Equal Numbers Of Protons Research Articles

AbInitio Nuclear Thermodynamics.

We propose a new MonteCarlo method called the pinhole trace algorithm for abinitio calculations of the thermodynamics of nuclear systems. For typical simulations of interest, the computational speedup relative to conventional grand-canonical ensemble calculations can be as large as a factor of one thousand. Using a leading-order effective interaction that reproduces the properties of many atomic nuclei and neutron matter to a few percent accuracy, we determine the location of the critical point and the liquid-vapor coexistence line for symmetric nuclear matter with equal numbers of protons and neutrons. We also present the first abinitio study of the density and temperature dependence of nuclear clustering.

Nuclear effects in high-energy neutrino interactions

Neutrino telescopes like IceCube, KM3NeT and Baikal-GVD offer physicists the opportunity to study neutrinos with energies far beyond the reach of terrestrial accelerators. These neutrinos are used to study high-energy neutrino interactions and to probe the Earth through absorption tomography. Current studies of TeV neutrinos use cross sections which are calculated for free nucleons with targets which are assumed to contain equal numbers of protons and neutrons. Here we consider modifications of high-energy neutrino interactions due to two nuclear effects: modifications of the parton densities in the nucleus, referred to here as shadowing, and the effect of non-isoscalar targets, with unequal numbers of neutrons and protons. Both these effects depend on the interaction medium. Because shadowing is larger for heavier nuclei, such as iron, found in the Earth's core, it introduces a zenith-angle dependent change in the absorption cross section. These modifications increase the cross sections by 1-2\% at energies below 100 TeV (antishadowing), and reduce it by 3-4\% at higher energies (shadowing). Nuclear effects also alter the inelasticity distribution of neutrino interactions in water/ice by increasing the number of low inelasticity interactions, with a larger effect for $\nu$ than $\bar\nu$. These effects are particularly large in the energy range below a few TeV. These effects could alter the cross sections inferred from events with tracks originating within the active detector volume as well as the ratio $\nu/\bar\nu$ inferred from inelasticity measurements. The uncertainties in these nuclear effects are larger than the uncertainties on the free-proton cross sections and will thus limit the systematic precision of future high-precision measurements at neutrino telescopes.

Nuclear Symmetry Energy Extracted from Laboratory Experiments

The Equation of State (EOS) of uniform neutron-rich nucleonic matter of isospin asymmetry δ = (ρn — ρp)/ρ and density ρ can be expressed in terms of the energy per nucleon E (ρ, δ) within the parabolic approximation as(1) where Esym (ρ) = 1/2(∂2E(ρ, δ)/∂δ2)δ=0 ≈ E(ρ, 1) — E(ρ, 0) is the symmetry energy of asymmetric nuclear matter (ANM). It is approximately the energy cost of converting symmetric nuclear matter (SNM, with equal numbers of protons and neutrons) into pure neutron matter (PNM). Many interesting questions including the dynamics of supernova explosions, heavy-ion collisions, structures of neutron stars and rare isotopes, frequencies, and strain amplitudes of gravitational waves from both isolated pulsars and collisions involving neutron stars all depend critically on the EOS of neutron-rich nucleonic matter.

Nuclear matter parameters and optical model analysis of proton elastic scattering on the doubly magic nucleus 40Ca

Owing to its doubly magic nature having equal numbers of protons and neutrons, the 40Ca nuclear scattering can be successfully described by the optical model that assumes a spherical nuclear potential. Therefore, optical model analysis was employed to calculate the elastic scattering cross section for p+40Ca interaction at energies from 9 to 22 MeV as well as the polarization at energies from 10 to 18.2 MeV. New optical model parameters (OMPs) were proposed based on the best fitting to experimental data. It is found that the best fit OMPs depend on the energy by smooth relationships. The results were compared with other OMPs sets regarding their chi square values (χ2). The obtained OMP's set was used to calculate the volume integral of the potentials and the root mean square (rms) value of nuclear matter radius of 40Ca. In addition, 40Ca bulk nuclear matter properties were discussed utilizing both the obtained rms radius and the Thomas–Fermi rms radius calculated using spherical Hartree–Fock formalism employing Skyrme type nucleon–nucleon force. The nuclear scattering SCAT2000 FORTRAN code was used for the optical model analysis.

Nuclear Binding Near a Quantum Phase Transition.

How do protons and neutrons bind to form nuclei? This is the central question of abinitio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from abinitio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform MonteCarlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (^{4}He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.

Ab initio alpha-alpha scattering.

Processes such as the scattering of alpha particles ((4)He), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. In particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. It also substantially affects models of thermonuclear type Ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. In these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei--nuclei with even and equal numbers of protons and neutrons--is important for understanding background and resonant scattering contributions. First-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. Here we describe an ab initio calculation of alpha-alpha scattering that uses lattice Monte Carlo simulations. We use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the 'adiabatic projection method' to reduce the eight-body system to a two-cluster system. We take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field Monte Carlo simulations to compute an ab initio effective Hamiltonian for the two clusters. We find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. The approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. The methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of quarks and gluons.

Dark rotors in the late universe.

The tresino phase-transition that took place about 300 years after the big-bang, converted most baryons into almost equal numbers of protons and tresinos. Many of these become oppositely-charged rotating pairs or “rotors”. This paper examines the formation, evolution, disposition and observations of the protons and tresinos from the phase-transition to the present era. The solar corona is further examined within the same tresino phase-transition picture.

