Dear colleagues,
I’d like to use FLUKA to check the effect of muon polarization in the energy spectrum of the daughter electron in the decay. According to the PHYSICS card, SDUM=DECAYS, WHAT(1)=1 enables the polarization to be accounted for in the decay of pions and muons.
Is it possible to use a custom source.f routine to fix the polarization of the beam muon, by fixing the polarization cosines, by default set to:
TXPOL (NPFLKA) = -TWOTWO -2 is a flag for "no polarisation"
TYPOL (NPFLKA) = +ZERZER
TZPOL (NPFLKA) = +ZERZER
Reason why I ask is that I see that, in the POLARIZA card, this refers only to photons.
According to the PHYSICS card, SDUM=DECAYS, WHAT(1)=1 enables the polarization to be accounted for in the decay of pions and muons.
There’s no need to pass a PHYSICS card with SDUM=DECAYS to obtain the decay of pions (and kaons) into muons: they are active by default. Furthermore, muons from pion and kaon decay carry (spin) polarization, also out of the box, no extra card needed.
One then obtains a muon-spin-dependent emission direction and energy of e± (and corresponding neutrinos) from muon± decay.
But you raise a valid point: one may indeed define the polarization state not only of photon beams (with direct effect on the final state of Compton cattering and the photoelectric effect), but also the (spin) polarization state of muon beams (with direct effect on energy and angular distribution of emitted products), regardless of whether one uses the POLARIZA card or a dedicated user routine to directly set T{X,Y,Z}POL.
The manual page for the POLARIZA will be amended accordingly. Thanks for your post!