18,223 research outputs found
Status of the Zee-Babu model for neutrino mass and possible tests at a like-sign linear collider
We provide an updated scan of the allowed parameter space of the two-loop
Zee-Babu model for neutrino mass. Taking into account most recent experimental
data on as well as the mixing angle we obtain
lower bounds on the masses of the singly and doubly charged scalars of between
1 to 2 TeV, with some dependence on perturbativity and fine-tuning
requirements. This makes the scalars difficult to observe at LHC with 14 TeV
even with optimistic assumptions on the luminosity, and would require a
multi-TeV linear collider to see the scalar resonances. We point out, however,
that a sub-TeV linear collider in the like-sign mode may be able to observe
lepton flavour violating processes such as due to
contact interactions induced by the doubly charged scalar with masses up to
around 10 TeV. We investigate the possibility to distinguish the Zee-Babu model
from the Higgs triplet model using such processes.Comment: 12 pages, 7 figure
Comment on Reparametrization Invariance of Quark-Lepton Complementarity
We study the complementarity between quark and lepton mixing angles (QLC),
the sum of an angle in quark mixing and the corresponding angle in lepton
mixing is . Experimentally in the standard PDG parametrization, two such
relations exist approximately. These QLC relations are accidental which only
manifest themselves in the PDG parametrization. We propose reparametrization
invariant expressions for the complementarity relations in terms of the
magnitude of the elements in the quark and lepton mixing matrices. In the exact
QLC limit, it is found that and . Expressions with deviations
from exact complementarity are obtained. Implications of these relations are
also discussed.Comment: 5 pages and 1 figure. Implications for recent Daya-Bay neutrino data
on theta_{13} discusse
CP Test in the W Pair Production via Photon Fusion at NLC
We study the possibility to test CP invariance in the production via
photon fusion at NLC. The predictions of the CP violation effects are made
within two Higgs doublet extensions of the minimal standard model, where CP
violation is introduced by a neutral Higgs exchange in s channel in our case.
The width effect in the Higgs propagator on the CP violation effects is studied
in detail. The CP violation effects can be measured in some parameter region of
the extensions.Comment: 11 pages, Tex, UM-P-93/16, OZ-93/6 One figure not include
Comparison of structured observation and pictorial 24Â h recall of household activities to measure the prevalence of handwashing with soap in the community.
This study compared structured observation with a 24Â h pictorial recall of household activities ('sticker diary') to measure the prevalence of handwashing with soap (HWWS) in the community. The study was done within a cluster-randomised trial evaluating a handwashing promotion programme in Bihar, India. HWWS at key occasions in mothers and school children was measured by structured observation in 299 households from 32 villages. Sticker diaries recalling common activities, including personal hygiene, were used to measure HWWS in 299 households from a further 20 villages. Sticker diary HWWS prevalence estimates were about 13% points higher than structured observation estimates, but the differences varied by the type of handwashing occasion. This study confirms structured observation as the method of choice for the study of handwashing behaviours. The sticker diary method may be useful in large-scale surveys. Sticker diaries may overestimate HWWS at important occasions, but probably less so than conventional questionnaire tools
An attractor for dark matter structures
Cosmological simulations of dark matter structures have identified a set of
universal profiles, and similar characteristics have been seen in
non-cosmological simulations. It has therefore been speculated whether these
profiles of collisionless systems relate to accretion and merger history, or if
there is an attractor for the dark matter systems. Here we identify such a
1-dimensional attractor in the 3-dimensional space spanned by the 2 radial
slopes of the density and velocity dispersion, and the velocity anisotropy.
