New functors for estimation of helicity angle
This MR implements new functors for the estimation of the cosine of particle helicity angle. These functors were required in lhcb-dpa/project#221.
Two definitions of the helicity angle were implemented:
- The angle between the particle's momentum vector and its grandparent's momentum vector in the parent's rest frame (
MC_COSTHETAH,COSTHETAH). - The angle between the particle's momentum vector in the mother rest frame and the mother's momentum vector in the lab frame (
MC_COSTHETA,COSTHETA).
The implementation of the helicity angle functors relies on the new boost functor, which transforms the first argument (four-vector) into the frame, where the second argument (four-vector) is at rest.
Goes with DaVinci!1040 (merged).
Merge request reports
Activity
mentioned in merge request DaVinci!1040 (merged)
added RTA label
added DPA-WP3 label
- Resolved by Volodymyr Svintozelskyi
(Apologies for jumping in randomly)
I would avoid relying on the MCMother to give the result you expect from the physics point-of-view. Consider the case:
X-> Y(AB) CYou want the helicity angle of, for example, particle A, so, the angle between A and C in the rest frame of Y (or any equivalent formulation). The problem here is that what you say the mother particle of A is ill-defined; in the case of some EvtGen models it will be Y; but if you were to use for example any of the D_DALITZ models the mother of A would be X. In this sense, it is always better to be explicit on exactly what angle between which final state particles (and which frame) you are using.
Edited by Timothy David Evans - Last reply by Volodymyr Svintozelskyi
