Experimental Results on Ultrahigh-Energy Cosmic Rays and Asymptotic Behavior of the Total Cross Section for Nucleon–Nucleon Interaction

Results obtained by studying the energy dependence of the total cross section for nucleon–nucleon interaction are presented. The analytic parametrization proposed within axiomatic quantum field theory describes quantitatively a unified set of experimental data on proton–proton and antiproton–proton scattering. At collision energies above 86 GeV, the parameter values fitted to subsets of all available data and accelerator data alone were found to deviate from the respective asymptotic values. This indicates that the Froissart–Martin limit for the total cross section has not yet been reached in the case of these subsets. An approximation of the total nucleon–nucleon cross section measured in cosmic rays leads for some parameters to fitted values that, within 1.0 to 1.3 standard deviations, agree with the respective asymptotic values. This resultmay be viewed as an indication of the beginning of the asymptotic functional behavior of the total nucleon–nucleon cross section measured in cosmic rays of ultrahigh energy O(100 TeV). This is confirmed within the color glass condensate approach.     

Study of the charge dependence of the pion–nucleon coupling constant on the basis of data on low-energy nucleon–nucleon interactions

The relation between quantities that characterize the pion–nucleon and nucleon–nucleon interactions is studied with allowance for the fact that, at low energies, nuclear forces in nucleon–nucleon systems are mediated predominantly by one-pion exchange. On the basis of the values currently recommended for the low-energy parameters of the proton–proton interaction, the charged pion–nucleon coupling constant is evaluated at g_π²±/4π = 14.55(13). This value is in perfect agreement with the experimental value of g_π²±/4π = 14.52(26) found by the Uppsala Neutron Research Group. At the same time, the value obtained for the charged pion–nucleon coupling constant differs sizably from the value of the pion–nucleon coupling constant for neutral pions, which is g_π² 0/4π = 13.55(13). This is indicative of a substantial charge dependence of the coupling constant.     

Complete Set of Deuteron Analyzing Powers for dp Elastic Scattering at Intermediate Energies and Three Nucleon Forces

With the aim of clarifying roles of the 3NFs in nuclei experimental programs with the polarized deuteron beam at intermediate energies are in progress at RIKEN RI Beam Factory. As the first step, we have measured a complete set of deuteron analyzing powers in deuteron–proton elastic scattering at 250 and 294 MeV/nucleon. The obtained data are compared with the Faddeev calculations based on the modern nucleon–nucleon forces together with the Tucson–Melbourne’99, and UrbanaIX three nucleon forces.     

On the Renormalization of the One–Pion Exchange Potential and the Consistency of Weinberg’s Power Counting

Nogga, Timmermans and van Kolck recently argued that Weinberg’s power counting in the few–nucleon sector is inconsistent and requires modifications. Their argument is based on the observed cutoff dependence of the nucleon–nucleon scattering amplitude calculated by solving the Lippmann–Schwinger equation with the regularized one–pion exchange potential and the cutoff Λ varied in the range Λ = 2 . . . 20 fm^?1. In this paper we discuss the role the cutoff plays in the application of chiral effective field theory to the two–nucleon system and study carefully the cutoff–dependence of phase shifts and observables based on the one–pion exchange potential. We show that (i) there is no need to use the momentum–space cutoff larger than Λ ~ 3 fm^?1; (ii) the neutron–proton low–energy data show no evidence for an inconsistency of Weinberg’s power counting if one uses Λ ~ 3 fm^?1.     

Ground-state properties of closed-shell nucleus 56Ni with realistic nucleon–nucleon interactions

We have calculated the ground-state energy of the doubly magic nucleus ⁵⁶Ni within the framework of the Green’s function using the CD-Bonn and N³LO nucleon–nucleon potentials. For the sake of comparison, the same calculations are performed using the Brueckner–Hartree–Fock approximation. Both the continuous and conventional choices of single particle energies are used. Additional binding energy is obtained from the inclusion of the hole–hole scattering term within the framework of the Green function approach. In this study, comparison of the calculated ground-state energies, obtained by using the Brueckner–Hartree–Fock approach using continuous choice and different nucleon–nucleon potentials, with the experimental value is accomplished. The results show good agreement between the calculated values and the experimental one for the ⁵⁶Ni nucleus. The sensitivity of our results to the choice of the model space is examined.     

