Initial commit

Base modular structure (phase space, Fermi function)
Initial .gitignore

.gitignore

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+# =========================
+
+# 🐍 Python
+
+# =========================
+
+**pycache**/
+*.py[cod]
+*$py.class
+
+# C extensions
+
+*.so
+
+# Distribution / packaging
+
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+
+# =========================
+
+# 🧪 Virtual environments
+
+# =========================
+
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# =========================
+
+# 🧠 Type checking / linting
+
+# =========================
+
+.mypy_cache/
+.pytest_cache/
+.ruff_cache/
+.pyre/
+.hypothesis/
+
+# =========================
+
+# 📓 Jupyter / IPython
+
+# =========================
+
+.ipynb_checkpoints/
+
+# IPython
+
+profile_default/
+ipython_config.py
+
+# =========================
+
+# 📊 Data / outputs (customize!)
+
+# =========================
+
+# Ignore generated spectra, fits, etc.
+
+data/
+outputs/
+results/
+*.npy
+*.npz
+*.h5
+*.hdf5
+*.pkl
+
+# But keep small example data if needed
+
+# !data/example/
+
+# =========================
+
+# 🖼️ Plots
+
+# =========================
+
+*.png
+*.jpg
+*.jpeg
+*.pdf
+*.svg
+
+# =========================
+
+# 🧾 Logs
+
+# =========================
+
+*.log
+logs/
+
+# =========================
+
+# ⚙️ IDEs / Editors
+
+# =========================
+
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# =========================
+
+# 🐧 OS / Filesystem
+
+# =========================
+
+.DS_Store
+Thumbs.db
+
+# =========================
+
+# 🧮 Build / C / Fortran (for future physics libs)
+
+# =========================
+
+*.o
+*.out
+*.a
+*.mod
+
+# =========================
+
+# 🧵 HPC / SLURM
+
+# =========================
+
+slurm-*.out
+*.sbatch
+*.srun
+
+# =========================
+
+# 🔐 Secrets / configs
+
+# =========================
+
+.env.local
+.env.*.local
+*.key
+*.pem
+
+# =========================
+
+# 📦 Misc
+
+# =========================
+
+coverage.xml
+htmlcov/
+.cache/
+

beta_spectrum/__init__.py

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+# beta_spectrum/__init__.py
+
+from .constants import ALPHA
+from .units import T_to_W, W_to_T
+
+from .components.phase_space import PhaseSpace
+from .components.fermi import FermiFunction
+
+__all__ = [
+    "ALPHA",
+    "T_to_W",
+    "W_to_T",
+    "PhaseSpace",
+    "FermiFunction",
+]
+
+__version__ = "0.1.0"

beta_spectrum/base.py

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+# base.py
+from __future__ import annotations
+from abc import ABC, abstractmethod
+import numpy as np
+
+
+ArrayLike = np.ndarray
+
+
+class SpectrumComponent(ABC):
+    """
+    Base class for multiplicative components of beta-spectrum
+    """
+
+    @abstractmethod
+    def __call__(self, W: ArrayLike) -> ArrayLike:
+        """
+        Evaluate component  at total energy W (in m_e units)
+        """
+        pass

