Related papers: The nucleon resonance structure from exclusive $\p…
The so-called second resonance region of the nucleon comprises the states P11(1440), D13(1520) and S11(1535). During the last few years photoproduction experiments have largely contributed to a better understanding of these states, but the…
Spectra of p-p and pi-p scattering at beam momenta between 6 and 30 GeV/c have been reanalysed. These show strong excitation of N* resonances, the strongest one corresponding to the "scalar" P11 excitation (breathing mode) at m_o= 1400+-10…
High-statistics measurements of differential cross sections and spin density matrix elements for the reaction $\gamma p \to \phi p$ have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from…
We apply our method of complex scaling, valid for a general class of potentials, in a search for nucleon-nucleon S-matrix poles up to 2 GeV laboratory kinetic energy. We find that the realistic potentials JISP16, constructed from inverse…
Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined. Pole positions and residues of the $P_{11}$ partial wave are studied in a combined analysis of pion- and photo-induced reactions. We find the…
The first study of quasi-free Compton scattering on the neutron in the energy range of $E_{\gamma}=0.75 - 1.5$ GeV is presented. The data reveals a narrow peak at $W\sim 1.685$ GeV. This result, being considered in conjunction with the…
The quark-gluon properties of the nucleon are probed by a host of recent and planned experiments. These involve elastic, deep-inelastic, semi-inclusive deep-inelastic (SIDIS), and deeply-virtual Compton scattering. A light-front description…
Incoherent J/$\psi$ photoproduction in heavy ion ultraperipheral collisions (UPCs) provides a sensitive probe of localized, fluctuating gluonic structures within heavy nuclei. This study reports the first measurement of the photon-nucleon…
By extending the dynamical coupled-channels analysis performed in our previous work [Phys. Rev. C 88, 035209 (2013)] to include the available data of photoproduction of pi meson off the neutron, the transition amplitudes for the…
We study electron-induced single-pion production as a way to constrain the neutron structure of $^{40}$Ar, information that is necessary for neutrino experiments using argon detectors. The proposed experimental signal consists in detecting…
We report measurements of the exclusive neutral pion electroproduction cross section off protons at large values of $x_B$ (0.36, 0.48 and 0.60) and $Q^2$ (3.1 to 8.4 GeV$^2$) obtained from Jefferson Lab Hall A experiment E12-06-014. The…
We show how exclusive vector meson production off light ions can be used to probe the spatial distribution of small-$x$ gluons in the deuteron and $^3$He wave functions. In particular, we demonstrate how short range repulsive…
Semi-inclusive pi+ electroproduction on protons has been measured with the CLAS detector at Jefferson Lab. The measurement was performed on a liquid-hydrogen target using a 5.75 GeV electron beam. The complete five-fold differential cross…
The $f_0$(1500) meson resonance is one of several contenders to have significant mixing with the lightest glueball. This resonance is well established from several previous experiments. Here we present the first photoproduction data for the…
We study how the electromagnetic structure of the nucleon is influenced by a pion cloud. To this aim we make use of a constituent-quark model with instantaneous confinement and a pion that couples directly to the quarks. To derive the…
We report the first measurement of differential and total cross sections for the ${\gamma}d \to K^0{\Lambda}(p)$ reaction, using data from the CLAS detector at the Thomas Jefferson National Accelerator Facility. Data collected during two…
Open problems in the study of the nucleon structure using electromagnetic probes are discussed. The focus is on experimental aspects in the regime of strong interaction QCD. Significant progress in our understanding of the nucleon structure…
Nucleon resonance contributions to the polarized proton $g_1$ and $g_2$ structure functions are computed from resonance electroexcitation amplitudes extracted from CLAS exclusive meson electroproduction data. Including resonances in the…
We report on the low and moderate Q^2 nucleon spin structure measurements done at Jefferson Lab, examining specifically the inclusive program. We discuss what the data teach us about quark confinement and the emergence of the effective…
Using short distance QCD methods based on the operator product expansion, we calculate the $J/\psi$ photoproduction cross section in terms of the gluon distribution function of the nucleon. Comparing the result with data, we show that…