A search for resonances decaying into a Higgs boson and a new particle $X$ in the $XH\rightarrow qqbb$ final state with the ATLAS detector.

A search for resonances decaying into a Higgs boson ($H$) and a new particle ($X$) is reported, utilizing proton-proton collision data with the ATLAS detector at the CERN Large Hadron Collider. The particle $X$ is assumed to decay to a pair of light quarks, and the fully hadronic final state is analyzed. A two-dimensional phase space of $XH$ mass $vs. X$ mass is scanned for evidence of a signal. Upper limits are set on the production cross-section of the resonance as a function of $XH$ and $X$ masses.