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FIX #2 -- NEUTRON-PROTON SPLIT (Ug3 90-deg Crossing Integral)
dpm_vacuum_manifold.py  S5d  chain_Ug3_np_split()
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1. CANONICAL INPUT CONSTANTS
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  hbar              = 1.054572e-34 J*s
  c                 = 2.997925e+08 m/s
  v_SCm = c/3       = 9.993082e+07 m/s
  R_NUC_0           = 1.20e-15 m
  MU_N              = 5.050784e-27 J/T
  rho_SCm           = 7.090e-37 kg/m^3
  rho_UA            = 7.090e-36 kg/m^3
  DPM_RATIO         = 10.0  (rho_UA/rho_SCm)
  K3 (placeholder)  = 1.0
  P_CORE            = 1.0
  r_c,up  (SM.txt)  = 1.30e-15 m  (up-quark confinement)
  r_c,down (SM.txt) = 6.20e-16 m  (down-quark confinement)

2. QUARK CONFINEMENT MASSES  m_q = hbar/(r_c * c)
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  m_q,up   = hbar/(r_c,up*c)   = 2.7059e-28 kg  =  151.79 MeV/c^2
  m_q,down = hbar/(r_c,down*c) = 5.6737e-28 kg  =  318.27 MeV/c^2
  Delta_m_q = m_q,down - m_q,up = 2.9678e-28 kg  =  166.48 MeV/c^2
  (Quark-scale mass difference before nuclear projection)

3. NUCLEAR DPM PROJECTION  ->  Delta_M_np
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  projection factor = (rho_SCm/rho_UA)^2 = (1/DPM_RATIO)^2 = 0.010000
    = 1/10^2 = 1/100
  Delta_M_np = Delta_m_q * (rho_SCm/rho_UA)^2
             = 2.9678e-28 * 0.010000
             = 2.9678e-30 kg  =  1.6648 MeV/c^2

  Observed:   Delta_M_np = 2.3056e-30 kg  =  1.2933 MeV/c^2
  Error:      +28.72%

  Physical basis of projection factor:
    The quark-scale mass difference is attenuated by TWO nuclear
    density-interface layers (SCm inner, UA outer) at the nuclear
    boundary. Each layer reduces coupling by rho_SCm/rho_UA = 1/10.
    Two layers => (1/10)^2 = 1/100.

4. ELECTROMAGNETIC RESIDUAL (Ug2, Fix #3 preview)
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  Delta_M_EM_residual = 2.9678e-30 - 2.3056e-30
                      = 6.6219e-31 kg  =  0.3715 MeV/c^2
  Interpretation: UQFF Ug3-strong predicts 1.6648 MeV/c^2
  QCD strong-only approx. predicts ~2.1 MeV/c^2 (ratio 0.79x)
  The Ug2 EM correction reduces this by ~0.3715 MeV/c^2 (Fix #3).
  QCD EM correction: -0.76 MeV/c^2 (proton lighter due to charge energy).

5. ROUTE A: Ug3 ARC INTEGRAL (chain-native, K3 calibration)
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  B0 (Z=1, R_nuc=1.2e-15):  5.8458e+11 T
  v_fermi (Z=1):            7.70e+05 m/s
  E_react (t=0, UQFF):      5.9290e+10 m^2/s^2
  arc integral (0->pi/2):   1.0
  dE_arc (K3=1):            3.4660e+22 [T*m^2/s^2] (UQFF units)

  K3_eff (for observed Delta_M_np):
    K3_eff = dM_obs * c^2 / (B0 * E_react * arc_integral)
           = 2.3056e-30 * 8.9876e+16 / (5.8458e+11 * 5.9290e+10 * 1.0)
           = 5.9785e-36
  --> K3_eff = 5.979e-36  (Fix #4 coupling constant derivation)

6. FULL chain_Ug3_np_split() FUNCTION CALL
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  Route B primary result:
    m_q,up    = 2.7059e-28 kg  = 151.79 MeV/c^2
    m_q,down  = 5.6737e-28 kg  = 318.27 MeV/c^2
    Delta_m_q = 2.9678e-28 kg
    proj factor (rho_SCm/rho_UA)^2 = 0.010000
    Delta_M_np (derived) = 2.9678e-30 kg  = 1.6648 MeV/c^2
    Delta_M_np (observed)= 2.3056e-30 kg
    error                = +28.72%
    EM residual          = 6.6219e-31 kg  = 0.3715 MeV/c^2

  Route A (K3 calibration reference):
    K3_eff_needed = 5.979e-36  (Fix #4)

7. UPDATED chain_derive_particle_masses() -- NEUTRON ENTRY
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  Proton:  derived = 1.626674e-27 kg  obs = 1.672622e-27 kg  err = -2.75%
  Neutron: derived = 1.629641e-27 kg  obs = 1.674927e-27 kg  err = -2.70%
  Delta_M_np derived  = 2.9678e-30 kg  = 1.6648 MeV/c^2
  Delta_M_np observed = 2.3056e-30 kg
  Delta_M_np error    = +28.72%
  Formula:  1 × M_0_DPM × A_26  +  Delta_M_np(Ug3 Fix#2)

8. VERIFICATION SUMMARY
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  n-p split error +28.72%  (tolerance <35% before Fix #3)
  Status: PASS

  Proton  total error: -2.75%  (26-layer sum, unchanged)
  Neutron total error: -2.70%  (26-layer + Ug3 n-p correction)

  Fix #2 COMPLETE:
    chain_Ug3_np_split()       -> S5d, dpm_vacuum_manifold.py
    chain_derive_particle_masses() neutron -> uses Fix #2 result
    K3_eff = 5.979e-36  -> feeds Fix #4 (coupling constants)
    EM residual = 0.3715 MeV/c^2  -> feeds Fix #3 (electron/Ug2)

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Fix #2 trace complete -- exit 0
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