Speaker
Fabian Krinner
(M)
Description
Modern hadron-spectroscopy experiments such as COMPASS collect data
samples of unprecedented size, so that novel analysis techniques
become possible and necessary. One such technique is the freed-isobar
partial-wave analysis (PWA). In this approach, fixed parametrizations
for the amplitudes of intermediate states–commonly modeled using
Breit-Wigner shapes–are replaced by sets of step-like
functions that are determined from the data. This approach not only
reduces the model dependence of partial-wave analyses, but also allows
us to study the amplitudes of the intermediate states and their
dependence on the parent system.
Since such an approach leads to a dramatic increase in degrees of
freedom of the PWA model, continuous mathematical ambiguities may
appear in fits to data. We will show, how these ambiguities can be
identified and resolved without spoiling the advantage of
model-independence.
We will also present results of a freed-isobar PWA performed on the
large data set on diffractive production of three charged pions
collected by the COMPASS experiment, which consists of $46\times10^6$
exclusive events. We will focus on results for the wave with
spin-exotic quantum numbers $J^{PC}=1^{-+}$, in particular on its
decay into $\rho(770)+\pi^-$. Here, the freed-isobar PWA method
provides insight into the interplay of three- and two-particle
dynamics.
Primary author
Fabian Krinner
(M)