Different Methods for the Two-Nucleon T-Matrix in the Operator Form

We compare three methods to calculate the nucleon–nucleon t-matrix based on the three-dimensional formulation of Golak et al. (Phys Rev C 81:034006, 2010). In the first place we solve a system of complex linear inhomogeneous equations directly for the t-matrix. Our second method is based on iterations and a variant of the Lanczos algorithm. In the third case we obtain the t-matrix in two steps, solving a system of real linear equations for the k-matrix expansion coefficients and then solving an on-shell equation, which connects the scalar coefficients of the k- and t-matrices. A very good agreement among the three methods is demonstrated for selected nucleon–nucleon scattering observables using a chiral next-to-next-to-leading-order neutron–proton potential. We also apply our three-dimensional framework to the demanding problem of proton–proton scattering, using a corresponding version of the nucleon–nucleon potential and supplementing it with the (screened) Coulomb force, taken also in the three-dimensional form. We show converged results for two different screening functions and find a very good agreement with other methods dealing with proton–proton scattering.     

Relation between the charged and neutral pion–nucleon coupling constants in the Yukawa model

In the Yukawa-model framework for NN forces, a simple relation between the charged and neutral pion–nucleon coupling constants is derived. The relation implies that the charged pion–nucleon constant is larger than the neutral one since the np interaction is stronger than the pp interaction. The derived value of the charged pion–nucleon constant shows a very good agreement with one of the recent measurements. In relative units, the splitting between the charged and neutral pion–nucleon constants is predicted to be practically the same as that between the charged and neutral pion masses. The charge dependence of the NN scattering length arising from the mass difference between the charged and neutral pions is also analyzed.     

Single-nucleon and heavy recoil spectra in intermediate energy heavy-ion reactions

We study the nucleon emission spectra from a local large-volume hot zone formed in intermediate energy (～ 20–100 MeV/nucleon) heavy-ion reactions. The hot zone is continuously being cooled by nucleon emission while the cold nuclear matter surrounding the hot zone is being heated up by nucleon absorption until full thermal equilibrium is reached. The sequential evaporation from the equilibrated reaction complex is followed up. The recoil properties of the residual heavy fragments are also investigated.     

Tensor-Optimized Few-Body Model for s-Shell Nuclei

We propose a tensor-optimized few-body model (TOFM) in the few-body framework with bare nucleon–nucleon interaction. The physical concept of TOFM comes from the tensor-optimized shell-model (TOSM), which is applicable for the study of medium and heavy nuclei. The TOSM wave function describes the deuteron-like tensor correlation and provides a good reproduction of the binding energy with the bare nucleon–nucleon interaction. Using the spirit of the TOSM approximation, we show the performance of TOFM for s-shell nuclei. It is found that the TOFM can account for the contribution of the tensor interaction very well and almost reproduces the total energy and various energy components as compared with rigorous few-body calculations. The relative correlation function is also provided to improve the performance of TOSM for the study of heavy nuclei.     

Nucleon–nucleon scattering in the light of supersymmetric quantum mechanics

By exploiting supersymmetry-inspired factorization method together with a judiciously chosen deuteron ground-state wave function, approximate higher partial wave nucleon–nucleon potentials are generated. In this context, a minor modification is also introduced to the generated potentials. The n–p scattering phase shifts are computed and analysed via the phase function method.     

Analytical $$\boldsymbol{\alpha}\boldsymbol{+}\boldsymbol{\alpha}$$ Potential for Energy Range between 6 and 280 MeV

Physics of Atomic Nuclei - In this work we derive analytically a real $$\alpha+\alpha$$ potential using the JLM effective nucleon–nucleon (NN) interaction. The aim is to obtain analytically...     

