  The high-energy Diffuse Gamma-Ray Background (DGRB) is expected to be
produced by unresolved isotropically distributed astrophysical objects,
potentially including dark matter annihilation or decay emissions in galactic
or extragalactic structures. The DGRB has only been observed below 1 TeV; above
this energy, upper limits have been reported. Observations or stringent limits
on the DGRB above this energy could have significant multi-messenger
implications, such as constraining the origin of TeV-PeV astrophysical
neutrinos detected by IceCube. The High Altitude Water Cherenkov (HAWC)
Observatory, located in central Mexico at 4100 m above sea level, is sensitive
to gamma rays from a few hundred GeV to several hundred TeV and continuously
observes a wide field-of-view (2 sr). With its high-energy reach and large area
coverage, HAWC is well-suited to notably improve searches for the DGRB at TeV
energies. In this work, strict cuts have been applied to the HAWC dataset to
better isolate gamma-ray air showers from background hadronic showers. The
sensitivity to the DGRB was then verified using 535 days of Crab data and Monte
Carlo simulations, leading to new limits above 10 TeV on the DGRB as well as
prospective implications for multi-messenger studies.
