Narrow Results

In a previous work it was shown that the radius of a nucleus R is determined by the α-cluster structure and can be estimated on the number of α-clusters disregarding the number of excess neutrons. A hypothesis was also made that the radius R_m of a β-stable isotope, which is actually measured at electron scattering experiments, is determined by the volume occupied by the matter of the core plus the volume occupied by the charge of the peripheral α-clusters. In this paper it is shown that the condition R_m = R restricts the number of excess neutrons filling the core to provide the β-stability. The number of peripheral clusters can vary from 1 to 5 and the value of R for heavy nuclei almost does not change, whereas the number of the excess neutrons should change with the number of peripheral clusters to provide the condition of R_m = R. It can explain the path of the β-stability and its width. The radii R_m of the stable isotopes with 12 ≤ Z ≤ 83 and the alpha-decay isotopes with 84 ≤ Z ≤ 116 that are stable to β-decay have been calculated.

The α-cluster model is based on two assumptions that the proton–neutron pair interactions are responsible for adherence between α-clusters and that the NN-interaction in the α-clusters is isospin independent. It allows one to estimate the Coulomb energy and the short range inter-cluster bond energy in dependence on the number of clusters. The charge radii are calculated from the number of α-clusters too. Unlike the Weizsäcker formula in this model the binding energies of alpha-clusters and excess neutrons are estimated separately. The calculated values are in a good agreement with the experimental data.

The static properties of protons are useful for understanding the quark structure of the proton. In his work we have introduced the hypercentral constituent quark model and isospin dependent potentials. Here constituent quarks interact with each other via a potential in which we have taken into account the three-body force effect and the standard two-body potential contributions. According to our model the static properties of protons containing u and d quarks are better than the other models and closer to experimental results. The two key ingredients of this improvement are the effective quark–gluon hypercentral potentials, and hyperfine interaction and isospin dependence potential. Recently, Schrödinger equation has been solved by Giannini but we have solved the Dirac equation exact analytically and we have shown that a considerable improvement in the description of the static properties of proton is obtained with an isospin dependent potential and the complete interaction including spin and isospin terms reproduces the position of the quark.

Recently an experiment at Jefferson Lab has measured the proton form factor ratio, , down to Q² ~ 0.3 GeV² with unprecedented precision. Based on the results from this experiment, a re-analysis was carried out for the world data on proton form factors, and a new result was extracted for the proton charge radius. The new result is consistent with published CODATA results and is at odds with the new muonic hydrogen measurement at PSI.

We present the results of the new measurement, as well as discuss an upcoming experiment to measure the form factor ratio down to even lower Q².

In this paper, we have analyzed the proton form factor data by using a number of phenomenological parametrizations (models) and extracting the proton electric and magnetic radii. To this end, we performed a global fit to all available form factor data, with the virtual photon momentum squared $Q^2$ from $0.0002$ to nearly 10GeV² for electric form factor and from $0.015$ to 31GeV² for magnetic one. Special attention was given to the small structure shown by the form factor data near $Q^2=0.2$GeV². It was found that different models yield different structures with different numbers of minimum at this kinematics. Since the slope of form factor in the limit of $Q^2\to 0$ is influenced by this structure, the extracted proton radii are consequently different for different models. Our finding recommends that future experiments should focus on this kinematics instead of low $Q^2$. Experimental data with accuracies comparable to those of the latest data at low $Q^2$ would clearly help to clarify the effect of this structure on the proton charge radius. Interestingly, most of the extracted proton charge radii were found to be closer to the value obtained from the muonic hydrogen atom spectroscopy.

We assume that the Dirac neutrino possesses a physical non-standard model charge radius and a physical non-standard model anapole moment and calculate the contribution of these quantities to the anomalous magnetic moment of the muon a_μ using an unsubtracted dispersion relation. We find that these contributions can be important and allow us to set the bound .

We investigate the electromagnetic form factor of $D_s^{\ast }$ meson using $N_f=2$ twisted mass lattice quantum chromodynamics gauge configurations. The numerical simulations are carried out under twisted boundary conditions which are helpful to increase the resolution in momentum space. We determine electromagnetic form factors with more small four-momentum transfer, and further fit the charge radius for $D_s^{\ast }$ meson.

A method for the determination of the pairing-strength constants, in the neutron–proton (n–p) isovector plus isoscalar pairing case, is proposed in the framework of the BCS theory. It is based on the fitting of these constants to reproduce the experimentally known pairing gap parameters as well as the root-mean-squared (r.m.s) charge radii values. The method is applied to some proton-rich even–even nuclei. The single-particle energies used are those of a deformed Woods–Saxon mean field. It is shown that the obtained value of the ratio $G_{np}^{T=0}/G_{np}^{T=1}$ is of the same order as the ones, arbitrary chosen, of some previous works. The effect of the inclusion of the isoscalar n–p pairing in the r.m.s matter radii is then numerically studied for the same nuclei.

The influence of neutrons on charge changing cross-sections (${\sigma }_{\mathrm{\text{cc}}}$) in C isotopes on ${}^{12}$C and proton targets has been investigated in the framework of Glauber model. By comparing the theoretical results and experimental data, it is found out that the influence mainly comes from the projectile neutrons, and the ${\sigma }_{\mathrm{\text{cc}}}$ has a slight change with the increase of the neutron number. Besides, the calculations also illustrate that the influence gets bigger with the reduction of the incident energy.

${}^{14}$C is a beta decay isotope, its beta decay is very slow reflecting the stability of this nucleus and emitted from medium and heavy mass nuclei. The ${}^{14}$C result is in excellent agreement with the favored ground-state-to-ground-state transition according to the cluster model of Blendowske et al. We study nuclear structure properties of spin-1/2 heavy nuclei in the relativistic core-cluster model, that its cluster is ${}^{14}$C. According to this model for spin-1/2 heavy nuclei and for obtaining its wave function, we solve the Dirac equation with the new phenomenological potential by parametric Nikiforov–Uvarov method and then calculate the binding energy and charge radius.

In this paper, we have examined the nuclear structural properties of ^190–210Au isotopes within the framework of the Hartree–Fock–Bogoliubov Model. For the theoretical calculations, we have used the UNEDF2 and SKP interactions. The studies include the shape evolution, quadrupole deformation parameter ${\beta }_2$, nuclear electric quadrupole moment Q(b), single-particle energy levels, the binding energy per nucleon, nuclear charge radius, neutron rms radius, proton rms radius and neutron skin thickness. To analyze the accuracy of our theoretical results, we have presented the comparative analysis with experimental data and finite-range droplet model calculations. The adequate resemblance with experimental data is supporting our studies. We observe the oblate-prolate shape coexistence for ¹⁹⁰Au, ¹⁹³Au and ¹⁹⁵Au using the UNEDF2 interaction.

In this work, a new global formula of nuclear electric quadrupole moments is explicitly derived with respect to the spin, charge and mass number, charge radius and deformation parameters. The deformation parameters extracted from the mass model WS4 and HFB27^∗ are used to calculate the nuclear electric quadrupole moments at the ground states. The calculated results reproduce the measured data well for many isomers. The comparisons between the theoretical results and 527 measured data (Z ≥ 8, A ≥ 16) show that the root mean square deviations are 0.552 barn for WS4 and 0.657 barn for HFB27^∗, respectively. The results of this work are also compared with that of the microscopic shellmodel calculations and the least-squares fitting to the experimental data.