Exploring the lifetime frontier with a beam-dump experiment at CiADS

TL;DR

This paper proposes a cost-effective beam-dump experiment at CiADS to search for long-lived particles, especially dark photons, with significant sensitivity improvements over current limits, and discusses its potential at HIAF.

Contribution

It introduces a novel, low-cost beam-dump experimental setup at CiADS for detecting long-lived particles, with detailed sensitivity analysis for dark photons and potential at HIAF.

Findings

Probing unexcluded dark photon parameter space at 100 MeV mass and 10^{-9} to 10^{-8} kinetic mixing.

The proposed experiment is cost-effective with minimal instrumentation.

HIAF-BDE can explore new parameter regions for long-lived particles.

Abstract

We propose a beam-dump experiment (BDE) at the upcoming facility of China initiative Accelerator Driven System (CiADS), called CiADS-BDE, in order to search for long-lived particles (LLPs) predicted in various beyond-the-Standard-Model (BSM) theories. The experiment is to be located in the forward direction of the incoming low-energy proton beam at CiADS, leveraging the strong forward boost of the produced particles at the beam dump in general. The space between the dump and the detector is largely available, allowing for installation of veto materials and hence low levels of background events. We elaborate on the detector setup, and choose dark photon as a benchmark model for sensitivity study. We restrict ourselves to the signature of an electron-positron pair, and find that with 5 years' operation, unique, currently unexcluded parts of the parameter space for $\mathcal{O}(100)$ MeV dark-photon masses and $\mathcal{O}(10^{-9}\text{--}10^{-8})$ kinetic mixing can be probed at the CiADS-BDE. Furthermore, considering that there is no need to set up a proton beam specifically for this experiment and that the detector system requires minimal instrumentation, the experiment is supposed to be relatively cost-effective. Therefore, we intend this work to promote studies on the sensitivity reach of the proposed experiment to additional LLP scenarios, and in the end, the realization of the experiment. Incidentally, we study the sensitivity of the same BDE setups at the High Intensity Heavy-ion Accelerator Facility (HIAF), presently under construction near the CiADS program site, and conclude that HIAF-BDE could probe new parameter regions, too.