120869047
Elastic Scattering of 580-MeV Protons from He 3
The elastic differential cross section for $p$-$^{3}\mathrm{He}$ scattering has been measured at 580 MeV. The data are compared with a Glauber model calculation.
93503786
Quasi-Elastic Reactions with 600 MeV Protons
A measurement of the (p,2p) differential cross section dσ/dEdΩldΩ2 at 600 MeV on Deuterium and Helium-4 at the NASA Space Radiation Effects Laboratory is reported [1], [2]. Two coincident protons were detected with identical range telescopes. The energy sum of the outgoing protons was constrained to be equal to the incident energy minus the S-state proton separation energy, 2.2 and 20.4 MeV for D and He-4, respectively. By varying the detection angles symmetrically to the beam, events were selected with nuclear recoil momentum \(\vec q_r = \vec p_o - (\vec p_1 + \vec p_2 )\) along the beam line. Values of qr up to 370 MeV/c in D and 300 MeV/c in He-4 were observed.
120709149
Elastic scattering of 600-MeV protons from H, D, He-3, and He-4.
121222499
Elastic pd Scattering at 316, 364, 470, and 590 MeV in the Backward Hemisphere
The results of an investigation of the elastic $\mathrm{pd}$ differential cross section for center-of-mass angles between 91 and 164\ifmmode^\circ\else\textdegree\fi{} at energies of 316, 364, 470, and 590 MeV are presented. For center-of-mass scattering angles larger than 130\ifmmode^\circ\else\textdegree\fi{}, the cross sections at any given angle are within 10% of each other for the three largest energies. The extrapolated 180\ifmmode^\circ\else\textdegree\fi{} differential cross section observed in this experiment remains nearly constant from 316 to 590 MeV. This is in marked contrast to the rapid decrease in cross section with increasing energy observed by other investigators for both larger and smaller energies. Possible theoretical explanations of this behavior are mentioned.
118889987
Polarization Observables for Two-Pion Production off the Nucleon
We develop polarization observables for the processes {gamma}N {yields} {pi}{pi}N and {pi}N {yields} {pi}{pi}N, using both a helicity and hybrid helicity-transversity basis. Such observables are crucial if processes that produce final states consisting of a spin-1/2 baryon and two pseudoscalar mesons are to be fully exploited for baryon spectroscopy. We derive relationships among the observables, as well as inequalities that they must satisfy. We also discuss the observables that must be measured in ''complete'' experiments, and briefly examine the prospects for measurement of some of these observables in the near future.
122244010
Four-quark states in hyperon pair production
AbstractWe discuss the use of four-quark states as intermediates in the description ofp
$$\bar p$$
 scattering to exclusive hyperon anti-hyperon pairs. We use four energy-independent parameters to account for initial and final state interactions. Some experimentally observed features of these reactions are easily accounted for in this model, but a few features are not well described. We conclude that less crude initial and final state interactions may make the model more useful.
118587934
Rare dileptonic decays of \Lambda_b in a quark model
Hadronic form factors for the rare weak transitions $\Lambda_{b}\rightarrow\Lambda^{(*)}$ are calculated using a nonrelativistic quark model. The form factors are extracted in two ways. An analytic extraction using single component wave functions (SCA) with the quark current being reduced to its nonrelativistic Pauli form is employed in the first method. In the second method, the form factors are extracted numerically using the full quark model wave function (MCN) with the full relativistic form of the quark current. Although there are differences between the two sets of form factors, both sets satisfy the relationships expected from the heavy quark effective theory (HQET). Differential decay rates, branching ratios and forward-backward asymmetries (FBAs) are calculated for the dileptonic decays $\Lambda_{b}\rightarrow\Lambda^{(*)}\ell^{+}\ell^{-}$, for transitions to both ground state and excited daughter baryons. Inclusion of the long distance contributions from charmonium resonances significantly enhances the decay rates. In the MCN model the $\Lambda(1600)$ mode is the dominant mode in the $\mu$ channel when charmonium resonances are considered; the $\Lambda(1520)$ mode is also found to have a comparable branching ratio to that of the ground state in the $\mu$ channel.
119385803
Semileptonic decays of heavy {lambda} baryons in a quark model
The semileptonic decays of {lambda}{sub c} and {lambda}{sub b} are treated in the framework of a constituent quark model. Both nonrelativistic and semirelativistic Hamiltonians are used to obtain the baryon wave functions from a fit to the spectra, and the wave functions are expanded in both the harmonic-oscillator and the Sturmian bases. The latter basis leads to form factors in which the kinematic dependence on q{sup 2} is in the form of multipoles, and the resulting form factors fall faster as a function of q{sup 2} in the available kinematic ranges. As a result, decay rates obtained in the two models with the Sturmian basis are significantly smaller than those obtained with the harmonic-oscillator basis. In the case of the {lambda}{sub c}, decay rates calculated with the Sturmian basis are closer to the experimentally reported rates. However, we find a semileptonic branching fraction for the {lambda}{sub c} to decay to excited {lambda}{sup *} states of 11 to 19%, in contradiction to what is assumed in available experimental analyses. Our prediction for the {lambda}{sub b} semileptonic decays is that decays to the ground state {lambda}{sub c} provide a little less than 70% of the total semileptonic decay rate. For the decaysmore » {lambda}{sub b}{yields}{lambda}{sub c}, the analytic form factors we obtain satisfy the relations expected from heavy-quark effective theory at the nonrecoil point, at leading and next-to-leading orders in the heavy-quark expansion. In addition, some features of the heavy-quark limit are shown to naturally persist as the mass of the heavy quark in the daughter baryon is decreased.« less