984 research outputs found
A bottom-up approach to the strong CP problem
The strong CP problem is one of many puzzles in the theoretical description
of elementary particle physics that still lacks an explanation. While top-down
solutions to that problem usually comprise new symmetries or fields or both, we
want to present a rather bottom-up perspective. The main problem seems to be
how to achieve small CP violation in the strong interactions despite large CP
violation in weak interactions. Observation of CP violation is exclusively
through the Higgs--Yukawa interactions. In this paper, we show that with
minimal assumptions on the structure of mass (Yukawa) matrices they do not
contribute to the strong CP problem and thus we can provide a pathway to a
solution of the strong CP problem within the structures of the Standard Model
and no extension at the electroweak scale is needed. However, to address the
flavor puzzle, models based on minimal SU(3) flavor groups leading to the
proposed flavor matrices are favored. Though we refrain from an explicit a UV
completion of the Standard Model, we provide a simple requirement those models
should have to intrinsically not show a strong CP problem.Comment: 12 pages; v2: extended discussion, title changed to be more genera
Testing models with non-minimal Higgs sector through the decay t->q+WZ
We study the contribution of charged Higgs boson to the rare decay of the top
quark t->q+WZ (q=d,s,b) in models with Higgs sector that includes doublets and
triplets. Higgs doublets are needed to couple charged Higgs with quarks,
whereas the Higgs triplets are required to generate the non-standard vertex HWZ
at tree-level. It is found that within a model that respect the custodial SU(2)
symmetry and avoids flavour changing neutral currents by imposing discrete
symmetries, the decay mode t->b+WZ, can reach a branching ratio of order
0.0178, whereas the decay modes t->(d,s)+WZ, can reach a similar branching
ratio in models where flavour changing neutral currents are suppressed by
flavour symmetries.Comment: Typeset using REVTEX and EPSF, 5 pag, 2 figure
New Higgs signals induced by mirror fermion mixing effects
We study the conditions under which flavor violation arises in scalar-fermion
interactions, as a result of the mixing phenomena between the standard model
and exotic fermions. Phenomenological consequences are discussed within the
specific context of a left-right model where these additional fermions have
mirror properties under the new SU(2)_R gauge group.
Bounds on the parameters of the model are obtained from LFV processes; these
results are then used to study the LFV Higgs decays (H --> tau l_j, l_j = e,
mu), which reach branching ratios that could be detected at future colliders.Comment: 12 pages, 2 figures, ReVTex4, graphicx, to be published in Phys. Rev.
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