^{-47}) and the axial-vector potential V_11 (most stringent at λ ≈ 10^3 km: |g_A^e g_V^n| ≤ 2.2 × 10^{-25}, |g_A^e g_V^p| ≤ 2.2 × 10^{-24}), claiming an improvement of up to a factor of 17 over prior results.","tokens_in":2036,"tokens_out":636,"duration_ms":17610,"significance":"If the residual-signal attribution is robust, these bounds would constitute the most stringent constraints to date on long-range axial-axial and axial-vector electron-nucleon couplings, tightening limits on proposed new bosons and providing useful input for beyond-Standard-Model phenomenology.","major_comments":[{"comment":"The central claim rests on the assumption that any post-rotation residual in the comagnetometer signal, after subtraction of magnetic and geometric effects, is attributable solely to V_2 or V_11. The manuscript provides no quantitative error budget, data-selection criteria, or systematic-error analysis demonstrating that the ^{199}Hg-^{133}Cs response model is complete to better than the reported sensitivity (abstract and measurement-procedure paragraph). Unmodeled platform vibration, gradient drift, or orientation-correlated nonlinearity would directly loosen the quoted limits.","section":"abstract / measurement procedure"},{"comment":"No explicit statement is given of how the rotation-platform data are partitioned, how the known-effect model is fitted, or what χ² or residual statistics support the null result before the exotic-potential limits are derived. This information is required to assess whether the factor-of-17 improvement is statistically justified.","section":"data analysis"}],"minor_comments":[{"comment":"The abstract states the final bounds but supplies no numerical values for the force range λ at which the V_2 limits apply or the precise definition of “infinite range.”","section":"abstract"},{"comment":"Notation for the potentials (V_2, V_11) and coupling products should be cross-referenced to the explicit interaction Lagrangians or potentials in the theory section for clarity.","section":"theory"}],"recommendation":"major_revision","confidential_remarks":"The manuscript appears to be an experimental bounds paper whose soundness cannot be evaluated from the abstract alone; the full text must supply the missing systematic analysis before the central claim can be accepted."},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for their careful reading of the manuscript and for highlighting areas where additional detail would strengthen the presentation. We address each major comment below and will revise the manuscript to incorporate the requested information on systematic uncertainties and data analysis.","responses":[{"response":"We agree that the manuscript would benefit from an expanded quantitative error budget and explicit discussion of data-selection criteria. In the revised version we will add a dedicated subsection to the measurement-procedure description that quantifies contributions from platform vibration, gradient drift, and orientation-dependent nonlinearities, together with the criteria used to select valid data segments. These additions will demonstrate that the response model is complete at the level required to support the reported sensitivity.","revision_made":"yes","referee_comment":"[abstract / measurement procedure] The central claim rests on the assumption that any post-rotation residual in the comagnetometer signal, after subtraction of magnetic and geometric effects, is attributable solely to V_2 or V_11. The manuscript provides no quantitative error budget, data-selection criteria, or systematic-error analysis demonstrating that the ^{199}Hg-^{133}Cs response model is complete to better than the reported sensitivity (abstract and measurement-procedure paragraph). Unmodeled platform vibration, gradient drift, or orientation-correlated nonlinearity would directly loosen the quoted limits."},{"response":"We acknowledge that the current text does not provide sufficient detail on data partitioning, model fitting, and goodness-of-fit statistics. The revised manuscript will include a new subsection on data analysis that describes the partitioning of the rotation-platform data, the procedure used to fit the known magnetic and geometric contributions, and the χ² and residual statistics that support the null result prior to deriving the exotic-potential limits. This will allow readers to evaluate the statistical justification for the reported improvement.","revision_made":"yes","referee_comment":"[data analysis] No explicit statement is given of how the rotation-platform data are partitioned, how the known-effect model is fitted, or what χ² or residual statistics support the null result before the exotic-potential limits are derived. This information is required to assess whether the factor-of-17 improvement is statistically justified."}],"tokens_in":1545,"tokens_out":468,"duration_ms":22434,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main thing to know is that the paper gives new numerical upper limits on the couplings for the V2 axial-axial and V11 axial-vector potentials, with the strongest being |g_A^e g_A^n| ≤ 3.0 × 10^{-48} at infinite range and |g_A^e g_V^n| ≤ 2.2 × 10^{-25} near 10^3 km. These come from orienting the comagnetometer on a precision platform and looking for any signal beyond the subtracted magnetic and geometric terms.\n\nThe experiment applies a standard free-precession comagnetometer to Earth’s polarized spins in a way that produces concrete, range-dependent bounds. That is the actual advance: the numbers themselves are new and tighter than earlier work by the stated factor.\n\nThe load-bearing step is the claim that the post-rotation residual is attributable only to the exotic potentials once known effects are removed. If platform vibrations, field drifts, or response nonlinearities that track orientation were missed, the limits loosen and the improvement factor shrinks. The abstract states the final numbers without error budgets, so the full text needs to show the data cuts and systematic tests at the required level. If those checks are present and convincing, the result holds; otherwise the central claim is weaker than presented.