Search results for "Radius"
showing 10 items of 708 documents
Nuclear moments and charge radii of the171Hf ground state and isomer
2000
The magnetic moment, quadrupole moment and mean-square charge radial changes, relative to 172Hf, have been measured for the 171Hf ground state and the ½-[521] isomeric state, using on-line laser spectroscopy. The magnetic moments of the isomer and ground states are found to be + 0.526(16)µn and -0.674(12)µn, respectively. The spectroscopic quadrupole moment of the ground state is found to be +3.463(27) b. No change in mean-square charge radius is observed between the ground state and isomeric state. The observation of an inversion in the odd-even staggering at 171Hf is consistent with the suggested deformation trends.
Ab initio calculation of nuclear structure corrections in muonic atoms
2018
The measurement of the Lamb shift in muonic hydrogen and the subsequent emergence of the proton-radius puzzle have motivated an experimental campaign devoted to measuring the Lamb shift in other light muonic atoms, such as muonic deuterium and helium. For these systems it has been shown that two-photon exchange nuclear structure corrections are the largest source of uncertainty and consequently the bottleneck for exploiting the experimental precision to extract the nuclear charge radius. Utilizing techniques and methods developed to study electromagnetic reactions in light nuclei, recent calculations of nuclear structure corrections to the muonic Lamb shift have reached unprecedented precis…
Dilepton photoproduction on a deuteron target
2019
We investigate the sensitivity of the cross section for lepton pair production off a deuteron target, $\gamma d \to l^+ l^- d$, to the deuteron charge radius. We show that for small momentum transfers the Bethe-Heitler process dominates, and that it is sensitive to the charge radius such that a cross section ratio measurement of about $0.1 \%$ relative accuracy could give a deuteron charge radius more accurate that the current electron scattering value and sufficiently accurate to distinguish between the electronic and muonic atomic values.
The deuteron-radius puzzle is alive: A new analysis of nuclear structure uncertainties
2018
To shed light on the deuteron radius puzzle we analyze the theoretical uncertainties of the nuclear structure corrections to the Lamb shift in muonic deuterium. We find that the discrepancy between the calculated two-photon exchange correction and the corresponding experimentally inferred value by Pohl et al. [1] remain. The present result is consistent with our previous estimate, although the discrepancy is reduced from 2.6 $\sigma$ to 2 $\sigma$. The error analysis includes statistic as well as systematic uncertainties stemming from the use of nucleon-nucleon interactions derived from chiral effective field theory at various orders. We therefore conclude that nuclear theory uncertainty is…
Form factors in the 'point form' of relativistic quantum mechanics : single and two-particle currents
2004
Electromagnetic and Lorentz-scalar form factors are calculated for a bound system of two spin-less particles exchanging a zero-mass scalar particle. Different approaches are considered including solutions of a Bethe-Salpeter equation, a ``point form'' approach to relativistic quantum mechanics and a non-relativistic one. The comparison of the Bethe-Salpeter results, which play the role of an ``experiment'' here, with the ones obtained in ``point form'' in single-particle approximation, evidences sizable discrepancies, pointing to large contributions from two-body currents in the latter approach. These ones are constructed using two constraints: ensuring current conservation and reproducing …
Elastic electron deuteron scattering with consistent meson exchange and relativistic contributions of leading order
1999
The influence of relativistic contributions to elastic electron deuteron scattering is studied systematically at low and intermediate momentum transfers ($Q^2\leq 30$ fm$^{-2}$). In a $(p/M)$-expansion, all leading order relativistic $\pi$-exchange contributions consistent with the Bonn OBEPQ models are included. In addition, static heavy meson exchange currents including boost terms and lowest order $\rho\pi\gamma$-currents are considered. Sizeable effects from the various relativistic two-body contributions, mainly from $\pi$-exchange, have been found in form factors, structure functions and the tensor polarization $T_{20}$. Furthermore, static properties, viz. magnetic dipole and charge …
The RMS charge radius of the proton and Zemach moments
2010
On the basis of recent precise measurements of the electric form factor of the proton, the Zemach moments, needed as input parameters for the determination of the proton rms radius from the measurement of the Lamb shift in muonic hydrogen, are calculated. It turns out that the new moments give an uncertainty as large as the presently stated error of the recent Lamb shift measurement of Pohl et al.. De Rujula's idea of a large Zemach moment in order to reconcile the five standard deviation discrepancy between the muonic Lamb shift determination and the result of electronic experiments is shown to be in clear contradiction with experiment. Alternative explanations are touched upon.
Character of an 8− isomer of 130Ba
2002
Abstract The static moments and isomer shift of the J π = K π =8 − isomeric state in 130 56 Ba have been measured using the technique of collinear laser spectroscopy. The isomer has been found to have a magnetic dipole moment of −0.043(28) μ N and a static quadrupole moment of +2.77(30) b. These values have been used to assign the state as a two neutron 7 2 + [404]⊗ 9 2 − [514] configuration corresponding to a prolate shape. The half-life of the isomer has been confirmed as 9.54(14) ms. The change in the mean square charge radius was found to be 〈 r 2 〉 130m −〈 r 2 〉 130g–s =−0.0473(30) fm 2 .
SU(3) Chiral approach to meson and baryon dynamics
1999
We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and meson baryon interaction up to the first baryonic resonances. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, concretely the K^- p\to\Lambda(1405)\gamma reaction and the N^\ast (1535)N^\ast(1535)\pi and \eta couplings.
Recent progress on the chiral unitary approach to meson meson and meson baryon interactions
1999
We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented. Results for the extension of these ideas to the meson baryon sector are discussed, together with applications to kaons in a nuclear medium and $K^-$ atoms.