11,645 research outputs found
CP violation in the lepton sector with Majorana neutrinos
We study CP violation in the lepton sector in extended models with
right-handed neutrinos, without and with left-right symmetry, and with
arbitrary mass terms. We find the conditions which must be satisfied by the
neutrino and charged lepton mass matrices for CP conservation. These
constraints, which are independent of the choice of weak basis, are proven to
be also sufficient in simple cases. This invariant formulation makes apparent
the necessary requirements for CP violation, as well as the size of CP
violating effects. As an example, we show that CP violation can be much larger
in left-right symmetric models than in models with only additional right-handed
neutrinos, {\it i.e.}, without right-handed currents.Comment: 19 page
New vector-scalar contributions to neutrinoless double beta decay and constraints on R-parity violation
We show that in minimal supersymmetric standard model (MSSM) with R-parity
breaking as well as in the left-right symmetric model, there are new observable
contributions to neutrinoless double beta decay arising from hitherto
overlooked diagrams involving the exchange of one W boson and one scalar boson.
In particular, in the case of MSSM, the present experimental bounds on
neutrinoless double beta decay lifetime improves the limits on certain R-parity
violating couplings by about two orders of magnitude. It is shown that similar
diagrams also lead to enhanced rates for conversion in
nuclei, which are in the range accessible to ongoing experiments.Comment: Latex file; 9 pages; 3 figures available on reques
On Neutrino Masses and Family Replication
The old issue of why there are more than one family of quarks and leptons is
reinvestigated with an eye towards the use of anomaly as a tool for
constraining the number of families. It is found that, by assuming the
existence of right-handed neutrinos (which would imply that neutrinos will have
a mass) and a new chiral SU(2) gauge theory, strong constraints on the number
of families can be obtained. In addition, a model, based on that extra SU(2),
is constructed where it is natural to have one "very heavy" fourth neutrino and
three almost degenerate light neutrinos whose masses are all of the Dirac type.Comment: RevTex, 12 pages with 1 figure, minor changes to the text and added
acknowledgment
Decay of polarized muon at rest as a source of polarized neutrino beam
In this paper, we indicate the theoretical possibility of using the decay of
polarized muons at rest as a source of the transversely polarized electron
antineutrino beam. Such a beam can be used to probe new effects beyond standard
model. We mean here new tests concerning CP violation, Lorentz structure and
chirality structure of the charged current weak interactions. The main goal is
to show how the energy and angular distribution of the electron antineutrinos
in the muon rest frame depends on the transverse components of the antineutrino
beam polarization. Our analysis is model-independent and consistent with the
current upper limits on the non-standard couplings. The results are presented
in a limit of infinitesimally small mass for all particles produced in the
decay.Comment: elsart style, 11 pages, 2 eps figures, submitted do publicatio
Analyzing flow anisotropies with excursion sets in relativistic heavy-ion collisions
We show that flow anisotropies in relativistic heavy-ion collisions can be
analyzed using a certain technique of shape analysis of excursion sets recently
proposed by us for CMBR fluctuations to investigate anisotropic expansion
history of the universe. The technique analyzes shapes (sizes) of patches above
(below) certain threshold value for transverse energy/particle number (the
excursion sets) as a function of the azimuthal angle and rapidity. Modeling
flow by imparting extra anisotropic momentum to the momentum distribution of
particles from HIJING, we compare the resulting distributions for excursion
sets at two different azimuthal angles. Angles with maximum difference in the
two distributions identify the event plane, and the magnitude of difference in
the two distributions relates to the magnitude of momentum anisotropy, i.e.
elliptic flow.Comment: 5 pages, 4 figure
Seesaw Right Handed Neutrino as the Sterile Neutrino for LSND
We show that a double seesaw framework for neutrino masses with
exchange symmetry can lead to one of the righthanded seesaw partners of the
light neutrinos being massless. This can play the role of a light sterile
neutrino, giving a model that explains the LSND results. We get a very
economical scheme, which makes it possible to predict the full
neutrino mass matrix if CP is conserved. Once CP violation is included, effect
of the LSND mass range sterile neutrino is to eliminate the lower bound on
neutrinoless double beta decay rate which exists for the three neutrino case
with inverted mass hierarchy. The same strategy can also be used to generate a
natural model for LSND, which is also equally predictive for the CP
conserving case in the limit of exact symmetry.Comment: 13 pages and one figure; model extended to 3+2 cas
Lepton Flavor Violation and the Tau Neutrino Mass
We point out that, in the left-right symmetric model of weak interaction, if
mass is in the keV to MeV range, there is a strong correlation
between rare decays such as and
the mass. In particular, we point out that a large range of
masses are forbidden by the cosmological constraints on
in combination with the present upper limits on these processes.Comment: UMDHEP 94-30, 14 pages, TeX file, (some new references added
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