  Armed with a new solution to the four-body problem, we reanalyze the recent
Innsbruck observation of an Efimov resonance in three-body collisions of cesium
atoms, and show that it provides evidence of new, universal four-body physics
as well. Our theoretical treatment of four bosonic atoms in the limit of strong
two-body attraction suggests a ubiquitous result: namely, that resonantly-bound
states of all four atoms should occur whenever the two-body scattering length
is a specific fraction (0.43) of the value where a three-body Efimov resonance
occurs. A hitherto unanalyzed feature in the 2006 Innsbruck experiment supports
this universal prediction, and it provides the first known evidence to date
that a direct four-body recombination process plays a role. While we confirm
the conclusion reached previously by some studies that no true Efimov effect
exists for four particles, we demonstrate the existence of a universal class of
four-body states that are intimately connected with three-body Efimov states.
