37123844
Systematics of 8Li-induced radioactive beam reactions: E=13-20 MeV.
Elastic and inelastic scattering, one-nucleon transfers [mostly ${(}^{8}$Li, $^{7}\mathrm{Li}$)] and the ${(}^{8}$Li,\ensuremath{\alpha}) fusion-evaporation reaction have been studied on a variety of targets (A=1\char21{}58) at E${(}^{8}$Li)\ensuremath{\approxeq}13\char21{}20 MeV using the University of Michigan\char21{}University of Notre Dame radioactive nuclear beam (RNB) facility. The latter, which produces an energy-resolved (\ensuremath{\sim}500 keV FWHM), focused beam with intensity \ensuremath{\gtrsim}${10}^{6}$ $^{8}\mathrm{Li}$/s, permitted measurements to selected nuclear levels with cross sections down to approximately 1 mb/sr. Based on the systematics of the measured $^{8}\mathrm{Li}$ elastic scattering an appropriate $^{8}\mathrm{Li}$ optical potential was deduced. Large inelastic scattering cross sections (and B[E2\ensuremath{\uparrow}]) are observed for $^{8}\ensuremath{\rightarrow}^{8}$${\mathrm{Li}}_{0.98}^{\mathrm{*}}$. Large cross sections are also observed for the ${(}^{8}$Li${,}^{7}$Li) transfer reaction corresponding to quasielastic (viz., Q\ensuremath{\approxeq}0) neutron transfer to selected high spin excited levels in the residual nucleus. The ${(}^{8}$Li,\ensuremath{\alpha}) fusion-evaporation reaction also appears to be significant and can produce very-high-energy \ensuremath{\alpha} particles, viz., ${\mathit{E}}_{\mathrm{\ensuremath{\alpha}}}$\ensuremath{\gg}${\mathit{E}}_{\mathrm{beam}}$. Although observed using $^{8}\mathrm{Li}$, these features appear to be important for many RNB-induced reactions and they must be considered, for example, in nucleosyntheis calculations involving $^{8}\mathrm{Li}$ and other short-lived radioactive nuclei.
121478239
Breakup of B-8 at sub-Coulomb energies
43243436
Production of an isomeric, excited radioactive nuclear beam.
19324012
Fragmentation and splitting of Gamow-Teller resonances in Sn(3He,t)Sb charge-exchange reactions, A=112-124.
Fragmentation and splitting of the Gamow-Teller (GT) strength has been observed in a systematic study of the ([sup 3]He,[ital t]) charge-exchange reaction at [ital E]([sup 3]He)=200 MeV over the entire range of stable Sn isotopes. Triton energy spectra were observed with a high-resolution magnetic spectrometer at angles near [theta]=0[degree] where [Delta][ital L]=0 transitions are enhanced. Excitation energies, widths, 0[degree] cross sections, and strengths [ital B](GT) were determined. A theoretically predicted configuration splitting of the main GT component into two components, expected to be dominant near [ital A]=118 at the onset of the filling of the 1[ital h][sub 11/2] neutron orbital, could not be observed. This may be due to the fact that the total widths of the resonances of 5--6 MeV exceed the predicted splitting. A comparison of the 0[degree] cross sections for the transitions to the GT resonances and the isobaric analog states leads to strengths [ital B](GT) for the main Gamow-Teller components of typically 65% of the sum-rule value of 3([ital N][minus][ital Z]). Three to four additional Gamow-Teller fragments were observed in all final nuclei at lower excitation energies. The excellent energy resolution of the experiment made it possible to observe a pronounced fine structure in these low-lyingmore » resonances which is believed to be due to coupling to two-particle--two-hole doorway states. Also seen with all target nuclei was a systematic sequence of strong [ital J][sup [pi]]=1[sup +] states near the ground states in all Sb isotopes ([ital E][sub [ital x]]=0 to 220 keV). In addition, strong [Delta][ital L]=1 resonances were observed in all nuclei at excitation energies of typically 20 MeV. Furthermore, nonresonant background from quasifree charge exchange was observed. An average of [similar to]85% of all excess neutrons seems to contribute to this background in approximate agreement with results from ([ital e],[ital e][prime][ital p]) experiments.« less
2502593
Dependence of the cross section for inclusive pion double charge exchange on nuclear mass and charge.
Total reaction cross sections for inclusive pion double charge exchange have been obtained at incident pion energies of 180 and 240 MeV for /sup 4/He, /sup 6.7/Li, /sup 9/Be, /sup 12/C, /sup 16/O, /sup 40/Ca, /sup 103/Rh, and /sup 208/Pb. An explanation of the dependence of these cross sections upon the mass and charge of the target nucleus and the charge of the incident pion is suggested in terms of a phenomenological model in which successive single-charge-exchange processes compete with more probable processes such as quasifree scattering.
125696689
High-resolution study of Gamow-Teller transitions via the Fe-54(He-3, t)Co-54 reaction
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.
26570396
Measurement of the inclusive semielectronic D0 branching fraction.
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.
41501121
Can four-quark states be easily detected in baryon-antibaryon scattering?
We attempt to explain the experimental sparsity of diquonia candidates given the theoretical abundance of such states. We do this by investigating the lowest-order contributions of such states as intermediates in {ital p{bar p}} scattering into exclusive baryon-antibaryon final states. We find that the contributions depend on the partial widths for the meson-meson decays of the diquonia, and that resonant effects can be easily made to disappear. We conclude that if the meson-meson widths of diquonia are larger than about 50 MeV, most of these states will be extremely difficult to observe in {ital p{bar p}} scattering, for instance. We note that diquonia may offer a convenient means of describing some aspects of the dynamics of baryon-antibaryon scattering.
7361514
Continuum Study of Deconfinement at Finite Temperature.
Deconfinement and chiral symmetry restoration are explored in a confining, renormalizable, Dyson-Schwinger equation model of two-flavor QCD.An order parameter for deconfinement is introduced and used to establish that, in the chiral limit, deconfinement and chiral symmetry restoration are coincident at {ital T}{sub {ital c}}{approx_equal}150 MeV. The transitions are second order and each has the same critical exponent: {beta}{approx_equal}0.3. The deconfinement transition exhibits sensitivity to the current-quark mass. {ital f}{sub {pi}} and {ital m}{sub {pi}} change by less than 10{percent} for {ital T}{lt}0.7{ital T}{sub {ital c}}; however, as {ital T}{r_arrow}{ital T}{sub {ital c}}, thermal fluctuations cause the pion bound state contribution to the four-point quark-antiquark correlation function to disappear. {copyright} {ital 1996 The American Physical Society.}