The figure shows the expected oscillation signal for DUNE as a function of neutrino energy E v for some values of two neutrino properties: the mixing angle θ 13 and the CP-violating phase δ CP. To get a sense of the accuracy needed for the energy reconstruction in oscillation experiments, it is helpful to look at Figure 1. The precision with which neutrino oscillation properties can be extracted from such experiments then depends directly on the description of the final state of the neutrino–nucleus interaction. The accuracy of that reconstruction affects the extraction of neutrino oscillation parameters.īecause all modern experiments use nuclear targets, such as H 2O, CH n, and 40Ar, the energy reconstruction depends not only on the initial neutrino–nucleus interaction but also on the final-state interactions (FSI) of all particles. Unlike in any other nuclear physics experiment, in neutrino-induced reactions the beam energy is not known but must be reconstructed from the final state of the reaction. Thus, the neutrino energy must be reconstructed event by event from the final state of the reaction, at both the near and far detectors. A complication lies in the fact that the neutrino energy is not known because of the special production method of neutrinos as secondary decay products of hadrons, mostly pions and kaons, that were produced in primary reactions of protons with nuclei (see the sidebar titled Neutrino Beam Energy). From that comparison, one can extract the neutrino oscillation parameters, mixing angles, and possibly a CP invariance–violating phase. In these experiments, the event rate (flux multiplied by cross section) at a given neutrino energy E ν at a far detector is compared with that at a near detector at the same energy. It is also interesting from a practical point of view with regard to long-baseline experiments, such as T2K, MINOS, NOνA, and the future DUNE (formerly called LBNE), that attempt to extract neutrino properties from the observation of neutrino oscillations. It can provide valuable information about the electroweak response of nuclei to axial perturbations and, thus, supplement our previous knowledge from electron scattering experiments. The investigation of interactions of neutrinos with nuclei is interesting from the point of view of nuclear many-body theory (NMBT).
Present data seem to be sensitive to only one of them, as discussed in Section 2.2, below. Whereas the three vector form factors are reasonably well determined by electron-induced pion production on the nucleon, the three axial form factors are largely unknown. For example, for the Δ resonance, the transition current involves three vector form factors and three axial ones. The transition form factors to nucleon resonances are even less well known. The assumed dipole form of the axial vector form factors, however, cannot be checked further by experiment the vector form factors obtained from electron scattering show a significantly more complicated dependence on the squared four-momentum transfer Q 2 ( 2). This axial mass ( M A) has been determined in many neutrino experiments on nucleons (or deuterons) and assumes a value of approximately 1 GeV ( 1).
Neutrino interaction free#
It is usually reduced to a dipole ansatz, with one free parameter, the axial mass. For example, the nucleon's axial form factor is still poorly known. The interactions of neutrinos with nucleons can provide valuable information about axial properties and transition form factors.
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