554 research outputs found
Chiral dynamics and B to 3 pi decay
I discuss our knowledge of the scalar sector of QCD and how it impacts the
determination of the CKM angle \alpha from the isospin analysis of B\to \rho\pi
decay.Comment: invited talk at International Workshop on Heavy Quarks and Leptons,
Vietri sul Mare, Salerno, Italy, 27 May - 1 Jun 200
Higgs quartic coupling and neutrino sector evolution in 2UED models
Two compact universal extra dimensional models are an interesting class of
models for different theoretical and phenomenological issues, such as the
justification of having three standard model fermion families, suppression of
proton decay rate, dark matter parity from relics of the 6-dimensional Lorentz
symmetry, origin of masses and mixings in the standard model. However, these
theories are merely effective ones, with typically a reduced range of validity
in their energy scale. We explore two limiting cases of the three standard
model generations all propagating in the bulk or all localised to a brane, from
the point of view of renormalisation group equation evolutions for the Higgs
sector and for the neutrino sector of these models. The recent experimental
results of the Higgs boson from the LHC allow, in some scenarios, stronger
constraints on the cut-off scale to be placed, from the requirement of the
stability of the Higgs potential.Comment: 9 pages, 6 figures, accepted for publication in European Physical
Journal C. arXiv admin note: text overlap with arXiv:1306.485
Large Without the Desert
Even if the unification and supersymmetry breaking scales are around
to TeV, a large coupling may be entirely generated at low
energies through RGE evolution in the 5D MSSM. Independent of the precise
details of supersymmetry breaking, we take advantage of power law running in
five dimensions and a compactification scale in the TeV range to show
how the gluino mass may drive a large enough to achieve the required
GeV Higgs mass. This also allows for sub-TeV stops, possibly observable
at the LHC, and preserving GUT unification, thereby resulting in improved
naturalness properties with respect to the four dimensional MSSM. The results
apply also to models of "split families" in which the first and second
generation matter fields are in the bulk and the third is on the boundary,
which may assist in the generation of light stops whilst satisfying collider
constraints on the first two generations of squarks.Comment: 21 pages, 21 figures. Plots updated to published version, in JHE
Unification of gauge and Yukawa couplings
The unification of gauge and top Yukawa couplings is an attractive feature of
gauge-Higgs unification models in extra-dimensions. This feature is usually
considered difficult to obtain based on simple group theory analyses. We
reconsider a minimal toy model including the renormalisation group running at
one loop. Our results show that the gauge couplings unify asymptotically at
high energies, and that this may result from the presence of an UV fixed point.
The Yukawa coupling in our toy model is enhanced at low energies, showing that
a genuine unification of gauge and Yukawa couplings may be achieved.Comment: 5 pages, 2 figure; new results, extended discussion, conclusions
unchange
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