119068583
Inclusive pion double charge exchange in 4He at intermediate energies
A systematic experimental study of inclusive pion double charge exchange in 4He has been undertaken. The reaction 4He(pi+,pi-)4p was observed at incident energies 120, 150, 180, 240 and 270 MeV; the 4He(pi-,pi+)4n reaction was observed at incident energies 180 and 240 MeV. At each incident energy, the doubly differential cross section was measured at three to five outgoing pion laboratory angles between 25 deg and 130 deg. At each angle, cross sections were measured over the range of outgoing pion energies from 10 MeV up to the kinematic limit for the reaction in which the final state consists of the oppositely charged pion plus four free nucleons. 
The spectra of outgoing pions are strikingly different from those observed for the inclusive double charge exchange reaction in heavier nuclei, but resemble those observed in the (pi-,pi+) reaction in 3He. The forward-angle spectra in the 3He and 4He reactions exhibit a prominent peak at high outgoing pion energies. Interpretation of the peaks in 3He (4He) as a three- (four-)nucleon resonance is ruled out by kinematic analysis. The results of a calculation, wherein the double charge exchange reaction is assumed to proceed as two sequential single charge exchange interactions, suggest that the high-energy peak is naturally explained by this double scattering mechanism. Non-static treatment of the pi-N interactions and the inclusion of nuclear binding effects appear to be important in reproducing the shape of the energy spectra at forward angles.
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.
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.
43243436
Production of an isomeric, excited radioactive nuclear beam.
28323397
Very-high-energy light charged-particle production near 0 degrees in heavy-ion collisions, 9 <= E/A <= 40 MeV.
Very energetic light ions (primarily protons and alphas) with energies often approaching the full beam energy have been observed at or near {theta}=0{degree} in heavy-ion collisions, {ital Z}=8 to 28, {ital E}/{ital A}{dot =}9 to 40 MeV/nucleon from Ta and, in selected cases, Cu targets. Analysis of spectral shapes and angular distributions using a standard moving source model requires that the source velocity approaches the beam velocity as {theta}{r arrow}0{degree} and that the spectral slope parameters and apparent source temperatures be increased. Large values for the latter ({ital T}{sub {ital S}}{r arrow}16 MeV), which are typically twice as large as those deduced from complex fragment emission, are often required to fit the alpha particle spectra {theta}=0{degree}. Massive cluster transfer and other quasitransfer mechanisms may provide an alternative model for the generation of the {ital E}{r arrow}{ital E}{sub beam} alpha particles and other light fragments.
18134055
Localized shocks
A bstractWe study products of precursors of spatially local operators, Wxntn⋅⋅⋅Wx1t1$$ {W_x}_{{}_n}(tn)\cdot \cdot \cdot {W}_{x_1}\left({t}_1\right) $$, where Wx(t) = e− iHtWxeiHt. Using chaotic spin-chain numerics and gauge/gravity duality, we show that a single precursor fills a spatial region that grows linearly in t. In a lattice system, products of such operators can be represented using tensor networks. In gauge/gravity duality, they are related to Einstein-Rosen bridges supported by localized shock waves. We find a geometrical correspondence between these two descriptions, generalizing earlier work in the spatially homogeneous case.