Azimuthal single- and double-spin asymmetries in semi-inclusive deep-inelastic lepton scattering by transversely polarized protons

A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos (ϕ−ϕS) modulations provide evidence for a sizable worm-gear (II) distribution, $$ {g}_{1\mathrm{T}}^q\left(x,{\mathrm{p}}_T^2\right) $$ g 1 T q x p T 2 . Most of the other modulations are found to be consistent with zero with the notable exception of large sin (ϕS) modulations for charged pions and K+.

Quark mass function at finite density in real-time formalism

Chiral symmetry restoration of quarks is investigated at finite density in quantum chromodynamics. The critical chemical potentials at zero temperature, in which the chiral symmetry is restored, are calculated with the Schwinger-Dyson equation in the real-time formalism without the instantaneous exchange approximation. We present some properties of the quark mass functions and the quark propagators.

Generalized Single Excitation Configuration Interaction: An Investigation into the Impact of the Inclusion of Non-Orthogonality on the Calculation of Core-Excited States

<div>In this paper, we investigate different non-orthogonal generalizations of the configuration interaction with single substitutions (CIS) method for the calculation of core-excited states. Fully non-orthogonal CIS (NOCIS) has been described previously for singlets and doublets and this paper reports the extension to triplet molecules. In addition to NOCIS, we present a novel method, 1C-NOCIS(1C-NOCIS), for open-shell molecules which is intermediate between NOCIS and the static exchange approximation (STEX). We explore this hierarchy of spin-pure methods for singlet, doublet, and triplet molecules and conclude that, while NOCIS provides the best results and preserves the spatial symmetry of the wavefunction, 1C-NOCIS retains much of the accuracy of NOCIS at a dramatically reduced cost. For molecules with closed-shell ground states, STEX and 1C-NOCIS are identical.</div>

Generalized Single Excitation Configuration Interaction: An Investigation into the Impact of the Inclusion of Non-Orthogonality on the Calculation of Core-Excited States

<div>In this paper, we investigate different non-orthogonal generalizations of the configuration interaction with single substitutions (CIS) method for the calculation of core-excited states. Fully non-orthogonal CIS (NOCIS) has been described previously for singlets and doublets and this paper reports the extension to triplet molecules. In addition to NOCIS, we present a novel method, 1C-NOCIS(1C-NOCIS), for open-shell molecules which is intermediate between NOCIS and the static exchange approximation (STEX). We explore this hierarchy of spin-pure methods for singlet, doublet, and triplet molecules and conclude that, while NOCIS provides the best results and preserves the spatial symmetry of the wavefunction, 1C-NOCIS retains much of the accuracy of NOCIS at a dramatically reduced cost. For molecules with closed-shell ground states, STEX and 1C-NOCIS are identical.</div>

Possible Bose-Einstein Condensation of Polygonal Clusters in 2D-Materials

This study investigates the possibility of Bose-Einstein condensation (BEC) in 2D-nanoclusters. A ground state equilibrium structure involves the single phonon exchange approximation. At critical temperature, the specific heat, entropy, and free energy of the system can be determined. The results support the existence of BEC in nanoclusters, and they lead to predictions of the behaviour of 2Dmaterials at low temperatures.

Critical analysis of recent results on electron and positron elastic scattering on proton

Recent data on the cross section ratio for electron and positron elastic scattering on protons are discussed. A deviation from unity of this ratio constitutes a model independent signature of charge-odd contributions that arise from mechanisms beyond the one-photon approximation, as the exchange of two photons. The relevance of this issue is related to that fact that the information on the proton structure from lepton elastic (and inelastic) scattering holds only within a formalism based on the one photon exchange approximation. The present analysis shows that the deviations of the data from unity and from a previously developed theoretical approach lie within the theoretical and experimental errors. The data suggest that other reasons for explanation of the discrepancy between the electromagnetic proton form factors extracted from the experiments according to the polarized and the unpolarized methods are more likely.