unzhakov
876e1e3ab8
- 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
1.5 KiB
1.5 KiB
ESSM — Enhanced Spectrum Shape Method
Overview
The Enhanced Spectrum Shape Method (ESSM) extends the standard SSM by treating the small relativistic vector nuclear matrix element (sNME) as a free parameter alongside g_A. This allows simultaneous fitting of both the spectral shape AND the experimental half-life.
Motivation
The sNME is difficult to compute accurately in nuclear shell model because it involves contributions outside the valence shell. The CVC prediction gives a "canonical" value, but this assumes a perfect many-body theory — which finite valence spaces are not.
Algorithm
- Fix g_A at a trial value
- Vary sNME to simultaneously fit the experimental half-life
- Because the half-life depends quadratically on sNME, there are typically two solutions for each g_A:
- sNME(c): closer to the CVC value (closeCVC)
- sNME(f): further from the CVC value (farCVC)
- Compare both solutions' spectral shapes with the data
sNME Values for ⁹⁹Tc
| Model | g_A^eff | sNME(c) [fm³] | sNME(f) [fm³] | CVC sNME [fm³] |
|---|---|---|---|---|
| jj45pnb | 1.0 | 0.0666 | −0.0687 | −0.1705 |
| glekpn | 1.0 | 0.1140 | −0.0202 | −0.0080 |
Results from Song et al. (2025)
- Best fit: glekpn with g_A^eff = 1.2, sNME(f) = −0.0698 fm³, χ²_ν = 1.066
- Conclusion: Quenched g_A = 1.0–1.2 with farCVC sNME provides the best agreement with data