Conveners
Hadron Spectroscopy: (light mesons) - Parallel 2
- Gernot Eichmann (LIP & IST Lisboa)
Hadron Spectroscopy: (baryons) - Parallel 2
- Victor Mokeev (Thomas Jefferson National Accelerator Facility)
Hadron Spectroscopy: (light mesons, exotics) - Parallel 2
- Sean Dobbs (Florida State University)
Hadron Spectroscopy: (interactions) - Parallel 5
- Colin Gleason (Union College)
Hadron Spectroscopy: (baryons) - Parallel 2
- Simon Capstick
Hadron Spectroscopy: Parallel 2
- Alexander Ostrovidov (Flordia State University)
Hadron Spectroscopy: (Hyperons) - Parallel 2
- Michael Doring (George Washington U and Jefferson Lab)
Hadron Spectroscopy: Parallel 5
- Eulogio Oset
Hadron Spectroscopy: Parallel 1
- Bertram Kopf (Ruhr-Universitaet Bochum)
Recent results of coupled channel partial wave analyses with various $\bar{p}p$-annihilation, $\pi\pi$- and $\pi^-p$-scattering data performed with the powerful and user-friendly PAWIAN (Partial Wave Interactive Analysis) package will be presented. By considering analyticity and unitarity conditions using the K-matrix approach with Chew-Mandelstam functions, pole positions and decay branching...
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. GlueX, which has a linearly polarized photon beam and a large acceptance for both charged and neutral particles, has access to both the neutral, $\gamma...
We calculate, from Lattice QCD, the elastic $\pi \pi$ scattering amplitude in the isoscalar $I=0$ channel, and determine the $\sigma$ estate. We extract its lineshape for two different quark masses corresponding with $m_\pi \sim 330$ and $283$ MeV; where it is predicted that this state transitions from bound to virtual bound. In order to provide an accurate picture we use a high statistics...
We present a first calculation of the $K\gamma \to K\pi$ transition amplitude in the presence of a resonant $K^*$ from lattice quantum chromodynamics. In this process, the kaon interacts with a photon and scatters strongly to a $K\pi$ in the final state. The $K\pi$ state is in a lowest relative $S$ $\&$ $P$-wave, with the $K^*$ resonance appearing in the $P$-wave.
The matrix elements for the...
Using the worldโs 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...
Significant progress has been realized in studies of excited nucleon state structure (N program) from the data on exclusive meson electroproduction measured with the CLAS detector in Hall B at Jefferson Laboratory (JLab). Studies of N program give us the unique opportunity to explore the complex interplay of quark-gluon and meson-baryon degrees of freedom in the N* structure and the...
Recently structures in invariant mass distributions and excitation energy spectra have been attributed to triangular singularities as discussed in e.g., [1, 2] and in the review by Guo et al.[3]. These singularities emerge under specific kinematic conditions when new reaction channels open up. It will be shown that a triangular singularity associated with the opening of the ฮณp โ pa0 โ pฯ0ฮท...
The new results from the Bonn-Gatchina partial wave analysis are presented. The new solution includes the new data on the meson production off the neutron and the data on the omega-meson photoproduction. The spectrum and properties of the observed baryons are discussed.
The FROST experiment at Jefferson Lab used the CLAS detector in Hall B with the intention of performing a complete and over-determined measurement of the polarization observables associated with strangeness photoproduction, in combination with data from previous JLab experiments as part of the N* program. This was achieved by utilizing the FROST polarized target in conjunction with polarized...
I will summarize some of the recent results in meson spectroscopy in the light and heavy sectors, in particular for exotic candidates.
Stunning discoveries of the hadronic states,
$P_{\psi}$, $P_{\psi s}$, $T_{\psi}$, $T_{\psi s}$, and $T_{\psi\psi}$, that are manifestly different to the conventional meson and baryons, have energized the field of spectroscopy in recent years. New exotic states keep appearing thanks to the excellent detector performance of the LHCb experiment and scrupulous data analysis. In this talk,...
