Person: Mathieu, Vincent
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First Name
Vincent
Last Name
Mathieu
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física Teórica
Area
Física Teórica
Identifiers
3 results
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Item Three-body scattering: ladders and resonances(Journal of High Energy Physics, 2019) Mikhasenko, M.; Wunderlich, Y.; Jackura, A.; Mathieu, Vincent; Pilloni, A.; Ketzer, B.; Szczepaniak, A.P.We discuss unitarity constraints on the dynamics of a system of three interacting particles. We show how the short-range interaction that describes three-body resonances can be separated from the long-range exchange processes, in particular the one-pion-exchange process. It is demonstrated that unitarity demands a specific functional form of the amplitude with a clear interpretation: the bare three-particle resonances are dressed by the initial- and final-state interaction, in a way that is consistent with the considered long-range forces. We postulate that the resonance kernel admits a factorization in the energy variables of the initial- and the final-state particles. The factorization assumption leads to an algebraic form for the unitarity equations, which is reminiscent of the well-known two-body-unitarity condition and approaches it in the limit of the narrow-resonance approximation.Item Determination of the pole position of the lightest hybrid meson candidate(Physical review letters, 2019) Rodas Bilbao, Arkaitz; Pilloni, A.; Albaladejo, M.; Fernández Ramírez, César; Jackura, A.; Mathieu, Vincent; Mikhasenko, M.; Nys, J.; Pauk, V.; Ketzer, B.; Szczepaniak, A. P.Mapping states with explicit gluonic degrees of freedom in the light sector is a challenge, and has led to controversies in the past. In particular, the experiments have reported two different hybrid candidates with spin-exotic signature, pi¬_1(1400) and pi_1 (1600), which couple separately to eta pi and eta'pi. This picture is not compatible with recent Lattice QCD estimates for hybrid states, nor with most phenomenological models. We consider the recent partial wave analysis of the eta^(')pi system by the COMPASS Collaboration. We fit the extracted intensities and phases with a coupled-channel amplitude that enforces the unitarity and analyticity of the S matrix. We provide a robust extraction of a single exotic pi_1 resonant pole, with mass and width 1564 +/- 24 +/- 86 and 492 +/- 54 +/- 102 MeV, which couples to both eta^(')pi channels. We find no evidence for a second exotic state. We also provide the resonance parameters of the a_2 (1320) and a_2^' (1700).Item Pole position of the a_1 (1260) from tau-decay(Physical review D, 2018) Mikhasenko, M.; Pilloni, A.; Jackura, A.; Albadalejo, M.; Fernández Ramírez, César; Mathieu, Vincent; Nys, J.; Rodas Bilbao, Arkaitz; Ketzer, B.; Szczepaniak, Adam P.We perform an analysis of the three-pion system with quantum numbers J(PC) = 1(++) thornthorn produced in the weak decay of tau leptons. The interaction is known to be dominated by the axial meson alpha(1) (1260). We build a model based on approximate three-body unitary and fix the free parameters by fitting it to the ALEPH data on tau- -> pi(-)pi(+)pi(-)nu(tau) decay. We then perform the analytic continuation of the amplitude to the complex energy plane. The singularity structures related to the pi pi subchannel resonances are carefully addressed. Finally, we extract the alpha(1) (1260) pole position m(p)((a1(1260)) - i Gamma((a1(1260))(p) /2 with m(p)((a1(1260)) = (1209 +/- 4(-9)(+12)) MeV, Gamma((a1(1260))(p) = (576 +/- 11(-20)(+89)) MeV.