Quasielastic neutrino-nucleus scattering

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.

Photo- and Electroproduction of the Hypertriton on 3He

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 3He 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.Comment: 40 pages, 17 figures, submitted to Phys. Rev.

Strange-quark contribution to the ratio of neutral- to charged-current cross sections in neutrino-nucleus scattering

A formalism based on a relativistic plane wave impulse approximation is developed to investigate the strange-quark content ($g_{A}^{s}$) of the axial-vector form factor of the nucleon via neutrino-nucleus scattering. Nuclear structure effects are incorporated via an accurately calibrated relativistic mean-field model. The ratio of neutral- to charged-current cross sections is used to examine the sensitivity of this observable to $g_{A}^{s}$. For values of the incident neutrino energy in the range proposed by the FINeSSE collaboration and by adopting a value of $g_{A}^{s}=-0.19$, a 30% enhancement in the ratio is observed relative to the $g_{A}^{s}=0$ result.Comment: 20 pages, 6 figures, Revtex, Submitted to Phys. Rev.

Strange Particle Production Via The Weak Interaction

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.Comment: This paper was originally submitted to Physical Review C and published on 30 August, 201

Sensitivity of exclusive proton knockout spin observables to different Lorentz invariant representations of the NN interaction

Within the framework of the relativistic plane wave impulse approximation, we study the observable consequences of employing a complete Lorentz invariant representation of the NN scattering matrix in terms of 44 independent amplitudes, as opposed to the previously-employed, but ambiguous, five-term Lorentz invariant parametrization of the NN scattering matrix, for the prediction of complete sets of exclusive ($\vec{p},2 \vec{p}$) polarization transfer observables. Two kinematic conditions are considered, namely proton knockout from the $3s_{1/2}$ state of $^{208}$Pb at an incident energy of 202 MeV for coplanar scattering angles ($28.0^{\circ}, -54.6^{\circ}$), as well as an incident energy of 392 MeV for the angle pair ($32.5^{\circ}, -80.0^{\circ}$). The results indicate that certain spin observables are ideal for discriminating between the two representations.Comment: 19 pages, 5 figures, Revtex, To be published in Phys. Rev.

Calculation of a complete set of spin observables for proton elastic scattering from stable and unstable nuclei

A microscopic study of proton elastic scattering from unstable nuclei at intermediate energies using a relativistic formalism is presented. We have employed both the original relativistic impulse approximation (IA1) and the generalised impulse approximation (IA2) formalisms to calculate the relativistic optical potentials, with target densities derived from relativistic mean field (RMF) theory using the NL3 and FSUGold parameter sets. Comparisons between the optical potentials computed using both IA1 and IA2 formalisms, and the different RMF Lagrangians are presented for both stable and unstable targets. The comparisons are required to study the effect of using IA1 versus IA2 optical potentials, with different RMF parameter sets, on elastic scattering observables for unstable targets at intermediate energies. We also study the effect of full-folding versus the factorized form of the optical potentials on elastic scattering observables. As with the case for stable nuclei, we found that the use of the full-folding optical potential improves the scattering observables (especially spin observables) at low intermediate energy (e.g. 200MeV). No discernible difference is found at a projectile incident energy of 500 MeV. To check the validity of using localized optical potential, we calculate the scattering observables using non-local potentials by solving the momentum space Dirac equation. The Dirac equation is transformed to two coupled Lippmann-Schwinger equations, which are then numerically solved to obtain elastic scattering observables. The results are discussed and compared to calculations involving local coordinate-space optical potentials

Associated hyperon-kaon production via neutrino-nucleus scattering

We present the investigation of the neutrino-induced strangeness associated production on nuclei in the relativistic plane wave impulse approximation (RPWIA) framework at the intermediate neutrino energies. In this study, the elementary hadronic weak amplitudes are embedded inside the nuclear medium for the description of the exclusive channels of neutrino-nucleus interactions. These amplitudes are extracted using a model-dependent evaluation of the hadronic vertex using the Born term approximation in which the application of the Cabibbo V-A theory and SU(3) symmetry are assumed to be valid. The nuclear effects are included via the bound state wavefunctions of the nucleon obtained from the relativistic mean field (RMF) models. Two kinematics settings are used to examine various distributions of the differential cross section in the rest frame of the target nuclei. The numerical results are obtained for the neutrino-induced charged-current (CC) \,$\rm K^{^+}\Lambda$-production on bound neutrons in $1s^{1/2}$ and $1p^{3/2}$ orbitals of $^{12}$C. The angular distributions are forward peaked under both kinematic settings, whereas under the quasifree setting the cross sections tend mimic the missing momentum distribution of the bound nucleon inside the nucleus.Comment: This article is submitted to International Journal of Modern Physics E (nuclear physics) and accepted on 31 October 20l

Electromagnetic production of hypernuclei

A formalism for the electromagnetic production of hypernuclei is developed where the cross section is written as a contraction between a leptonic tensor and a hadronic tensor. The hadronic tensor is written in a model-independent way by expanding it in terms of a set of five nuclear structure functions. These structure functions are calculated by assuming that the virtual photon interacts with only one bound nucleon. We use the most recent model for the elementary current operator which gives a good description of the experimental data for the corresponding elementary process. The bound state wave functions for the bound nucleon and hyperon are calculated within a relativistic mean-field model. We calculate the unpolarized triple differential cross section for the hypernuclear production process e + 12C --> e + K+ + 12_Lambda{B} as a function of the kaon scattering angle. The nuclear structure functions are calculated within a particle-hole model. The cross section displays a characteristic form of being large for small values of the kaon scattering angle with a smooth fall-off to zero with increasing angle. The shape of the cross section is essentially determined by the nuclear structure functions. In addition, it is found that for the unpolarized triple differential cross section one structure function is negligible over the entire range of the kaon scattering angle.Comment: 33 pages, 13 figure