arXiv subjects

Ruihu Zhu

Publications and source records attributed to Ruihu Zhu.

6 recordsLinked to original sources

arXiv2026

Projected Sensitivity to Slow Muonphilic Dark Matter with Accelerator Muon Beams

The nature of dark matter (DM) remains one of the most enduring open questions in modern physics, and muonphilic DM has emerged as a promising scenario that complements traditional DM candidates. Following the recently established cosmic-ray muon scattering approach, we investigate the sensitivity for probing slow muonphilic DM with accelerator muon beams. A Geant4-based simulation framework is developed, incorporating the detector geometry from the PKMu muon tomography system and a dedicated elastic $\mu$-DM scattering process. The projected sensitivity is found to be largely insensitive to both the beam energy and the transverse beam size when the beam is fully contained within the detector acceptance. For a benchmark beam intensity of $10^5/\rm{s}$, the simulated pure-muon beam surpasses the existing cosmic-ray limit of $1.61\times10^{-17}$ cm$^2$ at $m_{\rm DM}=1$ GeV within approximately 11 seconds. A realistic muon beam phase-space distribution based on simulations for the High Intensity heavy-ion Accelerator Facility (HIAF) is also implemented, yielding projected limits that improve upon the cosmic-ray results by nearly two orders of magnitude in a one-day exposure. These results demonstrate that a beam-muon scattering experiment offers a robust and promising route toward significantly improved sensitivity to slow muonphilic DM.

hep-ex↗

arXiv2026

Production of lepton-flavor-violating scalars through resonant positive-muon annihilation on atomic electrons

We investigate an invisible lepton-flavor-violating scalar $\phi$ with exclusive $e-\mu$ couplings and study its resonant production via $\mu^+e^-\to\phi$ in fixed-target experiments. Since the effective center-of-mass energy is determined by the momentum of the initial-state bound electrons, atomic effects can significantly affect the resonance behavior. We therefore employ relativistic bound-state electron wave functions to calculate the production cross section and reveal a material-dependent broadening of the resonance lineshape. For the proposed HIAF experiment, fewer than one day of data taking ($6\times10^{10}$ MOT) can probe couplings at the $10^{-5}$ level at 90\% confidence level near resonance, demonstrating that high-intensity muon fixed-target experiments provide a powerful complementary probe of lepton-flavor violation.

hep-ph↗

arXiv2025

Numerical simulations of electron acceleration driven by heavy ion beams in plasma with alternating density gradients

Plasma-Based Acceleration (PBA) has been demonstrated using laser, electron, and proton drivers. However, significant challenges remain in achieving high efficiency, stable acceleration, and scalable energy gain. Heavy ion beam drivers, with their high kinetic energy, offer the potential for greater energy transfer to the witness beam. Unfortunately, limited by the relatively low velocity of heavy ion, the dephasing length is really short leading to a low energy gain of the witness beam. Conventional method that increase plasma density linearly is ineffective in this context because the mismatch between the RMS beam radius and plasma wavelength will make the wakefield degrade or even disappear. In this paper, we propose a method that periodically switches the witness beam between different accelerating phase, allowing it to shift between adjacent accelerating cavities. Therefore, the plasma density does not only strictly increase, but also decrease. This will help maintain the structure of wakefield and increase the energy gain of the witness beam.

physics.acc-ph↗

arXiv2025

Numerical investigations of heavy ion driven plasma wakefield acceleration

Plasma-Based Acceleration (PBA) has emerged as a promising approach to achieve ultra-high gradient particle acceleration. While extensive PBA studies have been conducted using laser, electron, and proton drivers, significant challenges remain in achieving high efficiency, stable acceleration, and scalable energy gain. Meanwhile, due to their higher beam charge density, heavier particle mass and higher kinetic energy, heavy-ion beam drivers represent an interesting direction in PBA research. In this paper, the plasma wakefield acceleration driven by heavy ion beam is studied for the first time, aiming to find the best mechanism for generating high-amplitude wakefields. Using the high intensity, high energy heavy ion beams provided by the High Intensity heavy-ion Accelerator Facility (HIAF), our simulations show that heavy ions can excite stable, high-amplitude plasma wakefields up to 6 GV/m, suitable for electron acceleration. These results show good performance of heavy ion beam drivers and their potential as a viable and promising approach in the field of PBA.

physics.acc-ph↗

arXiv2024

Performance and tolerance study of the rectilinear cooling channel for a muon collider

The muon collider has the potential to be a powerful tool for the exploration of frontiers in particle physics. In order to reach high luminosity, the 6D emittance of the muon beam needs to be reduced by several orders of magnitude. The cooling process for a muon collider involves two parts; initial six-dimensional cooling and final transverse cooling. This paper focuses on the former and proposes a conceptual design of the rectilinear cooling channel with additional dipole magnets. In this paper, we first introduce a general method for designing the rectilinear cooling channel. Subsequently, we apply this method to develop two rectilinear cooling channels before and after a bunch merging system. Furthermore, we investigate the impact on cooling performance by employing $π$-mode RF cavities and considering the effect of errors in the magnetic and RF fields.

physics.acc-ph↗

arXiv2024

Simulation studies on compensation for incoherent magnet error driven half-integer and 3rd-order resonances with space charge in HIAF-BRing

Magnet error driven resonances under space-charge-induced resonance crossing represents a significant limitation on beam intensity in low-injection-energy high-intensity synchrotrons. Unstable particle motion arises from the combined effects of space-charge-induced tune spread and magnetic field imperfections, which limits the intensity. This paper introduces a space-charge-Twiss modification to the Resonance Driving Terms (RDTs). The new RDTs are named modified RDTs. Modified RDTs aim to describe the nonlinear behavior under incoherent error driven resonances induced by the combined effect of space charge and magnetic field imperfections. The feasibility of the compensation scheme with modified RDTs is demonstrated through coasting-beam simulations under space-charge-induced half-integer and 3rd-order resonances, using the lattice of the High Intensity Heavy-Ion Accelerator Facility Booster Ring (HIAF-BRing). The simulations demonstrate that the compensation through minimizing modified RDTs significantly suppresses the emittance growth and the unstable particle motion. Besides, the effect of compensation scheme with modified RDTs against periodical resonance crossing is evaluated in bunched-beam simulations.

physics.acc-ph↗