B-matrix extension of polarimeter

B-matrix extension of polarimeter#

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from __future__ import annotations

import logging
from pathlib import Path
from warnings import filterwarnings

import jax.numpy as jnp
import matplotlib.pyplot as plt
import numpy as np
import polarimetry
import sympy as sp
from ampform.sympy import PoolSum
from IPython.display import display
from polarimetry import _to_index
from polarimetry.data import create_data_transformer, generate_meshgrid_sample
from polarimetry.io import (
    mute_jax_warnings,
    perform_cached_doit,
    perform_cached_lambdify,
)
from polarimetry.lhcb import load_model_builder, load_model_parameters
from polarimetry.lhcb.particle import load_particles
from sympy.physics.matrices import msigma
from tqdm.auto import tqdm

filterwarnings("ignore")
logging.getLogger("polarimetry.function").setLevel(logging.INFO)
mute_jax_warnings()
POLARIMETRY_DIR = Path(polarimetry.__file__).parent

Formulate expressions#

Reference subsystem 1 is defined as:

orientation-K.svg

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MODEL_CHOICE = 0
MODEL_FILE = POLARIMETRY_DIR / "lhcb/model-definitions.yaml"
PARTICLES = load_particles(POLARIMETRY_DIR / "lhcb/particle-definitions.yaml")
BUILDER = load_model_builder(MODEL_FILE, PARTICLES, model_id=MODEL_CHOICE)
IMPORTED_PARAMETER_VALUES = load_model_parameters(
    MODEL_FILE, BUILDER.decay, MODEL_CHOICE, PARTICLES
)
REFERENCE_SUBSYSTEM = 1
MODEL = BUILDER.formulate(REFERENCE_SUBSYSTEM, cleanup_summations=True)
MODEL.parameter_defaults.update(IMPORTED_PARAMETER_VALUES)
\[\begin{split} \vec\alpha = \sum_{\nu',\nu,\lambda} A^*_{\nu',\lambda}\vec\sigma_{\nu',\nu} A_{\nu,\lambda} / I_0 \\ \vec\beta = \sum_{\nu,\lambda',\lambda} A^*_{\nu,\lambda'} \vec\sigma_{\lambda',\lambda} A^*_{\nu,\lambda} / I_0 \\ B_{\tau,\rho} = \sum_{\nu,\nu',\lambda',\lambda} A^*_{\nu',\lambda'} \sigma_{\nu',\nu}^\tau A_{\nu,\lambda} \sigma_{\lambda',\lambda}^\rho \end{split}\]

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half = sp.Rational(1, 2)
λ, λp = sp.symbols(R"lambda \lambda^{\prime}", rational=True)
v, vp = sp.symbols(R"nu \nu^{\prime}", rational=True)
σ = [sp.Matrix([[1, 0], [0, 1]])]
σ.extend(msigma(i) for i in (1, 2, 3))

ref = REFERENCE_SUBSYSTEM
B = tuple(
    tuple(
        PoolSum(
            BUILDER.formulate_aligned_amplitude(vp, λp, 0, 0, ref)[0].conjugate()
            * σ[τ][_to_index(vp), _to_index(v)]
            * BUILDER.formulate_aligned_amplitude(v, λ, 0, 0, ref)[0]
            * σ[ρ][_to_index(λp), _to_index(λ)],
            (v, [-half, +half]),
            (vp, [-half, +half]),
            (λ, [-half, +half]),
            (λp, [-half, +half]),
        ).cleanup()
        for ρ in range(4)
    )
    for τ in range(4)
)
del ref
B = sp.Matrix(B)

Functions and data#

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progress_bar = tqdm(desc="Unfolding expressions", total=16)
B_exprs = []
for τ in range(4):
    row = []
    for ρ in range(4):
        expr = perform_cached_doit(B[τ, ρ].doit().xreplace(MODEL.amplitudes))
        progress_bar.update()
        row.append(expr)
    B_exprs.append(row)
progress_bar.close()
B_exprs = np.array(B_exprs)
B_exprs.shape