In this talk I summarize advances on calculations of hadron spectrum and structure observables using functional methods such as Dyson-Schwinger and Bethe-Salpeter equations. Systematic improvements in this approach have made it possible to address a wide range of problems from the baryon excitation spectrum to multiquark spectroscopy, form factors, parton distributions and other areas. I will...
In this talk we will discuss our recent works (2201.08253 and 2207.08563) in which we make analyses of several X and Z states. In the first part of the talk, we present a combined study of the BESIII spectra in which the Zc(3900) and Zcs(3985) states are seen, assuming that both are SU(3) partners. In the second part, a step further is taken and we analyze the...
The $X_0(2900)$ was observed by the LHCb and has been largely accepted as a $D^* \bar K^*$ molecule. Yet, the molecular picture gives rise to three spin states, with $J^P=0^+,1^+,2^+$, and only the $0^+$ state has been so far observed.
We present three methods to determine these extra states.
1) The $\bar B^0 \to D^{โ+} ฬ\bar D^{*0} K^โ$, looking at the $D^{*+} K^-$ spectrum.
2) The...
Hadronic molecules are composite systems of hadrons. Many hadron resonances observed in the last two decades are good candidates of hadronic molecules, including the X(3872), the hidden-charm Pc pentaquarks, the double-charm Tcc, etc. I will discuss the physics of hadronic molecules with a focus on the hidden-charm and double-charm ones.
Based on the 4.48x10^6\psi(3686) events, we will report on searches for the decay \psi(3686) and chi_cJ ->Lambda anti-Lambda, chi_cJ-> nK_S Lambda +c.c., and isospin violation decay \psi(3686) -> Lambda anti-Lambda pi0. Using data events of integrated luminosity 3.18/fb taken at sqrt s= 4.18 GeV, the decay e^+e^- -> pK anti-Lambda bar +c.c. is analyzed with partial wave analysis. The...
The LHCb collaboration recently discovered a doubly charmed tetraquark $T_{cc}$ with flavor $cc\bar u\bar d$ just below $DD^*$ threshold. This is the longest lived hadron with explicitly exotic quark content known to this date. We present the first lattice QCD study of $DD^*$ scattering in this channel, involving rigorous determination of pole singularities in the related scattering...
A detailed study of the nucleon resonances and their decays is an essential step towards exploring the low energy region of QCD. By analysing the excitation spectrum of (quasi-) free nucleons we are able to establish a baseline for comparisons with in-medium modifications. Of particular interest are the mixed-charged channels of double-pion photoproduction, as they are sensitive to sequential...
Our understanding of the physics of baryonic systems containing strangeness is limited by the scarcity of experimental data. Aiming at alleviating this deficit is lattice QCD, a numerical approach to solve the complex dynamics of strongly interacting systems of hadrons and nuclei. In this talk I will present the results obtained by the NPLQCD collaboration for two octet-baryon systems, with...
Phenomenological amplitudes obtained in partial-wave analyses of single-pion photoproduction are used to evaluate the contribution of this process to the Gerasimov--Drell--Hearn (GDH), Baldin, and Gell-Mann--Goldberger--Thirring (GGT) sum rules, by integrating up to 2 GeV in photon energy. Our study confirms that the single-pion contribution to all these sum rules converges even before the...
Understanding the dynamics of hadrons with different quark content is crucial to solve fundamental aspects of QCD as well as for the implications on the structure of dense stellar objects, such as neutron stars. The scarce statistics and lack of data in reactions for unstable hadrons, containing in particular strange and charm quarks, affect the accuracy of the current theoretical description...
We have performed calculations for the states $\Omega_{cc}$, $\Omega_{bc}$ and $\Omega_{bb}$ stemming from coupled channel interactions between the pseudoscalar or vector mesons and the $1/2^+$, $3/2^+$ baryons. In all cases, we find bound states or resonances, using the Bethe-Salpeter equation to unitarize the interaction of the coupled channels with the input for the potential obtained from...
