Multipole decomposition of Gamow–Teller strength

1987 ◽  
Vol 65 (6) ◽  
pp. 660-665 ◽  
Author(s):  
Murray A. Moinester
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
Present Report ◽  
Random Phase ◽  
Impulse Approximation ◽  
General Importance ◽  
Least Squares Fit ◽  
Distorted Wave Impulse Approximation ◽  
One Step ◽  
Gamow Teller

Doubly differential continuum cross sections from the 90Zr(p, n)90Nb reaction have been analyzed via a multipoledecomposition technique. No quasi-free charge-exchange background has been subtracted, following the assumption that the observed cross sections are primarily due to one-step charge-exchange leading to 1p–1h states of all multipolarities to all excitations. The theoretical shapes of the differential cross sections for each Jπ multipole have been taken from random-phase approximation (RPA)–distorted-wave impulse approximation (DWIA) calculations. The experimental dσ/dΩ, for each 1 MeV excitation-energy bin have been decomposed into different multipole components by a least squares fit. This RPA-based analysis should determine the Jπ = 1+ cross sections with different, and also fewer, assumptions than usual for describing the underlying background. It can be of general importance in determining the extent of possible quenching of Gamow–Teller (GT) strength. The present decomposition accounts for all the theoretically predicted GT strength. The purpose of the present report is to illustrate an analysis based on RPA–DWIA shapes rather than to present final-decomposition results.

Recent theoretical developments in nuclear charge-exchange reactions

1987 ◽  
Vol 65 (6) ◽  
pp. 614-625 ◽  
Author(s):  
J. Wambach
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
Spin Dynamics ◽  
Random Phase ◽  
Impulse Approximation ◽  
Linear Response Theory ◽  
Exchange Reactions ◽  
Intermediate Energies ◽  
Direct Reactions ◽  
P Type

The (p, n) and (n, p) charge-exchange reactions are a suitable tool in nuclear-structure studies. At intermediate energies, the interaction with the target resembles that between free nucleons, which makes the probes mostly susceptible to the spin dynamics of the nucleus. We review the current theoretical picture of nucleon–nucleus charge-exchange reactions. A brief introduction to the theory of direct reactions in the impulse approximation is given. We then discuss the random-phase approximation (RPA) linear response theory, which is widely used in the calculation of cross sections and related observables. To understand correctly the shape of the continuum cross sections, one needs a more sophisticated theory. We discuss suitable extensions of the RPA that incorporate spreading effects as well as escape effects. Charge-exchange reactions of the (n, p) type have important implications for the evolution of massive stars. The relevance for Type-II supernovae is discussed.

Studies of the (p,n) reaction at medium energies

1987 ◽  
Vol 65 (6) ◽  
pp. 566-573 ◽  
Author(s):  
J. W. Watson ◽  
B. D. Anderson ◽  
R. Madey
Keyword(s):  
Cross Sections ◽  
Differential Cross ◽  
Giant Resonance ◽  
Impulse Approximation ◽  
Differential Cross Sections ◽  
Analyzing Powers ◽  
Dipole Resonance ◽  
Spin Flip ◽  
Distorted Wave Impulse Approximation ◽  
Gamow Teller

We measured differential cross sections, analyzing powers, and the polarization-transfer coefficient [Formula: see text] for 135 MeV (p,n) reactions on 40Ca and 48Ca. The observed shapes for the analyzing-power angular distributions are in good overall agreement with distorted-wave-impulse-approximation calculations, and are more sensitive to nuclear structure than to whether or not spin transfer is involved. Measured spin-flip probabilities for [Formula: see text] combined with a multipole analysis of differential cross sections reveal that at 0°, the apparent continuum under and adjacent to the Gamow–Teller giant resonance is also primarily 1+ strength. A comparison of [Formula: see text] and [Formula: see text] shows no discernable signature of Gamow–Teller strength in the region –30 < Q(MeV) < –45. Utilizing information from high-resolution cross-section measurements and spin-flip probabilities, we decompose the spin-dipole resonance of 40Sc into its 0−, 1−, and 2− components.