(4, 4)

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progress_bar = tqdm(desc="Lambdifying", total=16)
B_funcs = []
for τ in range(4):
    row = []
    for ρ in range(4):
        func = perform_cached_lambdify(
            B_exprs[τ, ρ].xreplace(MODEL.parameter_defaults),
            backend="jax",
        )
        progress_bar.update()
        row.append(func)
    B_funcs.append(row)
progress_bar.close()
B_funcs = np.array(B_funcs)

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transformer = create_data_transformer(MODEL)
GRID_SAMPLE = generate_meshgrid_sample(MODEL.decay, resolution=400)
GRID_SAMPLE.update(transformer(GRID_SAMPLE))
X = GRID_SAMPLE["sigma1"]
Y = GRID_SAMPLE["sigma2"]
del transformer

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B_arrays = jnp.array([[B_funcs[τ, ρ](GRID_SAMPLE) for ρ in range(4)] for τ in range(4)])
B_norm = B_arrays / B_arrays[0, 0]
B_arrays.shape

(4, 4, 400, 400)

Plots#

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%config InlineBackend.figure_formats = ['png']

plt.rcdefaults()
plt.rc("font", size=16)
s1_label = R"$m^2\left(K^-\pi^+\right)$ [GeV$^2$]"
s2_label = R"$m^2\left(pK^-\right)$ [GeV$^2$]"
fig, ax = plt.subplots(figsize=(8, 6.8))
ax.set_title("$I_0 = B_{0, 0}$")
ax.set_xlabel(s1_label)
ax.set_ylabel(s2_label)
ax.set_box_aspect(1)
ax.pcolormesh(X, Y, B_arrays[0, 0].real)
fig.savefig("b00-is-intensity.png")
plt.show()

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%config InlineBackend.figure_formats = ['png']

plt.rcdefaults()
plt.rc("font", size=10)
fig, axes = plt.subplots(
    dpi=200,
    figsize=(11, 10),
    ncols=4,
    nrows=4,
    sharex=True,
    sharey=True,
)
fig.suptitle(
    R"$B_{\tau,\rho} = \sum_{\nu,\nu',\lambda',\lambda} A^*_{\nu',\lambda'}"
    R" \sigma_{\nu',\nu}^\tau A_{\nu,\lambda} \sigma_{\lambda',\lambda}^\rho$"
)
progress_bar = tqdm(total=16)
for ρ in range(4):
    for τ in range(4):
        ax = axes[τ, ρ]
        ax.set_box_aspect(1)
        if τ == 0 and ρ == 0:
            Z = B_arrays[τ, ρ].real
            ax.set_title(f"$B_{{{τ}{ρ}}}$")
            cmap = plt.cm.viridis
        else:
            Z = B_norm[τ, ρ].real
            ax.set_title(f"$B_{{{τ}{ρ}}} / B_{{00}}$")
            cmap = plt.cm.coolwarm
        mesh = ax.pcolormesh(X, Y, Z, cmap=cmap)
        cbar = fig.colorbar(mesh, ax=ax, fraction=0.047, pad=0.01)
        if τ != 0 or ρ != 0:
            mesh.set_clim(vmin=-1, vmax=+1)
            cbar.set_ticks([-1, 0, +1])
            cbar.set_ticklabels(["-1", "0", "+1"])
        if τ == 3:
            ax.set_xlabel(s1_label)
        if ρ == 0:
            ax.set_ylabel(s2_label)
        progress_bar.update()
progress_bar.close()
fig.tight_layout()
fig.savefig("b-matrix-elements.png")
plt.show()

Hypothesis:

\[\begin{split} B_{0,\rho} = \vec\beta B_{00} \\ B_{\tau,0} = \vec\alpha B_{00} \\ B_{00} = I_0 \end{split}\]

