%0 Journal Article
%A Mikhasenko, M.
%A Pilloni, A.
%A Jackura, A.
%A Albadalejo, M.
%A Fernández Ramírez, César
%A Mathieu, Vincent
%A Nys, J.
%A Rodas Bilbao, Arkaitz
%A Ketzer, B.
%A Szczepaniak, Adam P.
%T Pole position of the a_1 (1260) from tau-decay
%D 2018
%@ 2470-0010
%U https://hdl.handle.net/20.500.14352/13024
%X 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.
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