Minimal Walking Searched @ LHC

September 16, 2012

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The ALTAS collaboration at CERN is searching for the new spin one resonances predicted to exist in the most economical theory of walking technicolor constructed to date. The recent ATLAS paper can be found here.

Minimal Walking Models are a well known class of models put forward in 2004 by Francesco Sannino and Kimmo Tuominen. They suggested here technicolor models with technifermions in higher-dimensional representations of the technicolor gauge group and argued that these more “minimal” models required fewer flavors of technifermions in order to exhibit walking behavior, making it easier to pass precision electroweak tests.
For example, SU(2) and SU(3) gauge theories may exhibit walking with as few as two Dirac flavors of fermions in the adjoint or two-index symmetric representation. In contrast, at least eight flavors of fermions in the fundamental representation of SU(3) (and possibly SU(2) as well) are required to reach the near-conformal regime.
The nonperturbative dynamics of these theories continues to be heavily investigated using various methods, including lattice simulations. The first comprehensive effective Lagrangian for minimal walking models, featuring a light composite Higgs, spin-one states, tree-level unitarity, and consistency with phenomenological constraints was constructed in 2007 by Foadi, Frandsen, Ryttov and Sannino, and can be found here.

Any other effective Lagrangian, also coming from extra dimensions, but describing the same degrees of freedom ad with similar global symmetries will yield predictions similar to Minimal Walking Models. Is it possible then to distinguish different extensions of the standard model with in common a bosonic sector?
We need to discover particle states, like technibaryons, or Nambu-Goldstone excitations predicted by the underlying gauge structure of the new strongly coupled extension of the standard model. In other words from the observation of several new (composite) particle states one can deduce the new fundamental “lego-like” bricks fitting them all.