948 research outputs found
On suppressing the Higgsino-mediated proton decay in SUSY SO(10) GUT's
Using the freedom in SO(10) GUT's one can generalize the existing models
without changing the mass spectrum of fermions to obtain a significant
suppression of proton decay resulting from the baryon number violating
operators of dimension 5. In some limiting cases, their contributions can be
made negligible compared to the dimension 6 operators resulting from the heavy
gauge bosons exchange.Comment: 19 pages, 3 Postscript figures, 2 mpost figures, rearranged plots,
corrected typo
Relation between CKM and MNS Matrices Induced by Bi-Maximal Rotations in the Seesaw Mechanism
It is found that the seesaw mechanism not only explains the smallness of
neutrino masses but also accounts for the large mixing angles simultaneously,
even if the unification of the neutrino Dirac mass matrix with that of up-type
quark sector is realized. In this mechanism, we show that the mixing matrix of
the Dirac-type mass matrix gets extra rotations from the diagonalization of
Majorana mass matrix. Assuming that the mixing angles to diagonalize the
Majorana mass matrix are extremely small, we find that the large mixing angles
of leptonic sector found in atmospheric and long baseline reactor neutrino
oscillation experiments can be explained by these extra rotations. We also find
that provided the mixing angle around y-axis to diagonalize the Majorana mass
matrix vanishes, we can derive the information about the absolute values of
neutrino masses and Majorana mass responsible for the neutrinoless double beta
decay experiment through the data set of neutrino experiments. In the
simplified case that there is no CP phase, we find that the neutrino masses are
decided as and that there are no solution which
satisfy (inverted mass spectrum). Then, including all CP phases,
we reanalyze the absolute values of neutrino masses and Majorana mass
responsible for the neutrinoless double beta decay experiment.Comment: 19 pages, 7 figures, revtex4, to appear in J.PHYS.SOC.JA
Neutrino mixing and CP violation from Dirac-Majorana bimaximal mixture and quark-lepton unification
We demonstrate that only two ansatz can produce the features of the neutrino
mixing angles. The first ansatz comes from the quark-lepton grand unification;
is satisfied for left-handed neutrinos, where
are the Dirac mass eigenstates and are the flavour
eigenstates. The second ansatz comes from the assumption; is satisfied between the Dirac mass eigenstates
and the light Majorana neutrino mass eigenstates , where
is the bimaximal mixing matrix. By these two ansatz, the
Maki-Nakagawa-Sakata matrix is given by . We find that in this model the novel relation is satisfied, where and are
solar and CHOOZ angle respectively. This "Solar-CHOOZ Complementarity" relation
indicates that only if the CHOOZ angle is sizable, the solar
angle can deviate from the maximal mixing. We also infer the CP
violation in neutrino oscillations. The leptonic Dirac CP phase
is predicted as , where are the CKM parameters in Wolfenstein parametrization. Furthermore, we
remark that the ratio of the Jarlskog CP violation factor for quarks and
leptons is important, because the large uncertainty on is cancelled out
in the ratio, .Comment: 9 pages, no figures; v2 references added, v3 references adde
Unity of CP and T Violation in Neutrino Oscillations
In a previous work a simultaneous P- CP[P] and P- T[P] bi-probability plot
was proposed as a useful tool for unified graphical description of CP and T
violation in neutrino oscillation. The ``baseball diamond'' structure of the
plot is understood as a consequence of the approximate CP-CP and the T-CP
relations obeyed by the oscillation probabilities. In this paper, we make a
step forward toward deeper understanding of the unified graphical
representation by showing that these two relations are identical in its
content, suggesting a truly unifying view of CP and T violation in neutrino
oscillations. We suspect that the unity reflects the underlying CPT theorem. We
also present calculation of corrections to the CP-CP and the T-CP relations to
leading order in Delta m^2_{21} / Delta m^2_{31} and s^2_{13}.Comment: 20 references added, version to appear in "Focus Issue on Neutrino
Physics" of New Journal of Physic
Clone flow analysis for a theory inspired Neutrino Experiment planning
The presence of several clone solutions in the simultaneous measurement of
() has been widely discussed in literature. In this letter
we write the analytical formulae of the clones location in the
() plane as a function of the physical input pair
(). We show how the clones move with changing
. The "clone flow" can be significantly different if computed
(naively) from the oscillation probabilities or (exactly) from the
probabilities integrated over the neutrino flux and cross-section.
Using our complete computation we compare the clone flow of a set of possible
future neutrino experiments: the CERN SuperBeam, BetaBeam and Neutrino Factory
proposals. We show that the combination of these specific BetaBeam and
SuperBeam does not help in solving the degeneracies. On the contrary, the
combination of one of them with the Neutrino Factory Golden and Silver channel
can be used, from a theoretical point of view, to solve completely the
eightfold degeneracy.Comment: 23 pages, using epsfi
Scalar Bilepton Dark Matter
In this work we show that 3-3-1 model with right-handed neutrinos has a
natural weakly interacting massive particle (WIMP) dark mater candidate. It is
a complex scalar with mass of order of some hundreds of GeV which carries two
units of lepton number, a scalar bilepton. This makes it a very peculiar WIMP,
very distinct from Supersymmetric or Extra-dimension candidates. Besides,
although we have to make some reasonable assumptions concerning the several
parameters in the model, no fine tunning is required in order to get the
correct dark matter abundance. We also analyze the prospects for WIMP direct
detection by considering recent and projected sensitivities for WIMP-nucleon
elastic cross section from CDMS and XENON Collaborations.Comment: 21 pages, 8 figures, uses iopart.cls, same text as published version
with a small different arrangement of figure
Neutrino Physics at the Turn of the Millenium
Recent solar & atmospheric nu-data strongly indicate need for physics beyond
the Standard Model. I review the ways of reconciling them in terms of 3-nu
oscillations. Though not implied by data, bi-maximal nu-mixing models emerge as
a possibility. SUSY with broken R-parity provides an attractive way to
incorporate it, opening the possibility of testing nu-anomalies at high- energy
colliders such as the LHC or at the upcoming long-baseline or nu- factory
experiments. Reconciling, in addition, the LSND hint requires a fourth, light
sterile neutrino, nus. The simplest are the most symmetric scenarios, in which
2 of the 4 neutrinos are maximally-mixed and lie at the LSND scale, while the
others are at the solar scale. The lightness of nus, the nearly maximal
atmospheric mixing, and the solar/atmospheric splittings all follow naturally
from the assumed lepton-number symmetry and its breaking. These basic schemes
can be distinguished at neutral-current-sensitive solar & atmospheric neutrino
experiments such as SNO. However underground experiments have not yet proven
neutrino masses, as there are many alternatives. For example flavour changing
interactions can play an important role in the explanation of solar and
contained atmospheric data and could be tested e.g through \mu \to e + \gamma,
\mu-e conversion in nuclei, unaccompanied by neutrino-less double beta decay.
Conversely, a short-lived numu might play a role in the explanation of the
atmospheric data. Finally, in the presence of a nus, a long-lived heavy nutau
could delay the time at which the matter and radiation contributions to the
energy density of the Universe become equal, reducing density fluctuations on
smaller scales, thus saving the standard CDM scenario, while the light nue,
numu and nus would explain the solar & atmospheric data.Comment: Invited talk at 2nd International Conference on Non-Accelerator New
Physics (NANP-99), Dubna, June 28 - July 3, 199
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