Real time solar neutrino spectroscopy with Borexino phase 2

几十年来，对消失的太阳中微子的研究一直是粒子天体物理学中最大的问题之一。同时，这个问题被认为是可以解决的，因为物质中的中微子振荡很好地描述了所有的观测结果，包括来自Borexino的观测结果。就射电纯度而言，Borexino是世界上最干净的闪烁探测器，它的阈值也非常低，这使得人们能够首次实时测量基本聚变过程中的pp中微子。该资助申请与Borexino的第二阶段有关，由于进行了纯化活动，该阶段的背景更低。为了进一步改善测量，将在这笔拨款中建立两个新的校准源，以将校准区域扩展到更高的能量。从分析的角度来看，本论文将讨论两个主题。最重要的是首次测量中微子，这将从实验上证明这个循环的存在。在此背景下，我们将探讨太阳丰度问题。最近对光球线的三维建模表明，碳、氮和氧等重元素的丰度降低了20-40%。然而，这导致太阳模型和日震观测之间存在较大的差异。探测太阳内部丰度的唯一方法是中微子。这也将揭示一些恒星天体物理学的基本假设，即元素的均匀分布。在同样的分析中，对胡椒中微子的改进测量是可能的。这些搜索的主要背景是闪烁体中介子相互作用产生的11C。在这笔赠款内，将开发一种基于似然分析的新方法，以比现有方法更高的效率消除这些事件。在这项拨款中处理的另一个研究问题是8B光谱的低能量行为。所有实时太阳实验的最低数据点显示出与振荡相反的行为。因此，在很长一段时间内，人们讨论了其他非标准交互（NSI）场景。改进后的第2阶段数据将在这个方向上进行分析，并将区分不同的解决方案，或者至少强烈地约束参数。

For decades the study of missing solar neutrinos was one of the biggest problems in particle astrophysics. Meanwhile this problem is considered to be solved as neutrino oscillations in matter describe all observations well,including the ones from Borexino. Borexino is the worldwide cleanest - in terms of radio purity- scintillation detector and also has a very low threshold, which allowed a first real time measurement of even pp-neutrinos from the fundamental fusion process. This grant application is linked to phase 2 of Borexino, a phase with even lower background due to a performed purification campaign. To improve measurements further two new calibration sources will be built in this grant to extend the calibrated region to higher energies. From the analysis point of few two topics will be dealt with in this grant. Of high priority is the first ever measurement of CNO-neutrinos, which would experimentally prove the existence of this cycle. Within this context the solar abundance problem will be explored. Recent 3-D modeling of photosphere lines lead to a lower abundance of heavier elements like C,N and O by 20-40%. However, this causes some larger discrepancy between solar models and helioseismological observations. The only way to probe the abundancies in the interior of the Sun are CNO-neutrinos. This will also shed some light on fundamental assumptions in stellar astrophysics, namely the homogeneous distribution of elements. In the same analysis an improved measurement of the pep-neutrinos is possible. The major background for these searches is 11C produced by myon interactions in the scintillator. Within this grant a new method based on a likelihood analysis will be developed to remove these events with a higher efficiency than the current one. Another research question tackled in this grant is the low energy behavior of the 8B spectrum. The lowest data point of all real time solar experiments shows the opposite behavior one would expect from oscillations. Thus, for a long time other non-standard interaction (NSI) scenarios are discussed. The improved phase 2 data will be analyzed in this direction and will distinguish between the different solutions or at least strongly constrain the parameters.