Charge exchange reactions on medium and heavy mass targets at intermediate energies

2019 ◽  
Vol 35 (08) ◽  
pp. 2050045
Author(s):  
Pardeep Singh ◽  
Monika Singh ◽  
Neha Rani
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
Energy Charge ◽  
Impulse Approximation ◽  
Mass Region ◽  
Intermediate Energy ◽  
Exchange Reactions ◽  
Plane Wave Impulse Approximation ◽  
Text Type ◽  
Intermediate Energies

The nuclear isotopic structure can be understood easily via the intermediate-energy charge exchange reactions of (p, n) and [Formula: see text]He, [Formula: see text] type. In the current contribution, we present some results for charge exchange reactions induced by 3He on targets lying in mass region [Formula: see text] within the theoretical framework of plane wave impulse approximation (PWIA) and distorted wave impulse approximation (DWIA). Here, the recoil effects in PWIA have also been considered. Particularly, the angular distributions and the unit cross-sections have been calculated and compared with the available data. Further, the importance of inclusion of the exchange contribution in these reactions is also considered, which eventually enhance the matching with data.

scholarly journals Nuclear Structure Calculations for Two-Neutrino Double-βDecay

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
P. Sarriguren ◽  
O. Moreno ◽  
E. Moya de Guerra
Keyword(s):  
Charge Exchange ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Mean Field ◽  
Experimental Information ◽  
Exchange Reactions ◽  
Quasiparticle Random Phase Approximation ◽  
Nuclear Structure Calculations ◽  
Structure Calculations ◽  
Gamow Teller

We study the two-neutrino double-βdecay in76Ge,116Cd,128Te,130Te, and150Nd, as well as the two Gamow-Teller branches that connect the double-βdecay partners with the states in the intermediate nuclei. We use a theoretical microscopic approach based on a deformed self-consistent mean field with Skyrme interactions including pairing and spin-isospin residual forces, which are treated in a proton-neutron quasiparticle random-phase approximation. We compare our results for Gamow-Teller strength distributions with experimental information obtained from charge-exchange reactions. We also compare our results for the two-neutrino double-βdecay nuclear matrix elements with those extracted from the measured half-lives. Both single-state and low-lying-state dominance hypotheses are analyzed theoretically and experimentally making use of recent data from charge-exchange reactions andβdecay of the intermediate nuclei.

Heavy-ion reactions as spin probes

1987 ◽  
Vol 65 (6) ◽  
pp. 609-613 ◽  
Author(s):  
Sam M. Austin ◽  
N. Anantaraman ◽  
J. S. Winfield
Keyword(s):  
Cross Sections ◽  
Reaction Mechanisms ◽  
Heavy Ion ◽  
Spin Transfer ◽  
Calibration Function ◽  
Matrix Elements ◽  
Heavy Ion Reactions ◽  
One Step ◽  
The One ◽  
Gamow Teller

Heavy-ion reactions can be powerful probes for spin-transfer strength in nuclei, provided their reaction mechanism is simple so that a correlation can be established between cross sections and the relevant matrix elements. We discuss the desirable features of heavy-ion reactions in general and a series of tests of reaction mechanisms that have been carried out for two of the most favorable reactions; (6Li, 6He) and (12C, 12N). We establish that the (6Li, 6He) reaction is one-step in nature above 25 MeV∙nucleon−1 and establish a calibration function relating cross sections and Gamow–Teller matrix elements. We also find that the (12C, 12N) reaction is likely to be dominated by the one-step process above about 50 MeV∙nucleon−1.

Nucleon charge-exchange reactions at intermediate energies

1987 ◽  
Vol 65 (6) ◽  
pp. 536-548 ◽  
Author(s):  
W. G. Love ◽  
Amir Klein ◽  
M. A. Franey ◽  
K. Nakayama
Keyword(s):  
Charge Exchange ◽  
Random Phase ◽  
Impulse Approximation ◽  
Nucleon Nucleon ◽  
Large Momentum ◽  
Nuclear Excitation ◽  
Exchange Reactions ◽  
Charge Exchange Reaction ◽  
Intermediate Energies ◽  
Nucleon Nucleon Interaction

The nucleon charge–exchange reaction is investigated as a probe of isovector modes of nuclear excitation at both small and large momentum transfer. The calculated and extracted properties of the isovector nucleon–nucleon interaction are discussed and illustrated with an emphasis on incident energies in excess of 100 MeV. Particular emphasis is placed on spin observables and the roles played by different parts of the nucleon–nucleon coupling in their determination. Recent measurements of transverse polarization transfer at 0° in the charge-exchange continuum are compared with distorted wave impulse approximation calculations using random–phase approximation transition densities.

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