XVIII International Conference on Hadron Spectroscopy and Structure (HADRON2019)

The GlueX experiment, which is focused on studying the hadron spectrum using polarized photoproduction, completed its initial phase of data taking in the fall of 2018. These data will provide the opportunity to study production mechanisms of mesons as well as searches for new states in the hadron spectrum, including those with gluonic degrees of freedom. In addition, the GlueX collaboration...

The explanation of the large $e^{+}e^{-}\rightarrow\pi^{+}\pi^{-}% \Upsilon\left(ns\right) $ $\left( n=1,2,3\right) $ widths at $\sqrt {s}=10.866\pm0.002$ GeV near the $\Upsilon\left( 10860\right) $ peak [1], about two orders of magnitude larger than those for $\Upsilon\left(ns\right)$$\rightarrow\pi^{+}\pi^{-}%$ $\Upsilon\left(1s\right)$ $\left( n=2,3,4\right) ,$ has been in...

We study the the ground state for $a_1$ meson and the next radial excitation of $a_1$ meson from a quenched lattice QCD simulation with the truncated overlap fermions formalism based on the domain wall fermions. Our results are consistent with the experimental values.

Recent lattice data on smaller strange quark mass than the physical one allow us to study the strangeness dependence of connected observables as pseudoscalar decay constants and ($I=J=1$) -$\pi\pi$ -phase shifts for the first time. Moreover, we perform a global analysis on TrM $=c$ and $m_s=c$ trajectories, which guide new predictions on trajectories like $m_u=c$. Unitarized one-loop Chiral...

Deciphering the complicated structure around 4.2 GeV observed by many experiments, we embed only one charmoniumlike state $Y(4220)$ into the $J/\psi$ family, which plays a role of a scaling point when constructing higher charmonia above 4 GeV. To test this scenario, we provide the detailed decay properties of $Y(4220)$, and predict its partner as $\psi(4380)$ in a $4S$-$3D$ mixing scheme,...

I will review the status of mesons with heavy quarks. The insights these states give into QCD dynamics and the outstanding issues will be discussed. Specific examples of theoretical issues and needed experimental inputs are presented for heavy-light, quarkonium-like and possible exotics states.

We report a new measurement of the $e^+e^-\to \Upsilon(nS)\pi^+\pi^-$ ($n=1,2,3$) cross sections at energies from 10.52 to 11.02 GeV, where we observe a new structure in the energy dependence of the cross sections and find evidence for the $\Upsilon(1S)\pi^+\pi^-$ production below the $B\bar{B}$ threshold. Along with this we also present observation of $e^+e^- \to \gamma \chi_{c1}$ and...

We have performed a calculation of the DD¯, DD¯*, D*D¯, D*D¯* components in the wave function of the ψ(3770). For this we make use of the P03 model to find the coupling of ψ(3770) to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the e+e-→DD¯ reaction, from where we determine a form factor needed in the...

The nature of phi(2170) is still unclear. phi(2170) is proposed to be a traditional s s-bar state, an s s-bar g hybrid, a tetraquark state, a Lambda Lambda-bar bound state, or a phi KK resonance state. The predicted decay width of the individual explanations is quite different. Information from experiments on the known decay modes of phi(2170) is limited, and the measured values of mass and...

QCD Gaussian sum-rules are used to explore the vector ($J^{PC}=1^{--}$) strangeonium hybrid interpretation of the Y(2175). Using a two-resonance model consisting of the Y(2175) and an additional resonance, we find that the relative resonance strength of the Y(2175) in the Gaussian sum-rules is less than 5\% that of a heavier $2.9$ GeV state. This small relative strength presents a challenge...

The Belle II experiment at the SuperKEKB energy-asymmetric $e^+ e^-$ collider is a substantial upgrade of the B factory facility at the Japanese KEK laboratory. The design luminosity of the machine is $8\times 10^{35}$ cm$^{-2}$s$^{-1}$ and the Belle II experiment aims to record 50 ab$^{-1}$ of data, a factor of 50 more than its predecessor. With this data set, Belle II will be able...

