Proton Asymmetry Research Articles

Bulk and neutron–proton asymmetry coefficients of the semi-empirical mass formula tuned to ground state mass excess of AME2020 and/or FRDM(2012)

Davidson et al. has extended Seeger’s mass formula to non-zero excitation energies by introducing temperature-dependent coefficients in the liquid drop energy part of the semi-empirical mass formula, but did not consider the nuclear shape and shell effects. The semi-empirical mass formula of Davidson et al. is applicable for nuclear temperatures less than or equal to 4 MeV. The mass excess calculated using this mass formula with/without nuclear shape and shell effects does not reproduce the ground state mass excesses of the new atomic mass evaluation data AME2020 and/or FRDM(2012) with its coefficients at zero temperature. So, the coefficients of the semi-empirical mass formula with nuclear shape and shell effects are required to be tuned to reproduce the ground state mass excess of all the nuclei available in the recent atomic mass evaluation data AME2020 and/or FRDM(2012). The bulk and neutron–proton asymmetry coefficients of the semi-empirical mass formula of Davidson et al., including the nuclear shape and shell effects, have been tuned to reproduce the mass excess data for all known 9420 nuclei which include all the nuclei of AME2020 (Z = 1-118 and A = 1-295) and of FRDM(2012) (Z = 8-136 and A = 16-339, except 3456 nuclei which are also available in the AME2020 data) at zero temperature. The tuned bulk and neutron–proton asymmetry coefficients reproduce the ground state mass excess of the new atomic mass evaluation data AME2020 and/or FRDM(2012) within a difference of less than 1 MeV and can be used for the applications/investigations in the areas of physics where high energies are experienced or nuclei involved are in excited states, e.g., fusion–evaporation and fusion–fission processes in heavy-ion reactions. The mass excess calculated for the excited states of nuclei is compared with the excited state mass excess of the NUBASE2020 evaluation data and is in good agreement with it.

Forward-backward electron–proton asymmetry from a two-photon crossing of diabatic states of H[formula omitted] in linearly polarized intense laser field

Controlling spatial–temporal overlap between nuclear wave packets propagating on the coupled electronic states with opposite parity by intense laser field leads to a π periodic modulation in the symmetry breaking of the coupled forward–backward electron and proton motions. The most probable directionality of electron and proton moving simultaneously in opposite directions with total electron–proton asymmetry parameter Ae−ptot=0.62 occurs at fixed carrier-envelope phases of ϑ=15° and 195°. Analysis of the time evolution of the nuclear and the electronic-nuclear wave packets on the field-dressed potentials gives rise to newly insightful images of the nonlinear nonperturbative processes for the asymmetrical localization.

Constraining Neutron-Star Matter — Combination of heavy-ion experiments and multi-messenger astronomy

Describing supernova explosions or neutron-star collisions requires a deep understanding of properties of nuclear matter at supra-saturation densities, and extreme neutron over proton asymmetries. So far, our knowledge about dense matter provided by astrophysical observations in the cores of neutron stars remains limited. However, dense nuclear matter is also probed in terrestrial heavy-ion collision (HIC) experiments. We demonstrate how, within a novel approach, using Bayesian inference, combining data from astrophysical multi-messenger observations of neutron stars and from HICs at relativistic energies, one can improve our understanding of dense nuclear matter. The inclusion of HIC data probing the nuclear matter equation-of-state (EoS) at supra-saturation density has the effect of increasing the predicted pressure in the core of neutron stars relative to previous analyses, and shifts the neutron-star radii expectation towards larger values, in accordance with recent observations by the Neutron Star Interior Composition Explorer mission. More remarkable is that, though the sources and methods of observation are orthogonal, the constraints from HIC experiments and multimessenger observations are consistent with each other. It shows that both methods can be complementary at intermediate densities, and strengthen each other. Another conclusion is that in order to be even more constraining, the constraint of the EoS of asymmetric nuclear matter by HIC methods should be improved above twice saturation density, which should be feasible with future experiments with enhanced precision and higher bombarding energy.

Exploration of isospin asymmetry in the pseudospin symmetry with axially deformed scalar and vector potentials

Based on the similarity renormalization group (SRG) method, proton and neutron asymmetry in the nuclear pseudospin is investigated for the deformed system. We have checked influences of every term on the proton pseudospin splitting and their correlation with nuclear deformation. Further, we have found that dynamical term always made a similar effect on the proton pseudospin symmetry (PSS), which is different from the neutron case. By exerting its influence on the dynamical term, the vector–isovector [Formula: see text] potential gives the main contribution to the isospin asymmetry in the PSS except for several deeply bound states. The phenomenon that isospin asymmetry in the PSS becomes worse for the levels closer to the continuum and its reasons is disclosed.

