380 research outputs found

### Up-Down Unification just above the supersymmetric threshold

Large corrections to the quark mass matrices at the supersymmetric threshold
allow the theory to have identical Yukawa matrices in the superpotential. We
demonstrate that Up-Down unification can take place in a moderate quark-squark
alignment scenario with an average squark mass of the order 1 TeV and with
$\tan\beta>15$Comment: 12 pages, latex, two figure

### Minimal Ten-parameter Hermitian Texture Zeroes Mass Matrices and the CKM Matrix

Hermitian mass matrices for the up and down quarks with texture zeroes but
with the minimum number of parameters, ten, are investigated. We show how these
{\em minimum parameter} forms can be obtained from a general set of hermitian
matrices through weak basis transformations. For the most simple forms we show
that one can derive exact and compact parametrizations of the CKM mixing matrix
in terms of the elements of these mass matrices (and the quark masses).Comment: 14 pages.Talk given by M.B. at the MRST 98, ``Towards the Theory of
Everything", Montr\'eal, 13-15 May 199

### Canonical Constraints on Leptonic Cp Violation using UHCR neutrino fluxes

It is shown that one can in principle constrain the CP-violating parameter
delta from measurements of four independant |V_{ij}|^2, or three of them and a
ratio, in the leptonic sector. To quantify our approach, using unitarity, we
derive simple expressions in terms of four independant |V_{ij}|^2 for
cos(delta) and an expression for sin^2(delta) from J^2. Thus, depending on the
values of |V_{ij}| and their accuracy, we can set meaningful limits on |delta|.
To illustrate numerically, if |V_{u1}|^2 is close to 0.1 with a 10% precision,
and if |V_{e3}^2 is larger than 0.005 and for values of |V_{e2}|^2 and
|V_{u3}|^2 that stay within +-0.1 of the current experimental data leads to a
bound pi/2 < |delta| < pi. Alternatively, a certain combination of parameters
with values of |V_{e3}|^2 larger than 0.01 leads to a closed bound of 73 <
|delta| < 103. In general, we find that it is better to use |V_{u1}|^2 or
|V_{t1}|^2 as the fourth independant |V_{ij}|^2 and that over most of the
parameter space, delta is least sensitive to |V_{e3}|^2. With just three
independant measurements (solar, atmospheric and reactor) it is impossible to
set limits on the CP phase. In this respect, we study the use of ultra high
energy cosmic (UHCR) neutrino fluxes as the additional fourth information. We
find that within the SM, neutrino fluxes of all three flavours will be very
similar but that pushing current neutrino data to their extreme values still
allowed, ratios of cosmic neutrino fluxes can differ by up to 20%; such large
discrepancies could imply negligibly small CP-violation. We also study a non
radiative neutrino decay model and find that the neutrino fluxes can differ by
a factor of up to 3 within this model and that an accuracy of 10% on the
neutrino fluxes is sufficient to set interestin limits on delta.Comment: 8 pages, 2 figures, 5 table

### Neutrino Mixing and Leptogenesis in $\mu-\tau$ Symmetry

We study the consequences of the $Z_2$-symmetry behind the $\mu$--$\tau$
universality in neutrino mass matrix. We then implement this symmetry in the
type-I seesaw mechanism and show how it can accommodate all sorts of lepton
mass hierarchies and generate enough lepton asymmetry to interpret the observed
baryon asymmetry in the universe. We also show how a specific form of a
high-scale perturbation is kept when translated via the seesaw into the low
scale domain, where it can accommodate the neutrino mixing data. We finally
present a realization of the high scale perturbed texture through addition of
matter and extra exact symmetries.Comment: 29 pages, 1 figure, 3 tables. Complete re-analysis. Version to appear
in PR

### The limits on CP-odd four-fermion operators containing strange quark field

The bounds on the neutron electric dipole moment and T-odd nucleon-nucleon
interaction are used to extract the limits on the effective CP-odd four-fermion
operators containing strange quark field. This completes the study of the
dim=5,6 CP-odd operators built from the light-quark fields. The limits are very
strong and comparable to those obtained previously for operators containing up
and down flavors. We also analyze the shift of the axionic vacuum,
$\theta_{eff}$, induced by four-fermion operators in the presence of PQ
mechanism and conclude that this gives subleading contributions to CP-odd
observables as compared with the direct ones.Comment: 10 pages. Standard Latex. 1 eps figur

### Pure electroweak mechanism for the electric dipole moment of neutron in the Kobayashi-Maskawa model

The pure electroweak three-loop mechanism for the induced electric and
chromoelectric dipole moments of quarks is studied in the Kobayashi-Maskawa
model with three and four generations. In the standard three generation case,
this mechanism is found to produce a negligible contribution to the electric
dipole moment of neutron. In the presence of the fourth heavy generation,
however, pure electroweak corrections are important and might be several times
larger than the corresponding QCD contribution for the masses of heaviest
quarks $\sim$ 500-600 GeV. The resulting electric dipole moment of neutron
naturally arises at the level of $10^{-29} \,e\cdot cm$. The effects of the
fourth generation physics are parametrized at standard electroweak scale by the
presence of the effective charged right-handed currents.Comment: 6 pages, LATeX file, 4 figures available upon reques

### Constrained MSSM and the electric dipole moment of the neutron

We study the constraints on the CP-violating soft-breaking phases in the
minimal supersymmetric standard model using the limits on the chromoelectric
dipole moment of the strange quark extracted from the neutron EDM experiment.
Our investigation shows that the phase mediated by the gluino exchange diagram
has to be very small, $\phi\leq 8 10^{-4}$, for the common supersymmetric mass
of the order of 100 GeV. Then, solving the renormalization group equations
analytically by iterations, we calculate the electric dipole moment of the
neutron in the MSSM with CP-conserving soft-breaking parameters for the case of
three and four generations. For the three-generation case we resolve the
apparent discrepancies between order-of-magnitude estimates and numerical
calculations existing in the literature. In this case the EDM of the neutron
does not exceed $10^{-32} e cm$. For the four-generation case we show that
there is a significant enhancement which renders the EDM of the neutron at a
measurable level of $10^{-26}e cm$.Comment: 18 pages, LaTex, 2 fig

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