11 research outputs found
Charged Lepton Flavour Violation and (g-2)_mu in the Littlest Higgs Model with T-Parity: a clear Distinction from Supersymmetry
We calculate the rates for the charged lepton flavour violating decays l_i ->
l_j gamma, tau -> l pi, tau -> l eta, tau -> l eta', mu^- -> e^- e^+ e^-, the
six three body leptonic decays tau^- -> l_i^- l_j^+ l_k^- and the rate for mu-e
conversion in nuclei in the Littlest Higgs model with T-Parity (LHT). We also
calculate the rates for K_{L,S} -> mu e, K_{L,S} -> pi^0 mu e and B_{d,s} ->
l_i l_j. We find that the relative effects of mirror leptons in these
transitions are by many orders of magnitude larger than analogous mirror quark
effects in rare K and B decays analyzed recently. In particular, in order to
suppress the mu -> e gamma and mu^- -> e^- e^+ e^- decay rates and the mu-e
conversion rate below the experimental upper bounds, the relevant mixing matrix
in the mirror lepton sector V_Hl must be rather hierarchical, unless the
spectrum of mirror leptons is quasi-degenerate. We find that the pattern of the
LFV branching ratios in the LHT model differs significantly from the one
encountered in the MSSM, allowing in a transparent manner to distinguish these
two models with the help of LFV processes. We also calculate (g-2)_mu and find
the new contributions to a_mu below 10^{-10} and consequently negligible. We
compare our results with those present in the literature.Comment: 57 pages, 19 figures, 3 tables. Note added on the omitted term in
Z-penguin contribution. For an updated analysis see arXiv:0906.545
FCNC Processes in the Littlest Higgs Model with T-Parity: an Update
We update our 2006-2007 results for FCNC processes in the Littlest Higgs
model with T-parity (LHT). The removal of the logarithmic UV cutoff dependence
in our previous results through a new contribution to the Z^0-penguin diagrams
identified by Goto et al. and del Aguila et al., while making the deviations
from the SM expectations in the quark sector less spectacular, still allows for
sizable new physics effects in K -> pi nu anti-nu and K_L -> pi^0 l^+ l^-
decays and in the CP-asymmetry S_{psi phi} with the latter unaffected by the
new contribution. We extend our analysis by a study of the fine-tuning required
to fit the data on epsilon_K and by the inclusion of the decay K_L -> mu^+
mu^-. A number of correlations can distinguish this model from the custodially
protected Randall-Sundrum model analysed recently. We also reconsider lepton
flavour violating decays, including now a discussion of fine-tuning. While the
l_i -> l_j gamma decays are unaffected by the removal of the logarithmic cutoff
dependence, the branching ratios for decays with three leptons in the final
state, like mu -> 3 e are lowered by almost an order of magnitude. In spite of
this, the pattern of lepton flavour violation in the LHT model can still be
distinguished from the one in supersymmetric models.Comment: 30 pages, 14 figures, 5 tables. Clarifying comments added, matches
published versio
The Impact of Kaluza-Klein Fermions on Standard Model Fermion Couplings in a RS Model with Custodial Protection
We reconsider the impact of heavy vector-like fermions on the couplings of
standard model (SM) quarks to the SM gauge bosons W and Z and to the SM Higgs
boson H. Integrating out these fermions at tree level we derive general
formulae that can be used in any model containing such particles. We apply
these formulae to the case of the lightest Kaluza-Klein (KK) fermions in a
Randall-Sundrum (RS) model with a custodial protection of flavour conserving
and flavour violating couplings. We point out
that in this model also the couplings of and are
protected. In particular we demonstrate explicitly that this protection is not
spoiled by the mixing of the SM quarks with the KK fermions, which is
guaranteed by the underlying P_LR symmetry. We find that the impact of KK
fermions on the Z-couplings, while not negligible, is significantly smaller
than the one coming from the mixing of Z with the heavy KK gauge bosons Z_H and
Z'.The situation is similar for the W couplings with the only exception of the
tb coupling where the impact of KK fermions can in principle be larger than the
effects that are induced by gauge boson mixing. We also show explicitly that at
