The hunt for unparticles is on. ‘When the Large Hadron Collider turns on next year, most physicists will be scouring the high-energy data for new particles such as the Higgs boson. Not Howard Georgi of Harvard University in the US, though – he says he is on the look out for a new type of “stuff” altogether called “unparticles”. If it exists, it would mean that our Standard Model of particle physics is not the whole story, and that things other than particles fill the universe (Phys. Rev. Lett. 98 221601).
Unparticles would have properties in common with neutrinos, which have almost zero mass and are therefore nearly scale invariant. Neutrinos barely interact with matter – most of the time physicists can only infer their presence by calculating the “missing” energy and momentum after an interaction. By looking at the same interaction many times, a probability distribution is built up that tells more specifically how many and what sort of neutrinos are involved.
Georgi thinks that a similar technique could be used to search for evidence of unparticles. According to scale invariance, a distribution containing unparticles would become apparent because, oddly, it would look like a distribution for a fractional number of massless particles.’
See also: Professor proposes theory of unparticle physics. ‘Howard Georgi, a physicist at Harvard University, has recently published a paper on so-called unparticle physics, which suggests the existence of “unparticle stuff” that cannot be accounted for by the standard model. Appearing in a recent edition of Physical Review Letters, the paper says that unparticle stuff would be very different than anything seen before.’