246 research outputs found
Little Higgs Models and Electroweak Measurements
Using effective field theory approach, we study the constraints from
electroweak data on the SU(5)/SO(5), SU(6)/SP(6), SU(3)xU(1) little Higgs
models and their variations. We construct an effective theory valid above the
electroweak symmetry breaking scale in these models that includes dimension-six
operators induced by integrating out heavy fields. We calculate the constraints
on the models using the results of hep-ph/0412166, where bounds on arbitrary
linear combinations of flavor and CP conserving dimension-six operators are
given. We present the constraints in terms of the bounds on the masses of heavy
fermions and heavy gauge bosons. The constraints are often stringent, but in
some regions of the parameter space the constraints are mild enough and do not
imply significant fine-tuning.Comment: Small changes to the plots due to the change in numerical results in
hep-ph/0412166, text unchange
Duality in Sp and SO Gauge Groups from M Theory
We describe fivebrane configurations in M theory whose 4-d spacetime contains
N=1 supersymmetric Sp or SO gauge fields and fundamentals of these groups. We
show how field-theory dualities for Sp and SO groups can be derived using these
fivebrane configurations in M theory.Comment: 12 pages, LaTeX, four embedded figure
Disguising the Oblique Parameters
We point out a set of operator identities that relate the operators
corresponding to the oblique corrections to operators that modify fermion
couplings to the gauge bosons as well as operators that modify triple gauge
boson couplings. Such identities are simple consequences of the equations of
motion. Therefore the contributions from new physics to the oblique parameters
can be disguised as modifications of triple gauge boson couplings provided the
fermion couplings to the gauge bosons are suitably modified by higher
dimensional operators. Since the experimental constraints on triple gauge boson
couplings are much weaker than the constraints on the oblique parameters this
observation allows extra room for model building. We derive operator relations
in effective theories of the Standard Model with the electroweak symmetry
either linearly or nonlinearly realized and discuss applications of our
results.Comment: 12 pages. v2: two references adde
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