beta_spectrum/components/fermi.py

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+# components/fermi.py
+import numpy as np
+from scipy.special import loggamma
+
+from ..base import SpectrumComponent
+from ..constants import ALPHA
+from ..utils import nuclear_radius
+
+
+class FermiFunction(SpectrumComponent):
+    def __init__(self, Z: int, A: int):
+        self.Z = Z
+        self.A = A
+        self.alphaZ = ALPHA * Z
+        self.gamma = np.sqrt(1.0 - self.alphaZ**2)
+        self.R = nuclear_radius(A)
+
+    def __call__(self, W: np.ndarray) -> np.ndarray:
+        p = np.sqrt(W**2 - 1.0)
+
+        # Avoid division by zero
+        p = np.where(p == 0, 1e-30, p)
+
+        eta = self.alphaZ * W / p
+
+        # --- log components ---
+
+        # log prefactor
+        log_prefactor = np.log(2 * (1 + self.gamma))
+
+        # log power term
+        log_power = -2 * (1 - self.gamma) * np.log(2 * p * self.R)
+
+        # log gamma ratio
+        z = self.gamma + 1j * eta
+        log_gamma_complex = loggamma(z)
+        log_gamma_abs_sq = 2 * np.real(log_gamma_complex)
+
+        log_gamma_denom = 2 * loggamma(2 * self.gamma + 1).real
+
+        # log exponential
+        log_exp = np.pi * eta
+
+        logF = (
+            log_prefactor
+            + log_power
+            + log_gamma_abs_sq
+            - log_gamma_denom
+            + log_exp
+        )
+
+        return np.exp(logF)

beta_spectrum/components/finite_size.py

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+import numpy as np
+
+from beta_spectrum.constants import ALPHA
+from beta_spectrum.base import SpectrumComponent

beta_spectrum/components/phase_space.py

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+# components/phase_space.py
+import numpy as np
+from ..base import SpectrumComponent
+
+
+class PhaseSpace(SpectrumComponent):
+    def __init__(self, W0: float, m_nu: float = 0.0):
+        self.W0 = W0
+        self.m_nu = m_nu
+
+    def __call__(self, W: np.ndarray) -> np.ndarray:
+        p = np.sqrt(W**2 - 1.0)
+        Wv = self.W0 - W
+
+        # neutrino mass generalization
+        if self.m_nu == 0:
+            return p * W * Wv**2
+        else:
+            return p * W * Wv * np.sqrt(Wv**2 - self.m_nu**2)

beta_spectrum/constants.py

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+# constants.py
+ALPHA = 1 / 137.035999084  # fine-structure constant
+HBAR_C_MEV_FM = 197.3269804  # MeV * fm
+ME_MEV = 0.510998950  # MeV

beta_spectrum/spectrum.py

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+# spectrum.py
+import numpy as np
+from typing import List
+from .base import SpectrumComponent
+
+
+class BetaSpectrum:
+    def __init__(self, components: List[SpectrumComponent]):
+        self.components = components
+
+    def __call__(self, W: np.ndarray) -> np.ndarray:
+        result = np.ones_like(W)
+
+        for comp in self.components:
+            result *= comp(W)
+
+        return result

beta_spectrum/units.py

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+# units.py
+import numpy as np
+
+ME_KEV = 510.99895000  # keV electron mass
+
+
+def W_to_T(W: float | np.ndarray) -> np.ndarray:
+    return (W - 1.0) * ME_KEV
+
+
+def T_to_W(T_keV: float | np.ndarray) -> np.ndarray:
+    return T_keV / ME_KEV + 1.0

beta_spectrum/utils.py

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+# utils.py
+from .constants import HBAR_C_MEV_FM, ME_MEV
+
+
+def nuclear_radius(A: float) -> float:
+    r0_fm = 1.2  # fm
+    R_fm = r0_fm * A ** (1 / 3)
+
+    return R_fm / (HBAR_C_MEV_FM / ME_MEV)

pyproject.toml

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+[build-system]
+requires = ["setuptools>=61.0"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "beta-spectrum"
+version = "0.1.0"
+description = "High-precision beta spectrum calculation for nuclear physics"
+authors = [
+    { name = "Your Name" }
+]
+requires-python = ">=3.10"
+
+dependencies = [
+    "numpy",
+    "scipy",
+    "matplotlib"
+]
+
+[tool.setuptools.packages.find]
+where = ["."]
+
+[project.optional-dependencies]
+dev = [
+    "pytest",
+    "black",
+    "ruff",
+    "mypy"
+]
+
+[tool.mypy]
+python_version = "3.10"
+strict = true
+
+[tool.black]
+line-length = 88
+
+[tool.ruff]
+line-length = 88