Georgi, Howard2009-05-202007Georgi, Howard. 2007. Unparticle physics. Physical Review Letters 98, no. 22: 221601.0031-9007http://nrs.harvard.edu/urn-3:HUL.InstRepos:2961663I discuss some simple aspects of the low-energy physics of a nontrivial scale invariant sector of an effective field theory—physics that cannot be described in terms of particles. I argue that it is important to take seriously the possibility that the unparticle stuff described by such a theory might actually exist in our world. I suggest a scenario in which some details of the production of unparticle stuff can be calculated. I find that in the appropriate low-energy limit, unparticle stuff with scale dimension d_{[script U]} looks like a nonintegral number d_{[script U]} of invisible particles. Thus dramatic evidence for a nontrivial scale invariant sector could show up experimentally in missing energy distributions.en-US10.1103/PhysRevLett.98.221601