\n\nThis is useful for anyone tracking constraints on spin-dependent new bosons or running related precision measurements. It updates the exclusion regions in a direct way. The work shows straightforward engagement with the literature and the experimental method. I would send it to peer review so referees can examine the systematic control and data analysis in detail.","headline":"This tightens bounds on exotic electron-nucleon spin couplings by up to 17x via a rotating Hg-Cs comagnetometer, but the limits stand or fall on whether residuals after known-effect subtraction are fully explained by the model.","tokens_in":2589,"tokens_out":419,"would_cite":false,"duration_ms":20519,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"A rotating Hg-Cs comagnetometer tightens bounds on exotic long-range spin couplings by up to a factor of 17.","keywords":["spin-spin interactions","exotic forces","comagnetometer","long-range potentials","axial couplings","electron-nucleon interactions","new physics bounds"],"falsifier":"A repeated measurement that detects a statistically significant residual orientation-dependent signal larger than the reported coupling bounds after all known effects are subtracted would indicate either stronger exotic couplings or unaccounted systematics.","tokens_in":2796,"feed_emoji":"⚛️","tokens_out":812,"duration_ms":23800,"temperature":0.7,"pith_summary":"The paper reports a search for hypothetical forces that couple the spin of electrons to the spins of neutrons and protons over long distances. An optical free-precession comagnetometer containing polarized 199Hg and 133Cs atoms is mounted on a precision rotation platform so that its orientation relative to Earth can be changed in a controlled way. After subtracting ordinary magnetic and geometric effects, any remaining orientation-dependent signal is interpreted as a possible signature of new spin-dependent potentials V2 or V11. The resulting data yield new upper limits on the product of coupling constants, with the strongest improvements for infinite-range axial-axial interactions. These limits narrow the allowed strength of new bosons that might mediate such forces.","feed_headline":"Comagnetometer rotation tightens exotic spin force bounds by factor of 17","feed_subtitle":"New upper limits on electron-neutron and electron-proton couplings improve prior results for forces with ranges up to planetary scales.","key_machinery":"The optical 199Hg-133Cs free-precession comagnetometer on a precision rotation platform, which isolates orientation-dependent signals after subtracting known magnetic and geometric effects to bound exotic spin-dependent potentials V2 and V11.","core_discovery":"Using a 199Hg-133Cs free-precession comagnetometer mounted on a precision rotation platform, the experiment measures the response to changes in orientation and derives upper bounds on the dimensionless coupling constants for the axial-axial potential V2 and the axial-vector potential V11. For V2 at infinite range the bounds are |g_A^e g_A^n| ≤ 3.0 × 10^{-48} and |g_A^e g_A^p| ≤ 3.0 × 10^{-47}; for V11 the tightest limits reach |g_A^e g_V^n| ≤ 2.2 × 10^{-25} and |g_A^e g_V^p| ≤ 2.2 × 10^{-24} near λ ≈ 10^3 km. These represent improvements of up to a factor of 17 over prior results.","pith_inferences":["The same rotation technique could be applied with different atomic species to probe couplings involving other combinations of spins.","Cross-checks with independent experiments using torsion balances or different source masses could test whether the bounds are limited by systematics.","If future runs achieve lower noise, the same apparatus might reach sensitivities to shorter-range forces not yet constrained at this level."],"forward_implications":["The new limits apply to forces mediated by new bosons coupling to spin over distances from laboratory scales to the size of the Earth.","Tighter constraints on axial-axial couplings at infinite range reduce the allowed strength of certain proposed extensions to the Standard Model.","The method sets the most stringent bounds on long-range axial-axial and axial-vector couplings between electron spins and neutron and proton spins.","Results can be reinterpreted for other ranges λ to constrain different classes of new interactions."],"fun_headline_variants":["Comagnetometer rotation constrains exotic spin forces","New upper limits on long-range axial spin couplings","Hg-Cs sensor on rotator sets electron-nucleon bounds","V2 and V11 potentials limited via orientation scan","Platform rotation tightens spin-spin interaction bounds"],"cache_read_input_tokens":64,"weakest_assumption_plain":"The analysis assumes that after accounting for known magnetic and geometric effects, any remaining orientation-dependent signal in the comagnetometer must come from the exotic potentials rather than unidentified systematics.","fun_headline_variants_meta":{"raw":{"variants":["Comagnetometer rotation constrains exotic spin forces","New upper limits on long-range axial spin couplings","Hg-Cs sensor on rotator sets electron-nucleon bounds","V2 and V11 potentials limited via orientation scan","Platform rotation tightens spin-spin interaction bounds"]},"model":"grok-4.3","cost_usd":0.006932,"raw_usage":{"total_tokens":3215,"prompt_tokens":831,"num_sources_used":0,"completion_tokens":70,"cost_in_usd_ticks":69315500,"prompt_tokens_details":{"text_tokens":831,"audio_tokens":0,"image_tokens":0,"cached_tokens":64},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":2314,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":831,"tokens_out":70,"duration_ms":19573,"temperature":1.0,"reasoning_tokens":2314,"cache_read_input_tokens":64,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-02T00:29:36.153739+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A repeated measurement that detects a statistically significant residual orientation-dependent signal larger than the reported coupling bounds after all known effects are subtracted would indicate either stronger exotic couplings or unaccounted systematics.","supporting_citations":[],"review_version":1}