1,123 research outputs found
Sensitivity to new supersymmetric thresholds through flavour and CP violating physics
Treating the MSSM as an effective theory below a threshold scale Lambda, we
study the consequences of having dimension-five operators in the superpotential
for flavour and CP-violating processes. Below the supersymmetric threshold such
terms generate flavour changing and/or CP-odd effective operators of dimension
six composed from the Standard Model fermions, that have the interesting
property of decoupling linearly with the threshold scale, i.e. as 1/(Lambda
m_soft), where m_soft is the scale of soft supersymmetry breaking. The
assumption of weak-scale supersymmetry, together with the stringent limits on
electric dipole moments and lepton flavour-violating processes, then provides
sensitivity to Lambda as high as 10^7-10^9 GeV. We discuss the varying
sensitivity to these scales within several MSSM benchmark scenarios and also
outline the classes of UV physics which could generate these operators.Comment: 28 pages, 9 figure
Electric dipole and magnetic quadrupole moments of the boson via a CP-violating vertex in effective Lagrangians
The possibility of nonnegligible electric dipole ()
and magnetic quadrupole () moments induced by the most general
vertex is examined via the effective Lagrangian technique. It is assumed
that new heavy fermions induce an anomalous CP-odd component of the
vertex, which can be parametrized by an -invariant
dimension-six operator. This anomalous contribution, when combined with the
standard model CP-even contribution, lead to CP-odd electromagnetic properties
of the boson, which are characterized by the form factors and . It is found that is divergent, whereas is finite,
which reflects the fact that the latter cannot be generated at the one-loop
level in any renormalizable theory. Assuming reasonable values for the unknown
parameters, we found that e-cm,
which is eight orders of magnitude larger than the SM prediction and close to
the upper bound derived from the neutron electric dipole moment. The estimated
size of the somewhat less-studied moment is of the order of
e-cm^2, which is fifteen orders of magnitude above the SM
contribution.Comment: 7 pages, 6 figures, REVTEX styl
A large Muon Electric Dipole Moment from Flavor?
We study the prospects and opportunities of a large muon electric dipole
moment (EDM) of the order (10^{-24} - 10^{-22}) ecm. We investigate how natural
such a value is within the general minimal supersymmetric extension of the
Standard Model with CP violation from lepton flavor violation in view of the
experimental constraints. In models with hybrid gauge-gravity mediated
supersymmetry breaking a large muon EDM is indicative for the structure of
flavor breaking at the Planck scale, and points towards a high messenger scale.Comment: 12 pages, 12 figures. v3: References and Eq 28 fixed; conclusions
unchange
Electric Dipole Moments of Leptons in the Presence of Majorana Neutrinos
We calculate the two-loop diagrams that give a non-zero contribution to the
electric dipole moment d_l of a charged lepton l due to possible Majorana
masses of neutrinos. Using the example with one generation of the Standard
Model leptons and two heavy right-handed neutrinos, we demonstrate that the
non-vanishing result for d_l first appears in order O(m_l m_\nu^2 G_F^2), where
m_\nu is the mass of the light neutrino and the see-saw type relation is
imposed. This effect is beyond the reach of presently planned experiments.Comment: 13 page
The top quark electric dipole moment in an MSSM extension with vector like multiplets
The electric dipole moment (EDM) of the top quark is calculated in a model
with a vector like multiplet which mixes with the third generation in an
extension of the MSSM. Such mixings allow for new CP violating phases.
Including these new CP phases, the EDM of the top in this class of models is
computed. The top EDM arises from loops involving the exchange of the W, the Z
as well as from the exchange involving the charginos, the neutralinos, the
gluino, and the vector like multiplet and their superpartners. The analysis of
the EDM of the top is more complicated than for the light quarks because the
mass of the external fermion, in this case the top quark mass cannot be ignored
relative to the masses inside the loops. A numerical analysis is presented and
it is shown that the top EDM could be close to consistent with
the current limits on the EDM of the electron, the neutron and on atomic EDMs.
A top EDM of size could be accessible in collider experiments
such as the ILC.Comment: 21 pages and 5 figues. Accepted for publication in Physical Review
On Lorentz violation in Horava-Lifshitz type theories
We show that coupling the Standard Model to a Lorentz symmetry violating
sector may co-exist with viable phenomenology, provided that the interaction
between the two is mediated by higher-dimensional operators. In particular, if
the new sector acquires anisotropic scaling behavior above a "Horava-Lifshitz"
energy scale L_HL and couples to the Standard Model through interactions
suppressed by M_P, the transmission of the Lorentz violation into the Standard
Model is protected by the ratio L_HL^2/M_P^2. A wide scale separation,
L_HL<<M_P, can then make Lorentz-violating terms in the Standard Model sector
within experimental bounds without fine-tuning. We first illustrate our point
with a toy example of Lifshitz-type neutral fermion coupled to photon via the
magnetic moment operator, and then implement similar proposal for the
Ho\v{r}ava-Lifshitz gravity coupled to conventional Lorentz-symmetric matter
fields. We find that most radiatively induced Lorentz violation can be
controlled by a large scale separation, but the existence of instantaneously
propagating non-Lifshitz modes in gravity can cause a certain class of diagrams
to remain quadratically divergent above L_HL. Such problematic quadratic
divergence, however, can be removed by extending the action with terms of
higher Lifshitz dimension, resulting in a completely consistent setup that can
cope with the stringent tests of Lorentz invariance.Comment: 24 pages, Main results are very much strengthened in this new
version, where the gauge-choice independence of the main conclusion has been
proven. Furthermore a new extension that could improve the original model,
which completely eliminates the need of fine-tuning, is propose
The Chromoelectric Dipole Moment of the Top Quark in Models with Vector Like Multiplets
The chromoelectric dipole moment of the top quark is calculated in a model
with a vector like multiplet which mixes with the third generation in an
extension of the MSSM. Such mixings allow for new CP violating phases.
Including these new CP phases, the chromoelectric dipole moment that generates
an electric dipole of the top in this class of models is computed. The top
chromoelectric dipole moment operator arises from loops involving the exchange
of the W, the Z as well as from the exchange involving the charginos, the
neutralinos, the gluino, and the vector like multiplet and their superpartners.
The analysis of the chromoelectric dipole moment operator of the top is more
complicated than for the light quarks because the mass of the external fermion,
in this case the top quark mass, cannot be ignored relative to the masses
inside the loops. A numerical analysis is presented and it is shown that the
contribution to the top EDM could lie in the range ( ecm
consistent with the current limits on the EDM of the electron, the neutron and
on atomic EDMs. A top EDM of size ecm could be accessible
in collider experiments such as at the LHC and at the ILC.Comment: 17 pages, 6 figures. Accepted for publication in Phys. Rev.
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