PM: Search for a Cosmologically-Relevant Boson in Antimuon Decay

PM：在反μ子衰变中寻找与宇宙学相关的玻色子

• 批准号: 2209456
• 负责人: Juan Collar
• 金额: $ 41.17万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2209456&HistoricalAwards=false
• 关键词: PM; Search; Cosmologically; Relevant; Boson

Experiments performed at particle accelerator facilities typically involve the generation of very large signals in the detectors employed. This is the result of the high energies imparted to the accelerated projectiles, which in turn produce very energetic fragments in their collisions. Unexpected products of particle interactions in such experiments are the harbingers of new physics theories. When looking for these signatures of new physics, the traditional concentration has been to push towards higher and higher energies in the sought signals. This award will support an innovative departure from this trend, by concentrating instead on the observation of the smallest possible energies following the impact and decay of a beam of anti-muons striking germanium detectors built specifically for this purpose. The data collected will permit the team to significantly expand the present sensitivity to exotic modes of this decay, specifically one in which an unexpected new particle (a boson) is created. Such bosons have been predicted by many extensions of the Standard Model of particle interactions, a theory now known to be incomplete. By concentrating on low-energies, the search supported by this award will explore, for the first time, the possibility that these bosons are created with slow-enough speeds to be gravitationally bound to galaxies. This would enable them to play interesting roles in cosmological scenarios, including the still unresolved dark matter problem. This award will also support one graduate student towards the completion of their studies. Specialty germanium detectors will be developed with the characteristics required to investigate the mode of decay of an antimuon that generates the new boson and a tell-tale monochromatic low-energy positron. These devices will then be exposed to the M15/M20 surface muon beams at TRIUMF, the Canadian accelerator center. TRIUMF is one of two sources, both outside the US, able to provide the required muon energies for this search. Following short (one week) beam exposures, the pertinent region of boson phase space can be probed down to branching ratios as small as 1E-7, a vast advance with respect to previous searches of this type. Two main factors contribute to this excellent expected sensitivity: an improvement by more than three orders of magnitude in detector energy resolution with respect to previously employed large scintillator calorimeters, and the modest background rate expected in the tiny detectors to be used.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在粒子加速器设施上进行的实验通常涉及所使用的检测器中非常大的信号。这是赋予加速弹丸的高能量的结果，进而在其碰撞中产生非常有活力的碎片。在此类实验中，粒子相互作用的意外产物是新物理学理论的前提。在寻找新物理学的这些签名时，传统的集中度是在寻求的信号中朝着越来越高的能量推动。该奖项将通过集中精力观察到最小可能的能量，在撞击和衰减的一束抗Muons击中专门为此目的构建的反芒灭锗探测器之后，将支持与这一趋势的创新偏离。收集到的数据将使团队能够显着扩大当前的敏感性，以使该衰减的异国情调模式，特别是创建意外的新粒子（玻色子）。这类玻色子已经通过粒子相互作用的标准模型的许多扩展进行了预测，粒子相互作用的标准模型现在已知是不完整的。通过集中精力，该奖项支持的搜索将首次探讨这些玻色子的可能性以缓慢的速度产生，以重力与星系绑定。这将使他们能够在宇宙学场景中扮演有趣的角色，包括仍未解决的暗物质问题。该奖项还将支持一名研究生完成学习。将开发特殊的锗探测器，其特征是研究产生新的玻色子和一个讲述单色低能量的抗蛋白腐烂模式。然后，这些设备将暴露于加拿大加速器中心Triumf的M15/M20表面MUON光束。 Triumf是在美国以外的两个来源之一，能够为此搜索提供所需的MUON能量。在短短（一周）梁暴露之后，可以将相关区域的相关区域探测到小至1E-7的分支比率，相对于以前对这种类型的搜索，这是一个巨大的进步。两个主要因素促成了这种出色的预期灵敏度：相对于先前使用的大型闪烁量热仪的探测器能量分辨率的三个以上数量级的改进，以及将使用的狭义探测器中预期的适度背景速率。该奖项反映了NSF的法定任务，并通过评估了基金会的智力效果，以评估其法定范围，并经过评估。