34,536 research outputs found
New Physics and novel Higgs signals
We review some of the results of our recent work dealing with the novel type
of Higgs signals that arise when one considers extensions of the standard
model.
We discuss first possible deviations on the Higgs couplings due to heavy
particles, in the context of the MSSM and with large extra-dimensions. Then, we
present several models where it is possible to induce flavor violating Higgs
couplings, and probe them at future hadron colliders through the LFV Higgs
decay h-> tau mu or with rare top decays.Comment: Talk given at the X Mexican School of Particles and Fields, Playa del
Carmen, Mexico, 200
Top-Quark FCNC Decay t->cgg in Topcolor-assisted Technicolor Model
The topcolor-assisted technicolor (TC2) model predicts several pseudo-scalars
called top-pions and at loop level they can induce the FCNC top quark decay
t->cgg which is extremely suppressed in the Standard Model (SM). We find that
in the allowed parameter space the TC2 model can greatly enhance such a FCNC
decay and push the branching ratio up to 10^{-3}, which is much larger than the
predictions in the SM (10^{-9}) and in the minimal supersymmetric model
(10^{-4}). We also compare the result with the two-body FCNC decay t-> cg and
find that the branching ratio of t-> cgg is slightly larger than t-> cg. Such
enhanced FCNC top quark decays may serve as a good probe of TC2 model at the
future top quark factory.Comment: 11 pages, 4 figure
Clouds, Gravity, and Metallicity in Blue L Dwarfs: The Case of 2MASS J11263991–5003550
Optical and near-infrared spectroscopy of the newly discovered peculiar L dwarf 2MASS J11263991–5003550 are presented. Folkes et al. classified this source as a high proper motion L9±1 dwarf based on its strong H2O absorption at 1.4 μ m . We find that the optical spectrum of 2MASS J1126–5003 is in fact consistent with that of a normal L4.5 dwarf with notably enhanced FeH absorption at 9896 Å. However, its near-infrared spectrum is unusually blue, with strong H2O and weak CO bands similar in character to several recently identified "blue L dwarfs." Using 2MASS J1126–5003 as a case study, and guided by trends in the condensate cloud models of Burrows et al. and Marley et al., we find that the observed spectral peculiarities of these sources can be adequately explained by the presence of thin and/or large-grained condensate clouds as compared to normal field L dwarfs. Atypical surface gravities or metallicities alone cannot reproduce the observed peculiarities, although they may be partly responsible for the unusual condensate properties. We also rule out unresolved multiplicity as a cause for the spectral peculiarities of 2MASS J1126–5003. Our analysis is supported by examination of Spitzer mid-infrared spectral data from Cushing et al. which show that bluer L dwarfs tend to have weaker 10 μ m absorption, a feature tentatively associated with silicate oxide grains. With their unique spectral properties, blue L dwarfs like 2MASS J1126–5003 should prove useful in studying the formation and properties of condensates and condensate clouds in low-temperature atmospheres
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
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