Zou Bing-Song

A New Mechanism for Low Energy Pion Induced Double Charge Exchange Reaction

Using a method developed in theory of double beta decay[1], we propose a new mechanism, namely the two-nucleon pion absorption-emission mechanism for pion double charge exchange reaction at low energies. The calculations are compared with the experimental data of the angular distribution at and the excitation functions of the DCX reactions on , with energies . It is found that the contribution of this new mechanism is very important at low energies.

Contribution of highly excited intermediate states in the pion absorption-emission mechanism of double charge exchange

Abstract Within the framework of operator expansion approach for the pion absorption-emission mechanism of double charge exchange a summation over the leading terms of the infinite commutator series is performed. The contribution of highly excited states is estimated.

SHORT-RANGE CONTRIBUTION TO THE PION-NUCLEUS DOUBLE-CHARGE-EXCHANGE REACTION DUE TO QUARK-ANTIQUARK ANNIHILATION

Abstract We propose a new approach, namely a quark-antiquark annihilation mechanism, for the calculation of the short-range contribution to the pion double-charge-exchange (DCX) reaction. The angular distributions for the 26 Mg(π + , π − ) 26 Si reaction at 50 MeV and reactions for the 18 O at energies ranging from 24 to 79 MeV are calculated and compared with the data. The sensitivities of the calculation parameters in the model are discussed. We find that this process makes a large contribution to DCX and can account for most of the DIAS DCX cross sections in the forward-angle region at low energies.

Confining potential mode in Baryons spectrum

Based on the flux tube model, the effects of the confining potentials of different configurations, namely the Delta-type and the Y-type, on the spectra of baryons are studied on SUSF(6) basis. The baryon spectra are obtained in a unified manner. Our result shows that by employing either the Delta-mode or the Y-mode confining potential, one can achieve reasonable baryon spectra. The Delta-mode may be mostly effective for the short- and medium-distances, while the Y-mode may offer more contributions to the spectra for long-distances. Although the binding energies in baryon spectra may deviate by a few to several tens MeV for different modes, it is hard to determine either one to be dominant by simply evaluating the baryon spectra, One may need to invoke the baryon decay process to make further judgement.

Pion double-charge-exchange on calcium isotopes

We examine the contributions of the conventional sequential mechanism and the pion absorption-emission mechanism for the double charge exchange (DCX) on calcium isotopes. It is shown that by combining these two mechanisms the experimental data for the double isobaric analogue transitions can be reproduced quite well. The predictions for the low energy GS --> GS DCX on calcium isotopes are presented.

PION INDUCED DOUBLE CHARGE-EXCHANGE REACTION AT PURE NUCLEONIC LEVEL

The two pure nucleonic mechanisms (the conventional sequential mechanism and the two-nucleon pion absorption-emission mechanism[1]) are studied within a unified framework of Distorted Wave Impulse Approximation (DWIA). The distorted pion waves are obtained by solving the Klein-Gordon equation with the first-order optical potential. The difference between this approach and the eikonal approximation is showed. For the two-nucleon pion absorption-emission mechanism the effective Landau-Migadal interaction of Pines, et al.[2] is used for the two bound nucleons, the result is compared with that by using the Paris force. By combining these two mechanism the 0° excitation functions for the DCX reactions to the isobaric analog states on the 14C, 18O, 26Mg and 42Ca are calculated and compared with the experimental data.