Technical reports#
These pages are a collection of findings while working on ComPWA packages such as
ampform
, qrules
, and tensorwaves
. Most of these findings were not
implemented, but may become relevant later on or could be useful to other frameworks as
well.
TR 
Title 
Details 
Tags 
Status 


Square root over arrays with negative values 
This notebook investigates how to write a square root function in 
lambdification sympy 

Custom lambdification 
lambdification sympy 

Faster lambdification by splitting expressions 
This notebook investigates how to speed up 
lambdification sympy 

ChewMandelstam dispersion integrals 
This report formulates a symbolic dispersion integral to approach the lefthand cut in the form factor for arbitrary angular momentum. The integral is evaluated with SciPy’s 
physics sympy 

Investigation of analyticity 
physics 

Symbolic Kmatrix expressions 
Implementation of this report is tracked through ampform#67. 
physics 

Interactive 3D plots 
This report illustrates how to interact with 
tips 


This report is a sequel to TR005. In that report, the \(\boldsymbol{K}\) was constructed with a 
sympy 

Indexed free symbols 
This report has been implemented in ampform#111. Additionally, tensorwaves#427 makes it possible to lambdify 
sympy 

Symbolic expressions for Lorentzinvariant Kmatrix 
This report is a sequel to TR005. 
physics sympy 

Pvector 
physics sympy 

Helicity angles as symbolic expressions 
This report has been implemented in and ampform#177 and tensorwaves#345. The report contains some bugs which were also addressed in these PRs. 
physics sympy 

Extended DataSample performance 
ampform#198 makes it easier to generate expressions for kinematic variables that are not contained in the 
lambdification sympy 

Spin alignment with data 
In this report, we attempt to check the effect of activating spin alignment (ampform#245) and compare it with Figure 2 in [Marangotto, 2020]. 
physics 

Amplitude model with sum notation 
sympy 

Spin alignment implementation 
This report has been implemented through ampform#245. For details on how to use it, see this notebook. See also TR013 and TR014. 
physics sympy 

Symbolic integral 
This report investigates how to formulate a symbolic integral that correctly evaluates to 
sympy 

Symbolic phase space boundary for a threebody decay 
This reports shows how define the physical phase space region on a Dalitz plot using a Kibble function. 
physics sympy 

Intensity distribution generator with importance sampling 
This reports sets out how data generation with TensorWaves works and what would be the best approach to tackle tensorwaves#402. 
physics tensorwaves 

Integrating Jupyter notebook with Julia notebooks in MySTNB 
This report shows how to define a Julia kernel for Jupyter notebooks, so that it can be executed and converted to static pages with MySTNB. 
DX tips 

Amplitude analysis with zfit 
This reports builds a simple symbolic amplitude model with 
physics sympy tensorwaves 

Polarimeter vector field 
Mikhail Mikhasenko @mmikhasenko, 
physics polarimetry polarization 

Polarimetry: Computing the Bmatrix for Λc→pKπ 
The \(B\)matrix forms an extension of the polarimeter vector field \(\vec\alpha\) (arXiv:2301.07010, see also TR021) that takes the polarization of the proton into account. See arXiv:2302.07665, Eq. (B6). 
physics polarimetry polarization 

Support for Plotly plots in Technical Reports 
3d documentation jupyter sphinx 

Symbolic expressions and model serialization 
Investigation into dumping SymPy expressions to humanreadable format for model preservation. The notebook was motivated by the COMAPV workshop on analysis preservation. See also SymPy printing, parsing, and expression manipulation. 
documentation 

Rotated square root cut 
Investigation of the branch cut in the two Riemann sheets of a square root and what happens if the cut is rotated around \(z=0\). 

Visualization of the Riemann sheets for the singlechannel \(T\) matrix with one resonance pole 
This report investigates and reproduces the Riemann sheets shown in Fig. 50.1 and 50.2 of the PDG. The lineshape parametrization is directly derived with the \(K\)matrix formalism. The transition from the first physical sheet to the second unphysical sheet is derived using analytic continuation. 

Visualization of the Riemann sheets for the twochannel \(T\)matrix with one pole 
Following TR026, the Riemann sheets for the amplitude calculated within the \(K\)matrix formalism for the twochannel case are visualized. The method of transitioning from the first physical sheet to the unphysical sheets is extended to the two dimensional case using Eur. Phys. J. C (2023) 83:850 in order to visualize the third and the fourth unphysical sheet. 
Execution times
Document 
Modified 
Method 
Run Time (s) 
Status 

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27.76 
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