Composition of the nuclear periphery from antiproton absorption

Thirteen targets with mass numbers from 58 to 238 were irradiated with the antiproton beam from the Low Energy Antiproton Ring facility at CERN leading to the formation of antiprotonic atoms of these heavy elements. The antiproton capture at the end of an atomic cascade results in the production of more or less excited residual nuclei. The targets were selected with the criterion that both reaction products with one nucleon less than the proton and neutron number of the target be radioactive. The yield of these radioactive products after stopped-antiproton annihilation was determined using gamma-ray spectroscopy techniques. This yield is related to the proton and neutron density in the target nucleus at a radial distance corresponding to the antiproton annihilation site. The experimental data clearly indicate the existence of a neutron-rich nuclear periphery, a "neutron halo", strongly correlated with the target neutron separation energy Bn and observed for targets with Bn < 10 MeV. For two-target nuclei 106Cd and 144Sm, with larger neutron binding energies, a proton-rich nuclear periphery was observed. Most of the experimental data are in reasonable agreement with calculations based on current antiproton-nucleus and pion-nucleus interaction potentials and on nuclear densities deduced with the help of the Hartree-Fock-Bogoliubov approach. This approach was, however, unable to account for the 106Cd and 144Sm results.Comment: Latex (RevTeX,aps style), 13 pages + 12 Postscript figure

Deuteron Photodissociation in Ultraperipheral Relativistic Heavy-Ion on Deuteron Collisions

In ultraperipheral relativistic deuteron on heavy-ion collisions, a photon emitted from the heavy nucleus may dissociate the deuterium ion. We find deuterium breakup cross sections of 1.38 barns for deuterium-gold collisions at a center of mass energy of 200 GeV per nucleon, as studied at the Relativistic Heavy Ion Collider, and 2.49 barns for deuterium-lead collisions at a center of mass energy of 6.2 TeV, as proposed for the Large Hadron Collider. This cross section includes an energy-independent 140 mb contribution from hadronic diffractive dissociation. At the LHC, the cross section is as large as that of hadronic interactions. The estimated error is 5%. Deuteron dissociation could be used as a luminosity monitor and a `tag' for moderate impact parameter collisions.Comment: Final version, to appear in Phys. Rev. C. Diffractive dissociation included 10 pages with 3 figure

Information on antiprotonic atoms and the nuclear periphery from the PS209 experiment

In the PS209 experiments at CERN two kinds of measurements were performed: the in-beam measurement of X-rays from antiprotonic atoms and the radiochemical, off-line determination of the yield of annihilation products with mass number A_t -1 (less by 1 than the target mass). Both methods give observables which allows to study the peripheral matter density composition and distribution.Comment: LaTeX (espcrc1 style), 6 pages, 3 EPS figures, 1 table, Proceedings of the Sixth Biennal Conference on Low-Energy Antiproton Physics LEAP 2000, Venice, Ital

Neutron density distributions from antiprotonic 208Pb and 209Bi atoms

The X-ray cascade from antiprotonic atoms was studied for 208Pb and 209Bi. Widths and shifts of the levels due to the strong interaction were determined. Using modern antiproton-nucleus optical potentials the neutron densities in the nuclear periphery were deduced. Assuming two parameter Fermi distributions (2pF) describing the proton and neutron densities the neutron rms radii were deduced for both nuclei. The difference of neutron and proton rms radii /\r_np equal to 0.16 +-(0.02)_{stat} +- (0.04)_{syst} fm for 208Pb and 0.14 +- (0.04)_{stat} +- (0.04)_{syst} fm for 209Bi were determined and the assigned systematic errors are discussed. The /\r_np values and the deduced shapes of the neutron distributions are compared with mean field model calculations.Comment: 22 pages, 8 tables, 15 figure

Nucleon density in the nuclear periphery determined with antiprotonic x-rays: cadmium and tin isotopes

The x-ray cascade from antiprotonic atoms was studied for 106Cd, 116Cd, 112Sn, 116Sn, 120Sn, and 124Sn. Widths and shifts of the levels due to strong interaction were deduced. Isotopic effects in the Cd and Sn isotopes are clearly seen. The results are used to investigate the nucleon density in the nuclear periphery. The deduced neutron distributions are compared with the results of the previously introduced radiochemical method and with HFB calculations

Reevaluation of the role of nuclear uncertainties in experiments on atomic parity violation with isotopic chains

In light of new data on neutron distributions from experiments with antiprotonic atoms [ Trzcinska {\it et al.}, Phys. Rev. Lett. 87, 082501 (2001)], we reexamine the role of nuclear-structure uncertainties in the interpretation of measurements of parity violation in atoms using chains of isotopes of the same element. With these new nuclear data, we find an improvement in the sensitivity of isotopic chain measurements to ``new physics'' beyond the standard model. We compare possible constraints on ``new physics'' with the most accurate to date single-isotope probe of parity violation in the Cs atom. We conclude that presently isotopic chain experiments employing atoms with nuclear charges Z < 50 may result in more accurate tests of the weak interaction.Comment: 6 pages, 1 fig., submitted to Phys. Rev.

Strong interaction and E2 effect in even- A antiprotonic Te atoms

The x-ray cascade from antiprotonic atoms was studied for Te-122, Te-124, Te-126, Te-128, and Te-130. Widths and shifts due to the strong interaction were deduced for several levels. The E2 nuclear resonance effect was observed in all investigated nuclei. In Te-130 the E2 resonance allowed to determine level widths and shifts of the LS-split deeply bound (n,l)=(6,5) state, otherwise unobservable. The measured level widths and shifts, corrected for the E2-resonance effect, were used to investigate the nucleon density in the nuclear periphery. The deduced neutron distributions are compared with results of the previously introduced radiochemical method and with Hartree-Fock-Bogoliubov model calculations

Correlated many-body treatment of Breit interaction with application to cesium atomic properties and parity violation

Corrections from Breit interaction to basic properties of atomic 133Cs are determined in the framework of third-order relativistic many-body perturbation theory. The corrections to energies, hyperfine-structure constants, off-diagonal hyperfine 6S-7S amplitude, and electric-dipole matrix elements are tabulated. It is demonstrated that the Breit corrections to correlations are comparable to the Breit corrections at the Dirac-Hartree-Fock level. Modification of the parity-nonconserving (PNC) 6S-7S amplitude due to Breit interaction is also evaluated; the resulting weak charge of $^{133}$Cs shows no significant deviation from the prediction of the standard model of elementary particles. The neutron skin correction to the PNC amplitude is also estimated to be -0.2% with an error bound of 30% based on the analysis of recent experiments with antiprotonic atoms. The present work supplements publication [A. Derevianko, Phys. Rev. Lett. 85, 1618 (2000)] with a discussion of the formalism and provides additional numerical results and updated discussion of parity violation.Comment: 16 pages; 5 figs; submitted to Phys. Rev.