43243436
Production of an isomeric, excited radioactive nuclear beam.
125696689
High-resolution study of Gamow-Teller transitions via the Fe-54(He-3, t)Co-54 reaction
118339803
Pion Double Charge Exchange in p-shell Nuclei
Doubly differential cross sections for inclusive pion double charge exchange (DCX) on 6,7Li, 9Be, and 12C have been measured at the Los Alamos Meson Physics Facility with incident positive and negative pions of energies 120, 180, and 240 MeV. These new data, together with our previous studies of DCX on nuclei with A = 3, 4, 16, 40, 103, and 208, provide a detailed picture of the systematics of this reaction over the entire periodic table.
12221906
Measurements of discrete nuclear reactions induced by a radioactive 8Li beam.
Energy- and angle-resolved nuclear reactions, primarily one-nucleon stripping, have been observed for targets of CD{sub 2}, Be, and C, using a radioactive {sup 8}Li beam ({ital T}{sub 1/2}=842 ms) at {ital E}=14.3 MeV. The ({sup 8}Li,{sup 7}Li) neutron transfer reaction populating discrete final states was identified and angular distributions were obtained. This direct-reaction channel has large cross sections (10--100 mb/sr) due, in part, to the unique nuclear properties of {sup 8}Li. Implications for astrophysical abundances of Li isotopes may be significant.
121478239
Breakup of B-8 at sub-Coulomb energies
125276782
Search for isovector giant monopole resonances via the Sn-124(He-3,tn) reaction
The (He-3,t) reaction on Sn-124 at E(He-3)=199 MeV and the subsequent decay by neutron emission at backward angles were studied in an attempt to distinguish isovector monopole strength (spin-flip and non-spin-flip) at excitation energies above 25 MeV from the nonresonant continuum. The present approach is based on the assumption that a large fraction of the contributions to the continuum result from quasifree processes and breakup-pickup processes which leave the nucleus in low-lying excited states below the threshold for neutron emission. It was found, however, that even at high "apparent" excitation energies (above 30 MeV) the branching ratio for decay by neutrons was as high as similar to 50%, indicating that a large part of the nonresonant continuum may not be due to quasifree processes involving valence neutrons only. No evidence for monopole strength at high excitation energies was found, although the experiment had sufficient sensitivity and accuracy to detect isovector monopole strength based on theoretical predictions calculated in the framework of normal-mode collective excitations and the distorted-wave Born approximation.
34021352
Color-singlet quark-pair transmutation: Helicity amplitudes and partial-wave analysis.
Quark-pair transmutation via two gluons is the lowest-order, color-singlet process. In this paper the helicity amplitudes for this process are evaluated and a partial-wave analysis performed. The amplitudes for these annihilations are infrared divergent and this divergence is removed by giving the gluons a confinement mass. The results are generally dependent on this mass. Many of the features are similar to those of quark-pair annihilation into two gluons. Somewhat surprisingly, there is a large proportion of a ${1}^{+}$ partial wave. Threshold effects are understood in terms of threshold effects in pair annihilation into two gluons. However, there is a ``competition'' effect that depends on the ratio of masses of the initial- and final-quark pairs. For similar masses, singlet production dominates as expected, but for very dissimilar masses, singlet annihilation of the heavier pair competes with triplet production of the lighter pair. Some comments about the possible applications and extensions of this work are made. Obvious applications are to the Okubo-Zweig-Iizuka-rule-suppressed decays of quarkonia. Other applications include development of a quark-pair-creation model that differs from the usual $^{3}\mathrm{P}_{0}$ and $^{3}\mathrm{S}_{1}$ models.
23671598
N pi decays of baryons in a relativized model.
We calculate the [ital N][pi] decay amplitudes of baryon resonances in a semirelativistic version of the [sup 3][ital P][sub 0] model of hadron decays. We use relativized wave functions for the baryons and mesons, and include an intuitive modification of the usual [sup 3][ital P][sub 0] model. Our results are in reasonable agreement with the reported amplitudes for [ital all] known nonstrange resonances, and confirm a proposed solution to the mystery of the missing'' states.
41503347
Heavy quark symmetries and the decays B--> baryon+antibaryon.
We enumerate the form factors necessary to describe the two-body baryonic decays of B mesons.We use the symmetries of the heavy quark effective theory to arrive at some relations among these form factors, when at least one of the daughter baryons is heavy.
1769931
Soft pion emission in semileptonic B-meson decays.
An analysis of semileptonic decays of B mesons with the emission of a single soft pion is presented in the framework of the heavy-quark limit using an effective Lagrangian which implements chiral and heavy-quark symmetries. The analysis is performed at leading order of the chiral and inverse heavy mass expansions. In addition to the ground state heavy mesons some of their resonances are included. The estimates of the various coupling constants and form factors needed in the analysis are obtained using a chiral quark model. As the main result, a clear indication is found that the 0{sup +} and 1{sup +} resonances substantially affect the decay mode with a D{sup *} in the final state, and a less dramatic effect is also noticed in the D mode. An analysis of the decay spectrum in the D{sup *}-{pi}{sup 2} invariant mass is carried out, showing the main effects of including the resonances. The obtained rates show promising prospects for studies of soft pion emission in semileptonic B-meson decays in a B-meson factory where, module experimental cuts, about 10{sup 5} such decays in the D meson mode and 10{sup 4} in the D{sup *} mode could be observed per year.
16404791
Quasi-two-body decays of nonstrange baryons.
We examine the decays of nonstrange baryons to the final states Delta Pi, NRho, NEta, NEta', Nw, N.5 (1440)Pi, and Delta 3/2+(1600)Pi, in a relativized pair-creation (^3Po) model which has been developed in a previous study of the NPi decays of the same baryon states.As it is our goal to provide a guide for the possible discovery of new baryon states at CEBAF and elsewhere, we examine the decays of resonances which have already been seen in the partial-wave analyses, along with those of states which are predicted by the quark model but which remain undiscovered.The level of agreement between our calculation and the available widths from the partial-wave analyses in encouraging.