13.11.2018 15:15

Sonderseminar Sören Lange (Universität Gießen)

XYZ states at Belle and Belle II

In recent years, an increasing number of narrow states with heavy quarks has been observed, often denoted as XYZ states. Despite ongoing experimental and theoretical efforts, the underlying pattern is still not known completely. Some of the states reveal surprising properties such as isospin violation in the decay or electrical charge, implying a minimal quark content of 4 quarks. Interpretations as e.g. meson-meson molecules, tetraquarks, gluonic hybrids, but also kinematical threshold effects have been proposed. The present status of knowledge will be reviewed briefly, with emphasis on results of the Belle experiment.


The Belle II experiment, an upgrade of the Belle experiment, started data taking in 2018. In the final stage, up to 80 Million B mesons per day are planned, which will enable searches for yet non-observed XYZ states and yet non-observed XYZ decays, possibly even rare decays with permille level branching fractions. Multi-dimensional fits will provide sensitivity to widths of narrow states in the sub-MeV regime.


A new subdetector in Belle II is a pixel vertex detector with presently 4 Million pixels, which will significantly increase the reconstruction efficiency of threshold-near states. The readout system of the PXD requires highly parallelized processing on an FPGA farm (Field Programmable Gate Arrays) and optical links with high bandwidth of multi-gigabit per second.


As ongoing projects, the search for partner states of the X(3872) and the search for stable tetraquarks will be discussed.


Hörsaal HISKP, Raum 0.023

Kategorie: News, HISKP News, Kolloquium