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Extracting Angular Observables without a Likelihood and Applications to Rare Decays

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Beaujean Frederik , Chrząszcz Marcin , Serra Nicola , Van Dyk Danny ,
Project Rare decays of B-mesons and the physics of the early Universe
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Original article (peer-reviewed)

Journal Physical Review
Volume (Issue) D(91)
Page(s) 114012
Title of proceedings Physical Review

Open Access

Type of Open Access Repository (Green Open Access)


Our goal is to obtain a complete set of angular observables arising in a generic multi-body process. We show how this can be achieved without the need to carry out a likelihood fit of the angular distribution to the measured events. Instead, we apply the method of moments that relies both on the orthogonality of angular functions and the estimation of integrals by Monte Carlo techniques. The big advantage of this method is that the joint distribution of all observables can be easily extracted, even for very few events. The method of moments is shown to be robust against mismodeling of the angular distribution. Our main result is an explicit algorithm that accounts for systematic uncertainties from detector-resolution and acceptance effects. Finally, we present the necessary process-dependent formulae needed for direct application of the method to several rare decays of interest.