The Exo(tic) Had(ron) Collaboration started in 2023 to explore all aspects of exotic hadron physics, from predictions within lattice QCD, through reliable extraction of their existence and properties from experimental data, to descriptions of their structure within phenomenological models.
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Read allTwo Pathways for Accessing Amplitudes with Left-Hand Cuts in Finite Volumes
Accessing scattering amplitudes with lattice QCD has become a vital tool in our theoretical understanding of the excited hadron spectrum. A key component is the non-perturbative formalism which relates finite-volume lattice QCD spectra to infinite-volume reaction amplitudes, known as the Lüscher formalism. However, the standard framework is not valid for energies below threshold where cross-channel exchanges can produce left-hand cuts. Members of ExoHad have recently released two works which Read more
Towards a unified description of hadron scattering at all energies
The construction of general amplitudes satisfying symmetries and $S$-matrix constraints has been the primary tool in studying the spectrum of hadrons for over half a century. This work, carried out by Dominik Stamen (Bonn U.), Daniel Winney (Bonn U., HISKP), Arkaitz Rodas (ODU & JLab, co-PI), Cesar Fernandez-Ramirez (UNED), Vincent Mathieu (Barcelona U., co-PI), Gloria Montana (JLab), Alessandro Pilloni (Messina U., co-PI), and Adam Szczepaniak (Indiana U. & JLab, PI), presents a new Read more
Coulomb confinement in the Hamiltonian limit
The Gribov-Zwanziger scenario attributes the phenomenon of confinement to the instantaneous interaction term in the QCD Hamiltonian in the Coulomb gauge, which leads to a potential energy that increases linearly with the distance between a static quark-antiquark pair. Previous lattice studies of the $SU(2)$ Yang-Mills theory determined the corresponding (Coulomb) string tension, $\sigma_{C}$, to be about three times larger than the Wilson loop string tension, $\sigma_F$, far above Zwanziger's Read more
Reconciling gauge invariance and Reggeization of pion exchange
The Reggeized pion is expected to provide the main contribution to the forward cross section in light meson photoproduction reactions with charge exchange at high energies. Up until now, the pion exchange mechanism has been studied using phenomenological approaches. Given new and forthcoming high-precision data from JLab for a variety of photo- and electroproduction reactions in which the Reggeized pion plays a pivotal role, including the photoproduction of light exotic hybrid mesons, the JPAC Read more
A Constituent Model of Light Hybrid Meson Decays
The discovery of hybrid mesons will be greatly simplified if their couplings to decay channels are understood. To this end, Christian Farina (Pitt graduate student) and Eric Swanson (Pitt, co-PI), have modeled hybrid decay in terms of gluon dissociation as specified by the Hamiltonian of QCD in Coulomb gauge. The results indicate that direct observation of the light vector hybrid will be difficult, that the hybrid $\pi(1800)$ has distinct decay characteristics, and that a hybrid $\eta_1(1750)$ Read more