Investigations on the flavor-dependent axial charges of the octet baryons

We have investigated the axial charges of the ground octet baryons within the extended chiral constituent quark model, where all the possible compact five-quark Fock components $qqq(q\overline{q})(q=u,d,s)$ in the baryons are considered. The transition couplings between the three- and five-quark components in the baryons are assumed to be via the $^{3}{P}_{0}$ mechanism, which could reproduce the sea asymmetry in proton very well. The numerical results for the flavor-dependent axial charges of the octet baryons are comparable to those predicted by other theoretical approaches. It is shown that the singlet axial charges of the octet baryons, which should indicate total baryons spin arising from the spin of the quarks, fall in the range $0.45--0.75$ in present model. This is in consistent with the predictions by lattice QCD and chiral perturbation theory. It is also very interesting that the light quarks spin $\mathrm{\ensuremath{\Delta}}u$ and $\mathrm{\ensuremath{\Delta}}d$ in the $\mathrm{\ensuremath{\Lambda}}$ baryon are of small but negative values, which exactly vanish in the traditional three-quark model.

Nonlocal optical model for deuteron elastic scattering

Deuteron elastic scattering off light, intermediate, and heavy nuclei from 10Be to 120Sn corresponding to incident energies in the range 10–70 MeV is considered using the nonlocal model of Perey and Buck, which explicitly includes a Gaussian nonlocality (Perey and Buck. Nucl. Phys. A, 32, 353 (1962). doi:10.1016/0029-5582(62)90345-0). We obtain two sets of global nonlocal parameters, one for light 1p-shell nuclei and the other for intermediate and heavy ones. The geometrical parameters of each set are fixed, while the imaginary volume and imaginary surface depths vary linearly with both energy and the neutron–proton asymmetry of the target. Our best angular distribution fits are in very good agreement with the measured data. To test the model, we used our global parameters to predict the angular distributions for nuclei and energies that have not been included in the fitting procedure. The resulting χ2 values are as good as the values calculated using global local potentials in the literature or better, despite the fact that 12 out of the 15 parameters of the nonlocal potential are fixed. For the deuteron–nucleus scattering, we determined a nonlocality parameter of 0.45 fm, which compares well with the values obtained in previous works.

On the Dependence of the Nuclear Surface Diffuseness on the Neutron–Proton Asymmetry and Its Influence on the Evolution of the Single-Particle Spectra

On the Dependence of the Nuclear Surface Diffuseness on the Neutron–Proton Asymmetry and Its Influence on the Evolution of the Single-Particle Spectra

Isospin asymmetry and quantum statistical interpretation of nucleons

In this paper, a statistical model introducing analytical expressions of [Formula: see text] dependent quantum statistical parton distributions is presented to explore proton and neutron structures. A merely theoretical maximum entropy method is applied to obtain thermodynamical variables determining parton distributions accurately. This study provides considering proton and neutron isospin asymmetry in order to improve the consistency of the framework achievements with the experimental results. The presented approach is extended to evaluate modified neutron structure in an [Formula: see text]-[Formula: see text] state. Also, the uniqueness of gluon distribution in proton and neutron is surveyed for both cases of lonely nucleon and [Formula: see text]-[Formula: see text] system. Eventually, the predicted unpolarized structure functions and the spin structure functions, only based on the maximum entropy method, are compared to CERN, HERMES, SLAC and the other data sets. Finally, the correlation of the obtained distributions with the experimental observations confirms the proposed statistical model.

Amide Proton Transfer-Weighted MRI Might Help Distinguish Amnestic Mild Cognitive Impairment From a Normal Elderly Population.

Objectives: To evaluate whether 3D amide proton transfer weighted (APTw) imaging based on magnetization transfer analysis can be used as a novel imaging marker to distinguish amnestic mild cognitive impairment (aMCI) patients from the normal elderly population by measuring changes in APTw signal intensity in the hippocampus and amygdala.Materials and Methods: Seventy patients with aMCI and 74 age- and sex-matched healthy volunteers were recruited for routine MRI and APT imaging examinations. Magnetic transfer ratio asymmetry (MTRasym) of the amide protons (at 3.5 ppm), or APTw values, were measured in the bilateral hippocampus and amygdala on three consecutive cross-sectional APT images and were compared between the aMCI and control groups. The independent sample t-test was used to evaluate the difference in APTw values of the bilateral hippocampus and amygdala between the aMCI and control groups. Receiver operator characteristic analysis was used to assess the diagnostic performance of the APTw. The paired t-test was used to assess the difference in APTw values between the left and right hippocampus and amygdala, in both the aMCI and control groups.Results: The APTw values of the bilateral hippocampus and amygdala in the aMCI group were significantly higher than those in the control group (left hippocampus 1.01 vs. 0.77% p < 0.001; right hippocampus 1.02 vs. 0.74%, p < 0.001; left amygdala 0.98 vs. 0.70% p < 0.001; right amygdala 0.94 vs. 0.71%, p < 0.001). The APTw values of the left amygdala had the largest AUC (0.875) at diagnosis of aMCI. There was no significant difference in APTw values between the left and right hippocampus and amygdala, in either group. (aMCI group left hippocampus 1.01 vs. right hippocampus 1.02%, p = 0.652; healthy control group left hippocampus 0.77 vs. right hippocampus 0.74%, p = 0.314; aMCI group left amygdala 0.98 vs. right amygdala 0.94%, p = 0.171; healthy control group left amygdala 0.70 vs. right amygdala 0.71%, p = 0.726).Conclusion: APTw can be used as a new imaging marker to distinguish aMCI patients from the normal elderly population by indirectly reflecting the changes in protein content in the hippocampus and amygdala.

