Nucleon helicity asymmetries in quasielastic neutrino-nucleus interactions

Abstract

We investigate the helicity properties of the ejectile in quasi-elastic neutrino-induced nucleon-knockout reactions and consider the 12 C target as a test case. A formalism based on a relativistic mean-field model is adopted. The influence of final-state interactions is evaluated within a relativistic multiple-scattering Glauber approximation (RMSGA) model. Our calculations reveal that the helicity asymmetries A l in A(ν, ν ′ N ) processes are extremely sensitive to strange-quark contributions to the weak vector form-factors. Thereby, nuclear corrections, such as final-state interactions and off-shell ambiguities in the electroweak current operators, are observed to be of marginal importance. This facilitates extracting strange-quark information from the helicity asymmetry A l .

Paschos-Wolfenstein relation in a hadronic picture

“…We wish to stress that the available strangeness information still exhibits relatively large error flags. Moreover, there exist fundamental discrepancies between the experimentally favored positive µ s and most model predictions [33,38]. So, the values used here can be regarded as a model prediction for µ s and g s A which is compatible with currently available data.…”

“…We took Eq. (23) Well-covered examples are the ratio of proton-to-neutron NC reactions [24,26,39], NC to CC cross-section ratios [40,41], polarization asymmetries [38] and the Paschos-Wolfenstein relation for proton knockout PW p [24].…”

Relativistic description of final-state interactions in neutral-current neutrino and antineutrino cross sections

“…Therefore, ratios of cross sections have been proposed as alternative and useful tools to search for strangeness effects. The ratio of proton-to-neutron cross sections was proposed and discussed in [89][90][91][92][93][94][95]. This ratio is very sensitive to strange-quark effects because the axial strangeness s interferes with the isovector contribution to the axial form factor g A ≈ 1.27 with one sign in the numerator and with the opposite sign in the denominator.…”

Δ-mediated pion production in nuclei

“…To model nuclear effects, we turn to the relativistic plane-wave impulse approximation, using relativistic bound-state wave functions that are calculated in the Hartree approximation to the σ -ω Walecka model [43]. This approach was successfully applied in QE nucleon-knockout studies [31,[44][45][46] and includes the effects of Fermi motion, nuclear binding, and the Pauli exclusion principle in a natural way. Medium modifications of the particle are taken into account along the lines of Ref.…”