Nuclear Theory·nucl-th
17 papers—11 primary·6 cross-listed
We derive the equations to calculate the reduced width amplitudes (RWA) of the different size clusters and deformed clusters without any approximation. These equations named Laplace expansion method are applicable to the nuclear models which uses the Gaussian wave packets. The advantage of the method is demonstrated by the numerical calculations of the and RWAs in and .
Partha Pratim Bhaduri🇮🇳 · Abhijit Bhattacharyya🇮🇳
We have analyzed the data on production in proton-nucleus () collisions, available from the NA50 Collaboration in the SPS energy domain. The investigated data sets include the absolute production cross sections as well as -to-Drell Yan (DY) cross section ratios. An adapted version of two component QVZ model has been employed to calculate production cross sections. For both and DY production, nuclear modifications to the free nucleon structure functions are taken into account. For , final state interaction of the produced pairs with the nuclear medium is also taken into account, in accordance with the previously analyzed data. A satisfactory description of the data in collisions is obtained. Model calculations are extrapolated to low energy regime to predict the suppression in proton induced collisions at near threshold energies.
Xilin Zhang🇺🇸 · Gerald A. Miller🇺🇸
Recently the experimentalists in [PRL 116, 042501 (2016)] announced observing an unexpected enhancement of the electron-positron pair production signal in one of the Beryllium-8 nuclear transitions. The following studies have been focused on possible explanations based on introducing new types of particle. In this work, we improve the nuclear physics modeling of the reaction by studying the pair emission anisotropy and the interferences between different multipoles in an effective field theory inspired framework, and examine their possible relevance to the anomaly. The connection between the previously measured on-shell photon production and the pair production in the same nuclear transitions is established. These improvements, absent in the original experimental analysis, should be included in extracting new particle's properties from the experiment of this type. We then study the possibility of using the nuclear transition form factor to explain the anomaly. The reduction of the anomaly's significance by simply rescaling our predicted event count is also investigated.
D. J. Rowe · A. E. McCoy · M. A. Caprio
The nuclear collective models introduced by Bohr, Mottelson and Rainwater, together with the Mayer-Jensen shell model, have provided the central framework for the development of nuclear physics. This paper reviews the microscopic evolution of the collective models and their underlying foundations. In particular, it is shown that the Bohr-Mottelson models have expressions as macroscopic limits of microscopic models that have precisely-defined expressions in many-nucleon quantum mechanics. Understanding collective models in this way is especially useful because it enables the analysis of nuclear properties in terms of them to be revisited and reassessed in the light of their microscopic foundations.
A. J. Toubiana🇧🇷 · L. F. Canto🇧🇷 · M. S. Hussein🇧🇷
In this paper we revisit the one-dimensional tunnelling problem. We consider different approximations for the transmission through the Coulomb barrier in heavy ion collisions at near-barrier energies. First, we discuss approximations of the barrier shape by functional forms where the transmission coefficient is known analytically. Then, we consider Kemble's approximation for the transmission coefficient. We show how this approximation can be extended to above-barrier energies by performing the analytical continuation of the radial coordinate to the complex plane. We investigate the validity of the different approximations considered in this paper by comparing their predictions for transmission coefficients and cross sections of three heavy ion systems with the corresponding quantum mechanical results.
Fei Gao🇨🇳 · Lei Chang🇨🇳 · Yu-Xin Liu🇨🇳 · Craig D. Roberts🇺🇸 · Peter C. Tandy🇺🇸
A continuum approach to the kaon and pion bound-state problems is used to reveal their electromagnetic structure. For both systems, when used with parton distribution amplitudes appropriate to the scale of the experiment, Standard Model hard-scattering formulae are accurate to within 25% at momentum transfers GeV. There are measurable differences between the distribution of strange and normal matter within the kaons, e.g. the ratio of their separate contributions reaches a peak value of at GeV. Its subsequent -evolution is accurately described by the hard scattering formulae. Projections for kaon and pion form factors at timelike momenta beyond the resonance region are also presented. These results and projections should prove useful in planning next-generation experiments.
Hai-Ling Lao🇨🇳 · Fu-Hu Liu🇨🇳 · Bao-Chun Li🇨🇳 · Mai-Ying Duan🇨🇳
The kinetic freeze-out temperatures, , in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies are extracted by four methods: i) the Blast-Wave model with Boltzmann-Gibbs statistics (the BGBW model), ii) the Blast-Wave model with Tsallis statistics (the TBW model), iii) the Tsallis distribution with flow effect (the improved Tsallis distribution), and iv) the intercept in (the alternative method), where denotes the rest mass and denotes the effective temperature which can be obtained by different distribution functions. It is found that the relative sizes of in central and peripheral collisions obtained by the conventional BGBW model which uses a zero or nearly zero transverse flow velocity, , are contradictory in tendency with other methods. With a re-examination for in the first method in which is taken to be , a recalculation presents a consistent result with others. Finally, our results show that the kinetic freeze-out temperature in central collisions is larger than that in peripheral collisions.
Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺
Recent data on the deutron and He production in central Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) energies measured by the NA49 collaboration are analyzed within the model of the three-fluid dynamics (3FD) complemented by the coalescence model for the light-fragment production. The simulations are performed with different equations of state---with and without deconfinement transition. It is found that scenarios with the deconfinement transition are preferable for reproduction rapidity distributions of deuterons and He, the corresponding results well agree with the experimental data. At the same time the calculated transverse-mass spectra of He at midrapidity do not that nice agree with the experimental data. The latter apparently indicates that coalescence coefficients should be temperature and/or momentum dependent.
L. Coraggio🇮🇹 · L. De Angelis🇮🇹 · T. Fukui🇮🇹 · A. Gargano🇮🇹 · N. Itaco🇮🇹
We report on the calculation of Gamow-Teller and double-beta decay properties for nuclei around 132Sn within the framework of the realistic shell model. The effective shell-model Hamiltonian and Gamow-Teller transition operator are derived by way of many-body perturbation theory, without resorting to empirical effective quenching factor for the Gamow-Teller operator. The results are then compared with the available experimental data, in order to establish the reliability of our approach. This is a mandatory step, before we apply the same methodology, in forthcoming studies, to the calculation of the neutrinoless double-beta decay nuclear matrix element for nuclei that are currently considered among the best candidates for the detection of this process.
Murray Peshkin · Alexander Volya · Vladimir Zelevinsky
The quantum-mechanical theory of the decay of unstable states is revisited. We show that the decay is non-exponential both in the short-time and long-time limits using a more physical definition of the decay rate than the one usually used. We report results of numerical studies based on Winter's model that may elucidate qualitative features of exponential and non-exponential decay more generally. The main exponential stage is related to the formation of a radiating state that maintains the shape of its wave function with exponentially diminishing normalization. We discuss situations where the radioactive decay displays several exponents. The transient stages between different regimes are typically accompanied by interference of various contributions and resulting oscillations in the decay curve. The decay curve can be fully oscillatory in a two-flavor generalization of Winter's model with some values of the parameters. We consider the implications of that result for models of the oscillations reported by GSI.
Carl-Oscar Gullström · Andrea Rossi
We present a theory for how nucleon polarizability could be used to extract energy from nucleons by special electromagnetic conditions. A presentation of an experiment that validates the theory is presented. Also an new theory for a long range strong force is introduced by enhance the role of the meson in nucleon nucleon potential made from mixed isospin meson.
first authorsco-authorsvia INSPIRE