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arXiv · hep-ph/9907479

LAB observables for the muon polarization in K^+ --> π^+ μ^+ μ^-

D. Gomez Dumm·J. Vidal
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Abstract

We analyse the muon longitudinal polarization asymmetry Δ_long in the decay K^+ --> π^+ μ^+ mu^-. It is stressed that, since the muon helicities are not Lorentz-invariant quantities, the magnitude of Δ_long depends in general on the reference frame. We consider the muon helicities in the LAB system, and study the sensitivity of the longitudinal polarization asymmetry to the flavour-mixing parameters in the Standard Model for stopped and in-flight decaying K^+. A similar analysis is carried out for the decay K_L --> μ^+ μ^-. We find that in both cases the asymmetry is diluted when increasing the energy of the decaying kaons.

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D. Gomez Dumm, J. Vidal. 1999-07-23. LAB observables for the muon polarization in K^+ --> π^+ μ^+ μ^-. https://doi.org/10.1016/s0370-2693(99)00997-1

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