Speaker
Dr
Meng-Lin Du
(Helmholtz-Institut f\"ur Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universit\"at Bonn)
Description
Understanding the hadron spectrum is one of the premier challenges in particle
physics. For a long time, the quark model has served as an
ordering scheme and brought systematics into the hadron zoo.
However, many new hadrons that were observed since 2003, including the
lowest-lying positive-parity charm-strange mesons
$D_{s0}^*(2317)$ and $D_{s1}(2460)$,
do not conform with quark model expectations. Various modifications to the quark model
and alternative approaches have been proposed ever since to explain their low masses and decay
properties. We demonstrate that if the lightest scalar (axial vector) states are
assumed to owe their existence to non-perturbative $\pi /
\eta/K$-$D^{(*)}/D_s^{(*)}$ scattering, various puzzles in the $D$-meson
spectrum get resolved. Most importantly the ordering of the lightest strange and
non-strange scalars becomes natural. We show the
well constrained amplitudes for Goldstone-Boson-$D/D^*$ scattering are fully
consistent with recent high quality data on $B^-\to \pi^-\pi^- D^+$ final
states. This implies that the lowest quark-model positive-parity charm mesons, together
with their bottom cousins, if realized in nature, do not form the ground-state multiplet.
This is similar to the pattern that has been established for the scalar mesons
made from light up, down and strange quarks, where the lowest multiplet is considered to
be made of states not described by the quark model.
In a broader view, the hadron spectrum must be viewed as more than a collection
of quark model states.
Primary author
Dr
Meng-Lin Du
(Helmholtz-Institut f\"ur Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universit\"at Bonn)
Co-authors
Prof.
Christoph Hanhart
(Institute for Advanced Simulation, Institut f\"ur Kernphysik and J\"ulich Center for Hadron Physics, Forschungszentrum J\"ulich)
Dr
De-Liang Yao
(Instituto de F\'isica Corpuscular (IFIC), Centro Mixto CSIC-Universidad de Valencia, Institutos de Investigaci\'on de Paterna)
Prof.
Feng-Kun Guo
(Institute of Theoretical Physics, Chinese Academy of Sciences)
Prof.
Juan Nieves
(Instituto de F\'isica Corpuscular (IFIC), Centro Mixto CSIC-Universidad de Valencia, Institutos de Investigaci\'on de Paterna)
Dr
Miguel Albaladejo
(Departamento de F\'\i sica,Universidad de Murcia)
Mr
Pedro Fernandez-Soler
(Instituto de F\'isica Corpuscular (IFIC), Centro Mixto CSIC-Universidad de Valencia, Institutos de Investigaci\'on de Paterna)
Prof.
Ulf-G. Meissner
(Helmholtz-Institut f\"ur Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universit\"at Bonn)
