Related papers: Systematics in nucleon matrix element calculations
In the Standard Model of particle physics, the axial current is not conserved, due both to fermion masses and to the axial anomaly. Using perturbative quantum chromodynamics, we calculate matrix elements of the local and non-local axial…
We perform a full next-to-leading analysis of the the available experimental data on the polarized structure function g_1 of the nucleon, and give a precise determination of its singlet axial charge together with a thorough assessment of…
We provide a short introduction to the one-nucleon sector of chiral perturbation theory and address the issue of power counting and renormalization. We discuss the infrared regularization and the extended on-mass-shell scheme. Both allow…
A joint fit to neutrino-nucleon scattering and pion electroproduction data is performed to evaluate the nucleon axial form factor in the two-component model consisting of a three-quark intrinsic structure surrounded by a meson cloud.…
We discuss electromagnetic currents in the point-form formulation of relativistic quantum mechanics. The construction is along a spectator model and implies that only one quark is explicitly coupled to the photon, but nevertheless many-body…
We report results on the nucleon structure obtained from the lattice quantum chromodynamics calculation. These include the axial, electromagnetic, $\pi NN$, and scalar form factors. The calculation is carried out at $\beta = 6$ on a $16^3…
The fluctuations and correlations of matrix elements of cross sections are investigated in open systems that are chaotic in the classical limit. The form of the correlation functions is discussed within a statistical analysis and tested in…
We study the electromagnetic contribution to elastic neutrino-proton and neutrino-neutron scattering processes. The neutrino electromagnetic charge, magnetic, electric, and anapole form factors of both diagonal and transition types in the…
An analysis is presented of the ground state baryon's (N and \Delta) masses and axial couplings in the combined 1/Nc and chiral expansions. Renormalization and alternative power counting schemes are discussed to one loop (NNLO). An…
A critical appraisal is given of a recent analysis of the quark-mass and finite-size dependence of unquenched lattice QCD data for the nucleon mass. We use this forum to estimate the boundary of the chiral regime for nucleon properties.
I discuss developments in the area of nucleon resonance excitations that are necessary to bring our understanding of nucleon structure in the regime of strong QCD to a qualitatively new level. They involve the collection of high quality…
We address the issue of a consistent power counting scheme in manifestly Lorentz-invariant baryon chiral perturbation theory. We discuss the inclusion of vector mesons in the calculation of the nucleon electromagnetic form factors. We…
We calculate the axial charges of the proton and its resonances in the framework of the constituent quark model, which is extended to include the $qqqq\bar{q}$ components. If 20% admixtures of the $qqqq\bar{q}$ components in the proton are…
We present a lattice QCD calculation of the nucleon axial charge, gA, using a variational approach. After a brief outline of how the variational method is applied to the calculation of form factors, we present results for gA using this…
We report lattice QCD results on the axial charges of ground and excited nucleon states of both parities. This is the first study of these quantities with approximately chiral (CI) fermions. Two energy levels in the range of the negative…
The nucleon-nucleon t-matrix is calculated directly as function of two vector momenta for different realistic NN potentials. The angular and momentum dependence of the full amplitude is studied and NN observables are calculated.
The progress on the lattice computation of low moments of both the unpolarised and polarised nucleon structure functions is reviewed with particular emphasis on continuum and chiral extrapolations and comparison between quenched and…
We calculate the nucleon axial form factor up to the leading one-loop order in a covariant chiral effective field theory with the $\Delta(1232)$ resonance as an explicit degree of freedom. We fit the axial form factor to the latest lattice…
The chiral extrapolation of the nucleon mass, M_n, is investigated using data coming from 2-flavour partially-quenched lattice simulations. A large sample of lattice results from the CP-PACS Collaboration is analysed using the leading…
The electromagnetic excitation of the nucleon resonances is studied in the framework of Constituent Quark Models. Particular attention is devoted to the transition to the $\Delta$ resonance and to the issue of a possible deformation of…