O(v^2/M_{KK}^2) the fermion-Higgs couplings of a Higgs placed on the infrared
(IR) brane is not affected by the KK contributions up to strongly chirally
suppressed contributions. The corrections to the CKM matrix, in particular the
breakdown of its unitarity, are found to be small. We also investigate the
right-handed couplings of W that are generated through the mixing with
KK-fermions and introduce a 3x3 matrix that describes the pattern of flavour
violation in these new interactions of the standard W.Comment: 40 pages, 8 figures. Comments added, references added, typos
correcte
A Comparative Study of Contributions to in the RS Model
We contrast the impact of Higgs mediated flavor changing neutral currents on
epsilon_K in the framework of a warped extra dimension that was recently
calculated by Azatov et al. with the older results for Kaluza-Klein gluon
induced corrections to that observable. We find that the most stringent
constraint on the KK scale for a Higgs field localized on the infrared brane
for reasonable additional assumptions comes from KK gluon exchange. In the case
of a bulk Higgs field we show that for certain scenarios the Higgs contribution
can in fact exceed the KK gluon contribution. In the course of this analysis we
also describe in detail the different renormalization procedures that have to
be employed in the KK gluon and Higgs cases to relate the new physics at high
energies to low energy observables.Comment: 13 pages, 5 figures. Extended discussion, references added, typos
correcte
FCNC PROCESSES IN THE LITTLEST HIGGS MODEL WITH T-PARITY: AN UPDATE
We update our 2006-2007 results for FCNC processes in the Littlest Higgs model with T-parity (LHT). The removal of the logarithmic UV cutoff dependence in our previous results through a new contribution to the Z(0)-penguin diagrams identified by Goto et al. and del Aguila et al., while making the deviations from the SM expectations in the quark sector less spectacular, still allows for sizable new physics effects in K -> pi nu(nu) over bar and K(L) -> pi(0)l(+)l(-) decays and in the CP-asymmetry S(psi phi) with the latter unaffected by the new contribution. We extend our analysis by a study of the fine-tuning required to fit the data on epsilon(K) and by the inclusion of the decay K(L) -> mu(+)mu(-). A number of correlations can distinguish this model from the custodially protected Randall-Sundrum model analysed recently. We also reconsider lepton flavour violating decays, including now a discussion of fine-tuning. While the l(i) -> l(j)gamma decays are unaffected by the removal of the logarithmic cutoff dependence, the branching ratios for decays with three leptons in the final state, like mu -> 3e are lowered by almost an order of magnitude. In spite of this, the pattern of lepton flavour violation in the LHT model can still be distinguished from the one in supersymmetric models
FCNC Processes in the Littlest Higgs Model with T-Parity: a 2009 Look
We update our 2006-2007 results for FCNC processes in the Littlest Higgs model with T-parity (LHT). The removal of the logarithmic UV cutoff dependence in our previous results through a new contribution to the Z^0-penguin diagrams identified by Goto et al. and del Aguila et al., while making the deviations from the SM expectations in the quark sector less spectacular, still allows for sizable new physics effects in K -> pi nu anti-nu and K_L -> pi^0 l^+ l^- decays and in the CP-asymmetry S_{psi phi} with the latter unaffected by the new contribution. We extend our analysis by a study of the fine-tuning required to fit the data on epsilon_K and by the inclusion of the decay K_L -> mu^+ mu^-. A number of correlations can distinguish this model from the custodially protected Randall-Sundrum model analysed recently. We also reconsider lepton flavour violating decays, including now a discussion of fine-tuning. While the l_i -> l_j gamma decays are unaffected by the removal of the logarithmic cutoff dependence, the branching ratios for decays with three leptons in the final state, like mu -> 3 e are lowered by almost an order of magnitude. In spite of this, the pattern of lepton flavour violation in the LHT model can still be distinguished from the one in supersymmetric models