$\tau \rightarrow 3\pi + \nu_\tau$ PWA at Belle: Neural Net Magic and Big Dima's Black Box

by Andrei Rabusov (TUM)

Thursday 14 Jul 2022, 09:30 → 11:00 Europe/Berlin

In many searches for New Physics one needs to know parameters of
various hadron form-factors.  In case of the axial form-factor, different
measurements significantly disagree about the mass and
width of the $a_1(1260)$ --- the axial meson ground state. Moreover, the
COMPASS experiment has observed a potential new hadron resonance, the
$a_1(1420)$, that does not fit into the Quark Model. The main goal of this
analysis is to verify the existence of $a_1(1420)$ in different experimental
conditions at the Belle detector and to reveal a clear picture on $a_1(1260)$
by studying 50 million events of the tauon decay to three charged pions
and a tau neutrino. In contrast to previous analyses of this decay, I
use the partial-wave decomposition method, which enables us to extract
detailed information of such a complicated hadron system. I am going to
present the preliminary results on the $a_1(1260)$ and $a_1(1420)$, as well as
as on pseudo-scalar and spin-exotic components using 20% of the Belle data.
After completing the analysis, these results can be used in the
measurements of tauon electric and magnetic dipole moments and tauon
Michel parameters.