Pole position of the a_1 (1260) from tau-decay
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2018
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American Physical Society
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Abstract
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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© American Physical Society.
This work was supported by the German Bundesministerium für Bildung und Forschung, the U.S. Department of Energy under Grants No. DE-AC05-06OR23177 and No. DE-FG02-87ER40365, Research Foundation—Flanders (FWO), PAPIIT-DGAPA (UNAM, Mexico) under Grants No. IA101717 and No. IA101819, CONACYT(Mexico)underGrantNo.251817,U.S.National Science Foundation under Grant No. PHY-1415459,Ministerio de Ciencia, Innovación y Universidades (Spain) Grants No. FPA2016-77313-P and No. FPA2016-75654-C2-2-P, and Universidad Complutense de Madrid.