UCLA CUORE Neutrino Physics Research Program

中微子是宇宙中最丰富的粒子之一，但我们不知道它们的许多性质。例如，我们不知道它们的绝对质量尺度或它们的粒子-反粒子性质。由于它们的丰富性，即使是很小的质量也可能对理解它们在我们宇宙演化中的作用产生深远的影响。知道中微子是否是它们自己的反粒子可能会对理解我们宇宙的物质-反物质不对称性产生影响。无中微子双β衰变（NLDBD）实验解决了这两个基本问题。双β衰变是一种罕见的核衰变，当它在能量上有利时，已经在几个核中测量到。有些原子核对普通的β衰变是稳定的，但对双β衰变是不稳定的，在双β衰变中，原子核中的两个中子同时转化为质子，并发射出两个电子。双β衰变可以通过几种模式进行。实验测量的过程，即同时发射两个电子反中微子的双中微子模式，完全由已知物理学描述。NLDBD是一种尚未被探测到的衰变，它不涉及处于终态的中微子，这必然表明中微子是它们自己的反粒子。在意大利阿塞尔吉的格兰萨索实验室（LNGS）进行的CUORE（Cryogenic Underground Observatory for Rare Events）实验是下一代寻找NLDBD的实验之一。它使用130-Te同位素，设计灵敏度为40-70 meV之间的有效中微子质量，这取决于核结构计算。UCLA团队的主要硬件职责包括与米兰和南卡罗来纳州团队合作，对所有前端电子设备进行测试，并在LNGS安装和调试电子系统。他们的分析重点将是通过蒙特卡罗模拟来理解剩余背景源。CUORE中使用的技术是基于毫开尔文测辐射热法的，是该领域最具创新性和规模最大的技术之一。如果他们的电子产品被证明是设计好的，它可能会影响其他领域。NLDBD实验解决了具有超越粒子和核物理学的科学影响的基本物理问题。例如，如果中微子是马约拉纳粒子，而中微子质量来自跷跷板机制，轻子扇区可能违反CP（电荷宇称）对称性，并导致宇宙的物质和反物质不对称性。该小组还将帮助培训本科生和NSF-REU学生的研究计划，并为他们提供中微子物理学和现代探测器技术的研究经验。

Neutrinos are amongst the most abundant particles in the Universe and yet we do not know many of their properties. For example, we do not know their absolute mass scale or their particle-antiparticle nature. Because of their abundance, even a small mass could have far-reaching consequences for understanding their role in the evolution of our Universe. Knowing if neutrinos are their own antiparticles could have implications in understanding the matter-antimatter asymmetry of our Universe. Neutrino-less double beta decay (NLDBD) experiments address these two fundamental questions. Double beta decay is a rare nuclear decay that has been measured in several nuclei when it is energetically favorable. Some nuclei are stable against ordinary beta decay but are unstable for double beta decay in which two neutrons in the nucleus are simultaneously converted to protons and two electrons are emitted. Double beta decay can proceed through several modes. The experimentally measured process, the two-neutrino mode in which two electron antineutrinos are also emitted, is completely described by known physics. NLDBD is an as-yet-undetected decay that involves no neutrinos in the final state and necessarily would indicate that neutrinos are their own antiparticle. The rate of such decays determines the scale for the effective neutrino mass.The CUORE (Cryogenic Underground Observatory for Rare Events) experiment at the Gran Sasso laboratory (LNGS), Assergi, Italy, is one of the next generation experiments to search for NLDBD. It uses the 130-Te isotope with a design sensitivity to the effective neutrino mass ranging between 40-70 meV, depending on nuclear structure calculations. The UCLA group's major hardware responsibilities include the testing of all the front-end electronics and the installation and commissioning of the electronics system at LNGS in collaboration with the Milan and South Carolina groups. Their analysis focus will be on understanding of the residual background sources through Monte Carlo simulations.The technology being used in CUORE which is based on milliKelvin bolometry is one of the most innovative and largest scale in the field. If their electronics proves out as designed, it will likely influence other fields. The NLDBD experiments address fundamental physics issues that have a scientific impact beyond particle and nuclear physics. For example, if neutrinos are Majorana particles and neutrino masses are from the See-Saw Mechanism, the lepton sector could violate CP (Charge-Parity) symmetry and contribute to the matter and anti-matter asymmetry of the Universe. The group will also help train undergraduate and NSF-REU students in their research programs and provide them with research experiences in neutrino physics and modern detector technology.