This attractor effectively removes one degree of freedom from the Jeans
equation. It also allows us to speculate on a new fluid interpretation for the
Jeans equation, with an effective polytropic index for the dark matter
particles between 1/2 and 3/4. If this attractor solution holds for other
collisionless structures, then it may hold the key to break the mass-anisotropy
degeneracy, which presently prevents us from measuring the mass profiles in
dwarf galaxies uniquely.Comment: 7 pages, 2 figures, comments welcom
Unitarity boomerangs of quark and lepton mixing matrices
The most popular way to present mixing matrices of quarks (CKM) and leptons
(PMNS) is the parametrization with three mixing angles and one CP-violating
phase. There are two major options in this kind of parametrizations, one is the
original Kobayashi-Maskawa (KM) matrix, and the other is the Chau-Keung (CK)
matrix. In a new proposal by Frampton and He, a unitarity boomerang is
introduced to combine two unitarity triangles, and this new presentation
displays all four independent parameters of the KM parametrization in the quark
sector simultaneously. In this paper, we study the relations between KM and CK
parametrizations, and also consider the quark-lepton complementarity (QLC) in
the KM parametrization. The unitarity boomerang is discussed in the situation
of the CK parametrization for comparison with that in the KM parametrization in
the quark sector. Then we extend the idea of unitarity boomerang to the lepton
sector, and check the corresponding unitarity boomerangs in the two cases of
parametrizations.Comment: 18 latex pages, 4 figures. Version accepted for publication in PL
Systematic search for successful lepton mixing patterns with nonzero theta_13
We perform a systematic search for simple but viable lepton mixing patterns.
Our main criterion is that the mixing matrix can be parameterized by three
rotation angles, which are simple fractions of pi. These simple rotation angles
possess exact expressions for their sines and cosines, and often arise in the
flavor symmetry models. All possible parameterizations of the mixing matrix are
taken into account. In total, twenty successful mixing patterns are found to be
consistent with the latest neutrino oscillation data (including the recent T2K
results) in the CP conserving case, whereas fifteen mixing patterns are allowed
in the maximal CP violating case. Potential radiative corrections to the
constant mixing patterns are also calculated by solving the renormalization
group equations.Comment: 10 pages, 4 figures, 2 tables; version to be published in Nuclear
Physics
Deglacial Tropical Atlantic Subsurface Warming Links Ocean Circulation Variability to the West African Monsoon
Multiple lines of evidence show that cold stadials in the North Atlantic were accompanied by both reductions in Atlantic Meridional Overturning Circulation (AMOC) and collapses of the West African Monsoon (WAM). Although records of terrestrial change identify abrupt WAM variability across the deglaciation, few studies show how ocean temperatures evolved across the deglaciation. To identify the mechanism linking AMOC to the WAM, we generated a new record of subsurface temperature variability over the last 21 kyr based on Mg/Ca ratios in a sub-thermocline dwelling planktonic foraminifera in an Eastern Equatorial Atlantic (EEA) sediment core from the Niger Delta. Our subsurface temperature record shows abrupt subsurface warming during both the Younger Dryas (YD) and Heinrich Event 1. We also conducted a new transient coupled ocean-atmosphere model simulation across the YD that better resolves the western boundary current dynamics and find a strong negative correlation between AMOC strength and EEA subsurface temperatures caused by changes in ocean circulation and rainfall responses that are consistent with the observed WAM change. Our combined proxy and modeling results provide the first evidence that an oceanic teleconnection between AMOC strength and subsurface temperature in the EEA impacted the intensity of the WAM on millennial time scales
Lepton-flavour-violating tau decays from triality
Motivated by flavour symmetry models, we construct theories based on a
low-energy limit featuring lepton flavour triality that have the
flavour-violating decays and as the main phenomenological signatures of physics beyond
the standard model. These decay modes are expected to be probed in the near
future with increased sensitivity by the Belle II experiment at the SuperKEKB
collider. The simple standard model extensions featured have doubly-charged
scalars as the mediators of the above decay processes. The phenomenology of
these extensions is studied here in detail.Comment: 24 pages, 4 figures Additional references and neutrino mass
discussion added. Matches version accepted for publication in Physical Review
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