Speaker
Description
Neutrino physics is entering a precision era and an important goal is to measure with high accuracy the neutrino oscillation parameters, to look for CP violation in the lepton sector, etc., for which the simultaneous knowledge of neutrino and antineutrino cross sections in the same energy region for a given nuclear target is required to reduce the systematics to a few percent level. In the few GeV energy region of neutrinos and antineutrinos, the contribution to the total scattering cross section comes from the quasielastic, inelastic, and deep inelastic scattering processes. The inelastic scattering region is quite intriguing as it excites various nucleon and delta resonances lying in the first and higher resonance regions starting with $P_{33}(1232)$, followed by $P_{11}(1440)$, $D_{13}(1520)$, $S_{11}(1535)$ resonances, etc. These resonances then decay to various meson-baryon channels leading to the production of mesons in the inelastic region. Moreover, in this region, along with the resonance excitations, the non-resonant background contribution also gives rise to mesons in the final state. Since the information about the axial vector nature of these resonances is very limited both experimentally as well as theoretically, therefore, in order to understand the inelastic scattering region of (anti)neutrinos, the study of meson production in the weak sector is important.
In this work, we study neutrino induced single meson production viz. $1\pi$, $1K$, $1\eta$, and associated particle production from the free nucleon target. The hadronic current receives contribution from the background terms as well as from the nucleon and delta resonance excitations. We have considered only those nucleon/delta resonances~($R$) which are present in the PDG having spin $\frac{1}{2}$ and $\frac{3}{2}$ and mass~($M_{R}$) in the range $<$ 2 GeV with significant branching ratio in any particular meson decay mode. In the neutrino induced processes, the weak hadronic current contains the vector as well as the axial vector current. The vector current of the weak interaction is related to the electromagnetic current through the conserved vector current (CVC) hypothesis and for the axial vector current, PCAC and the Goldberger-Treiman relation are used. The $Q^2$ dependent form factors from the electroproduction are used to determine the weak vector form factors in the vector current and for the axial vector current, generally a dipole form factor is assumed. The couplings at the strong $MNN^\prime$ and $MNR$ vertices determined from the meson photoproduction, are used for the strong couplings of the neutrino induced meson production. Thus, in neutrino induced meson production, the couplings and the form factors from the photoproduction and electroproduction, respectively, are used as inputs. We shall present and discuss the results for the total and differential scattering cross sections for the meson production induced by the (anti)neutrinos.
