Abstract
Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons ${D_{s0}^*(2317)}$ and ${D_{s1}(2460)}$, were observed that do not conform with quark model expectations. It was recently demonstrated that various puzzles in the charm meson spectrum find a natural resolution, if the SU(3) multiplets for the lightest scalar and axial-vector states, amongst them the ${D_{s0}^*(2317)}$ and the ${D_{s1}(2460)}$, owe their existence to the nonperturbative dynamics of Goldstone-Boson scattering off $D_{(s)}$ and $D^*_{(s)}$ mesons. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. In this work we demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the ${B^-\to D^+\pi^-\pi^- }$ provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, 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.
Highlights
Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons DÃs0ð2317Þ and Ds1ð2460Þ, have been observed that do not conform with quark-model expectations
We demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the B− → Dþπ−π− provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, 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
One of the currently most challenging problems in fundamental physics is to understand the nonperturbative regime of Quantum Chromodynamics (QCD), the fundamental theory for the interaction of quarks and gluons
Summary
We will employ here the next-to-leading order (NLO) version whose free parameters have been fixed to the Goldstone-boson–charm-meson scattering lengths determined in fully dynamical LQCD in channels without disconnected diagrams [32] Later it was demonstrated [39] that these coupled-channel amplitudes properly predict the energy levels generated in LQCD (with a pion mass Mπ ≃ 391 MeV) for the isospin-1=2 channel even beyond the threshold [40]. Note that the trajectory of the pole displayed, in particular that in a certain parameter range resonance poles exist in the complex energy plane below threshold, is common for two-meson states in a relative S-wave This feature is discussed in quite general terms in Ref. We show that our resolution to these puzzles is backed by precise experimental data by showing that the amplitudes with the two DÃ0 states are fully consistent with the LHCb measurements of the reaction
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