Polarimetry in Λc⁺ → p K⁻ π⁺

Contents

Polarimetry in Λc⁺ → p K⁻ π⁺#

10.1007/JHEP07(2023)228 10.48550/arXiv.2301.07010 10.5281/zenodo.7544989

\(\Lambda^+_\mathrm{c}\) polarimetry using the dominant hadronic mode

The polarimeter vector field for multibody decays of a spin-half baryon is introduced as a generalisation of the baryon asymmetry parameters. Using a recent amplitude analysis of the \(\Lambda^+_\mathrm{c} \to p K^- \pi^+\) decay performed at the LHCb experiment, we compute the distribution of the kinematic-dependent polarimeter vector for this process in the space of Mandelstam variables to express the polarised decay rate in a model-agnostic form. The obtained representation can facilitate polarisation measurements of the \(\Lambda^+_\mathrm{c}\) baryon and eases inclusion of the \(\Lambda^+_\mathrm{c} \to p K^- \pi^+\) decay mode in hadronic amplitude analyses.

https://doi.org/10.1007/JHEP07(2023)228
Symbolic expressions

Compute the amplitude model over large data samples with symbolic expressions.

Default amplitude model
JSON grids

Reuse the computed polarimeter field in any amplitude analysis involving \(\Lambda_\mathrm{c}^+\).

Exported distributions
Inspect interactively

Investigate how parameters in the amplitude model affect the polarimeter field.

Interactive visualization
Compute polarization

Learn how to determine the polarization vector using the polarimeter field.

Determination of polarization
Download this website as a single PDF file
_static/polarimetry.pdf

This website shows all analysis results that led to the publication of LHCb-PAPER-2022-044. More information on this publication can be found on the following pages:

Behind SSO login (LHCb members only)

Python package#

PyPI package Supported Python versions

Each of the pages contain code examples for how to reproduce the results with the Python package hosted at github.com/ComPWA/polarimetry. However, to quickly get import the model in another package, it is possible to install the package from PyPI:

pip install polarimetry-lc2pkpi

Each of the models can then simply be imported as

import polarimetry

model = polarimetry.published_model("Default amplitude model")
model.intensity.cleanup()
\[\displaystyle \sum_{\lambda_{0}=-1/2}^{1/2} \sum_{\lambda_{1}=-1/2}^{1/2}{\left|{\sum_{\lambda_0^{\prime}=-1/2}^{1/2} \sum_{\lambda_1^{\prime}=-1/2}^{1/2}{A^{1}_{\lambda_0^{\prime}, \lambda_1^{\prime}, 0, 0} d^{\frac{1}{2}}_{\lambda_1^{\prime},\lambda_{1}}\left(\zeta^1_{1(1)}\right) d^{\frac{1}{2}}_{\lambda_{0},\lambda_0^{\prime}}\left(\zeta^0_{1(1)}\right) + A^{2}_{\lambda_0^{\prime}, \lambda_1^{\prime}, 0, 0} d^{\frac{1}{2}}_{\lambda_1^{\prime},\lambda_{1}}\left(\zeta^1_{2(1)}\right) d^{\frac{1}{2}}_{\lambda_{0},\lambda_0^{\prime}}\left(\zeta^0_{2(1)}\right) + A^{3}_{\lambda_0^{\prime}, \lambda_1^{\prime}, 0, 0} d^{\frac{1}{2}}_{\lambda_1^{\prime},\lambda_{1}}\left(\zeta^1_{3(1)}\right) d^{\frac{1}{2}}_{\lambda_{0},\lambda_0^{\prime}}\left(\zeta^0_{3(1)}\right)}}\right|^{2}}\]

For more examples of how to use the codebase, see the following pages.

Table of contents

Tip

Several cross-checks with Julia can be found here.

Tip

Figures for the paper can be downloaded here:

Figure 2:

total-polarimetry-field-watermark.svg

Figure 3a:

polarimetry-field-L1520-unaligned-watermark.svg

Figure 3b:

polarimetry-field-L1520-aligned-watermark.svg

Figure 4:

polarimetry-field-norm-uncertainties-watermark.svg

All other exported figures can be found here.

Notebook execution times

Document

Modified

Method

Run Time (s)

Status

amplitude-model

2026-01-05 21:50

cache

9.68

✅

appendix/alignment

2026-01-05 21:51

cache

54.74

✅

appendix/angles

2026-01-05 21:51

cache

1.87

✅

appendix/benchmark

2026-01-05 21:54

cache

209.02

✅

appendix/dynamics

2026-01-05 21:55

cache

17.35

✅

appendix/homomorphism

2026-01-05 21:55

cache

2.03

✅

appendix/ls-model

2026-01-05 21:56

cache

83.07

✅

appendix/model-serialization

2026-01-05 21:57

cache

26.43

✅

appendix/pc-pv-currents

2026-01-05 22:16

cache

1141.02

✅

appendix/phase-space

2026-01-05 22:16

cache

18.86

✅

appendix/serialization

2026-01-05 22:17

cache

49.81

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appendix/widget

2026-01-05 22:23

cache

407.95

✅

cross-check

2026-01-05 22:24

cache

7.95

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index

2026-01-05 22:24

cache

1.69

✅

intensity

2026-01-05 22:36

cache

743.19

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polarimetry

2026-01-05 22:45

cache

511.54

✅

resonance-polarimetry

2026-01-05 23:51

cache

3984.58

✅

uncertainties

2026-01-06 00:06

cache

891.04

✅

zz.polarization-fit

2026-01-06 00:07

cache

94.02

✅
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