Lane cc pn

docs/examples/index.md

@@ -16,6 +16,7 @@ Every notebook also runs in [Google Colab](https://colab.research.google.com/):
 /examples/notebooks/example_jlm
 /examples/notebooks/kd03_neutron_dxs_demo
 /examples/notebooks/builtin_omps_uq
+/examples/notebooks/qepn_analyzing_power
 /examples/notebooks/tabulated_density_demo
 /examples/notebooks/chuq_kduq_comp
 /examples/notebooks/volume_integrals
@@ -54,6 +55,9 @@ Every notebook also runs in [Google Colab](https://colab.research.google.com/):
   walks through posterior sampling, solver setup, and interval construction
   for several of the built-in uncertainty quantified optical potentials in `jitr`.
   [![Open in Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/beykyle/jitr/blob/main/examples/notebooks/builtin_omps_uq.ipynb)
+- [Analyzing power of the quasi-elastic (p,n) reaction](/examples/notebooks/qepn_analyzing_power)
+  pulls nine angular distributions from EXFOR, solves the coupled Lane channels for the charge-exchange transition to the isobaric analog state, and propagates the KDUQ, WLH and CHUQ posteriors through to the analyzing power, an observable that depends almost entirely on the isovector spin-orbit potential.
+  [![Open in Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/beykyle/jitr/blob/main/examples/notebooks/qepn_analyzing_power.ipynb)
 - [Tabulated neutron and proton densities](/examples/notebooks/tabulated_density_demo)
   shows how to grab the tabulated nuclear densities in `jitr`.
   [![Open in Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/beykyle/jitr/blob/main/examples/notebooks/tabulated_density_demo.ipynb)

docs/regression-tests.md

@@ -9,21 +9,30 @@ TALYS. Reference CSVs are committed; neither external code is required in CI.
 uv run pytest tests/regression/
 ```
 
-## Frescox cases (F1–F8)
-
-Eight elastic-scattering cases against LLNL
-[Frescox](https://github.com/LLNL/Frescox), all for p/n + `78Ni`:
-
-| Case | Projectile | E\_lab (MeV) | Source deck |
-|------|-----------|-------------|-------------|
-| F1   | p | 6.9   | `B1-example-el.out` (block 1) |
-| F2   | p | 11.0  | `B1-example-el.out` (block 2) |
-| F3   | p | 49.35 | `B1-example-el.out` (block 3) |
-| F4   | p | 100   | `B1-high-el.in` (block 1) |
-| F5   | p | 200   | `B1-high-el.in` (block 2) |
-| F6   | n | 49.35 | `B1_n-high-el.in` (block 1) |
-| F7   | n | 100   | `B1_n-high-el.in` (block 2) |
-| F8   | n | 200   | `B1_n-high-el.in` (block 3) |
+## Frescox cases (F1–F10)
+
+Ten cases against LLNL [Frescox](https://github.com/LLNL/Frescox): eight
+elastic for p/n + `78Ni`, and two quasi-elastic `(p,n)` to the isobaric
+analog state of `48Ca`.
+
+| Case | Reaction | Projectile | E\_lab (MeV) | Source deck |
+|------|----------|-----------|-------------|-------------|
+| F1   | elastic | p | 6.9   | `B1-example-el.out` (block 1) |
+| F2   | elastic | p | 11.0  | `B1-example-el.out` (block 2) |
+| F3   | elastic | p | 49.35 | `B1-example-el.out` (block 3) |
+| F4   | elastic | p | 100   | `B1-high-el.in` (block 1) |
+| F5   | elastic | p | 200   | `B1-high-el.in` (block 2) |
+| F6   | elastic | n | 49.35 | `B1_n-high-el.in` (block 1) |
+| F7   | elastic | n | 100   | `B1_n-high-el.in` (block 2) |
+| F8   | elastic | n | 200   | `B1_n-high-el.in` (block 3) |
+| F9   | `48Ca(p,n)48Sc(IAS)` | p | 25 | `Ca48_pn_IAS_25MeV.in` |
+| F10  | `48Ca(p,n)48Sc(IAS)` | p | 35 | `Ca48_pn_IAS_35MeV.in` |
+
+F9 and F10 exercise `jitr.xs.quasielastic_pn` rather than
+`jitr.xs.elastic`. Frescox does its own channel-spin algebra, so they are an
+independent check on the spin-flip terms of the `(p,n)` amplitude, which the
+elastic cases cannot see. jitR reproduces both to better than 1.3e-4 at every
+angle.
 
 ## TALYS cases (T1–T4)