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ComPWA / qrules

Rule-based particle reaction problem solver on a quantum number level
https://qrules.rtfd.io
Apache License 2.0
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Use different formalism (helicity, canonical) in production and decay #6

Open apitka opened 5 years ago

apitka commented 5 years ago

If we want to have it:

Technically one can use a different formalism in the production and decay process.

Helicity Ampltude: A_H = Norm D-Function A_lam1,lam2 * D-Function B_lam3,lam4 with production amplitudes A and decay amplitudes B

One can replace e.g. only A_lam_1,lam_2 by (prodction process)

A_lam1,lam2 = CG_lamlam CG_LS aLS

and leave B_lam3,lam4 (decay process) unchanged. This would mean canonical amplitudes for production and helicity amplitudes for decay.

E.g. J/psi -> gamma f2 with f2 --> pi0 pi0

Use canonical amplitudes for the f2 decay: L=2 S=0 Use helicity amplitudes for the production process: F12, F11 , F01 Canonical production amplitudes would be: aLS = a01, a21, a22, a23, a43

This feature might in particular be usefull for channels with a photon.

zhang-jingqing commented 5 years ago

this is possible if we mix the different amplitude configurations when generate the input xml file. The C++ part will only translate canonical part of xml to the canonical amplitudes and let the rest to be helicity amplitudes

spflueger commented 5 years ago

Ok, good to know. Then it should be rather easy to do. I will do that next week. Btw can't you then just use the helicity and canonical formalism interchangeably at every single decay node?

zhang-jingqing commented 5 years ago

Yes. I think we can. The C++ part only translate the HelicityDecay nodes which contain a CanonicalSum node, by putting the ClebschGordan as a prefactor, and get the orbital angular momentum from the CanonicalSum. If there is no CanonicalSum node, C++ part will take it as a helicity amplitude.

spflueger commented 5 years ago

Ok, very good. I think the implementation on the expert system side should be fairly easy. But I need to change the user interface a bit so that the use is able to choose the formalism for each individual interaction node (decay node)