One of the biggest goals of the LHC is to discover the Higgs boson, the only particle in the Standard Model that has not yet been observed. In general, physicists are pretty confident that the Higgs does in fact exist, although they have spent a lot of effort searching for the particle in less powerful accelerators without success. While patiently waiting for the LHC to reach its full energy and a Higgs particle to leave a signature in a detector, some physicists are investigating alternative scenarios. One of the most recent proposals is that the Higgs is not a particle, but an unparticle called the Unhiggs.
The Unhiggs idea was first suggested in a paper published in November 2009 by physicists David Stancato and John Terning of the University of California, Davis. The Unhiggs is not all that different from the Higgs, except that it demonstrates unparticle behavior and, subsequently, does not fit in with the Standard Model. While a particle has discrete parameters, the Unhiggs’ parameters are continuous. In this sense, the Unhiggs is itself a continuum, and can be thought of as a collection of many Higgs bosons, each carrying a fraction of the Unhigg’s total value.
“In particle physics, we are used to dealing with (surprise) particles,” Adam Falkowski, a physicist at Rutgers University, told PhysOrg.com. Falkowski and Manuel Pérez-Victoria of the University of Granada are also investigating the possibility of the Unhiggs. “One property of particles is a well defined mass. For an unstable particle (such as the Higgs boson in the Standard Model), we can experimentally determine the mass by measuring the momenta of its decay products and computing the so-called invariant mass. Particles show as bumps, or resonances, in the invariant mass spectrum or other kinematical distributions.
“Unparticles, on the other hand, do not have a well defined mass; in fact, an unparticle can be thought of as a superposition of an infinite number of particles with different masses. For this reason, unparticles don’t show up as resonances. Instead, they show up as subtle modifications of kinematical distributions measured by experiment, and therefore they can be difficult to spot.” …