Conveners
Hadron spectroscopy
- Nils Hüsken (JGU Mainz)
Hadron spectroscopy
- Igor Danilkin
Hadron spectroscopy
- Alessandro Pilloni (Messina U. and INFN Catania)
Hadron spectroscopy
- Igor Danilkin
Hadron spectroscopy
- Annalisa D'Angelo
The exact dynamics of the quarks and gluons inside the nucleon are a long-standing question in hadron physics. To shed more light on this topic, the excitation spectrum of the nucleons needs to be measured and compared to theoretical models like constituent quark models or lattice QCD calculations. Until now, several predicted resonances - especially at high masses - have not been found by...
Within the strong interaction, the emergence of so-called baryon resonances, such as the nucleon resonance N(1535)1/2-, can be observed. These states can be predicted by the theory of quantum chromodynamics, for example by quark models. However, more resonances are theoretically predicted than have been experimentally found, which is known under the name of the missing-resonance problem....
The three narrow $P_c$ states decaying to J/ψp observed by the LHCb experiment are consistent with earlier predictions for one $\bar D\Sigma_c$ and two $\bar D^*\Sigma_c$ bound states. Their strange partners are expected to exist. Here we present evidence for the production of these $N^*$ resonances with hidden strangeness in various reactions, such as γp → ϕp, γp → K$\Lambda$, γp → KΣ, γp...
This talk focuses on a recent work aiming at determining the composition of certain $N^*$ and $\Delta$ resonances, i.e. whether they are compact states formed directly by quarks and gluons, or hadronic molecules generated from the meson-baryon interaction. The information of the resonance poles is provided by a comprehensive coupled-channel approach, the J\"{u}lich-Bonn model. $13$ states that...
First hidden-charm pentaquark candidate with strangeness, $P_{\psi s}^\Lambda(4338)$, was recently discovered in $B^-\to J/\psi\Lambda\bar{p}$ by the LHCb Collaboration. $P_{\psi s}^\Lambda(4338)$ shows up as a bump at the $\Xi_c\bar{D}$ threshold in the $J/\psi\Lambda$ invariant mass ($M_{J/\psi\Lambda}$) distribution. The $M_{J/\psi\Lambda}$ distribution also shows a large fluctuation at the...
I will discuss scalar and tensor charmonium resonances determined using lattice QCD. Working at $m_\pi\approx 391$ MeV, more than 200 finite-volume energy levels are computed and these are used in extensions of the Lüscher formalism to determine infinite volume scattering amplitudes. Working in the approximation where charm-annihilation is forbidden, the ground state $\chi_{c0}(1P)$ and...
The PDG lists the $\Lambda(1405)$ state, a baryon with quantum numbers $I(J^{P}) = 0 (\frac{1}{2}^{-})$ and strangeness $S = -1$, an object of interest given the difficulties encountered in obtaining this state from quark models. There are discrepancies in the literature whether experimental data is compatible with one or two nearby poles in this region, and what the position of those poles in...
We investigated the meson-baryon scattering using time-order perturbation theory (TOPT) based on the covariant chiral effective field theory. Renormalized scattering amplitudes are obtained by solving the integral equations with the full off-shell dependence of effective potentials and applying subtractive renormalization. Our formalism has been successfully applied to the pion-nucleon...
Decays into three particles are often described in terms of two-body resonances and a non-interacting spectator particle. To go beyond this simplest isobar model, crossed-channel rescattering effects need to be accounted for. We quantify the importance of these rescattering effects in three-pion systems for different decay masses and angular-momentum quantum numbers. We provide amplitude...
The recent BESIII data on Jpsi-> gamma eta(1405/1475) -> gamma KKbar pi
, which is significantly more precise than earlier eta(1405/1475)-related data, enables quantitative discussions on eta(1405/1475) at the previously unreachable level. We conduct a three-body unitary coupled-channel analysis of experimental Monte Carlo outputs for Jpsi-> gamma eta(1405/1475) -> gamma KKbar pi. The KKbar...
In electron-positron annihilation, the process of e+e- -> chi_c1 can occur via the
production of two virtual photons or through neutral current, therefore being suppressed with
respect to the normal annihilation process via one virtual photon. Using a dedicated scan sample
around the chi_c1 mass, the direct production of chi_c1 has been established for the first time
in experiments....
