33.61 turns the neutron’s “negative charge radius” into a translation court: within one preregistered low-Q² window and one frozen correction / normalization aperture, GEn(Q²) must keep a stable positive near-zero slope across datasets and extraction routes, that slope must map stably to the effective mean-squared charge radius, and preregistered spatial inversions must yield a reproducible cancellation-style profile with stable r0, robust Cn/Kn, holdout replication, and clean pseudo-data / truncation / perturbation / constraint null separation; under V02/V08/V09-compatible translation, “negative charge radius” remains only one neutron low-Q² slope and inversion readout ledger rather than a neutron ontology noun.
Use this section as a compact machine-readable EFT reference.
33.61 asks the neutron electric form factor to pass a translation court. The admissible claim is not that any fitted phrase “negative charge radius” names a neutron object, but that one frozen low-Q² aperture preserves a positive near-zero slope of GEn(Q²) and a cancellation-style inversion profile across routes, datasets, and methods.
Measurement begins with the neutron electric form factor curve and full covariance. The hard outputs are the near-zero slope sign in a preregistered low-Q² window, the stability of the mapping to the effective mean-squared charge radius, and the inversion-derived spatial indicators r0, Cn, and Kn that score the zero crossing, inner–outer sign reversal, and cancellation consistency across energy regions, facilities, and extraction routes.
The audit locks the aperture before any verdict. The low-Q² window, fit families, radiative corrections, normalization rules, and allowed systematic variations are preregistered; two independent extraction routes and two inversion families run in parallel; labels or normalization constants stay blinded during fitting and inversion; a held-out data portion validates but may not define the headline claim; and charge-neutrality is enforced consistently, with any alternative implementation treated only as a parallel aperture.
Null pressure must show that the cancellation profile is not a method artifact. Monotonic pseudo-data with matched sampling and correlations must fail to produce a stable zero crossing or robust sign reversal; reversible truncation of the low-Q² window may not flip the slope sign arbitrarily; small perturbations to radiative corrections, two-photon exchange, or normalization may not reverse the direction of the result; and alternative charge-neutrality implementations may not create or erase the profile by themselves.
Support requires a stable low-Q² slope sign across multiple datasets and at least two extraction routes, a reproducible cancellation-style inversion profile with stable r0 and robust Cn/Kn across inversion families, and nulls plus holdouts that fail to build the same pattern. Falsification follows from slope-sign drift, monotonic inversions with no stable zero crossing, nulls that reproduce comparable profiles, or held-out validation collapse. The named adversaries are limited low-Q² coverage, correction-model dependence, and regularization or constraint coupling that dominates the data.
So the chapter closes only one translated neutron low-Q² slope and inversion ledger aligned with the V02/V08/V09 interface lane. “Negative charge radius” may survive only as a slope-sign and inversion-readout term, not as a neutron ontology noun or literal spatial object. Its clean onward value is to hand a disciplined cancellation-profile grammar to 33.62, 33.63, and 33.64.