Measurement of the neutron decay electron-antineutrino angular correlation by the aCORN experiment

The aCORN experiment measures the neutron decay electron-antineutrino correlation ($a$-coefficient) using a novel method based on an asymmetry in proton time-of-flight for events where the beta electron and recoil proton are detected in delayed coincidence. We report the data analysis and result from the second run at the NIST Center for Neutron Research, using the high-flux cold neutron beam on the new NG-C neutron guide end position: $a = -0.10758 \pm 0.00136 (\mbox{stat}) \pm 0.00148 (\mbox{sys})$. This is consistent within uncertainties with the result from the first aCORN run on the NG-6 cold neutron beam. Combining the two aCORN runs we obtain $a = -0.10782 \pm 0.00124 (\mbox{stat}) \pm 0.00133 (\mbox{sys})$, which has an overall relative standard uncertainty of 1.7 \%. The corresponding result for the ratio of weak coupling constants $\lambda = G_A/G_V$ is $\lambda = -1.2796\pm 0.0062$.

Neck configuration of Cm and Cf nuclei in the fission state within the relativistic mean field formalism

A correlation is established between the neutron multiplicity and the neutrons number in the fission state of Curium and Californium isotopes within a microscopic study using relativistic mean field formalism. The study includes the isotopes of Cm and Cf nuclei near the valley of stability, and hence is likely to play an important role in the artificial synthesis of superheavy nuclei. The static fission path, the neutron$-$proton asymmetry, the evolution of the neck and their composition in terms of nucleon numbers are also estimated. We find a maximum ratio for average neutron to proton density, which is about $1.6$ in the breakdown of the liquid$-$drop picture for $^{248}$Cm and $^{252}$Cf. A strong dependence of the neutron$-$proton asymmetry on the neutron multiplicity in an isotopic chain is also observed.

Inclusive W boson QCD predictions and lepton charge asymmetry in proton–proton collisions at = 14 TeV

Inclusive W ([Formula: see text]) boson QCD predictions and lepton charge asymmetry in proton–proton collisions at [Formula: see text] = 14 TeV is performed in this study. Total and fiducial cross section predictions are obtained up to next to next to leading order (NNLO) QCD corrections using Monte Carlo for FeMtobarn processes (MCFM) MC generator. To validate the predictions, a detailed comparison of NNLO QCD calculations with 8 TeV CMS results is performed. To discuss the advantage of the higher order QCD predictions on the scale uncertainty, a scale dependence study is presented based on the choice of renormalization (μR) and factorization (μF) scale variations. W boson – lepton charge asymmetry and differential cross section as a function of lepton pseudorapidity at [Formula: see text] = 14 TeV are further performed in 11 |η| regions.

Landscape of α preformation probability for even–even nuclei in medium mass region

The behavior of α cluster preformation probability, in α decay, is a rich source of the structural information, such as the clustering, pairing, and shell evolution in heavy nuclei. Meanwhile, the experimental α decay data have been very recently compiled in the newest table NUBASE2016. Through a least square fit to the available experimental data of nuclear charge radii plus the neutron skin thickness, we obtain a new set of parameters for the two-parameter Fermi nucleon density distributions in target nuclei. Subsequently, we make use of these refreshed inputs, involved in the density-dependent cluster model, to extract α preformation factor () for a large range of medium α emitters with N < 126 from the newest data table. Besides checking the supposed smooth pattern of Pα in the open-shell region, the special attention has been paid to those exotic α-decaying nuclei around the Z = 50 and N = 82 shell closures. Moreover, the correlation between the α preformation factor and the microscopic correction of nuclear mass, corresponding to the effect of shell and pairing plus deformation, is in particular investigated, to pursue the valuable knowledge of the Pα pattern over the nuclide chart. The feature of α preformation factor along with the neutron–proton asymmetry is then detected and discussed to some extent.

Decomposition of the Experimental Raman and Infrared Spectra of Acidic Water into Proton, Special Pair, and Counterion Contributions.