In this article, we study simple hadron scattering models provided by the PYTHIA8 Monte Carlo event generator, intended to consider the overlap of multiple strings at low transverse dimensions. Firstly, we studied a so-called new model for generating the transverse momentum of hadrons during the string fragmentation process. Secondly, close packing of strings is taken into account by making...
We present the properties of open heavy mesons in hot mesonic matter based on a self-consistent theoretical approach that takes into account chiral and heavy-quark spin-flavor symmetries. The heavy-light meson-meson unitarized scattering amplitudes in coupled channels incorporate thermal corrections as well as the dressing of the heavy mesons with the self-energies [1, 2]. As a result, the...
Over the past two decades, a large number of exotic states has been discovered at various accelerator facilities. Many of these states are located close to certain hadron-hadron thresholds and therefore can be considered as potential candidates for hadronic molecules. In this talk, we will review the classical Weinberg formalism that was developed to assess whether the deuteron is composite or...
We evaluate theoretically the interaction of the open bottom and strange systems $\bar B\bar K$, $\bar B^* \bar K$, $\bar B\bar K^*$ and $\bar B^*\bar K^*$ to look for possible bound states which could correspond to exotic non--quark-antiquark mesons since they would contain at least one $b$ and one $s$ quarks. The s-wave scattering matrix is evaluated implementing unitarity by means of the...
We perform a calculation of the interaction of the $ D \bar{D} $, $ D_{s} \bar{D}_{s} $ coupled channels and find two bound states, one coupling to $ D \bar{D} $ and another one at higher energies coupling mostly to $D_{s}^{+} D_{s}^{-}$. We identify this latter state with the $X_{0}(3930)$ seen in the $D^{+} D^{-}$ mass distribution in the $B^+ \to D^{+} D^{-} K^{+} $ decay, and also show...
The exact eigenenergies of the T4c, T4b, T2bc tetraquarks are calculated within the extended transitional Hamiltonian approach. The IBM, as proposed by Arima and Iachello [1], includes two types of bosons with angular momentum L = 0 (s bosons) and L = 2 (d bosons). To investigate the properties of tetraquarks, similar to that of the two-level system, a four-level system is considered here. To...
Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA, is home to several experiments studying strange baryons using electro- and photoproduction on a range of different targets. In this presentation we will review recent results with a focus on the CLAS(12) and GlueX experiments. We will also give a short outlook towards future measurements performed with a KLong beam.
With the large datasets on ๐+๐โannihilation at the ๐ฝ/๐ and ๐(3686) resonances collected at the BESIII experiment, multi-dimensional analyses making use of polarization and entanglement can shed new light on the production and decay properties hyperon-antihyperon pairs. In a series of recent studies performed at BESIII, significant transverse polarization of the (anti)hyperons has been observed...
Among the light baryons, the $J^\pi = \frac{1}{2}^-$ $\Lambda(1405)$ baryon is an important special case by sitting just below the $\bar{K}N$ threshold and decaying almost exclusively to $\Sigma\pi$. It has long been hypothesized to be either a molecular bound state or a continuum resonance, or that it is a simple quark-model resonance, the $P$-wave companion of the $\Lambda(1520)$. In...
We study for the first time the $p\Sigma^-\to K^-d$ and $K^-d\to p\Sigma^-$ reactions close to threshold and show that they are driven by a triangle mechanism, with the $\Lambda(1405)$, a proton and a neutron as intermediate states, which develops a triangle singularity close to the $\bar{K}d$ threshold. We show that the cross section, well within measurable range, is very sensitive to...
Quantum Chromo Dynamics (QCD) is our current best description of interactions between quarks and gluons and it not only predicts the existence of the well understood mesons (two-quark) and baryons (three-quark) it also predicts exotic Tetra, Penta and Hexaquark states.
