TA-COL-2021-020

The new Facility for Antiproton and Ion Research (FAIR) is currently
being built at GSI in Darmstadt (Germany), where the PANDA experiment
represents the central part of the hadron physics programme. The field
of hadron spectroscopy has gained new momentum by the discovery of
various new hadronic resonances especially in the charmonium sector over
the past two decades. The nature of many of the so-called
charmonium-like exotic XYZ states are, however, not yet understood.
Precise measurements of hadron properties are mandatory to sort out
different theoretical models and clarify the nature of these new states.
A well known example is the X(3872) (now χc1(3872)) ---
although being the first of the new charmonium-like states discovered
since 2003, the nature of this state is still not understood.

The most important ingredients to address this issue are measurements of
the mass, natural width and in particular the shape of the
χc1(3872). While a high statistic analysis (the most precise one
up to now) recently published by LHCb demonstrated very limited power to
identify the nature, it will be shown, that high-precision energy scan
experiments carried out with pbar-p annihilation at PANDA will have
a high impact on resolving the current ambiguities.