2,700 research outputs found
Jarlskog-like invariants for theories with scalars and fermions
Within the framework of theories where both scalars and fermions are present,
we develop a systematic prescription for the construction of CP-violating
quantities that are invariant under basis transformations of those matter
fields. In theories with Spontaneous Symmetry Breaking, the analysis involves
the vevs' transformation properties under a scalar basis change, with a
considerable simplification of the study of CP violation in the scalar sector.
These techniques are then applied in detail to the two Higgs-doublet model with
quarks. It is shown that there are new invariants involving scalar-fermion
interactions, besides those already derived in previous analyses for the
fermion-gauge and scalar-gauge sectors.Comment: 12 pages, Latex, no figure
Mass matrices and eigenstates for scalars / pseudoscalars; indirect CP violation, mass hierarchies and symmetry breaking
I study indirect CP violation for neutral kaons, and extend it to large
values of the CP-violating parameter (taken to be real). I show how and at
which condition there can exist a continuous set of basis in which the kinetic
and mass terms in the Lagrangian can be diagonalized simultaneously. An
ambiguity results for the mass spectrum, which then depends on the basis. In
particular, for fixed (positive) (mass)^2 of the CP eigenstates K^0_1, K^0_2,
and for certain ranges of values of the CP-violating parameter, a negative
(mass)^2 can arise in the CP-violating basis. Under certain conditions, even a
small perturbation, by lifting the ambiguity, can strongly alter the pattern of
masses. These investigations extend in a natural way to indirect CP violation
among a set of Higgs-like doublets. The C-odd commutator [K^0, K^0 bar], or its
equivalent for Higgs multiplets, plays an important role. The condition for its
vanishing and its consequences are among the main concerns of this work.Comment: LaTeX2e, 35 pages, 10 postscript figures + 1 log
Triangular Textures for Quark Mass Matrices
The hierarchical quark masses and small mixing angles are shown to lead to a
simple triangular form for the U- and D-type quark mass matrices. In the basis
where one of the matrices is diagonal, each matrix element of the other is, to
a good approximation, the product of a quark mass and a CKM matrix element. The
physical content of a general mass matrix can be easily deciphered in its
triangular form. This parameterization could serve as a useful starting point
for model building. Examples of mass textures are analyzed using this method.Comment: 10 pages, no figure
High overtones of Dirac perturbations of a Schwarzschild black hole
Using the Frobenius method, we find high overtones of the Dirac quasinormal
spectrum for the Schwarzschild black hole. At high overtones, the spacing for
imaginary part of is equidistant and equals to
, ( is the black hole mass), which
is twice less than that for fields of integer spin. At high overtones, the real
part of goes to zero. This supports the suggestion that the
expected correspondence between quasinormal modes and Barbero-Immirzi parameter
in Loop Quantum Gravity is just a numerical coincidence.Comment: 5 pages, Latex, 3 figures, Physical Review D.,at pres
Quark mixings and flavor changing interactions with singlet quarks
Aspects of the quark mixings and flavor changing interactions are
investigated in electroweak models with singlet quarks. The effects on the
ordinary quark mixing are determined in terms of the quark masses and the
parameters describing the mixing between the ordinary quarks q and the singlet
quarks Q (q-Q mixing). Some salient features arise in the flavor changing
interactions through the q-Q mixing. The unitarity of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix within the ordinary quark sector is
violated, and the flavor changing neutral currents (FCNC's) appear both in the
gauge and scalar couplings. The flavor changing interactions are calculated
appropriately in terms of the q-Q mixing parameters and the quark masses, which
really exhibit specific flavor structures. It is found that there are
reasonable ranges of the model parameters to reproduce the ordinary quark mass
hierarchy and the actual CKM structure even in the presence of q-Q mixing. Some
phenomenological effects of the singlet quarks are also discussed. In
particular, the scalar FCNC's may be more important in some cases, if the
singlet quarks as well as the extra scalar particles from the singlet Higgs
fields have masses 100 GeV -- 1 TeV.Comment: 32 pages, 7 figures, added reference
Tree-level FCNC in the B system: from CP asymmetries to rare decays
Tree-level Flavor-Changing Neutral Currents (FCNC) are characteristic of
models with extra vector-like quarks. These new couplings can strongly modify
the B^0 CP asymmetries without conflicting with low--energy constraints. In the
light of a low CP asymmetry in B --> J/\psi K_{S}, we discuss the implications
of these contributions. We find that even these low values can be easily
accommodated in these models. Furthermore, we show that the new data from B
factories tend to favor an O(20) enhancement of the b --> d l \bar{l}
transition over the SM expectation.Comment: 5 pages, 4 figures. Accepted version in PRD. Updated analysis with
the new results from BaBar and BELLE. Figures enlarged, small typos
corrected. Conclusions essentially unchange
Unification and fermion mass relations in low string scale D-brane models
In this talk, gauge coupling evolution is analyzed in D-brane inspired models
with two Higgs doublets and a U(3)xU(2)xU(1)^N gauge symmetry. In particular,
we focus on D-brane configurations with two or three abelian factors. We find
that the correct hypercharge assignment of the Standard Model particles is
reproduced for six viable models distinguished by different brane
configurations. We also investigate the bottom tau quark mass relation and find
that the correct low energy m_b / m_\tau ratio is obtained for equal b-\tau
Yukawa couplings at a string scale around 10^3 TeV.Comment: 10 pages, 3 figures. Talk presented at the ``Corfu Summer
Institute'', Corfu-Greece, September 4-14, 2005. To appear in the proceedings
of RTN workshop on the Quest for Unification Theory Confronts Experimen
Cobertura do solo e frequĂȘncia de espĂ©cies em pastagem nativa apĂłs queima, Pantanal, MS.
bitstream/CPAP/56595/1/CT65.pdfFormato Eletronico
Fundamental CP-violating quantities in a SU(2)U(1) model with many Higgs doublets
We consider a SU(2)U(1) gauge theory with many scalar doublets,
but without fermions. We devise a systematic method of constructing quantities
which are invariant under changes of basis of the scalar fields, but acquire a
minus sign under a general CP transformation. Those quantities provide a
basis-independent way of checking for the existence of CP violation.Comment: (Latex file, 9 pages). CMU-preprin
Feynman Rules in the Type III Natural Flavour-Conserving Two-Higgs Doublet Model
We consider a two Higgs-doublet model with symmetry, which implies a
rather than 0 relative phase between the vacuum expectation
values . The corresponding Feynman rules are derived
accordingly and the transformation of the Higgs fields from the weak to the
mass eigenstates includes not only an angle rotation but also a phase
transformation. In this model, both doublets couple to the same type of
fermions and the flavour-changing neutral currents are naturally suppressed. We
also demonstrate that the Type III natural flavour-conserving model is valid at
tree-level even when an explicit symmetry breaking perturbation is
introduced to get a reasonable CKM matrix. In the special case , as the ratio runs from 0 to ,
the dominant Yukawa coupling will change from the first two generations to the
third generation. In the Feynman rules, we also find that the charged Higgs
currents are explicitly left-right asymmetric. The ratios between the left- and
right-handed currents for the quarks in the same generations are estimated.Comment: 16 pages (figures not included), NCKU-HEP/93-1
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