Experiments taking place at Thomas Jefferson Lab in Virginia, USA using the upgraded CLAS12 detector system allows a detailed...
During two data taking compains in 2011-18 LHCb experiment has collected large samples of beauty and charm hadrons produced in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. These samples are used to study properties and decays of conventional mesons. In this contribution a summary of the LHCb experimental results released in 2022 is presented.
The vast majority of hadrons are not stable with respect to the strong interactions, and are seen as resonant enhancements in the scattering of the lightest stable hadrons. Recent developments have enabled the determination of hadron resonance properties from scattering amplitudes determined from lattice QCD. A summary of the approach will be given, and examples will be presented for...
Accessing the hadron spectrum from Quantum ChromoDynamics (QCD) poses several challenges given its non-perturbative nature and the fact that most states couple to multi-particle decay modes. Although challenging, advances in both theoretical and numerical techniques have allowed us to determine few-body systems directly from QCD. A synergistic approach between lattice QCD and scattering theory...
We perform a theoretical study of the $D_s^{+}\to \pi^{+}\pi^{+}\pi^{-}\eta$ decay. We look first at the basic $D_s^{+}$ decay at the quark level from external and internal emission. Then hadronize a pair or two pairs of $q\bar{q}$ states to have mesons at the end. Posteriorly the pairs of mesons are allowed to undergo final state interaction, by means of which the $a_0(980)$, $f_0(980)$,...
We study the $\Omega(2012)$ which was measured in the Belle experiment. We conduct a study of the interaction of the $\bar K \Xi^*$, $\eta \Omega$($s$-wave) and $\bar K \Xi$($d$-wave) channels within a coupled channel unitary approach. We also present a mechanism for $\Omega_c \to \pi^+ \Omega(2012)$ production through an external emission Cabibbo favored weak decay mode, where the...
Classification of tetraquarks states using SU(6) spin-flavor symmetry alongwith SU(3) and SU(2)is done by using Young tableau method. We also have predicted the tetraquark masses and their decay widths by using the extension of Gursey- Radicati mass formula and our results are in very close agreement with the available experimental and theoretical data.
Generation of mass within the Standard Model is typically attributed to the Higgs boson. Yet, alone, the Higgs can only explain a few percent of the proton mass. The remainder must be produced by another source. The answer lies in nonlinear, nonperturbative phenomena within the gauge sector of quantum chromodynamics; in fact, at the most fundamental level, in the emergence of a mass-scale...
This presentation will focus on recent advances in understanding the internal structure of baryons and their low-lying excitations. The results are founded on the first-principles approach of Lattice QCD, complemented by Hamiltonian effective field theory (HEFT), a nonperturbative extension of effective field theory incorporating the Luscher formalism.
We'll commence with the low-lying...
In Coulomb gauge QCD, there exists an instantaneous chromo-electric interaction between static quark-antiquark pairs. Studying this interaction is an effective way to probe aspects of quark confinement, as the confining behavior of this โCoulomb potentialโ is related to the confining behavior of the Wilson potential in non-gauge fixed QCD. A clearer picture of the mechanism of confinement...
The hidden charm pentaquark states Pc(4312), Pc(4440), and Pc(4457) can be well assigned as \barD^(*)Sigma_c molecules, which are related by heavy quark spin symmetry. To further study the pentaquark states in the molecular picture, we have taken the heavy quark diquark symmetry to predict the Xicc Sigmac and barD T_cc molecules. Such kind of molecules belong to new molecule that are not...
We perform a unitary coupled channel study of the interaction of the $D^{*+} D^0, D^{*0} D^+$ channels and find a state barely bound, very close to isospin $I=0$. The width obtained is small, of the order of $80 \;{\rm keV}$, tied to the width of the $D^*$ states, short of the experimental one,
but which would certainly be bigger upon consideration of the experimental resolution. We perform...
