Dark matter search in a Beam-Dump eXperiment (BDX) at Jefferson Lab -- 2018 update to PR12-16-001

TL;DR

This paper updates the BDX dark matter search proposal at Jefferson Lab, incorporating background assessments and simulations to demonstrate improved sensitivity and exclusion limits with a proposed 285-day run.

Contribution

It provides a comprehensive update with background validation and optimized analysis strategies for the BDX experiment, enhancing its potential to detect or constrain dark matter.

Findings

Confirmed the experiment's sensitivity improvements with 285 days of data

Validated background suppression and simulation framework

Projected significant exclusion limits in dark matter parameter space

Abstract

This document complements and completes what was submitted last year to PAC45 as an update to the proposal PR12-16-001 "Dark matter search in a Beam-Dump eXperiment (BDX)" at Jefferson Lab submitted to JLab-PAC44 in 2016. Following the suggestions contained in the PAC45 report, in coordination with the lab, we ran a test to assess the beam-related backgrounds and validate the simulation framework used to design the BDX experiment. Using a common Monte Carlo framework for the test and the proposed experiment, we optimized the selection cuts to maximize the reach considering simultaneously the signal, cosmic-ray background (assessed in Catania test with BDX-Proto) and beam-related backgrounds (irreducible NC and CC neutrino interactions as determined by simulation). Our results confirmed what was presented in the original proposal: with 285 days of a parasitic run at 65 $\mu$A (corresponding to $10^{22}$ EOT) the BDX experiment will lower the exclusion limits in the case of no signal by one to two orders of magnitude in the parameter space of dark-matter coupling versus mass.