Spin effects in ppˉp\bar p interaction and their possible use to polarize antiproton beams

Low energy $p\bar p$ interaction is considered taking into account the polarization of both particles. The corresponding cross sections are calculated using the Paris nucleon-antinucleon optical potential. Then they are applied to the analysis of the polarization buildup which is due to the interaction of stored antiprotons with polarized protons of a hydrogen target. It is shown that, at realistic parameters of a storage ring and a target, the filtering mechanism provides a noticeable polarization in a time comparable with the beam lifetime.Comment: 10 pages, 4 figure

Nuclear Anapole Moments in Single Particle Approximation

Nuclear anapole moments of $\;^{133}$Cs, $\;^{203,205}$Tl, $\;^{207}$Pb, $\;^{209}$Bi are treated in the single-particle approximation. Analytical results are obtained for the oscillator potential without spin-orbit interaction. Then the anapole moments are calculated numerically in a Woods-Saxon potential which includes spin-orbit interaction. The results obtained demonstrate a remarkable stability of nuclear anapole moment calculations in the single-particle approximation.Comment: 20 pages, LateX, One figure available upon request, BINP-93-11

Virtual Pion Scattering

We propose a theory which exploits the charge-exchange reactions ($^3$He,$^3$H$\pi^+$) and (p,n$\pi^+$) as effective sources of virtual pions. We consider processes in which the creation of virtual pions is followed by conventional coupled-channel pion scattering to discrete nuclear states. This picture allows us to incorporate successful theories of pion scattering and utilize virtual pions as probes of the nuclear matter. For coherent pion production we clearly demonstrate that the shift of the coherent peak position in the excitation function of $^3$He-A relative to $^3$He-N scattering is determined entirely by the pion nucleus rescattering.Comment: 10 pages, revtex 3, 2 figures attached in file figures.u

The anapole moment and nucleon weak interactions

From the recent measurement of parity nonconservation (PNC) in the Cs atom we have extracted the constant of the nuclear spin dependent electron-nucleon PNC interaction, $\kappa = 0.442 (63)$; the anapole moment constant, $\kappa_a = 0.364 (62)$; the strength of the PNC proton-nucleus potential, $g_p = 7.3 \pm 1.2 (exp.) \pm 1.5 (theor.)$; the $\pi$-meson-nucleon interaction constant, $f_\pi \equiv h_\pi^{1} = [9.5 \pm 2.1 (exp.) \pm 3.5 (theor.)] \times 10^{-7}$; and the strength of the neutron-nucleus potential, $g_n = -1.7 \pm 0.8 (exp.) \pm 1.3 (theor.)$.Comment: Uses RevTex, 12 pages. We have added an explanation of the effect of finite nuclear siz

Conductivity of 2D many-component electron gas, partially-quantized by magnetic field

The 2D semimetal consisting of heavy holes and light electrons is studied. The consideration is based on assumption that electrons are quantized by magnetic field while holes remain classical. We assume also that the interaction between components is weak and the conversion between components is absent. The kinetic equation for holes colliding with quantized electrons is utilized. It has been stated that the inter-component friction and corresponding correction to the dissipative conductivity $\sigma_{xx}$ {\it do not vanish at zero temperature} due to degeneracy of the Landau levels. This correction arises when the Fermi level crosses the Landau level. The limits of kinetic equation applicability were found. We also study the situation of kinetic memory when particles repeatedly return to the points of their meeting.Comment: 13 pages, 1 figur

Nuclear magnetization distribution and hyperfine splitting in Bi82+^{82+} ion

Hyperfine splitting in Bi$^{82+}$ and Pb$^{81+}$ ions was calculated using continuum RPA approach with effective residual forces. To fix the parameters of the theory the nuclear magnetic dipole moments of two one- particle and two one-hole nuclei around $^{208}$Pb were calculated using the same approach. The contribution from velocity dependent two-body spin- orbit residual interaction was calculated explicitly. Additionally, the octupole moment of $^{209}$Bi and the hfs in muonic bismuth atom were calculated as well in the same approach. All the calculated observables, except the electronic hfs in $^{209}$Bi, are in good agreement with the data. We argue for more accurate measurement of the octupole moment and the muonic hfs for $^{209}$Bi.Comment: 11 pages, 5 figure

Nuclear Spin-Isospin Correlations, Parity Violation, and the fπf_\pi Problem

The strong interaction effects of isospin- and spin-dependent nucleon-nucleon correlations observed in many-body calculations are interpreted in terms of a one-pion exchange mechanism. Including such effects in computations of nuclear parity violating effects leads to enhancements of about 10%. A larger effect arises from the one-boson exchange nature of the parity non-conserving nucleon- nucleon interaction, which depends on both weak and strong meson-nucleon coupling constants. Using values of the latter that are constrained by nucleon-nucleon phase shifts leads to enhancements of parity violation by factors close to two. Thus much of previously noticed discrepancies between weak coupling constants extracted from different experiments can be removed.Comment: 8 pages 2 figures there should have been two figures in v

No Sommerfeld resummation factor in e+e- -> ppbar ?

The Sommerfeld rescattering formula is compared to the e+e- -> ppbar BaBar data at threshold and above. While there is the expected Coulomb enhancement at threshold, two unexpected outcomes have been found: |G^p (4M_p^2)|= 1, like for a pointlike fermion, and moreover data show that the resummation factor in the Sommerfeld formula is not needed. Other e+e- -> baryon-antibaryon cross sections show a similar behavior near threshold.Comment: 9 pages, 6 figure

MeV-mass dark matter and primordial nucleosynthesis

The annihilation of new dark matter candidates with masses $m_X$ in the MeV range may account for the galactic positrons that are required to explain the 511 keV $\gamma$-ray flux from the galactic bulge. We study the impact of MeV-mass thermal relic particles on the primordial synthesis of $^2$H, $^4$He, and $^7$Li. If the new particles are in thermal equilibrium with neutrinos during the nucleosynthesis epoch they increase the helium mass fraction for m_X\alt 10 MeV and are thus disfavored. If they couple primarily to the electromagnetic plasma they can have the opposite effect of lowering both helium and deuterium. For $m_X=4$--10 MeV they can even improve the overall agreement between the predicted and observed $^2$H and $^4$He abundances.Comment: 11 pages, 10 figures, references and two appendices added, conclusions unchanged; accepted for publication in Phys.Rev.

The Nuclear Response in Delta-Isobar Region in the (3 ⁣^3\!He,t) Reaction

The excitation of a $\Delta$-isobar in a finite nucleus in charge--exchange ($^3\!$He,t) reaction is discussed in terms of a nuclear response function. The medium effects modifying a $\Delta$- and a pion propagation were considered for a finite size nucleus. The Glauber approach has been used for distortion of a $^3\!$He and a triton in the initial and the final states. The effects determining the peak positions and its width are discussed. Large displacement width for the $\Delta$ - h excitations and considerable contribution of coherent pion production were found for the reaction on $^{12}$C.Comment: 29 pages including 8 figures, IU/NTC 92-3