JPAC, COMPASS collaboration (235 authors)Bordalo, P.Franco, C.Nunes, A.S.Quaresma, M.Quintans, C.Ramos, S.Silva, L.Stolarski, M.2019-02-042019-02-042018-04-10http://dx.doi.org/10.1016/j.physletb.2018.01.017http://hdl.handle.net/10400.26/27385We present a new amplitude analysis of the $\eta\pi$ $D$-wave in $\pi^- p\to \eta\pi^- p$ measured by COMPASS. Employing an analytical model based on the principles of the relativistic $S$-matrix, we find two resonances that can be identified with the $a_2(1320)$ and the excited $a_2^\prime(1700)$, and perform a comprehensive analysis of their pole positions. For the mass and width of the $a_2$ we find $M=(1307 \pm 1 \pm 6)$~MeV and $\Gamma=(112 \pm 1 \pm 8)$~MeV, and for the excited state $a_2^\prime$ we obtain $M=(1720 \pm 10 \pm 60)$~MeV and $\Gamma=(280\pm 10 \pm 70)$~MeV, respectively.engjournal article2019-02-04