Three-Dimensional Low-Momentum Interaction in Two-Body Bound State Calculations

The deuteron binding energy and wave function are calculated by using the recently developed three-dimensional form of low-momentum nucleon–nucleon (NN) interaction. The homogeneous Lippmann–Schwinger equation is solved in momentum space by using the low-momentum two-body interaction, which is constructed from Malfliet–Tjon potential. The results for both, deuteron binding energy and wave function, obtained with low-momentum interaction, are compared with the corresponding results obtained with bare potential.     

Signatures of Central Collisions in Inelastic Nucleon–Nucleon Scattering

Physics of Particles and Nuclei Letters - Nucleon–nucleon collisions with impact-parameter values below the nucleon quark-core radius are considered and experimental signatures for selecting...     

Transverse momentum spectra of the produced hadrons at SPS energy and a random walk model

The transverse momentum spectra of the produced hadrons have been compared to a model, which is based on the assumption that a nucleus–nucleus collision is a superposition of isotropically decaying thermal sources at a given freeze-out temperature. The freeze-out temperature in nucleus–nucleus collisions is fixed from the inverse slope of the transverse momentum spectra of hadrons in nucleon–nucleon collision. The successive collisions in thessss nuclear reactions leads to gain in transverse momentum, as the nucleons propagate in the nucleus following a random walk pattern. The average transverse rapidity shift per collision is determined from the nucleon–nucleus collision data. Using this information, we obtain parameter-free result for the transverse momentum distribution of produced hadrons in nucleus–nucleus collisions. It is observed that such a model is able to explain the transverse mass spectra of the produced pions at SPS energies. However, it fails to satisfactorily explain the transverse mass spectra of kaons and protons. This indicates the presence of collective effect which cannot be accounted for, by the initial state collision broadening of transverse momentum of produced hadrons, the basis of random walk model.     

Approximation properties of the Paris potential of nucleon–nucleon interaction

The phenomenological Paris potential of nucleon–nucleon interaction is analyzed in terms of the independence of the coefficients of various components. Analysis of the determinant of the Gram matrix reveals the extremely high dependences of the coefficients, demanding a revision of the system of basic functions.     

Neutron–Deuteron Scattering Observables at E lab = 14.1 MeV

Inelastic neutron–deuteron scattering is studied on the basis of configuration-space Faddeev equations. Calculated are neutron–deuteron breakup amplitudes using AV14 nucleon–nucleon potential at incident neutron energy of 14.1 MeV. The results of calculations are presented for the differential cross sections under quasi free scattering and space–star configurations, and compared with those of the previous calculations and experimental data. The choice of the cutoff radius R _cutoff for asymptotic conditions is discussed.     

Production cross sections of multiply charged fragments in heavy ion interactions at 150–200 MeV/nucleon

A total of 1720 ¹⁶O-emulsion nucleus interactions at 150–200 MeV/nucleon have been investigated. Production cross sections of multiply charged projectile fragments are given. It is found that the cross section for the production of N, C, B and Be projectile fragments in ¹⁶O-nucleus interactions is similar at 0.2 and 2 GeV/nucleon. The fragmentation cross sections for Li and He are larger at 0.2 than at 2 GeV/nucleon.     

Evidence for existence of multiply charged argon ions in anomalous cosmic rays

The spectrum of Ar ions in anomalous cosmic rays in the energy range 14–42 MeV/nucleon was measured in the PLATAN-5 experiment at the Mir space station in 1994–1997. The spectrum is analyzed along with the data obtained by the SIS instrument on the ACE spacecraft in the circumterrestrial space. On the basis of the comparison of the spectra recorded within and beyond the magnetosphere, the average effective charge of ACR argon ions has been estimated. The estimate obtained is much larger than unity at energies exceeding 22 MeV/nucleon. The ion charge gradually increases with an increase in energy and reaches the value Q = 4 at an energy of 38 MeV/nucleon.