Unparticle Self-Interactions and Their Collider Implications

In unparticle physics, operators of the conformal sector have self-interactions, and these are unsuppressed for strong coupling. The 3-point interactions are completely determined by conformal symmetry, up to a constant. We do not know of any theoretical upper bounds on this constant. Imposing current experimental constraints, we find that these interactions mediate spectacular collider signals, such as $pp -> U -> UU -> \gamma \gamma \gamma \gamma$,$\gamma \gamma ZZ$,$ZZZZ$,$\gamma \gamma l^+ l^-$,$ZZ l^+ l^-$,and$4l$, with cross sections of picobarns or larger at the Large Hadron Collider. Self-interactions may therefore provide the leading discovery prospects for unparticle physics.