Search results for "Charge density"
showing 10 items of 206 documents
Lower bound on the proton charge radius from electron scattering data
2019
The proton charge-radius determinations from the electromagnetic form-factor measurements in electron-proton scattering require an extrapolation to zero momentum transfer ($Q^2=0$) which is prone to model-dependent assumptions. We show that the data at finite momentum transfer can be used to establish a rigorous lower bound on the proton charge radius. Using the available $ep$ data at low $Q^2$, we obtain $R_E > 0.850(1)$ fm as the lower bound on the proton radius. This reaffirms the discrepancy between the $ep$ and muonic-hydrogen values, while bypassing the model-dependent assumptions that go into the fitting and extrapolation of the $ep$ data.
Relativistic corrections to the elastic electron scattering fromPb208
1976
In the present work we have calculated the differential cross sections for the elastic electron scattering from $sup 208$Pb using the charge distributions resulting from various corrections. The point proton and neutron mass distributions have been calculated from the spherical wave functions for $sup 208$Pb obtained by Kolb et al. The relativistic correction to the nuclear charge distribution coming from the electromagnetic structure of the nucleon has been accomplished by assuming a linear superposition of Gaussian shapes for the proton and the neutron charge form factor. Results of this calculation are quite similar to an earlier calculation by Bertozzi et al., who have used a different …
Particle tracking in kaon electroproduction with cathode-charge sampling in multi-wire proportional chambers
2011
Abstract Wire chambers are routinely operated as tracking detectors in magnetic spectrometers at high-intensity continuous electron beams. Especially in experiments studying reactions with small cross-sections the reaction yield is limited by the background rate in the chambers. One way to determine the track of a charged particle through a multi-wire proportional chamber (MWPC) is the measurement of the charge distribution induced on its cathodes. In practical applications of this read-out method, the algorithm to relate the measured charge distribution to the avalanche position is an important factor for the achievable position resolution and for the track reconstruction efficiency. An al…
Nuclear moments and charge radii of neutron-deficient francium isotopes and isomers
2015
Collinear laser fluorescence spectroscopy has been performed on the ground and isomeric states of $^{204,206}\mathrm{Fr}$ in order to determine their spins, nuclear moments, and changes in mean-squared charge radii. A new experimental technique has been developed as part of this work which much enhances the data collection rate while maintaining the high resolution. This has permitted the extension of this study to the two isomeric states in each nucleus. The investigation of nuclear $g$ factors and mean-squared charge radii indicates that the neutron-deficient Fr isotopes lie in a transitional region from spherical towards more collective structures.
Systematics of nuclear charge distributions in Fe, Co, Ni, Cu, and Zn deduced from muonic x-ray measurements
1976
The results of precise measurements of the energies of the $2{p}_{\frac{3}{2}}\ensuremath{\rightarrow}1{s}_{\frac{1}{2}}$ and $2{p}_{\frac{1}{2}}\ensuremath{\rightarrow}1{s}_{\frac{1}{2}}$ muonic x-ray transitions of $^{54}\mathrm{Fe}$, $^{56}\mathrm{Fe}$, $^{57}\mathrm{Fe}$, $^{58}\mathrm{Fe}$, $^{59}\mathrm{Co}$, $^{58}\mathrm{Ni}$, $^{60}\mathrm{Ni}$, $^{61}\mathrm{Ni}$, $^{62}\mathrm{Ni}$, $^{64}\mathrm{Ni}$, $^{63}\mathrm{Cu}$, $^{65}\mathrm{Cu}$, $^{64}\mathrm{Zn}$, $^{66}\mathrm{Zn}$, $^{68}\mathrm{Zn}$, and $^{70}\mathrm{Zn}$, are reported. Using a highly linear digitally stabilized Ge(Li) spectrometer system, the absolute energies and energy shifts between nuclei were measured with…
Nuclear ground-state properties in a relativistic Meson-Field theory
1986
We investigate the ability of a relativistic Mean-Field theory to reproduce nuclear ground state properties by an exhaustive fit to experimental data. We find that the bulk properties of nuclei from16O to208Pb can be adjusted very well. There remain problems with level density and fluctuations in the charge density similar as in fits using the conventional Skyrme Hartree-Fock model.
Sensitivity of the isotope shift to the distribution of nuclear charge density
2019
It is usually assumed that the field isotope shift (FIS) is completely determined by the change of the averaged squared values of the nuclear charge radius $\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}$. Relativistic corrections modify the expression for FIS, which is actually described by the change of $\ensuremath{\langle}{r}^{2\ensuremath{\gamma}}\ensuremath{\rangle}$, where $\ensuremath{\gamma}=\sqrt{1\ensuremath{-}{Z}^{2}{\ensuremath{\alpha}}^{2}}$. In the present paper we consider corrections to FIS which are due to the nuclear deformation and due to the predicted reduced charge density in the middle of the superheavy nuclei produced by a very strong proton repulsion (hole in the n…
Reply to "Comment on `Breakdown of the expansion of finite-size corrections to the hydrogen Lamb shift in moments of charge distribution'"
2016
To comply with the critique of the Comment [J. Arrington, arXiv:1602.01461], we consider another modification of the proton electric form factor, which resolves the "proton-radius puzzle". The proposed modification satisfies all the consistency criteria put forward in the Comment, and yet has a similar impact on the puzzle as that of the original paper. Contrary to the concluding statement of the Comment, it is not difficult to find an ad hoc modification of the form factor at low $Q$ that resolves the discrepancy and is consistent with analyticity constraints. We emphasize once again that we do not consider such an ad hoc modification of the proton form factor to be a solution of the puzzl…
The pion quasiparticle in the low-temperature phase of QCD
2017
We extend our previous studies [PhysRevD.90.054509, PhysRevD.92.094510] of the pion quasiparticle in the low-temperature phase of two-flavor QCD with support from chiral effective theory. This includes the analysis performed on a finite temperature ensemble of size $20\times 64^3$ at $T\approx 151$MeV and a lighter zero-temperature pion mass $m_{\pi} \approx 185$ MeV. Furthermore, we investigate the Gell-Mann--Oakes-Renner relation at finite temperature and the Dey-Eletsky-Ioffe mixing theorem at finite quark mass.
The pion quasiparticle in the low-temperature phase of QCD
2015
We investigate the properties of the pion quasiparticle in the low-temperature phase of two-flavor QCD on the lattice with support from chiral effective theory. We find that the pion quasiparticle mass is significantly reduced compared to its value in the vacuum, by contrast with the static screening mass, which increases with temperature. By a simple argument, near the chiral limit the two masses are expected to determine the quasiparticle dispersion relation. Analyzing two-point functions of the axial charge density at non-vanishing spatial momentum, we find that the predicted dispersion relation and the residue of the pion pole are simultaneously consistent with the lattice data at low m…