R&D for SuperKEKB Electron Beam Polarization Upgrade

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• 批准号: SAPPJ-2021-00035
• 负责人: Roney, Michael
• 金额: $ 1.93万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=743126
• 关键词: R&D; SuperKEKB; Electron; Beam; Polarization

This is a proposal for accelerator R&D needed to upgrade the Japanese-based SuperKEKB electron-positron collider with polarized electrons, which opens a new discovery program. The aim is to take physics with polarized beam in the late 2020's. The upgrade requires a polarized electron source, a spin rotator system, and a Compton polarimeter.  This request is for beam dynamics and spin tracking studies coupled with developing conceptual designs for the spin rotator and Compton polarimeter. This polarization upgrade is included in the KEK Roadmap 2022-2026 and Belle II SNOWMASS submission. SuperKEKB's 10.58GeV center-of-mass energy collisions are at the world's highest luminosities. The Belle II detector, located at the interaction point (IP), is designed to measure weak interaction parameters and search for new physics, such as dark sector particles, with unprecedented precision and sensitivity. In June 2020, SuperKEKB delivered a world-record instantaneous luminosity of 2.4x10^34/cm^2s^1. Belle II will collect data through to the early 2030's. Upgrading SuperKEKB with polarization opens a unique program to measure weak neutral-current interaction strengths of unprecedented precision separately for multiple flavours. Measurements of Z-boson couplings to b-quark, c-quark and muons will improve on existing world-average precisions by many factors and will see a 100-fold improvement on the charm-beauty universality precision. Including electron and tau measurements, polarization will give the most precise measurement of a key Standard Model parameter, sin^2theta_W, from a single experiment, probe its running, and provide unique sensitive to New Physics. Eighty-percent transversely polarized electrons are to be injected into the High Energy Ring(HER). The spin is then rotated for longitudinal collisions at the IP, and then back to vertical using solenoidal and dipole fields. A Compton polarimeter will monitor longitudinal polarization with ~1% precision in real-time. Per-mil polarization will be measured at Belle II using tau polarization asymmetries. Initial spin rotator concepts have been developed and now additional dedicated manpower is required to move the studies forward. We request a postdoc and two graduate students and funds for an engineering conceptual design of the spin rotator combined-function magnet. The HQP will work on accelerator physics to develop the design requirements of the spin rotators as well as the Compton polarimeter parts of the project. Spin rotator work will involve beam dynamics studies needed to integrate the spin rotators into the HER with a minimal loss of luminosity and polarization. The engineering conceptual design of the combined-function magnet is needed for more realistic beam dynamics studies. Once a full conceptual design is in hand, the project would proceed to the detailed design of this hardware. Funding for travel for project meetings and workshops and for dedicated computer resources is also requested.

这是一个加速器研发的建议，需要升级日本的SuperKEKB电子-正电子对撞机与极化电子，这开启了一个新的发现计划。其目标是在2020年代末用偏振光束进行物理学研究。升级需要一个极化电子源、一个自旋旋转器系统和一个康普顿偏振计，这项要求是为了进行束流动力学和自旋跟踪研究，同时发展自旋旋转器和康普顿偏振计的概念设计。这一极化升级包括在KEK 2022-2026年路线图和贝儿II SNOWMASS提交文件中。SuperKEKB的10.58GeV质心能量碰撞是世界上最高的亮度。位于相互作用点（IP）的贝儿II探测器旨在以前所未有的精度和灵敏度测量弱相互作用参数和寻找新的物理，如暗扇区粒子。2020年6月，SuperKEKB创造了2.4x10^34/cm^2s^1的世界纪录瞬时亮度。贝儿二号将收集到2030年初的数据。通过极化升级SuperKEKB开启了一个独特的程序，可以分别测量多种口味的微弱中性电流相互作用强度，其精度前所未有。Z玻色子与b夸克、c夸克和μ子耦合的测量将在许多方面提高现有的世界平均精度，并将使魅力普适性精度提高100倍。包括电子和τ测量在内，极化将从单个实验中给出标准模型关键参数sin^2 θ_W的最精确测量，探测它的运行，并为新物理学提供独特的灵敏度。百分之八十的横向极化电子将被注入高能环（HER）。然后旋转自旋以在IP处进行纵向碰撞，然后使用螺线管和偶极场返回到垂直。康普顿偏振计将以约1%的精度实时监测纵向偏振。将在贝儿II使用tau偏振不对称性测量每密耳偏振。最初的尾旋旋转器概念已经发展出来，现在需要更多的专门人员来推进研究。我们要求一个博士后和两个研究生和资金的自旋旋转组合功能磁铁的工程概念设计。HQP将致力于加速器物理学，以开发自旋旋转器的设计要求以及该项目的康普顿偏振计部分。自旋旋转器的工作将涉及需要整合到HER的自旋旋转器的亮度和偏振的损失最小的光束动力学研究。为了更真实的束流动力学研究，需要对组合功能磁体进行工程概念设计。一旦有了完整的概念设计，该项目将着手进行这一硬件的详细设计。还要求为参加项目会议和讲习班的旅费以及专用计算机资源提供经费。