https://doi.org/10.1140/epjc/s10052-019-7506-9
Regular Article - Theoretical Physics
Polarization in (quasi-)two-body decays and new physics
1
Laboratoire de Physique Corpusculaire de Clermont-Ferrand, IN2P3/CNRS Université Blaise Pascal, 63177, Aubière Cedex, France
2
Dipartimento di Fisica dell’ Universita’ di Genova and I.N.F.N.-Sez. Genova, Via Dodecaneso, 33, 16146, Genoa, Italy
Received:
4
April
2019
Accepted:
25
November
2019
Published online:
5
December
2019
We consider two-body and quasi-two-body decays of the type 
, where 
and 
are spin-1/2 fermions and B a spin-0 or spin-1 boson. After recalling the non-covariant formalism for decay amplitudes, we derive the expression of the differential decay width and of the polarizations of the final spinning particles, both on- and off-shell. We find an intriguing geometrical interpretation of the results about the polarization. We also illustrate some methods for measuring the polarizations of the resonances and for optimizing data analysis. Then we propose applications to semi-leptonic weak decays, with a major attention to the T-odd component of the polarization; this may help to find, simultaneously, possible time-reversal violations and hints to physics beyond the standard model. We suggest also a CPT test. Last, we discuss some T-odd observables for the production process of and for the study of the strong final state interactions of non-leptonic decays.
© The Author(s) 2019
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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