31 research outputs found
Higgs mediated lepton flavor violating tau decays and in effective theories
The size of the branching ratios for the and decays induced by a lepton flavor violating Higgs
interaction is studied in the frame of effective field theories.
The best constraint on the vertex, derived from the know
measurement on the muon anomalous magnetic moment, is used to impose the upper
bounds and , which are more stringent than current experimental
limits on this class of transitions.Comment: 6 pages, 3 figure
Decays Z' -> \gamma\gamma\gamma{} and Z -> \gamma\gamma\gamma{} in the minimal 331 model
The possibility of a significant effect of exotic particles on the
Z'->\gamma\gamma\gamma{} and Z->\gamma\gamma\gamma{} decays is investigated in
the context of the minimal 331 model. This model, which is based in the
SU_C(3)xSU_L(3)xU_X(1) gauge group, predicts the existence of many exotic
charged particles that can significantly enhance the decay widths. It is found
that the standard model prediction for the Z->\gamma\gamma\gamma{} decay
remains essentially unchanged, as the new physics effects quickly decouples. On
the other hand, it is found that the contributions of the new exotic quarks and
gauge bosons predicted by this model lead to a branching fraction for the
Z'->\gamma\gamma\gamma{} decay of about 10^(-6), which is about three orders of
magnitude larger than that of the Z->\gamma\gamma\gamma{} decay.Comment: 20 pages and 20 figure
Effective Lagrangian description of Higgs mediated flavor violating electromagnetic transitions: implications on lepton flavor violation
Higgs mediated flavor violating electromagnetic interactions, induced at the
one--loop level by a nondiagonal vertex, with and charged
leptons or quarks, are studied within the context of a completely general
effective Yukawa sector that comprises --invariant
operators of up to dimension--six. Exact formulae for the one--loop and couplings are presented and their related
processes used to study the phenomena of Higgs mediated lepton flavor
violation. The experimental limit on the decay is used to
derive a bound on the branching ratio of the
transition, which is 6 orders of magnitude stronger than the current
experimental limit. Previous results on the and decays are reproduced. The possibility of detecting signals
of lepton flavor violation at colliders is explored through the
reaction, putting special emphasis on the
final state. Using the bound imposed on the vertex by the current
experimental data on the muon anomalous magnetic moment, it is found that about
half a hundred events may be produced in the International Linear Collider.Comment: 18 pages, 12 figure
Bilepton effects on the WWV^* vertex in the 331 model with right-handed neutrinos via a SU_L(2)XU_Y(1) covariant quantization scheme
In a recent paper, we investigated the effects of the massive charged gauge
bosons (bileptons) predicted by the minimal 331 model on the off-shell vertex
WWV^* (V=gamma, Z) using a SU_L(2) X U_Y(1) covariant gauge-fixing term for the
bileptons. We proceed along the same lines and calculate the effects of the
gauge bosons predicted by the 331 model with right-handed neutrinos. It is
found that the bilepton effects on the WWV^* vertex are of the same order of
magnitude than those arising from the SM and several of its extensions,
provided that the bilepton mass is of the order of a few hundred of GeVs. For
heavier bileptons, their effects on the WWV^* vertex are negligible. The
behavior of the form factors at high energies is also discussed as it is a
reflect of the gauge invariance and gauge independence of the WWV^* Green
function obtained via our quantization method.Comment: Replaced to match published versio
Study of the lepton flavor-violating decay
The lepton flavor violating decay is studied in the
context of several extended models that predict the existence of the new gauge
boson named . A calculation of the strength of the lepton flavor
violating coupling is presented by using the most general
renormalizable Lagrangian that includes lepton flavor violation. We used the
experimental value of the muon magnetic dipole moment to bound this coupling,
from which the parameter
is constrained and it is found that
for a
boson mass of 2 TeV. Alongside, we employed the experimental
restrictions over the and processes
in the context of several models that predict the existence of the
gauge boson to bound the mentioned coupling. The most restrictive bounds come
from the calculation of the three-body decay. For this case, it was found that
the most restrictive result is provided by a vector-like coupling, denoted as
, for the case, finding around for a
boson mass of 2 TeV. We used this information to estimate the
branching ratio for the decay. According to the analyzed
models the least optimistic result is provided by the Sequential model,
which is of the order of for a boson mass around 2 TeV.Comment: Revised versio
Higgs mediated Double Flavor Violating top decays in Effective Theories
The possibility of detecting double flavor violating top quark transitions at
future colliders is explored in a model-independent manner using the effective
Lagrangian approach through the () decays. A
Yukawa sector that contemplates invariants of up to
dimension six is proposed and used to derive the most general flavor violating
and CP violating and vertices of renormalizable type.
Low-energy data, on high precision measurements, and experimental limits are
used to constraint the and vertices and then used to
predict the branching ratios for the decays. It is found
that this branching ratios may be of the order of , for a
relative light Higgs boson with mass lower than , which could be more
important than those typical values found in theories beyond the standard model
for the rare top quark decays () or . %% LHC experiments, by using a total integrated luminosity of of data, will be able to rule out, at 95% C.L., DFV top quark
decays up to a Higgs mass of 155 GeV/ or discover such a process up to a
Higgs mass of 147 GeV/.Comment: 24 pages, 11 figure