804 research outputs found
Relating the scalar flavour-changing neutral couplings to the CKM matrix
We build a class of two-Higgs-doublet models in which the flavour-changing
couplings of the neutral scalars are related in an exact way to elements of the
quark mixing matrix. In this framework, we explore the different possibilities
for CP violation and find some interesting scenarios, like a realization of the
superweak idea without CP violation in the -meson system. In another
scenario the neutral scalars can be relatively light, and their contributions
to the -- transitions can alter the standard-model predictions
for CP violation in that system.Comment: 12 pages LATEX, no figure
Classification and Application of Triangular Quark Mass Matrices
The hierarchical structure in the quark masses and mixings allows its ten
physical parameters to be most conveniently encoded in mass matrices of the
upper triangular form. We classify these matrices in the hierarchical, minimal
parameter basis where the mismatch between the weak and mass eigenstates
involves only small mixing angles. Ten such pairs are obtained for the up and
down quarks. This analysis can be used to classify texture zeros of general
mass matrices. For hermitian mass matrices with five texture zeros, this method
yields immediately five pairs of textures with simple, analytic predictions for
the quark mixings. Comparison with data indicates that, of the five pairs,
three are disfavored, one is marginally acceptable, while the fifth fits well.Comment: 18 pages, ReVTe
Quark mixings as a test of a new symmetry of quark Yukawa couplings
Based on the hierarchy exhibited by quarks masses at low energies, we assume
that Yukawa couplings of up and down quarks are related by
at grand unification scales. This ansatz gives rise to a symmetrical CKM matrix
at the grand unification (GU) scale. Using three specific models as
illustrative examples for the evolution down to low energies, we obtain the
entries and asymmetries of the CKM matrix which are in very good agreement with
their measured values. This indicates that the small asymmetry of the CKM
matrix at low energies may be the effect of the renormalization group evolution
only.Comment: LaTeX file, 10 pages including 1 tabl
Desperately Seeking Non-Standard Phases via Direct CP Violation in Process
Attributing the recent CLEO discovery of to originate
(primarily) from the fragmentation of an off-shell gluon () via , , we emphasize that many such states () should
materialize. Indeed the hadronic fragments () of states are closely
related to those seen in . A particular
final state of considerable interest is . Signals from such states
in decays can be combined to provide a very sensitive search for CP
violating phase(s) from non-standard physics. The method should work even if
the contribution of these source(s) to the rates is rather small () to
the point that a comparison between theory and experiment may find it extremely
difficult to reveal the presence of such a new physics.Comment: 16 pages, 5 figure
Two-Nucleon Scattering without partial waves using a momentum space Argonne V18 interaction
We test the operator form of the Fourier transform of the Argonne V18
potential by computing selected scattering observables and all Wolfenstein
parameters for a variety of energies. These are compared to the GW-DAC database
and to partial wave calculations. We represent the interaction and transition
operators as expansions in a spin-momentum basis. In this representation the
Lippmann-Schwinger equation becomes a six channel integral equation in two
variables. Our calculations use different numbers of spin-momentum basis
elements to represent the on- and off-shell transition operators. This is
because different numbers of independent spin-momentum basis elements are
required to expand the on- and off-shell transition operators. The choice of on
and off-shell spin-momentum basis elements is made so that the coefficients of
the on-shell spin-momentum basis vectors are simply related to the
corresponding off-shell coefficients.Comment: 14 pages, 8 Figures, typos correcte
CPT- and B-Violation: The p-pbar Sector
The CPT symmetry of relativistic quantum field theory requires the total
lifetimes of particles and antiparticles be equal. Detection of pbar lifetime
shorter than tau_p > O(10^32) yr would signal breakdown of CPT invariance, in
combination with B-violation. The best current limit on tau_pbar, inferred from
cosmic ray measurements, is about one Myr, placing lower limits on
CPT-violating scales that depend on the exact mechanism. Paths to CPT breakdown
within and outside ordinary quantum mechanics are sketched. Many of the
limiting CPT-violating scales in pbar decay lie within the weak-to-Planck
range.Comment: 6 pages, LaTeX, .sty file included; based on contribution to CPT98
Conference; minor changes, accepted by Mod. Phys. Lett.
Neutrino-Neutrino Scattering and Matter-Enhanced Neutrino Flavor Transformation in Supernovae
We examine matter-enhanced neutrino flavor transformation
() in the region above the neutrino
sphere in Type II supernovae. Our treatment explicitly includes contributions
to the neutrino-propagation Hamiltonian from neutrino-neutrino forward
scattering. A proper inclusion of these contributions shows that they have a
completely negligible effect on the range of - vacuum
mass-squared difference, , and vacuum mixing angle, , or
equivalently , required for enhanced supernova shock re-heating.
When neutrino background effects are included, we find that -process
nucleosynthesis from neutrino-heated supernova ejecta remains a sensitive probe
of the mixing between a light and a with a
cosmologically significant mass. Neutrino-neutrino scattering contributions are
found to have a generally small effect on the
parameter region probed by -process nucleosynthesis. We point out that the
nonlinear effects of the neutrino background extend the range of sensitivity of
-process nucleosynthesis to smaller values of .Comment: 38 pages, tex, DOE/ER/40561-150-INT94-00-6
CP-Violating Observables in Tagged -- Decays
We perform a systematic study of CP-violating observables in \ddbar\ decays.
We show that given a final state, which may be a CP eigenstate or not, all the
observables can in principle be measured if decay-time information is available
and if, for CP non-eigenstates, both decay rates into and are
considered. As an illustration of our analysis we discuss an effective
superweak scenario.Comment: 9 pages LATEX, no figure
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