Session E3: Accelerator-based Dark Sector Searches

Accelerator-based Light Dark Sector Searches

Elucidating the nature of dark matter is one of the central challenges in fundamental physics. While WIMP searches have been driving experimental efforts during the last decades, a growing interest in light (sub-GeV) dark matter has recently emerged. Such possibility could arise naturally if the dark matter is part of a dark sector neutral under all Standard Model forces. This talk will review search strategies for light dark sector at accelerators, discuss recent results from the BABAR and Belle collaborations, and briefly introduce a new proposal, the Light Dark Matter eXperiment.   

Sub-GeV Dark Matter Searches with Neutrino Detectors at Proton Beam Sources

There is overwhelming cosmological evidence that there exists a gravitationally interacting dark matter, yet its microscopic properties remain a mystery. After decades of searching, deep underground detectors have not definitively observed dark matter interactions directly. On the other hand, direct detection experiments do not constrain dark matter models below about a GeV, and there is a rich set of sub-GeV dark matter models can be directly accessed with accelerators. In one class of models, accelerators produce dark matter via new sub-GeV mediators (e.g., dark photons), and then the dark matter is subsequently detected by large neutrino detectors. The MiniBooNE detector, which ran for a decade measuring short baseline neutrino oscillations, was used in the first dedicated sub-GeV dark matter search with a proton beam in 2014 at Fermilab. An 8-GeV proton beam was directed to a steel beam dump to reduce neutrino backgrounds, and the results of this run will be presented. On the same beam, there are new liquid argon time-projection chambers being built for the short baseline neutrino program, and these new detectors offer exciting opportunities for dark matter searches in future beam dump running. The projected sensitivity of these new detectors will also be discussed.   

Searching for dark photons at Jefferson Lab

Dark photons are a proposed new vector force carrier which could interact with the Standard Model via kinetic mixing and decay visibly to lepton pairs or invisibly. The search parameter space for such a particle is described by its mass and coupling strength to the Standard Model. Visible searches look for a bump of excess events in the invariant mass spectrum of reconstructed lepton pairs whereas invisible searches look for evidence of a dark photon in the reconstructed missing mass spectrum. Dark photons could be the leading interaction between the Standard Model and the hidden sector. Jefferson Lab is an ideal search facility for dark photons due to its high intensity electron beam. This talk covers the current status of the ongoing experimental program at Jefferson Lab to search for signatures of dark photons. The following experiments will be discussed: the A Prime Experiment (APEX) in Hall A, the Heavy Photon Search (HPS) in Hall B, the DarkLight Experiment in the Low Energy Recirculator Facility and the proposed Beam Dump Experiment (BDX). Both APEX and HPS have taken data previously and have approved future running. The status and running of DarkLight and the experimental reach of the BDX experiment will be discussed. These experiments contribute to a comprehensive search for evidence of dark photons with masses up to 1~GeV in both the visible and invisible decay hypotheses with a range of couplings to the Standard Model that allow for searches with both short and long-lived dark photons. This talk summarizes the physics and impact of Jefferson Lab experiments.   

The JLab Eta Factory (JEF) experiment at Jefferson Lab

The GlueX spectrometer is a large acceptance spectrometer installed in Hall~D at Jefferson Lab with good coverage for both charged and neutral particles. In particular photons in the forward direction are detected using the Forward Calorimeter, an array of lead glass blocks. The main physics program is to search for evidence for hybrid mesons. The recently-approved JLab Eta Factory (JEF) experiment extends the GlueX physics program to study rare decays of $\eta$ mesons with a particular emphasis on the $\eta\to\pi^0\gamma\gamma$ channel. In addition to probing $\mathcal{O}(p^6)$ terms in chiral perturbation theory, this channel can be used to search for evidence for lepto-phobic dark matter. A potential extension to the Standard Model posits a dark gauge boson ($B$) that couples predominately with quarks and can be observed in the $\eta\to\gamma B$, $B\to\pi^0\gamma$ decay chain. The JEF program also plans to search for C-violating/P-conserving decays of the $\eta$ meson. In order to achieve the requisite resolution to observe these rare channels, this experiment calls for an upgrade to the existing GlueX Forward Calorimeter. After a brief description of the GlueX detector, I will focus on the JEF program with a particular emphasis on the $B$-boson search and I will discuss plans for the future.