Search results for "Nucleon"
showing 10 items of 1041 documents
SEMICLASSICAL DESCRIPTION OF SPIN EXCITATIONS OF THE PARTICLE-CORE INTERACTION SYSTEM
1993
A model Hamiltonian describing a nucleon moving in a shifted oscillator well and inter-acting with a harmonic core through a quadrupole-quadrupole term is semiclassically treated. The solutions of the linearised equations of motion are quantised by the Bohr-Sommerfeld procedure. Among the four RPA modes, there is one which corresponds to the harmonic vibration of the spin degree of freedom. This mode is analogous to the spin wave mode describing a system of interacting spins placed in a magnetic field. The state describes a harmonic wobbling motion around a stationary state belonging to the ground rotational band.
Strange nucleon form-factors
2017
Abstract A broad program measuring parity-violation in electron-nuclear scattering has now provided a large set of precision data on the weak-neutral-current form-factors of the proton. Under comparison with well-measured electromagnetic nucleon form-factors, these measurements reveal the role of the strange quark sea on the low-energy interactions of the proton through the strange-quark-flavor vector form-factors. This review will describe the experimental program and the implications of the global data for the strange-quark vector form-factors. We present here a new fit to the world data.
Introducing the Pietarinen expansion method into the single-channel pole extraction problem
2013
We present a new approach to quantifying pole parameters of single-channel processes based on a Laurent expansion of partial-wave T matrices in the vicinity of the real axis. Instead of using the conventional power-series description of the nonsingular part of the Laurent expansion, we represent this part by a convergent series of Pietarinen functions. As the analytic structure of the nonsingular part is usually very well known (physical cuts with branch points at inelastic thresholds, and unphysical cuts in the negative energy plane), we find that one Pietarinen series per cut represents the analytic structure fairly reliably. The number of terms in each Pietarinen series is determined by …
Initial state anisotropies and their uncertainties in ultrarelativistic heavy-ion collisions from the Monte Carlo Glauber model
2011
In hydrodynamical modeling of heavy-ion collisions, the initial-state spatial anisotropies are translated into momentum anisotropies of the final-state particle distributions. Thus, understanding the origin of the initial-state anisotropies and their uncertainties is important before extracting specific QCD matter properties, such as viscosity, from the experimental data. In this work we review the wounded nucleon approach based on the Monte Carlo Glauber model, charting in particular the uncertainties arising from modeling of the nucleon-nucleon interactions between the colliding nucleon pairs and nucleon-nucleon correlations inside the colliding nuclei. We discuss the differences between …
Shell effects in damped collisions ofSr88withYb176at the Coulomb barrier energy
2014
This work is a study of the influence of shell effects on the formation of binary fragments in damped collision. We have investigated binary reaction channels of the composite system with $Z=108$ produced in the reaction $^{88}\mathrm{Sr}$${+}^{176}$Yb at an energy slightly above the Bass barrier (${E}_{\text{c.m.}}/{E}_{\text{Bass}}=1.03$). Reaction products were detected by using the two-arm time-of-flight spectrometer CORSET at the K130 cyclotron of the Department of Physics, University of Jyv\"askyl\"a. The mass-energy distribution of primary binary fragments has been measured. For targetlike fragments heavier than 190 u, which correspond to a mass transfer as large as twenty nucleons o…
Is the standard, parity-non-conserving, nucleon-nucleus interaction a surface one?
1995
Abstract Claims that the standard single-particle, parity-non-conserving, nucleon-nucleus interaction, V pnc = ct · 1 2 { σ · p , ϱ(r)} , is a surface one are considered. It is shown that examination of integrands entering some quantity involving Vpnc leads to quite puzzling results. These are further supported by a similar examination for a term [ σ · p , ϱ(r) ] which is odd under time-reversal, but has a priori a well-defined surface character. Alternative approaches to determine whether Vpnc is a surface or volume interaction are developed, based on using wave functions as test functions. From these approaches, the volume character of Vpnc is unambiguous.
Decays of theY97isomers to the single neutron nucleusZr97
1996
The decays of the 9/2(+) and of the three-quasiparticle high spin isomer in Y-97 have been investigated following on-line mass separation with the ion-guide technique. Spins and parities for several of the lowest-lying levels in the daughter nucleus Zr-97 are revised and configurations are proposed. In particular, the 2264 keV level is identified as the h(11/2) single-neutron level. The population of a cascade on top of the h(11/2) level provides evidence for Gamow-Teller beta decay of the high-spin Y-97 isomer. Levels and transition rates are qualitatively well reproduced by regarding Zr-97 as a single-neutron nucleus with respect to the doubly closed Zr-96 core.
Exclusive measurement of breakup reactions with the one-neutron halo nucleus11Be
2003
Electromagnetic and nuclear inelastic scattering of the halo nucleus ${}^{11}\mathrm{Be}$ have been investigated by a measurement of the one-neutron removal channel, utilizing a secondary ${}^{11}\mathrm{Be}$ beam with an energy of 520 MeV/nucleon impinging on lead and carbon targets. All decay products, i.e., ${}^{10}\mathrm{Be}$ fragments, neutrons, and $\ensuremath{\gamma}$ rays have been detected in coincidence. Partial cross sections for the population of ground and excited states in ${}^{10}\mathrm{Be}$ were determined for nuclear diffractive breakup as well as for electromagnetically induced breakup. The partial cross sections for ground-state transitions have been differentiated fur…
Response of asymmetric nuclear matter to isospin-flip probes
1999
Abstract We investigate the RPA response of asymmetric nuclear matter to external fields which induce charge exchange between nucleons, both at zero and finite temperature. Closed expressions are obtained for the RPA response in each spin channel when the nucleon–nucleon interaction is of the Skyrme type. Exchange terms are fully taken into account. We consider the transferred momentum, asymmetry and temperature as the relevant parameters of our study. Special emphasis is given to the role of neutron excess in relation to the collective states at low momentum.
RPA susceptibility of asymmetric nuclear matter at finite temperatures with Skyrme interactions
1997
Abstract We investigate the thermal RPA response of asymmetric nuclear matter interacting through various Skyrme interactions characterized by the value of the effective nucleon mass. Our study concentrates on the evolution of collective states according to the variations of the transferred momentum, temperature and asymmetry ratio. The differences and similarities between the roles of neutron excess and of thermal excitation are discussed. It is shown that the limit of meaningful nuclear asymmetries, namely Y close to 1/3, must be reached in order to observe sizable effects in the structure patterns, a fact that brings support to calculations of dynamical response that resort to symmetric …