Nowadays, experimentally observed states that are often assigned to the light meson or charmonium sector might indicate an exotic nature. Such exotic particles include glueballs, hybrids, and tetraquarks. Not only do these states pose a theoretical challenge, but experimentally it is often difficult to distinguish exotic and non-exotic matter and to characterise their nature. In such cases, it...
The GlueX experiment at Jefferson Lab explores the light meson spectrum via photoproduction, using a 9 GeV polarized photon beam incident on a liquid hydrogen target, and a near-hermetic detector. Recent results from our search for exotics will be presented.
We determine from lattice QCD the $I=0,\,1,\,2$ $\pi \pi$ elastic scattering amplitudes for various quark masses. We study the quark mass dependence of the $\sigma$ resonance and observe that, as an unstable particle, its pole position determination is very noisy. By performing a full dispersive analysis, we drastically reduce the systematic uncertainties associated with model extractions of...
The Belle and Belle~II experiments have collected a $1.4~\mathrm{ab}^{-1}$ sample of $e^+e^-$ collision data at centre-of-mass energies near the $\Upsilon(nS)$ resonances. These data include a 19.2~fb$^{-1}$ sample collected near the $\Upsilon(10753)$ resonance to probe its potentially exotic nature. We present several results related to the following processes: $e^+e-\to \Upsilon(nS)\eta$,...
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...
In this talk, I will show that the Born-Oppenheimer approximation for QCD provides a rigorous and unified framework for the study of conventional and exotic hidden-heavy hadrons. In this approximation, a hidden-heavy hadron corresponds to an energy level in a potential that increases linearly at large interquark distances. The spectrum of the lowest confining potential contains conventional...
The High Acceptance Di-lepton Spectrometer (HADES) collaboration at GSI employs a pion beam to examine the characteristics of baryonic resonances and their decay channels. This pion-beam facility enables the generation of baryonic resonances at a fixed center of mass energy ($\sqrt{s}$), i.e. in the S-channel. Consequently, these beams possess a significant advantage over proton-induced...
The High Acceptance Di-Electron Spectrometer (HADES) [1], installed at GSI/FAIR Helmholtzzentrum in Darmstadt, was designed for spectroscopy of positron-electron pairs in heavy-ion reactions in the SIS-18 energy range (1-2 GeV/nucleon). The main goal of this experiment is to study inclusive e+e- production in pion, proton and ion induced reactions at various energies to provide information...
The MUon Scattering Experiment (MUSE) at the Paul Scherrer Institute aims to address the proton radius puzzle which comes from the discrepancy of the proton charge radius measured by hydrogen spectroscopy and electron-proton scattering. While the discrepancy is clearly observed in classical hydrogen and muonic hydrogen spectroscopy results, there is no muon-proton scattering cross-section...
Precision measurements of the properties of trapped antihydrogen offer stringent tests of fundamental principles underlying particle physics and general relativity, such as Lorentz and CPT invariance and the Einstein Equivalence Principle. In this presentation I will give an overview of the ALPHA antihydrogen experiment at CERN including recent results from spectroscopy and observations of the...
After a quick summary of LHCb’s history in measuring exotic candidates, I will discuss the latest measurements from the LHCb experiment in the field of exotic hadrons, including searches tetraquark and pentaquark candidates. I will conclude by giving a few thoughts on possible targets for future observations with the Run 3 data sample that is now being collected.
It has recently been understood that the emergence of left-hand cuts from long-range interactions creates significant complications in extracting infinite-volume observables from lattice QCD finite-volume spectra:
(i) the famous Lüscher method fails below the left-hand cut and
(ii) the effective range expansion used to extract the low energy parameters has a very limited domain of...
After a brief introduction to the concept of hadronic molecules I will explain which kinds of observables are sensitive to a molecular component and which are not. The ideas will then be applied to properties of the $X(3872)$, data for the $Y(4230)$ and finally to the lowest lying positive parity open charm mesons.
In this talk, I will delve into our recent lattice QCD investigations focusing on dibaryons and dimeson systems featuring at least two heavy quarks. I will particularly highlight our research on doubly charm and bottom-charm tetraquarks, which are of contemporary scientific interest.