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def plot_field(vx, vy, v_abs, ax, strides=12, cmap=plt.cm.viridis_r):
    mesh = ax.quiver(
        X[::strides, ::strides],
        Y[::strides, ::strides],
        vx[::strides, ::strides].real,
        vy[::strides, ::strides].real,
        v_abs[::strides, ::strides],
        cmap=cmap,
    )
    mesh.set_clim(vmin=0, vmax=+1)
    return mesh


def plot(x, y, z, strides=14):
    plt.rcdefaults()
    plt.rc("font", size=16)
    fig, ax = plt.subplots(figsize=(8, 6.8), tight_layout=True)
    ax.set_box_aspect(1)
    v_abs = jnp.sqrt(x.real**2 + y.real**2 + z.real**2)
    mesh = plot_field(x, y, v_abs, ax, strides)
    color_bar = fig.colorbar(mesh, ax=ax, pad=0.01)
    return fig, ax, color_bar

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%config InlineBackend.figure_formats = ['svg']

fig, ax, cbar = plot(
    x=B_norm[3, 0],
    y=B_norm[1, 0],
    z=B_norm[2, 0],
    strides=10,
)
ax.set_title(
    R"$B_{\tau, 0} / B_{00} = \sum_{\nu',\nu,\lambda}"
    R" A^*_{\nu',\lambda}\vec\sigma_{\nu',\nu} A_{\nu,\lambda} / I_0$"
)
ax.set_xlabel(Rf"{s1_label}, $\quad\alpha_z$")
ax.set_ylabel(Rf"{s2_label}, $\quad\alpha_x$")
cbar.set_label(R"$\left|\vec{\alpha}\right|$")
fig.savefig("alpha-field.svg")
plt.show()

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%config InlineBackend.figure_formats = ['svg']

fig, ax, cbar = plot(
    x=B_norm[0, 3],
    y=B_norm[0, 1],
    z=B_norm[0, 2],
    strides=10,
)
ax.set_title(
    R"$B_{0,\rho} / B_{00} = \sum_{\nu,\lambda',\lambda} A^*_{\nu,\lambda'}"
    R" \vec\sigma_{\lambda',\lambda} A^*_{\nu,\lambda} / I_0$"
)
ax.set_xlabel(Rf"{s1_label}, $\quad \beta_z = B_{{03}}$")
ax.set_ylabel(Rf"{s2_label}, $\quad \beta_x = B_{{01}}$")
cbar.set_label(R"$\left|\vec{\beta}\right|$")
fig.savefig("beta-field.svg")
plt.show()

Note that \(|\alpha| = |\beta|\):

α_abs = jnp.sqrt(jnp.sum(B_norm[1:, 0] ** 2, axis=0))
β_abs = jnp.sqrt(jnp.sum(B_norm[0, 1:] ** 2, axis=0))
np.testing.assert_allclose(α_abs, β_abs, rtol=1e-14)

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%config InlineBackend.figure_formats = ['png']

fig, axes = plt.subplots(
    figsize=(11, 6),
    ncols=2,
    sharey=True,
    tight_layout=True,
)
for ax in axes:
    ax.set_box_aspect(1)
ax1, ax2 = axes
ax1.set_title(R"$\alpha$")
ax2.set_title(R"$\beta$")
ax1.pcolormesh(X, Y, α_abs.real, cmap=plt.cm.coolwarm).set_clim(vmin=-1, vmax=+1)
ax2.pcolormesh(X, Y, β_abs.real, cmap=plt.cm.coolwarm).set_clim(vmin=-1, vmax=+1)
ax1.set_xlabel(s1_label)
ax2.set_xlabel(s1_label)
ax1.set_ylabel(s2_label)
fig.savefig("alpha-beta-comparison.png")
plt.show()
https://github.com/ComPWA/compwa.github.io/assets/29308176/c7268301-11c9-45f2-a5ec-4c2928352a68
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