World-record data samples collected by the BESIII detector provide an ideal laboratory for hadron spectroscopy studies. Using 10 billion event and 2.7 billion event samples collected at the $J/\psi$ and $\psi(2S)$ resonances of charmonium, respectively, detailed studies of light hadrons and charmonium decays are conducted. Scan samples above 4 GeV allow for investigations into exotic candidate...
The structure of the $\Lambda(1405)$ resonance has challenged hadron physicists for more than forty years. Its structure is controversially debated as either: an antikaon-nucleon bound state, a dynamically generated baryon resembling a meson-baryon molecule, or a resonance with $\pi\Sigma$ and $\bar{K}N$ poles. Experimental results vary in line shape and peak position, depending on reaction...
The Λ(1405) hyperon (JP = 1/2−), situated just below the ¯KN threshold, has been a long-standing candidate for an exotic ¯KN molecular structure. Chiral-unitary models propose that it consists of two isospin I = 0 poles with different couplings to the ¯KN and Σ0π0 systems, leading to a line shape that deviates from a relativistic Breit-Wigner distribution. The GlueX experiment at Jefferson Lab...
Exploring EMC-style ratios for x>1 provides critical insights into the EMC effect. Inclusive scattering from nuclei at Bjorken x>1 and high Q2 is particularly sensitive to the distribution of high-momentum quarks, often referred to as 'superfast quarks.' These quarks, which carry momentum exceeding that of a nucleon, are linked to the short-distance structure of nuclei. This region presents a...
Hadronic resonances are emergent phenomena of Quantum Chromodynamics at intermediate energies. Almost all resonances decay not only to two, but also to three or more particles. Parametrizing three-body dynamics in terms of unitary coupled-channel amplitudes is, therefore, a prerequisite for the extraction of resonances from experiment and also from finite-volume lattice QCD spectra. In the...
Cascade hyperons, despite being discovered over half a century ago, remain considerably less studied compared to the non-strange $\Delta$ and $N$ baryons. This disparity is primarily due to the energetic challenges associated with producing two strange quarks. The objective of this analysis is to provide the first cross-section measurements for the ground state cascade, $\Xi^-$, using electron...
This presentation covers recent advancements in the refined simulations of double pion electroproduction for CLAS22. Double pion production provides a valuable probe of baryon structure, requiring accurate simulations for proper interpretation of experimental data. The presentation addresses the feasibility of extending the kinematic coverage beyond CLAS12, discussing resolution and acceptance...
The Continuous Electron Beam Accelerator Facility, CEBAF, at the Thomas Jefferson National Accelerator Facility has been conducting world class nuclear physics experiments for nearly thirty years. I will give an overview of the current experimental program as well as an overview of the machines tentative schedule for the next several years. I will also present possible future machine...
The High-Acceptance Di-Electron Spectrometer (HADES) operates at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, using pion, proton, and heavy-ion beams provided by the SIS-18 synchrotron [1]. In February 2022, the HADES Collaboration measured proton-proton collisions at 4.5 GeV momentum using the upgraded setup as part of the FAIR-Phase0 program.
One of the key objectives of...
The X17 anomaly refers to a bump seen in the pair production spectrum of the decay to ground state of excited Be8 nuclei. This was first observed in 2015 at the ATOMKI Van de Graaf generator and was repeated using He4 and C12. The most prominent explanation is a hidden-sector boson that mediates a “fifth force” that couples to dark matter and has small kinetic mixing with the electromagnetic...
Due to the non-perturbative nature of QCD in the present low temperature universe, the vacuum has hidden underlying structures. We are making experimental studies to study the structure through precision spectroscopy of meson-nucleus bound systems. Recently we reported the first quantitative evaluation of the chiral condensate in the nuclear matter observed in the spectroscopy of pionic atoms....
The precise mechanism underlying spin-flavor symmetry breaking in QCD is unknown but is illuminated by the behavior of high momentum quarks in the nucleon. Conventionally, high partons have been studied by extracting the neutron-to-proton structure function ratio via fits to nuclear DIS data. However, these fits rely on model-dependent, theoretical descriptions of nuclear effects.
The...
The hadron spectrum offers deep insights into the strong force, the origin of hadronic mass, quark confinement, and the transition from quarks and gluons to observable particles. While the quark structure of hadrons is well understood, most of their mass arises from the binding force rather than the quarks themselves — this is a largely uncharted territory whose exploration has been attracting...
The system of η and η′ offers a flavor-conserving laboratory to test the low-energy QCD and to search for new physics Beyond the Standard Model. The symmetry properties of QCD at low-energy, such as the chiral symmetry or the axial anomalies, are manifested in the decays of η and η′. Thus, a study of η/η′ will yield light on our understanding of the origin and the dynamics of QCD...
The implementation of general principles, like analyticity and unitarity, can help to constrain the determination of hadronic properties from lattice QCD (LQCD).
We present the LQCD calculation of the pion vector form factor over spacelike and timelike kinematics, with a pion mass of approximately $284$ MeV.
We go beyond the elastic timelike region, and implement for the first time the...
The first excited state of the nucleon dominates many nuclear phenomena at energies above the pion-production threshold and plays a prominent role in the physics of the strong interaction. The study of the N to $\Delta$ transition form factors (TFFs) allows to shed light on key aspects of the nucleonic structure that are essential for the complete understanding of the nucleon dynamics. In this...
The photoproduction of vector mesons off the proton serves as a crucial probe of the gluon content within the nucleon. Near-threshold J/psi photoproduction provides a unique opportunity to investigate the Gravitational Form Factors of gluons, which are related to the mass, pressure, and force distributions within the proton. Furthermore, this reaction allows for the exploration of exotic...
J/ψ near-threshold photoproduction plays a key role in the physics program at the Thomas Jefferson National Accelerator Facility (JLab) 12 GeV upgrade due to the wealth of information it has to offer. Near threshold, J/ψ 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...
SpinQuest is the Fermilab's high-luminosity Drell-Yan experiment that aims to explore the interaction of 120 GeV proton beam with transversely polarized ammonia (NH$_3$), and deuterated ammonia (ND$_3$) targets to probe the Sivers functions of light quark flavors in the nucleon sea. A non-vanishing sea quark Sivers functions provide evidence of their orbital angular momentum, which would...
The transverse single-spin asymmetry (TSSA) measures the asymmetry in particle production relative to the plane defined by the transverse spin axis and the momentum direction of a polarized hadron. TSSAs have emerged as a powerful tool for exploring Quantum Chromodynamics (QCD), offering insights into the dynamics of initial-state hadrons and the hadronization process. In J/ψ production, which...
In this talk, I will report some recent progress in extracting the gluonic gravitational form factors (GFFs) from near threshold heavy quarkonium productions. Particularly, I will discuss the effect of the next-to-leading order (NLO) corrections on the extraction of the GFFs, where the singlet quark contribution will also emerge. With the NLO corrections, I will remark on the theoretical...
Recent advancements in both theoretical frameworks and experimental methodologies have significantly enhanced our understanding of the internal mechanical properties of nucleons, particularly the role of gluonic contributions. Central to this investigation are the gravitational form factors, which encapsulate the nucleon’s energy, momentum, pressure, and shear distributions. These form factors...