Hadrons are strongly interacting systems whose dynamics is driven by complex intercommunication between quarks and gluons. The theory of strong interaction, Quantum ChromoDynamics (QCD) , is supposed to describe all particles, however, due to numerical complexity we are still far away from reaching this goal. In such a situation, experimental knowledge about existing resonances becomes...
Standard lattice calculations of the glueball spectrum rely on effective mass plots and asymptotic exponential fits of two-point correlators, and involve various numerical challenges.
In this work, we propose an alternative procedure to extract glueball masses, based on the computation of the smeared spectral densities that encode information about the towers of states with given quantum...
J/psi near threshold photoproduction plays a key role in the physics program at the Thomas Jefferson National Accelerator Facility (JLab) in the 12 GeV era. J/psi photoproduction proceeds through the exchange of gluons in the t-channel and is expected to provide unique insight about the nucleon gluonic form factors and the nucleon mass radius.
The CLAS Collaboration, which uses the CEBAF...
The XYZ exotic states discovered in the hadronic sector with two heavy quarks constitute one of the most important open problems in particle theory. In this talk, I show that an effective field theory derived from QCD, the Born Oppenheimer effective field theory (BOEFT), can describe exotics of any composition. I show the results of the Schr\"odinger coupled equations that describe hybrids,...
We critically discuss the algorithmic process of estimating spectral densities using the Hansen-Lupo-Tantalo method. A novel approach at finite volume is deployed to extract the spectrum of lattice gauge theories. As a case study, our discussion takes as an example the study of beyond-Standard-Model (BSM) symplectic gauge theories with matter field consisting of a mixed fermion...
Symplectic gauge theories provide exciting models for composite physics beyond the Standard Model. They are of interest for both composite Dark Matter and composite Higgs models. I study $Sp(4)$ gauge theory with fundamental fermions as well as fermions in the two-index antisymmetric representation on the lattice. I report on their spectrum for both singlet and non-singlet mesons, and the...
The large $N_\text{c}$ limit of QCD is a simplification of the theory that preserves most of its non-perturbative features and has been used by many phenomenological approaches to QCD. However, subleading $N_\text{c}$ effects are hard to estimate and can lead to incorrect predictions. In this talk, I will discuss how we are using lattice simulations to study these subleading Nc effects in the...
Isgur and Capstick [1] predict a total of 44 cascade states below 2.5 GeV. Currently, there are only six Ξ states that have at least three-star ratings in the PDG [2], with the production mechanism of these states still remaining mostly elusive. The goal of the “Very Strange” [3] project is to study the quasi-real photoproduction of cascades to search for missing and new states. The new data...
Lattice QCD results for isospin $I=\frac{1}{2}$ $D\pi$ scattering are presented. Utilizing a series of $N_{\text{f}}=2+1$ Wilson-Clover ensembles with pion masses of $m_\pi \approx 132, 208, 305$ and $317$ MeV, various two-particle operators are constructed and the corresponding finite-volume spectra are determined. The $S$ and $P$-wave scattering phase shifts are then extracted using the...
I use the Born-Oppenheimer EFT (BOEFT) formalism to study the effect of meson-antimeson thresholds on the quarkonium spectrum. In this talk, I introduce the leading order BOEFT lagrangian for the system with inputs on the potentials from recent lattice studies on string breaking. For below threshold quarkonium states, I show results for the threshold corrections obtained in two ways: by...
The KLong Experiment in Jefferson Lab Hall D will use a secondary beam of neutral kaons and a modified setup of the GlueX experiment to perform strange hadron spectroscopy. By achieving a flux on the order of $1×10^4$ KL/sec, KLF will allow a broad range of measurements that improve the statistics of previous world data by several orders of magnitude.
The experiment will measure both...
One of the most puzzling aspects of the Standard Model is that the overwhelming majority of the mass of hadronic systems arises from massless and nearly massless objects. From the little that we do understand, we know that mass generation is intricately connected to the internal structure of hadronic systems. Somewhat counter intuitively, it is some of the lightest hadronic objects, the...
