Modern Physics Letters A

Parton distribution functions, which represent the flavor and spin structure of the nucleon, provide invaluable information in illuminating quantum chromodynamics in the confinement region. Among various processes that measure such parton distribution functions, semi-inclusive deep inelastic scattering is regarded as one of the golden channels to access transverse momentum dependent parton distribution functions, which provide a 3D view of the nucleon structure in momentum space. The Jefferson Lab experiment E06-010 focuses on measuring the target single and double spin asymmetries in the reaction with a transversely polarized ³He target in Hall A with a 5.89 GeV electron beam. A leading pion and the scattered electron are detected in coincidence by the left High-Resolution Spectrometer at 16° and the BigBite spectrometer at 30° beam right, respectively. The kinematic coverage concentrates in the valence quark region, x ~ 0.1–0.4, at Q² ~ 1–3 GeV². The Collins and Sivers asymmetries of ³He and neutron are extracted. In this review, an overview of the experiment and the final results are presented. Furthermore, an upcoming 12-GeV program with a large acceptance solenoidal device and the future possibilities at an electron–ion collider are discussed.

A three-parametric two-sided deformation of Heisenberg algebra (HA), with p, q-deformed commutator in the L.H.S. of basic defining relation and certain deformation of its R.H.S., is introduced and studied. The third deformation parameter μ appears in an extra term in the R.H.S. as pre-factor of Hamiltonian. For this deformation of HA we find novel properties. Namely, we prove it is possible to realize this (p, q, μ)-deformed HA by means of some deformed oscillator algebra. Also, we find the unusual property that the deforming factor μ in the considered deformed HA inevitably depends explicitly on particle number operator N. Such a novel N-dependence is special for the two-sided deformation of HA treated jointly with its deformed oscillator realizations.

We propose an interesting mechanism to reconcile the recent experiments of the Michelson–Morley type and slowdown of the velocity of light in dark matter with a fractional electric charge when the index of refraction of dark matter depends on the frequency of a photon. After deriving the formula for the velocity of light in a medium with the index of refraction n(ω) in a relativistic regime, it is shown that the local anisotropy of the light speed is proportional to the second order in n(ω) - 1. This result implies that the experiments of the Michelson–Morley type do not give rise to a stringent constraint on the slowdown of the velocity of light in dark matter with electric charge.

Covariant scalar fields exhibit divergences when quantized in two or more spacetime dimensions: n ≥ 2. Does perturbation theory, effective theories, the renormalization group, etc., tell us all there is to know about these problems? An alternative approach identifies the cause of divergences as due to the effort to multiplicatively relate two measures that are mutually singular, while the cure for those divergences is to introduce an O(ℏ) counterterm that converts mutually singular measures into equivalent measures. This procedure leads to a nontrivial, divergence-free formulation for all n≥2. Finally, a critical comparison of the new methods with traditional procedures is given.

The radial sensitivity of the elastic scattering of the weakly-bound ⁶Li and halo ⁶He nuclei on medium-mass ⁶⁴Zn target and heavy target ²⁰⁸Pb is examined around the Coulomb barrier energies. We present that very good agreement between theoretical and experimental results have been obtained with small χ²/N values. The fusion cross-section and volume integrals of the potentials have been deduced from the theoretical calculations for all studied systems at relevant energies. We have also analyzed the elastic scattering of the ⁶He+²⁰⁸Pb system at E_lab = 14, 16, 18, 22, 27 MeV in order to investigate whether there is a dispersion relation between the real and imaginary parts of the optical potential.

The eγ collider is better suited to study single production of the gauge bosons. In this paper, we first consider the contributions of the three-site Higgsless (3SHL) model and the left–right twin Higgs (LRTH) model to the standard model (SM) processes eγ→eZ and eγ→ν_eW, and then study single production of the new neutral and charged gauge bosons predicted by these two models via eγ collision in the future high energy e⁺e^- linear collider experiments. We find that the correction effects of 3SHL model on the processes eγ→eZ and eγ→ν_eW might be detected in the future, while this is not the case for the LRTH model. The process eγ→eZ' can give rise to different signatures in the 3SHL and LRTH models and thus can be used to distinguish these two kinds of new physics models at the high energy e⁺e^- linear colliders.

Theories with large extra dimensions may be tested using sterile neutrinos living in the bulk. A bulk neutrino can mix with a flavor neutrino localized in the brane leading to unconventional patterns of neutrino oscillations. A resonance phenomenon, strong mixing between the flavor and the sterile neutrino, allows one to determine the radius of the large extra dimension. If our brane is curved, then the sterile neutrino can take a shortcut through the bulk, leading to an apparent superluminal neutrino speed. The amount of "superluminality" is directly connected to parameters determining the shape of the brane. On the experimental side, we suggest that a long baseline neutrino beam from CERN to NESTOR neutrino telescope will help to clarify these important issues.