Related papers: Gauge invariance and hadron structure
Based on a sumrule for the nucleon spin we expand quark and gluon orbital angular momentum operators and derive an evolution matrix for higher moments of the corresponding distributions. In combination with the spin-dependent DGLAP-matrix…
Starting from covariant expressions, a gauge independent separation of orbital and spin angular momentum for electrodynamics is presented. This results from the non-symmetric canonical energy momentum tensor of the electromagnetic field.…
By assuming that there is no significant intrinsic polarization of the gluon, we have computed the polarized quark contributions to the proton's spin under SU(3) flavor symmetry breaking for the polarized sea and have performed a global…
Distribution functions in hard processes can be described by quark-quark correlators, nonlocal matrix elements of quark fields. Color gauge invariance requires inclusion of appropriate gauge links in these correlators. For transverse…
The interpretation of virtual gluons as ghosts in the non-linear gluonic structure of QCD permits the formulation and realization of a manifestly gauge-invariant and Lorentz covariant theory of interacting quarks/anti-quarks, for all values…
The large density of gluons, which is present shortly after a nuclear collision at very high energies, can lead to the formation of a condensate. We identify a gauge-invariant order parameter for condensation based on elementary…
A unified set of predictions for pion, kaon and nucleon gravitational form factors is obtained using a symmetry-preserving truncation of each relevant quantum field equation. A crucial aspect of the study is the self-consistent…
We review recent progress in the understanding of the spin structure of the nucleon. For the free nucleon the issues addressed include the status of the Bjorken and Ellis-Jaffe sum-rules and the role of the axial anomaly. We outline recent…
The phenomenological sum-rule-based approach is used to discuss the quark composition dependence of some static and quasi-static electroweak characteristics of nucleons.The role of nonvalence degrees of freedom, the nucleon sea partons…
In recent decades, the spin and transverse momentum of quarks and gluons were found to play integral roles in the structure of the nucleon. Simultaneously, the onset of gluon saturation in hadrons and nuclei at high energies was predicted…
Following the recent studies of the trickiness in spin and orbital angular momentum of the vector gauge fields, we perform here a parallel analysis for the tensor gauge field, which has certain relation to gravitation. Similarly to the…
Gauge invariance is essential for making physically meaningful predictions. In superconductors, mean-field Hamiltonians that explicitly break $U(1)$ symmetry often yield gauge-dependent results. While this issue has been resolved for linear…
A calculation of the current-quark-mass-dependence of nucleon static electromagnetic properties is necessary in order to use observational data as a means to place constraints on the variation of Nature's fundamental parameters. A Poincare'…
We present the full decomposition of the momentum fraction carried by quarks and gluons in the pion and the kaon. We employ three gauge ensembles generated with $N_f=2+1+1$ Wilson twisted-mass clover-improved fermions at the physical quark…
A common quark potential that captures the essential traits of the QCD quark-gluon dynamics is expected to (i) interpolate between a Coulomb-like potential (associated with one-gluon exchange) and the infinite wall potential (associated…
Several examples for the role of orbital angular momentum and spin-orbit correlations in hadron structure are discussed.
We propose a gauge-invariant description for the Higgs mechanism by which a gauge boson acquires the mass. We do not need to assume spontaneous breakdown of gauge symmetry signaled by a non-vanishing vacuum expectation value of the scalar…
It is shown that intrinsic orbital motion of the valence quarks has large influences on the spin-dependent as well as the spin-averaged nucleon structure functions. Its connection with the observed ``very small contribution of quark spin to…
Using gauge invariant hadronic two- and three- density correlators we extract information on the spatial distributions of quarks in hadrons, and on hadron shape and multipole moments within quenched lattice QCD. Combined with the…
The magnetic moment and vanishing charge of a Dirac neutrino are physically observable quantities and must not depend on the choice of gauge in a consistent quantum field theory. We verify this statement explicitly at the one loop level in…