6 research outputs found
Stuckelberg Axions and the Effective Action of Anomalous Abelian Models 1. A unitarity analysis of the Higgs-axion mixing
We analyze the quantum consistency of anomalous abelian models and of their
effective field theories, rendered anomaly-free by a Wess-Zumino term, in the
case of multiple abelian symmetries. These models involve the combined
Higgs-Stuckelberg mechanism and predict a pseudoscalar axion-like field that
mixes with the goldstones of the ordinary Higgs sector. We focus our study on
the issue of unitarity of these models both before and after spontaneous
symmetry breaking and detail the set of Ward identities and the organization of
the loop expansion in the effective theory. The analysis is performed on simple
models where we show, in general, the emergence of new effective vertices
determined by certain anomalous interactions.Comment: 67 pages, 26 figures, replaced with revised final version, to appear
on JHE
Windows over a New Low Energy Axion
We outline some general features of possible extensions of the Standard Model
that include anomalous U(1) gauge symmetries, a certain number of axions and
their mixings with the CP-odd Higgs sector. As previously shown, after the
mixing one of the axions becomes a physical pseudoscalar (the axi-Higgs) that
can take the role of a modified QCD axion. It can be driven to be very light by
the same non-perturbative effects that are held responsible for the solution of
the strong CP-problem. At the same time the axi-Higgs has a sizeable gauge
interaction, which is not allowed to the Peccei-Quinn axion, possibly
explaining the PVLAS results. We point out that the Wess-Zumino term, typical
of these models, can be both interpreted as an anomaly inflow from higher
dimensional theories (second window) but also as a result of partial decoupling
of an extra Higgs sector (and of a fermion) that leaves behind an effective
anomalous abelian theory (first window) in a broken St\"{u}ckelberg phase. The
possibility that the axi-Higgs can be heavy, of the order of the Higgs mass or
larger, however, can't be excluded. The potentialities for the discovery of
this particle and of anomaly effects in the neutral current sector at the LHC
are briefly discussed in the context of a superstring inspired model (second
window), but with results that remain valid also if any of the two
possibilities is realized in Nature.Comment: 17 pages, 8 Figs, replaced with revised final version, to appear on
Phys.Lett.
Finite Temperature Schwinger Model with Chirality Breaking Boundary Conditions
The -flavour Schwinger Model on a finite space and
subject to bag-type boundary-conditions at und is solved at
finite temperature . The boundary conditions depend on a real
parameter and break the axial flavour symmetry. We argue that this
approach is more appropriate to study the broken phases than introducing small
quark masses, since all calculations can be performed analytically. In the
imaginary time formalism we determine the thermal correlators for the
fermion-fields and the determinant of the Dirac-operator in arbitrary
background gauge-fields. We show that the boundary conditions induce a CP-odd
-term in the effective action. The chiral condensate, and in particular
its T- and L- dependence, is calculated for fermions. It is seen to
depend on the order in which the two lengths and are sent to
infinity.Comment: One reference added plus one corrected, final version as to be
published in Annals of Physic