Fix json multichannelbw

[mmikhasenko]

Closes #87

A major problem has been found in implementation of Multichannel BW, in the way how couplings are computed.
The couplings themselves appear only for Flatte. So these values were modified to be consistent with the correct implementation.

• fix json
• fix julia
• fix python

Python side

MultichannelBreitWigner is imported, so since it was matched, the problem might be there as well

from ampform_dpd.dynamics import (
    BreitWigner,
    ChannelArguments,
    EnergyDependentWidth,
    MultichannelBreitWigner,
    P,
    SimpleBreitWigner,
)

[redeboer]

MultichannelBreitWigner is imported, so since it was matched, the problem might be there as well

from ampform_dpd.dynamics import (
    BreitWigner,
    ChannelArguments,
    EnergyDependentWidth,
    MultichannelBreitWigner,
    P,
    SimpleBreitWigner,
)

These features are not released, see here. But good to be aware for future developments.

[mmikhasenko]

The problem should be somewhere here, then,

• definition of MBW
• function to create from dict

[mmikhasenko]

@redeboer could you please help understanding your definition,

m^2-s-imG
G = sum Gi
#
Gi = 1/m * g^2 * 2p/sqrt(s)

In the code, I do not recognize the Gi expression.

[mmikhasenko]

@redeboer do the tests at the PR check the validation points of json in python code?

I'm surprised to see that the json is modified, python code is not modified, but test button is green.

[redeboer]

There are some tests, it seems
ComPWA/ampform-dpd@0.2.0...0.2.1rc0#diff-37a837280345b38e5d2b0707adb33df844b8d44971fcae9fcb1aa340073d16cf
But could well be that they don't cover the part of the code that you're referring to.

[mmikhasenko]

JSON has cross check evaluation, it is surprising that these are not evaluated or pass, given that the lineshape for L1405 changed

[redeboer]

it is surprising that these are not evaluated

Not really. Like I said, this was coded together in an afternoon and is therefore only in a release candidate. Serialization is currently not our priority list.

[mmikhasenko]

This issue is looking forward for being resolved :)

[mmikhasenko]

ping @redeboer

Let's check if your MultichannelBreitWigner does the same as this,
https://github.com/mmikhasenko/HadronicLineshapes.jl/blob/main/src/shapes.jl#L22-L31

before merging, I would like to see,

1. json is changed, python code gives different results as before (as expected, or as julia)
2. the python code is fixed, dependencies are updated
3. python code gives the same result as expected, or as julia