We investigate the semileptonic B−c→ ̄νll X decays with X(=X(3930),X(3940),X(4160)) resonances. We take into account these resonances as dynamically generated from the vector–vector interaction in the charm sector. The X(3930) and X(3940) states are D∗ ̄D∗ molecules and the X(4160) is D∗s ̄D∗s molecule. We also look at the production of D∗ ̄D∗ and D∗s ̄D∗s close to threshold and we make...

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We will briefly review the Regge approach to the hadron spectrum and advocate a dynamical emergence of principal quantum number in the known spectrum of light non-strange mesons. Further we show how the linear radial trajectories with universal slope can be extended to heavy quarkonia and give a qualitative string interpretation. After that we propose a novel and non-string mechanism leading...

With the world’s largest sample of J/psi 1.3 billion events accumulated at the BESIII detector offers a unique opportunity to study light hadron spectroscopy and decays. In this presentation, recent results of the light hadron physics at BESIII will be highlighted. The BESIII experiment has made significant progresses on the light hadron spectroscopy in the J/psi decays, including the...

COMPASS is a multi-purpose fixed-target experiment at CERN aimed at studying the structure and spectrum of hadrons. The two-stage spectrometer has a large acceptance over a wide kinematic range. Thus, it can be used to investigate a wide range of reactions. Diffractive production of mesons is studied with a negative hadron beam with a momentum of $190~\text{GeV}/c$. So far, COMPASS has...

We report a robust prediction of heavy $K^\ast$ meson, which can be viewed as the excited Kaon state with hidden charm, through a study of the three-body system $KD\bar{D}^\ast$ using the fixed-center approximation to the Feddeev equations [1]. The two-body interactions are stringently constrained by the experimental as well as theoretical investigations. Concrete coupled channel three-body...

The quark model has been applied with considerable success to mass spectra, strong and electromagnetic decays of hadrons. In these approaches only the degrees of freedom of the valence quark are retained, thus the pions are simply treated as interacting $q\bar{q}$ pairs, which are identical to the $\rho$ mesons except for the spin quantum number. Meanwhile, from the point of view of QCD the...

Radiative transitions between charmonium states have been widely studied theoretically and experimentally as probes reflecting their internal structure. In particular, since the constituent quark model can classify the excited states systematically, it has been useful tools for exploring undiscovered states and determining the quantum number of newly observed states. In recent years, the...

The KLOE-2 experiment completed its data-taking at the e+e- DAPHNE collider in Frascati, achieving the integrated luminosity goal of more than 5 fb-1 at the phi peak. KLOE-2 represents the continuation of KLOE with an upgraded detector and an extended physics program, which includes the study of light meson properties and decay dynamics with unprecedented statistics. The new data sample,...

The primary goal of the GlueX experiment at Jefferson Lab is to search for and map the spectrum of light hybrid mesons. Many experiments have studied and reported evidence of exotic mesons decaying into $\eta\pi$ and $\eta'\pi$ final states. With a large acceptance to both charged and neutral particles, GlueX has access to both the neutral, $\gamma p\to\eta^{(')}\pi^{0}p$, and charged,...

We propose a tetraquark mixing framework for the two light-meson nonets in the $J^P = 0^+$ channel, the light nonet $f_0(500), f_0(980), a_0(980), K_0^∗(800)$ and the heavy nonet $f_0(1370), f_0(1500), a_0(1450), K_0^∗(1430)$. According to this framework, one can introduce two types of tetraquark with different spin configuration, $|J, J_{12}, J_{34}⟩ = |000⟩, |011⟩$, where $J$ is the spin...

In this work we discuss how to construct the Regge trajectories for light mesons and baryons in the context of a bottom-up holographic model consisting on a five-dimensional AdS background deformed with a quadratic function in the holographic coordinate. We fit the scalar meson $f_0$, vector meson rho, baryons with spin $1/2^+$ and spin $3/2^+$ trajectories. These results are in fine...