Precision studies of inclusive response of light nuclei

The project is determined to perform a high precision electron-induced nuclear experiments on oxygen and carbon that will for the first time allow a complete study of the electromagnetic properties of light nuclei and provide a vital new input to deficient existing models of nuclear structure and dynamics, employed to interpret signals detected in the accelerator-based neutrino experiments. Extensive worldwide experimental and theoretical efforts gathered around neutrino facilities clearly show that the precise measurements of neutrino masses, mixing angles and CP- violating phase represent the highest priority of today's particle and nuclear physics. New accelerator-based neutrino oscillation experiments, dedicated to investigate these topics, are already underway (T2K) or are scheduled for the near future (DUNE). They combine proton accelerators acting as high power muonic neutrino sources, with a series of (near and far) detectors that use carbon (MiniBooNE, T2K), water (T2K) or argon (MicroBooNE, DUNE) as a detector medium. In these detectors the neutrinos are identified indirectly, predominantly through the inclusive charged current quasi elastic scattering (CCQE) by detecting corresponding leptons emerging from the reaction. The number of muonic neutrinos tagged in the far detector as a function of energy, known as neutrino oscillation, gives direct access to the neutrino properties. The principal challenge of such measurements is not knowing the energy of the incoming neutrinos. Due to the production process, it cannot be determined from the parameters of the accelerator, nor can be uniquely reconstructed using kinematic properties of the detected charged particles. Hence, to relate the measured distribution of muons to the energy distribution of neutrinos, data need to be studied in conjunction with Monte-Carlo simulations that include cross-sections for all involved reactions. Unfortunately, the theoretical models used to describe the electromagnetic and weak interaction of leptons with nuclei are presently, in spite all the efforts, still incomplete and unreliable. The main reason lies in the lack of electron scattering data, needed to validate the available theories. To overcome this problem, new, dedicated electron scattering measurements on oxygen, and carbon in the correct energy range are needed. With the proposed project we intend to provide the first-ever measurement of the inclusive cross-section for 16O(e,e') and 12C(e,e') at the energy below 700MeV, which coincides with the oscillation maximum of the T2K experiment. The experiment led by the Slovenian team and supported by the foreign collaborators will be performed at the MAMI facility using high-resolution spectrometers of the A1 Collaboration. The cross-sections measured at carefully chosen 400 different kinematic points at various energy and momentum transfers in both quasi elastic and delta resonance regimes, will shed light on all key components of the electron-nucleus interaction. In the nuclear physics community such data are much-awaited and are crucially needed to answer fundamental questions about the nuclear structure, like quenching of the Coulomb sum rule, and to improve the available theoretical models. The proposed experiment fits well within the time frame of a three-year project, encompassing one year for experimental groundwork and data taking and two years for data analysis and preparation of the publications. In the experiment we will use well- established experimental techniques and employ only standard experimental equipment, tested in a long series of past experiment. With the collected high statistics data we expect to see significant discrepancies between the data and models. This should motivate improvements of the available theoretical calculations, allow significant advances of the nuclear physics, ensure an unbiased interpretation of the oscillation results and clear the way to a better understanding of neutrinos.