中性流光子/π介子弱产生的双核子流散射过程的理论研究

A good understanding of (anti)neutrino-nucleons and (anti)neutrino-nuclei interactions is crucial to reduce systematic uncertainties in oscillation experiments. Over the last decade, NOMAD, MiniBooNE, SciBooNE, MINOS and more recently T2K and MINERνA have obtained a wealth of data on the cross sections of neutrino-nucleus interactions. Two of the possible reaction channels, photon production and pion production induced by neutral current interactions (NCγ and NCπ), turns out to be the largest backgrounds in (anti)neutrino oscillation experiments (such as MiniBooNE and SK detector of T2K) where electromagnetic showers from electrons (positrons) and photons are not distinguishable. As it was shown that the two-nucleon current plays an important role in the neutrino-nuclei charge current quasielastic scattering, the contribution of two-nucleon current is expected to be important in NCγ and NCπ reactions..In this project, we will develop a theoretical model for two-nucleon current NCγ/NCπ reaction at energies of interest for current and future neutrino oscillation experiments. As a natural extension of our model for single-nucleon current NCγ reaction, the model is based on a systematic many-body expansion of the gauge boson absorption modes that includes many-body mechanisms, as well as the excitation of Δ isobars. With our microscopic model, we will calculate the contribution from the two-nucleon current NCγ/NCπ reaction to the electron-like irreducible background at the MiniBooNE and T2K (SK) experiemnts..Our project is important to improve our present knowledge of electroweak interactions on nucleons and nuclei, and also to determinate the neutrino properties precisely.

准确理解中微子核子以及中微子原子核散射过程，对于降低中微子振荡实验的系统误差至关重要。在过去的十年中，NOMAD，MiniBooNE等合作组积累了大量中微子原子核散射的实验数据。由于MiniBooNE和T2K（SK）的探测器不能区分电子和光子信号，因此，中性流光子产生过程（NCγ）和中性流π介子产生过程（NCπ）就会对电子（反）中微子的探测信号造成很大干扰。研究表明，双核子流过程在中微子原子核的电荷流准弹性散射过程中有很大贡献，因此进一步研究双核子流在NCγ和NCπ过程中的贡献就显得非常重要。基于我们建立的描述NCγ单核子流过程的模型，我们将构建描述中性流光子/π介子产生的双核子流过程的理论模型，并计算双核子流过程在MiniBooNE以及T2K（SK）探测器上产生的事例数，进而探讨对实验数据分析的影响。本研究对于加深我们对中微子散射过程的理解，提高测量中微子性质的精度具有重要意义。

准确理解中微子核子以及中微子原子核散射过程，对于降低中微子振荡实验的系统误差至关重要。研究表明，双核子流过程在中微子原子核的电荷流准弹性散射过程中有很大贡献，因此进一步研究双核子流在中性流光子和π介子产生过程中的贡献就显得非常重要。在本项目中，我们构建了描述中性流光子/π介子产生的双核子流过程的理论模型，这加深了我们对中微子原子核相互作用的多体机制的了解。我们也初步计算了双核子流光子产生过程在T2K探测器上产生的事例数，并与MiniBooNE和T2K实验的分析人员进行了交流，我们的结果对于MiniBooNE和T2K实验的数据分析提供了理论依据。此外，我们也加入了中国江门中微子实验国际合作组，本项目也为我们下一步围绕江门中微子实验开展相关理论研究提供了铺垫。