647 research outputs found
Observing Nucleon Decay in Lead Perchlorate
Lead perchlorate, part of the OMNIS supernova neutrino detector, contains two
nuclei, 208Pb and 35Cl, that might be used to study nucleon decay. Both would
produce signatures that will make them especially useful for studying
less-well-studied neutron decay modes, e.g., those in which only neutrinos are
emitted.Comment: 6 pages, 2 figure
High scale mixing unification and large neutrino mixing angles
Starting with the hypothesis that quark and lepton mixings are identical at
or near the GUT scale, we show that the large solar and atmospheric neutrino
mixing angles together with the small reactor angle can be understood
purely as a result of renormalization group evolution. The only requirements
are that the three neutrinos must be quasi degenerate in mass and have same CP
parity. It predicts that the common Majorana mass for the neutrinos must be
larger than 0.1 eV making the idea testable in the currently planned or ongoing
experiments searching for neutrinoless-double-beta decay.Comment: 10 pages, eight figure, two tables; new material added; results
remain unchange
The little flavons
Fermion masses and mixing matrices can be described in terms of spontaneously
broken (global or gauge) flavor symmetries. We propose a little-Higgs inspired
scenario in which an SU(2)xU(1) gauge flavor symmetry is spontaneously (and
completely) broken by the vacuum of the dynamically induced potential for two
scalar doublets (the flavons) which are pseudo-Goldstone bosons remaining after
the spontaneous breaking--at a scale between 10 and 100 TeV--of an approximate
SU(6) global symmetry. The vacuum expectation values of the flavons give rise
to the texture in the fermion mass matrices. We discuss in detail the case of
leptons. Light-neutrino masses arise by means of a see-saw-like mechanism that
takes place at the same scale at which the SU(6) global symmetry is broken. We
show that without any fine tuning of the parameters the experimental values of
the charged-lepton masses,the neutrino square mass differences and the
Pontecorvo-Maki-Nakagawa-Sakata mixing matrix are reproduced.Comment: 13 pages, revTeX4. Version to be published in PR
What can we learn from neutrinoless double beta decay experiments?
We assess how well next generation neutrinoless double beta decay and normal
neutrino beta decay experiments can answer four fundamental questions. 1) If
neutrinoless double beta decay searches do not detect a signal, and if the
spectrum is known to be inverted hierarchy, can we conclude that neutrinos are
Dirac particles? 2) If neutrinoless double beta decay searches are negative and
a next generation ordinary beta decay experiment detects the neutrino mass
scale, can we conclude that neutrinos are Dirac particles? 3) If neutrinoless
double beta decay is observed with a large neutrino mass element, what is the
total mass in neutrinos? 4) If neutrinoless double beta decay is observed but
next generation beta decay searches for a neutrino mass only set a mass upper
limit, can we establish whether the mass hierarchy is normal or inverted? We
base our answers on the expected performance of next generation neutrinoless
double beta decay experiments and on simulations of the accuracy of
calculations of nuclear matrix elements.Comment: Added reference
Lepton flavor violating signals of a little Higgs model at the high energy linear colliders
Littlest Higgs model predicts the existence of the doubly charged
scalars , which generally have large flavor changing couplings
to leptons. We calculate the contributions of to the lepton
flavor violating processes and , and compare our numerical results with the current
experimental upper limits on these processes. We find that some of these
processes can give severe constraints on the coupling constant and the
mass parameter . Taking into account the constraints on these free
parameters, we further discuss the possible lepton flavor violating signals of
at the high energy linear collider
experiments. Our numerical results show that the possible signals of
might be detected via the subprocesses in the future experiments.Comment: 16 pages, 7 figures. Discussions and references added, typos
correcte
Q ball inflation
We show that inflation can occur in the core of a Q-ball.Comment: 11 pages, latex2e, no figure, references added, final version to
appear in PR
Fermion Masses and Mixings in the Little Flavon Model
We present a complete analysis of the fermion masses and mixing matrices in
the framework of the little flavon model. In this model textures are generated
by coupling the fermions to scalar fields, the little flavons, that are
pseudo-Goldstone bosons of the breaking of a global SU(6) symmetry. The Yukawa
couplings arise from the vacuum expectation values of the flavon fields, their
sizes controlled by a potential a la Coleman-Weinberg. Quark and lepton mass
hierarchies and mixing angles are accomodated within the effective approach in
a natural manner.Comment: 11 pages, RevTeX4, version to appear on Phys. Rev.
Neutrinoless double-beta decay and effective field theory
We analyze neutrinoless double -decay (\nbb-decay) mediated by heavy
particles from the standpoint of effective field theory. We show how symmetries
of the \nbb-decay quark operators arising in a given particle physics model
determine the form of the corresponding effective, hadronic operators. We
classify the latter according to their symmetry transformation properties as
well as the order at which they appear in a derivative expansion. We apply this
framework to several particle physics models, including R-parity violating
supersymmetry (RPV SUSY) and the left-right symmetric model (LRSM) with mixing
and a right-handed Majorana neutrino. We show that, in general, the pion
exchange contributions to \nbb-decay dominate over the short-range
four-nucleon operators. This confirms previously published RPV SUSY results and
allows us to derive new constraints on the masses in the LRSM. In particular,
we show how a non-zero mixing angle in the left-right symmetry model
produces a new potentially dominant contribution to \nbb-decay that
substantially modifies previous limits on the masses of the right-handed
neutrino and boson stemming from constraints from \nbb-decay and vacuum
stability requirements.Comment: 37 pages. Accepted for publication in PR
Additional Nucleon Current Contributions to Neutrinoless Double Beta Decay
We have examined the importance of momentum dependent induced nucleon
currents such as weak-magnetism and pseudoscalar couplings to the amplitude of
neutrinoless double beta decay in the mechanisms of light and heavy Majorana
neutrino as well as in that of Majoron emission. Such effects are expected to
occur in all nuclear models in the direction of reducing the light neutrino
matrix elements by about 30%. To test this we have performed a calculation of
the nuclear matrix elements of the experimentally interesting nuclei A = 76,
82, 96, 100, 116, 128, 130, 136 and 150 within the pn-RQRPA. We have found that
indeed such corrections vary somewhat from nucleus to nucleus, but in all cases
they are greater than 25 percent. In the case of heavy neutrino the effect is
much larger (a factor of 3). Combining out results with the best presently
available experimental limits on the half-life of the neutrinoless double beta
decay we have extracted new limits on the effective neutrino mass (light and
heavy) and the effective Majoron coupling constant.Comment: 31 pages, RevTex, 3 Postscript figures, submitted to Phys. Rev.
Recent advances in neutrinoless double beta decay search
Even after the discovery of neutrino flavour oscillations, based on data from
atmospheric, solar, reactor, and accelerator experiments, many characteristics
of the neutrino remain unknown. Only the neutrino square-mass differences and
the mixing angle values have been estimated, while the value of each mass
eigenstate still hasn't. Its nature (massive Majorana or Dirac particle) is
still escaping. Neutrinoless double beta decay (-DBD) experimental
discovery could be the ultimate answer to some delicate questions of elementary
particle and nuclear physics. The Majorana description of neutrinos allows the
-DBD process, and consequently either a mass value could be measured or
the existence of physics beyond the standard should be confirmed without any
doubt. As expected, the -DBD measurement is a very difficult field of
application for experimentalists. In this paper, after a short summary of the
latest results in neutrino physics, the experimental status, the R&D projects,
and perspectives in -DBD sector are reviewed.Comment: 36 pages, 7 figures, To be publish in Czech Journal of Physic
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