We study the sensitivity of neutral-current neutrino-nucleus scattering to the strange-quark content of the axial-vector form factor of the nucleon. A model-independent formalism for this reaction is developed in terms of eight nuclear structure functions. Taking advantage of the insensitivity of the ratio of proton $(\nu,\nu' p)$ to neutron $(\nu,\nu' n)$ yields to distortion effects, we compute all structure functions in a relativistic plane wave impulse approximation approach. Further, by employing the notion of a bound-state nucleon propagator, closed-form, analytic expressions for all nuclear-structure functions are developed in terms of an accurately calibrated relativistic mean-field model. Using a strange-quark contribution to the axial-vector form factor of $g_{A}^{s}=-0.19$, a significant enhancement in the proton-to-neutron yields is observed relative to one with $g_{A}^{s}=0$.Comment: 23 pages, 12 figures, Revtex, Submitted to Phys. Rev.

Differential cross sections of the photo-and electroproduction of the hypertriton have been calculated by utilizing modern nuclear wave functions and the elementary operator of KAON-MAID. It is found that a proper treatment of Fermi motion is essential for the two processes.While the average momentum approximation can partly simulate the Fermi motion in the process, the "frozen nucleon" assumption yields very different results, especially at lower energies. The Coulomb effect induced by the interaction between the positively charged kaon and the hypertriton is found to be negligible. The influence of higher partial waves is also found to be relatively small, in contrast to the finding of the previous work. The off-shell assumption is found to be very sensitive in the case of electroproduction rather than in photoproduction. It is shown that the few available experimental data favor the assumption that the initial nucleon is off-shell and the final hyperon is on-shell. This seems to be reasonable, since the hyperon in the hypertriton is less bound than the nucleon in the initial 3 He nucleus. The effect of the missing resonance D 13 (1895) is more profound in the longitudinal cross sections. Excluding this resonance reduces the longitudinal cross sections by one order of magnitude, but does not change the effects of various off-shell assumptions on the cross sections.

A model for coinfection in multiple strain infectious diseases is developed to incorporate coinfection statuses, immune and infection history, and cross immunity. It is solved for the symmetric interior equilibrium through the use of a ladder operator formalism inspired by quantum mechanical methods. We find that coinfection can fundamentally affects transmission dynamics with important epidemiologic and evolutionary consequences. It can significantly shift the distribution of age at infection for highly antigenically diverse pathogens so that in small host populations, an evolutionary strategy maximizing individual strain transmissibility might be less optimal than one which maximizes the total prevalence of all strains in the system. Alternatively, mechanisms which inhibit coinfection and thus increase total infection prevalence may be evolutionarily advantageous.

The differential cross sections for the neutrino-induced weak charged current production of strange particles in the threshold energy region are presented. The general representation of the weak hadronic current is newly developed in terms of eighteen unknown invariant amplitudes to parametrize the hadron vertex. The Born term approximation is used for the numerical calculations in the framework of the Cabibbo theory and SU(3) symmetry. For unpolarized octet baryons four processes are investigated, whereas in the case of polarized baryons only one process is chosen to study the sensitivity of the differential cross section to the various polarizations of the initial state nucleon and the final state hyperon.

Based on the relativistic plane-wave impulse approximation for quasielastic ( p ជ ,p ជ Ј) and (p ជ ,n ជ ) polarization observables, we provide quantitative estimates of nuclear medium modifications of the NN interaction. We employ a 40 Ca target for proton energies ranging from 135 to 300 MeV at a momentum transfer of 1.97 fm Ϫ1 . Compared to former calculations, we have generated new meson-exchange parameters for the relativistic NN amplitudes between 80 and 200 MeV. Finally, the results are compared to the limited available data.