> Suppose the decay a -> b+c , we know the 4 vectors of b and c. We need
> to know the phi angle of b on the a rest frame. First, we took the
> boost vector :
>
> TVector3 boost = -(b+c).BoostVector()
>
> then,
>
> b->Boost(boost);
>
> Could someone tell us which is the direction of the Z axis on the "a"
> rest frame: the lab Z axis or the direction "a"? If we are doing
> something wrong, what is the right way to get this angle?
>
haven't seen this question answered, so:
both reference frames have their axes parallel, so Z-axis in the rest frame
of "a" coincides with the Z-axis in the lab frame.
best, Pasha
P.S. this choice is pretty obvious: otherwise one needs a special effort
to define direction of the axes in the rest frame of "a"...
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