RefineDecay's cross-validation still scored the held-out equivalents on a
studentized chi^2, while the absorption/modulation surfaces were switched to a
sigma-independent Rmeas-like agreement (sum|Is-Iref|/sum|Iref|) precisely
because a correction can "pass" a studentized gate by reshaping sigma without
tightening the intensities. The decay slope scales sigma up on late /
high-angle frames, so it is exposed to the same loophole. Score it the same
way.
On the rotation battery this rejects a spurious slope on a mis-indexed
monoclinic (P2_1) case: the studentized gate had accepted a physically absurd
-74 A^2 "decay" that cross-validated yet collapsed the error model (ISa
7.1 -> 1.1) and CC1/2 (to ~2%); the fractional gate scores it a -50% held-out
loss and skips it. A small genuine ~3 A^2 decay on another crystal now
cross-validates and engages, with CC1/2 unchanged. Every other crystal is
unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 4.8
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