We present a study of the spectra and strong decay widths of heavy baryons. The masses of single heavy baryons up to the D-wave are calculated within a constituent quark model, employing both the three-quark and quark-diquark schemes. We calculated the decay widths of the ground and excited single heavy baryons into the charmed baryon-(vector/pseudoscalar) meson pairs and the (octet/...
Charmed baryon spectroscopy can provide unique insights into QCD at low energies. The large data sample accumulated by the Belle experiment at the KEKB asymmetric-energy e^{+}e^{-} collider enables new opportunities to study charmed baryons. We present recent measurements of charmed baryons at Belle, including studies of Omega_c -> Xi pi, Xi K and Omega K, Lambda_c -> p Ks Ks and p Ks eta,...
In the past two decades, one of the most puzzling phenomena discovered in hadron physics is that a nominal hadronic state can actually correspond to two poles on the complex energy plane. This phenomenon was first noticed for the Λ(1405), then for K1(1270), and to a lesser extent for D∗0(2300). In this talk, I show explicitly how the two-pole structures emerge from the underlying universal...
In recent years, a plethora of exotic states have been observed in the experimental facilities. Some of these states, of tetraquark and pentaquark types, were predicted previously in approaches based on Effective Field Theories, unitarity of the S-matrix, and chiral and heavy quark spin symmetries. In this talk, I will review some of the predictions made in the local hidden gauge approach on...
We revisit the present status of the lightest nonet of hybrid mesons with quantum numbers J^{PC} = 1^{-+}, that includes the resonance \Pi_1(1600) as well as the recently discovered \eta_1(1855). In the framework of an hadronic approach, predictions for not-yet measured decay rates of the two resonances listed above as well as for the not yet found members of the nonet (an isoscalar with a...
Recent lattice QCD calculations predict the existence of hybrid mesons, which are mesons with gluonic degrees of freedom. By mapping out the hybrid meson spectrum, we can gain insight into how the gluon contributes to the properties of bound states in QCD. The $\pi_1(1600)$ is a candidate for the lightest hybrid meson. This state has exotic quantum numbers of $J^{PC}=1^{-+}$, which are...
Using the world’s largest samples of J/\psi and \psi(3686) events produced in e^+e^- annihilation, BESIII is uniquely positioned to study light hadrons in radiative and hadronic charmonium decays. In particular, exotic hadron candidates including multiquark states, hybrid mesons and glueballs can be studied in high detail. Recent highlights from the light hadron spectroscopy program, including...
The nature and identification of N and 𝛥 excitations and the search for missing baryonic resonances are still open issues in the present hadron spectroscopy scenario.
In photon-induced interactions some couplings with the nucleons could be enhanced, as well as the chance of observing signatures of these poorly known resonances. However, the integrated information available from unpolarized...
The discoveries of the pentaquark states and $XYZ$ mesons in the charmed quark sector initiated a new epoch in hadron physics, where exotic multi-quark states beyond the conventional valence three quark and quark-antiquark systems has been unambiguously observed. Similar structure may be evidenced in the light, $uds$ sector in meson photoproduction, where access to a low momentum exchange and...
We analyze all the available data on differential cross sections, total cross sections, and $K^*$ spin density matrix elements for $K^{*+}\Sigma^0$ and $K^{*0}\Sigma^+$ photoproduction off proton in an effective Lagrangian approach. The data are well reproduced, and the contributions from the $s$-channel nucleon resonance and $t$-channel $\kappa$ meson exchange diagrams are discussed.
The light meson spectrum is explored with the GlueX experiment at Jefferson Lab using a real photon beam with energies of up to 12 GeV that is incident on a liquid hydrogen target. At these high energies, the dominant meson photoproduction mechanism in forward direction is the exchange of Reggeons. Understanding the production mechanism is essential for ongoing searches of exotic hybrid mesons...
In the domain of hadron spectroscopy, the investigation of meson resonances plays a pivotal role. This study focuses on the significance of two-pion photoproduction as a prominent avenue for studying meson resonances in the $\pi\pi$ system. By employing the Regge formalism, our model incorporates the background contribution from the well-known ``Deck Mechanism" and emphasizes the significant...