Textbooks describe excess protons in liquid water as hydronium (H3O+) ions, although their true structure remains lively debated. To address this question, we have combined Raman and infrared (IR) multivariate curve resolution spectroscopy with ab initio molecular dynamics and anharmonic vibrational spectroscopic calculations. Our results are used to resolve, for the first time, the vibrational spectra of hydrated protons and counterions and reveal that there is little ion-pairing below 2 M. Moreover, we find that isolated excess protons are strongly IR active and nearly Raman inactive (with vibrational frequencies of ∼1500 ± 500 cm-1), while flanking water OH vibrations are both IR and Raman active (with higher frequencies of ∼2500 ± 500 cm-1). The emerging picture is consistent with Georg Zundel's seminal work, as well as recent ultrafast dynamics studies, leading to the conclusion that protons in liquid water are primarily hydrated by two flanking water molecules, with a broad range of proton hydrogen bond lengths and asymmetries.

Fragmentation analysis of α-induced reactions using clusterization approach

The dynamics of α-induced reactions are worked out over an incident beam energy Eα∼10–15 MeV using targets of different masses. The decay patterns of odd mass compound systems 117Sb⁎, 145Pm⁎ and 191Ir⁎ formed in α+113In, α+141Pr and α+187Re reactions are investigated in view of n-evaporation data. The methodology of collective clusterization is applied by optimizing the neck-length parameter ΔR and the DCM calculated cross-sections find nice agreement with the experimental data. The resulting compound systems with ACN=117–191 cover a wide range of compound nucleus mass, and hence give an opportunity to explore various aspects related to the dynamics involved. Moreover the neutron–proton asymmetry dependence is explored in terms of the Bulk constant (α) (in the liquid drop binding energy expression) and radius term Ri and its consequent influence on the fragmentation structure of these compound systems is investigated.

Evolution of triaxial shapes at large isospin: Rh isotopes

Abstract The rotational response as a function of neutron–proton asymmetry for the very neutron-rich isotopes of Rh (116–119Rh) has been obtained from the measurement of prompt γ rays from isotopically identified fragments, produced in fission reactions at energies around the Coulomb barrier. The measured energy “signature” splitting of the yrast bands, when compared with the Triaxial Projected Shell Model (TPSM) calculations, shows the need for large, nearly constant, triaxial deformations. The present results are compared with global predictions for the existence of non axial shapes in the periodic table in the case of very neutron-rich nuclei Rh isotopes. The predicted trend of a second local maximum for a triaxial shape around N ∼ 74 is not found.

Corrigendum to “Fragmentation contribution to the transverse single-spin asymmetry in proton–proton collisions” [Phys. Lett. B 723 (4–5) (2013) 365–370

Corrigendum to “Fragmentation contribution to the transverse single-spin asymmetry in proton–proton collisions” [Phys. Lett. B 723 (4–5) (2013) 365–370

Neutron single-particle structure of molybdenum isotopes within the dispersive optical model

The evolution of neutron single-particle spectra in molybdenum isotopes was calculated on the basis of the dispersive optical model over the region extending from stable isotopes to the neutron drip line. The question of how the dependence of surface absorption on the neutron–proton asymmetry and the weakening of spin–orbit interaction affect the single-particle spectra in question is studied. The results agree with the concept according to which the shell effect becomes weaker near the neutron drip line.

Dispersive optical-model potential for protons in 100 ⩽ A ⩽ 132 even–even tin isotopes

Data on single-particle energies, differential elastic-scattering cross sections, and total cross sections for proton-induced reactions on stable tin isotopes were analyzed on the basis of the dispersive optical model. Good agreement with experimental data was obtained by setting the parameters of the dispersive optical potential to values averaged over the tin isotopic chain and by assuming that the dependence of surface absorption on the neutron–proton asymmetry is close to a traditional dependence. Predictive calculations for single-particle proton spectra and total reaction cross sections were performed for the doubly magic isotopes 100,132Sn. The calculated values of the energy gap between the 1h11/2–1g7/2 and 1g7/2–2d5/2 states were found to be in good agreement with the results of calculations performed with allowance for the tensor component of the effective nucleon–nucleon interaction.

Self-similarity of proton spin and asymmetry of jet production

Self-similarity of jet production in polarized p + p collisions is studied. The concept of z-scaling is applied for description of proton spin. New data on the double longitudinal spin asymmetry, ALL, of inclusive jets produced in proton-proton collisions at √s = 200 GeV measured by the STAR Collaboration at RHIC are analyzed in the framework of z-scaling approach. A hypothesis of self-similarity and fractality of the proton spin structure are formulated. A possibility to extract information on spin-dependent fractal dimensions of proton from the asymmetry of jet production is justified. The spin-dependent fractal dimension of proton in process \(\vec p + \vec p \to jet + X\) is estimated.