Nuclear lattice simulations using symmetry-sign extrapolation

Projection Monte Carlo calculations of lattice Chiral Effective Field Theory suffer from sign oscillations to a varying degree dependent on the number of protons and neutrons. Hence, such studies have hitherto been concentrated on nuclei with equal numbers of protons and neutrons, and especially on the alpha nuclei where the sign oscillations are smallest. Here, we introduce the “symmetry-sign extrapolation” method, which allows us to use the approximate Wigner SU(4) symmetry of the nuclear interaction to systematically extend the Projection Monte Carlo calculations to nuclear systems where the sign problem is severe. We benchmark this method by calculating the ground-state energies of the 12C, 6He and 6Be nuclei, and discuss its potential for studies of neutron-rich halo nuclei and asymmetric nuclear matter.

Electrochemical studies for the determination of an antibiotic drug, d-cycloserine, in pharmaceutical and human biological samples

An antibiotic drug, d-cycloserine (CYS), in phosphate buffer at different pH values was electrochemically studied using a gold electrode. A well-resolved, irreversible, diffusion-controlled voltammetric peak was obtained at 0.873V in a pH 9.2 phosphate buffer solution with an ionic strength of 0.2M. The experimental conditions, such as the solution pH and scan rate, were optimized. The pH dependence suggested that equal numbers of protons and electrons were involved in the electrochemical oxidation of CYS. A plausible oxidation mechanism was proposed. Under the selected conditions, the dependence on the concentration of CYS revealed that the detection limit for CYS was 3.3×10−8M for differential pulse voltammetry and 4.91×10−8M for square wave voltammetry. The proposed method was successfully applied to the determination of CYS in drug capsules and urine samples. The electrode exhibits good reproducibility and stability. In addition, the influence of various foreign species was studied.

Superallowed Gamow–Teller decay of the doubly magic nucleus 100Sn

The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During β(+)-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy for the decay of (100)Sn, the heaviest doubly magic nucleus with equal numbers of protons and neutrons. In the β-decay of (100)Sn, a large fraction of the strength is observable because of the large decay energy. We determine the largest Gamow-Teller strength so far measured in allowed nuclear β-decay, establishing the 'superallowed' nature of this Gamow-Teller transition. The large strength and the low-energy states in the daughter nucleus, (100)In, are well reproduced by modern, large-scale shell model calculations.

A Comparison of the Charges of the Electron, Proton and Neutron

IT has recently been suggested by Bondi and Ly ttleton1,2 that the magnitudes of the electric charges on the proton and electron may differ by a little more than one part in 1018, in which case electrostatic forces would cause the universe to expand. In fact, Piccard and Kessler3 attempted to detect such a difference in 1925, and found that a molecule of carbon dioxide did not have an electric charge greater than 2×10−19 e, where —e is the electronic charge, from which they concluded that the magnitudes of the proton and electron charges were the same to within 5 parts in 1021, assuming that matter was built entirely of protons and electrons. Since matter also contains neutrons, they have assumed in effect that the neutron has a charge equal to that of a hydrogen atom; but the neutron might equally well have a charge opposite to that of a hydrogen atom, in which case their experiment does not settle the point at issue, since carbon dioxide contains equal numbers of protons and neutrons (to within 0.1 per cent). It therefore seemed desirable to find whether matter in which there is an excess of neutrons is electrically neutral. We have found that the charge on an argon atom (18 protons, 18 electrons and 22 neutrons) is not greater than 8×10−20 e and that on a nitrogen molecule (14 protons, 14 electrons and 14 neutrons) is not greater than 12 × 10−20 e. Treating the charges on nitrogen and argon as the sums of charges on protons, electrons and neutrons, it is deduced that the proton charge is (1±4×10−20)e and the charge on the neutron is less than 4 × −20 e.

Zur phänomenologischen theorie der kernmaterie

A semi-empirical formulation of the independent particle model for nuclear matter is given. Apart from the energy-dependence of the single-particle potential (effective mass), the rearrangement energy is also taken into account. An extension of this theory for real nuclei is shown to be related to the Weizsäcker-Bethe-formula and to the optical model for nuclear reactions. The undetermined parameters of the theory are adjusted to fit the corresponding experimental material. The single-particle potentials, the rearrangement energies and the optical potentials for protons and neutrons can then be calculated as functions of the neutron excess. The corresponding data for nuclear matter are obtained by taking equal numbers of protons and neutrons.

Periodicity in the structure of the electron envelopes and nuclei of atoms Communication 2. Classification of the atomic nuclei of the elements on the basis of the packing effect and the layered structure of the atomic nucleus

1. A rectilinear-diameter rule is proposed for the packing effect curve. It states that this curve is the locus of points equidistant from a rectilinear diameter passing through the critical point of the packing effect (Ca 20 48 ). The equation for the rectilinear diameter in terms of the atomic number is given. It is shown that the characteristic points determining the position of the packing-effect curve coincide with the minimum points of the atomic-volume curve. 2. With the aid of concepts of hemonucleus nuclei (equal numbers of protons and neutrons) and heteronucleon nuclei (number of neutrons exceeds number of protons), the correspondence between the compositions of the nucleus and of its electron atmosphere is examined. 3. On the basis of an examination of the breaks in continuity on the diagram of number of nucleons plotted against atomic number, a hypothesis is advanced concerning the layered structure of the nucleus, the maximum number of helions in the layers being 2, 8, 18, and 33. An attempt has been made to extend the “exclusion principle” to the helion model of the nucleus, in order to explain the existence of four layers of helions to the nucleus. 4. It has been established that a correspondence exists between the four cycles of Mendeleev's system of elements and the four layers in the structures of the nucleus and between the number of elements in the periods and the number of protons (entering into the composition of the helions) in the layers of nuclei. The periodicity in the structure of the electron envelopes is brought into relationship with that of the layers in the atomic nucleus.