Regularization of the Coulomb scattering problem

Exact solutions of the Schr\"odinger equation for the Coulomb potential are used in the scope of both stationary and time-dependent scattering theories in order to find the parameters which define regularization of the Rutherford cross-section when the scattering angle tends to zero but the distance r from the center remains fixed. Angular distribution of the particles scattered in the Coulomb field is investigated on the rather large but finite distance r from the center. It is shown that the standard asymptotic representation of the wave functions is not available in the case when small scattering angles are considered. Unitary property of the scattering matrix is analyzed and the "optical" theorem for this case is discussed. The total and transport cross-sections for scattering of the particle by the Coulomb center proved to be finite values and are calculated in the analytical form. It is shown that the considered effects can be essential for the observed characteristics of the transport processes in semiconductors which are defined by the electron and hole scattering in the fields of the charged impurity centers.Comment: 20 pages, 6 figure

Extraction of bounds on time-reversal non-invariance from neutron reactions

Ratios involving on-resonance measurements of the three-fold and five-fold correlation cross sections for which the dependence on some of the unknown spectroscopic data is eliminated are considered. Closed form expressions are derived for the statistical distributions of these ratios. Implications for bounds on the variance of matrix elements of time reversal non-invariant nucleon-nucleon interactions are considered within a Bayesian framework and the competitiveness with bounds from other experiments is evaluated. The prospects for null five-fold correlation measurements improving by an order of magnitude or more upon the current bound on a parity-conserving T-odd interaction are good.Comment: 14 pages, to be published in Physics Letters

Measurement of the neutron electric dipole moment by crystal diffraction

An experiment using a prototype setup to search for the neutron electric dipole moment by measuring spin-rotation in a non-centrosymmetric crystal (quartz) was carried out to investigate statistical sensitivity and systematic effects of the method. It has been demonstrated that the concept of the method works. The preliminary result of the experiment is $d_{\rm n}=(2.5\pm 6.5)\cdot 10^{-24}$ e$\cdot$cm. The experiment showed that an accuracy of $\sim 2.5\cdot 10^{-26}$ e$\cdot$cm can be obtained in 100 days data taking, using available quartz crystals and neutron beams.Comment: 13 pages, 4 figure

Photon emissivity of the electrosphere of bare strange stars

We consider the spectrum, emissivity and flux of the electromagnetic radiation emitted by the thin electron layer (the electrosphere) at the surface of a bare strange star. In particular, we carefully consider the effect of the multiple and uncorrelated scattering on the radiation spectrum (the Landau-Pomeranchuk-Migdal effect), together with the effect of the strong electric field at the surface of the star. The presence of the electric field strongly influences the radiation spectrum emitted by the electrosphere. All the radiation properties of the electrons in the electrosphere essentially depend on the value of the electric potential at the quark star surface. The effect of the multiple scattering, which strongly suppresses radiation emission, is important only for the dense layer of the electrosphere situated near the star's surface and only for high values of the surface electric potential of the star. Hence a typical bremsstrahlung radiation spectrum, which could extend to very low frequencies, could be one of the main observational signatures even for low temperature quark stars.Comment: 29 pages, 9 figures, accepted for publication in Ap

Collapse-and-revival dynamics of strongly laser-driven electrons

The relativistic quantum dynamics of an electron in an intense single-mode quantized electromagnetic field is investigated with special emphasis on the spin degree of freedom. In addition to fast spin oscillations at the laser frequency, a second time scale is identified due to the intensity dependent emissions and absorptions of field quanta. In analogy to the well-known phenomenon in atoms at moderate laser intensity, we put forward the conditions of collapses and revivals for the spin evolution in laser-driven electrons starting at feasible $10^{18}$ W/cm$^2$.Comment: 18 pages, 4 figure

Testing T Invariance in the Interaction of Slow Neutrons with Aligned Nuclei

The study of five-fold (P even, T odd) correlation in the interaction of slow polarized neutrons with aligned nuclei is a possible way of testing the time reversal invariance due to the expected enhancement of T violating effects in compound resonances. Possible nuclear targets are discussed which can be aligned both dynamically as well as by the "brute force" method at low temperature. A statistical estimation is performed of the five-fold correlation for low lying p wave compound resonances of the $^{121}$Sb, $^{123}$Sb and $^{127}$I nuclei. It is shown that a significant improvement can be achieved for the bound on the intensity of the fundamental parity conserving time violating (PCTV) interaction.Comment: 22 pages, 5 figures, published versio

Photon emission from bare quark stars

We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures T\sim 0.1-1 MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy for this mechanism is much larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the mean field bremsstrahlung exceeds the one from the tunnel e^{+}e^{-} pair creation as well. We demonstrate that the LPM suppression of the photon emission is negligible.Comment: 35 pages, 5 figure

Determination of SU(6) Clebsch-Gordan Coefficients and Baryon Mass and Electromagnetic Moment Relations

We compute and tabulate the Clesbsch--Gordan coefficients of the $SU(6) \supset SU(3) \times SU(2)$ product ${\overline{\bf 56}} \otimes {\bf 56}$, which are relevant to the nonrelativistic spin-flavor symmetry of the lightest baryons. Under the assumption that the largest representation in this product, the ${\bf 2695}$, gives rise to operators in a chiral expansion that produce numerically small effects, we obtain a set of relations among the masses of the baryons, as well as among their magnetic dipole and higher multipole moments. We compare the mass relations to experiment, and find numerical predictions for the $\Sigma^0$-$\Lambda$ mass mixing parameter and eighteen of the twenty-seven magnetic moments in the ${\bf 56}$.Comment: 33 pages, latex (aps revtex), no figure