Semivisible Jets: Dark Matter Undercover at the LHC

Area of Science:

• Particle Physics
• Cosmology
• High Energy Physics

Background:

• Dark matter may be a composite particle accessible through a weakly coupled portal.
• Production at the Large Hadron Collider (LHC) could lead to QCD-like showers of stable invisible dark matter and unstable states decaying to the Standard Model.
• Such semivisible jets, driven by a leptophobic Z' resonance, present a signature with significant missing energy aligned with jets, currently leading to low acceptance in LHC searches.

Purpose of the Study:

• To propose a new search strategy for composite dark matter at the LHC.
• To demonstrate the effectiveness of transverse mass as a discriminator between semivisible jet signals and QCD background.
• To establish the discovery and exclusion reach for Z' masses within a specific parameter space.

Main Methods:

• Simulating QCD-like showers for hidden-sector particles produced at the LHC.
• Analyzing the signature of semivisible jets characterized by missing energy.
• Utilizing the transverse mass, computed from final-state jets and missing energy, as a key observable.
• Assuming Z' coupling to Standard Model quarks similar to Z(0).

Main Results:

• The transverse mass is shown to be a powerful discriminator against QCD background for semivisible jet events.
• The proposed search strategy can discover Z' masses up to 2.5 TeV.
• Exclusion of Z' masses up to 3.5 TeV is possible.

Conclusions:

• A novel search strategy using transverse mass significantly enhances the sensitivity to composite dark matter signals at the LHC.
• The proposed method overcomes limitations of current LHC searches that veto semivisible jet events.
• This approach opens a new avenue for dark matter detection through semivisible jets, with significant reach at future LHC runs.