On a two-lattice crystal a second lattice deposits intensity on one reciprocal
position but not its symmetry mate, so a contaminated reflection is a one-sided
resolution-normalised-E outlier that poisons the operator I(h)/I(Rh) correlation
in SearchSpaceGroup Stage A. On EP_cs_02-424 under -A this dropped the monoclinic
2-fold CC to 0.326 (below the 0.5 gate) -> the crystal was under-called P1 instead
of P2_1. The existing --reject-outliers cannot see it: it rejects WITHIN a P1 orbit,
but the poison is a BETWEEN-orbit effect (inflates orbit h, not its mate Rh).
Add SearchSpaceGroupOptions::max_e_squared_for_cc (default 9.0, i.e. E>3): after the
resolution-normalised Esq[] is computed, drop the extreme-E tail from the correlation
pairs only (the absence stage keeps the full range - that is where the screw signal
lives). Clean Wilson-distributed data almost never reaches E^2=9 (P ~ 0.01-0.3%), so
it is self-targeting - it trims the overlap tail without touching genuine reflections.
EP_cs_02-424 -A: 2-fold CC 0.326 -> 0.64 -> P2_1 (= XDS). Full 24-crystal rotation
battery (pre/post): only EP_cs_02-424 changed (P1 -> P2_1, SG match 20 -> 21/24); all
23 others bit-identical, including the marginal cubic Ins_I_3 (still I23, carried by
the systematic-b rescue). A Friedel-merge-the-search alternative was tried and rejected
(net-negative: did not fix EP424 and regressed Ins_I_3 -> I222).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 4.8
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