发表机构
Indian Association for the Cultivation of Science; University of Calcutta（印度科学培育协会; 加尔各答大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究探讨了在 $\mu$TRISTAN 对撞机的 $\mu^+e^-$ 模式下，通过四轻子特征搜索电子耦合媒介子，预测对轻质量赝标量耦合灵敏度达 $10^{-5}$，显著超越现有界限。
AI 中文摘要
主要与电子耦合的媒介子，在 $B$ 工厂的运动学范围之上仍受到较弱约束，这一区域在强子对撞机上难以触及，且仅被现有 $e^+e^-$ 数据部分覆盖。我们指出，拟议中的 $\mu$TRISTAN 对撞机的不对称 $\mu^+e^-$ 模式，在 $\sqrt{s}=346$~GeV 下运行，非常适合这一窗口，并量化了其对两种最小实现的探测能力：一种类轴子粒子和一种 $Z'$ 规范玻色子，它们被视为与电子电流的有效相互作用。两者均从电子线辐射出并衰变为电子-正电子对，产生一个共同的四轻子特征，其标准模型对应过程受到良好控制。在电子-正电子不变质量中进行的共振搜索，针对媒介子质量在 $5.5$ 至 $300$~GeV 之间，预计在轻端给出约 $10^{-5}$ 量级耦合的 $95\\%$~CL 灵敏度，对赝标量而言比现有界限改善超过四个数量级，对矢量而言改善最多两个数量级，并为所考虑的最重质量提供了唯一约束。
英文摘要
Mediators coupled predominantly to the electron remain weakly constrained above the kinematic reach of the $B$~factories, a region that is difficult to access at hadron colliders and only partially covered by existing $e^+e^-$ data. We point out that the asymmetric $μ^+e^-$ mode of the proposed $μ$TRISTAN collider, operating at $\sqrt{s}=346$~GeV, is well suited to this window, and quantify its reach for two minimal realisations: an axion-like particle and a $Z'$ gauge boson, treated as effective interactions with the electron current. Both are radiated off the electron line and decay to an electron-positron pair, giving a common four-lepton signature whose Standard Model counterpart is under good control. A resonance search in the electron-positron invariant mass, performed for mediator masses between $5.5$ and $300$~GeV, yields projected $95\%$~CL sensitivities to couplings of order $10^{-5}$ at the light end of this range, improving on existing bounds by more than four orders of magnitude for the pseudoscalar and by up to two orders of magnitude for the vector, and providing the only constraint on the heaviest masses considered.
Comments30 pages, 10 figures, 3 tables
