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unzhakov 876e1e3ab8 Add massive neutrino support and improve CSV/CLI output

- Add neutrino mass parameter to SpectrumConfig and CLI interface
- Update PhaseSpace component to handle neutrino mass effects properly
- Update CSV headers to show basic endpoint and all transition types
- Add --csv-verbosity option to CLI with 'full' and 'concise' options
- Fix comparison plots to properly show linear scale variations
- Add comprehensive tests for neutrino mass functionality

2026-07-02 10:33:28 +03:00

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Nuclear Shell Model for β Decay

Overview

The Nuclear Shell Model (NSM) is the primary theoretical framework for computing nuclear matrix elements (NMEs) in β decay. For forbidden nonunique decays like ⁹⁹Tc, the NSM computes one-body transition densities (OBTDs) that weight the single-particle transitions contributing to the decay.

Key Codes

Code	Description	Valence Spaces
NUSHELLX	Standard NSM code	Multiple (pf, sdg, etc.)
KSHELL	High-performance NSM	Custom valence spaces

Valence Spaces for ⁹⁹Tc

glekpn (Mach interaction)

Protons: 0f₇/₂, 0f₅/₂, 2p₃/₂, 2p₁/₂, 1g₉/₂
Neutrons: 0g₉/₂, 0g₇/₂, 1d₅/₂, 1d₃/₂, 2s₁/₂

jj45pnb (Brown-Lisetskiy interaction)

Protons: 0f₅/₂, 2p₃/₂, 2p₁/₂, 1g₉/₂
Neutrons: 0g₇/₂, 1d₅/₂, 1d₃/₂, 2s₁/₂, 0h₁₁/₂

OBTDs for ⁹⁹Tc

Transition	OBTD (glekpn)	OBTD (jj45pnb)
1g₇/₂ → 1g₉/₂	0.00994	0.01107
2d₅/₂ → 1g₉/₂	0.47752	−0.43985

Key insight: The dominant transition is 2d₅/₂ → 1g₉/₂ with OBTD ≈ 0.478. The jj45pnb model gives opposite sign for this transition.

sNME and CVC

The small relativistic vector NME (sNME) is related to the large vector NME via the CVC hypothesis:

sNME = (R/√10) · [W₀ − (m_n − m_p) + E_C] · l-NME

where E_C is the Coulomb displacement energy. For ⁹⁹Tc, [W₀ − (m_n − m_p)] = −0.487 MeV (small Q-value makes this critical).

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