{
  "format_version": 3,
  "claim_formal": {
    "subject": "neutron lifetime discrepancy between beam and bottle experiments",
    "property": "difference defined as (beam lifetime) minus (bottle lifetime)",
    "operator": "<",
    "operator_note": "The claim asserts beam < bottle by more than 1 second. Formally: (beam_lifetime - bottle_lifetime) < -1.0. If the difference is positive (beam > bottle) or within [-1, 0], the claim is FALSE. We use the world-average values reported in the physics literature for each method.",
    "threshold": -1.0,
    "unit": "seconds"
  },
  "claim_natural": "The mean neutron lifetime measured in beam experiments is more than 1 second shorter than the lifetime obtained from ultracold-neutron bottle experiments.",
  "evidence": {
    "B1": {
      "type": "empirical",
      "label": "U.S. DOE: beam lifetime 887.7 +/- 2.2 s, bottle lifetime 878.5 +/- 0.8 s",
      "sub_claim": null,
      "source": {
        "name": "U.S. Department of Energy, Office of Science",
        "url": "https://www.energy.gov/science/articles/mystery-neutron-lifetime",
        "quote": "One method measures it as 887.7 seconds, plus or minus 2.2 seconds."
      },
      "verification": {
        "status": "verified",
        "method": "full_quote",
        "coverage_pct": null,
        "fetch_mode": "live",
        "credibility": {
          "domain": "energy.gov",
          "source_type": "government",
          "tier": 5,
          "flags": [],
          "note": "Government domain (.gov)"
        }
      },
      "extraction": {
        "value": "887.7",
        "value_in_quote": true,
        "quote_snippet": "One method measures it as 887.7 seconds, plus or minus 2.2 seconds."
      }
    },
    "B2": {
      "type": "empirical",
      "label": "Quanta Magazine: beam ~14 min 48 s, bottle ~14 min 39 s, gap ~9 s",
      "sub_claim": null,
      "source": {
        "name": "Quanta Magazine",
        "url": "https://www.quantamagazine.org/neutron-lifetime-puzzle-deepens-but-no-dark-matter-seen-20180213/",
        "quote": "The gap between the world-average bottle and beam measurements has only grown slightly \u2014 to nine seconds"
      },
      "verification": {
        "status": "verified",
        "method": "full_quote",
        "coverage_pct": null,
        "fetch_mode": "live",
        "credibility": {
          "domain": "quantamagazine.org",
          "source_type": "unknown",
          "tier": 2,
          "flags": [],
          "note": "Unclassified domain \u2014 verify source authority manually"
        }
      },
      "extraction": {
        "value": "9.0",
        "value_in_quote": true,
        "quote_snippet": "The gap between the world-average bottle and beam measurements has only grown sl"
      }
    },
    "A1": {
      "type": "computed",
      "label": "Computed difference (beam - bottle) from DOE values",
      "sub_claim": null,
      "method": "explain_calc('beam_lifetime - bottle_lifetime')",
      "result": "9.200000000000045 s",
      "depends_on": []
    },
    "A2": {
      "type": "computed",
      "label": "Computed difference (beam - bottle) from Quanta values",
      "sub_claim": null,
      "method": "Quanta Magazine reported gap",
      "result": "9.0 s (beam > bottle)",
      "depends_on": []
    },
    "A3": {
      "type": "computed",
      "label": "Claim evaluation: is (beam - bottle) < -1.0?",
      "sub_claim": null,
      "method": "compare(difference, '<', -1.0)",
      "result": "False",
      "depends_on": []
    }
  },
  "cross_checks": [
    {
      "description": "DOE computed difference vs Quanta reported gap",
      "values_compared": [
        "9.200000000000045",
        "9.0"
      ],
      "agreement": true,
      "fact_ids": []
    }
  ],
  "adversarial_checks": [
    {
      "question": "Could the claim be using a non-standard definition where 'beam' refers to a different measurement technique?",
      "verification_performed": "Searched web for 'neutron lifetime beam experiment definition method'. All sources consistently define beam experiments as measuring decay products (protons) from cold neutron beams, yielding ~887-888 s. Bottle experiments trap ultracold neutrons and count survivors, yielding ~878-879 s. No alternative definition found.",
      "finding": "The two methods are universally defined consistently across all sources. Beam always gives the longer lifetime.",
      "breaks_proof": false
    },
    {
      "question": "Is there any recent measurement where a beam experiment produced a shorter lifetime than the bottle average?",
      "verification_performed": "Searched web for 'neutron lifetime beam experiment new result 2024 2025'. Checked PDG 2024 data. The most recent beam measurement is YUE 2013 at 887.7 +/- 1.2 s. No beam experiment has ever produced a result below the bottle average of ~878 s. The BL2 experiment at NIST is ongoing but has not published a result contradicting this.",
      "finding": "No beam experiment result is shorter than the bottle average. The discrepancy has persisted since the 2000s with beam consistently higher.",
      "breaks_proof": false
    },
    {
      "question": "Could 'shorter' in the claim refer to something other than the numerical value (e.g., measurement duration)?",
      "verification_performed": "Linguistic analysis of the claim. 'The mean neutron lifetime measured in beam experiments is more than 1 second shorter' unambiguously refers to the numerical value of the measured lifetime.",
      "finding": "The claim clearly refers to the measured lifetime value, not the experiment duration. No alternative reading is plausible.",
      "breaks_proof": false
    }
  ],
  "verdict": {
    "value": "DISPROVED",
    "qualified": false,
    "qualifier": null,
    "reason": null
  },
  "key_results": {
    "beam_lifetime_s": 887.7,
    "bottle_lifetime_s": 878.5,
    "difference_beam_minus_bottle_s": 9.200000000000045,
    "claim_threshold_s": -1.0,
    "operator": "<",
    "claim_holds": false,
    "actual_direction": "beam is LONGER than bottle (opposite of claim)"
  },
  "generator": {
    "name": "proof-engine",
    "version": "0.10.0",
    "repo": "https://github.com/yaniv-golan/proof-engine",
    "generated_at": "2026-03-28"
  },
  "proof_py_url": "/proofs/the-mean-neutron-lifetime-measured-in-beam-experim/proof.py",
  "citation": {
    "doi": "10.5281/zenodo.19489848",
    "concept_doi": "10.5281/zenodo.19489847",
    "url": "https://proofengine.info/proofs/the-mean-neutron-lifetime-measured-in-beam-experim/",
    "author": "Proof Engine",
    "cite_bib_url": "/proofs/the-mean-neutron-lifetime-measured-in-beam-experim/cite.bib",
    "cite_ris_url": "/proofs/the-mean-neutron-lifetime-measured-in-beam-experim/cite.ris"
  },
  "depends_on": []
}