186 research outputs found
Radiative neutrino mass generation linked to neutrino mixing and neutrinoless double beta decay predictions
We discuss the connection between the origin of neutrino masses and their mixings which arises in a class of scenarios with radiatively induced neutrino masses. In these scenarios, the neutrino mass matrix acquires textures with two entries close to zero in the basis where the charged-lepton mass matrix is diagonal. This results in specific constraints on the neutrino mixing parameters,which leads to the prediction of (i) a normal ordering of neutrino masses with the lightest neutrino mass in the ∼meV range, and (ii) testable correlations among the various mixing angles, including a non-zero θ13 angle with its exact value correlated with the values of the atmospheric angle θ23 and the CP phase δ. We quantify the impact of deviations from exact zeroes in the mass matrix texture, and connect it to the amount of hierarchy among Yukawa couplings. These scenarios of radiative neutrino mass generation also give rise to new short-range contributions to neutrinoless double beta decay, which dominate over the usual light-neutrino exchange contribution. As a result, this class of models can have a sizable neutrinoless double beta decay rate, in the range of upcoming experiments despite the normal mass ordering of neutrinos
Mass Hierarchy, Mixing, CP-Violation and Higgs Decay---or Why Rotation is Good for Us
The idea of a rank-one rotating mass matrix (R2M2) is reviewed detailing how
it leads to ready explanations both for the fermion mass hierarchy and for the
distinctive mixing patterns between up and down fermion states, which can be
and have been tested against experiment and shown to be fully consistent with
existing data. Further, R2M2 is seen to offer, as by-products: (i) a new
solution of the strong CP problem in QCD by linking the theta-angle there to
the Kobayashi-Maskawa CP-violating phase in the CKM matrix, and (ii) some novel
predictions of possible anomalies in Higgs decay observable in principle at the
LHC. A special effort is made to answer some questions raised.Comment: 47 pages, 9 figure
A Bayesian technique for improving the sensitivity of the atmospheric neutrino L/E analysis
This paper outlines a method for improving the precision of atmospheric
neutrino oscillation measurements. One experimental signature for these
oscillations is an observed deficit in the rate of charged-current
interactions with an oscillatory dependence on , where
is the neutrino propagation distance, and is the neutrino
energy. For contained-vertex atmospheric neutrino interactions, the
resolution varies significantly from event to event. The
precision of the oscillation measurement can be improved by incorporating
information on resolution into the oscillation analysis. In
the analysis presented here, a Bayesian technique is used to estimate the
resolution of observed atmospheric neutrinos on an
event-by-event basis. By separating the events into bins of
resolution in the oscillation analysis, a significant improvement in
oscillation sensitivity can be achieved.Comment: 12 pages, 7 figures, submitted to Nucl. Instrum. Methods A,
accompanies arXiv:1208.2915 [hep-ex
On the Corner Elements of the CKM and PMNS Matrices
Recent experiments show that the top-right corner element () of the
PMNS, like that () of the CKM, matrix is small but nonzero, and suggest
further via unitarity that it is smaller than the bottom-left corner element
(), again as in the CKM case (). An attempt in
explaining these facts would seem an excellent test for any model of the mixing
phenomenon. Here, it is shown that if to the assumption of a universal rank-one
mass matrix, long favoured by phenomenologists, one adds that this matrix
rotates with scale, then it follows that (A) by inputting the mass ratios
, and , (i) the corner elements are
small but nonzero, (ii) , , (iii)
estimates result for the ratios and , and
(B) by inputting further the experimental values of and
, (iv) estimates result for the values of the corner elements
themselves. All the inequalities and estimates obtained are consistent with
present data to within expectation for the approximations made.Comment: 9 pages, 2 figures, updated with new experimental data and more
detail
Performance of the MIND detector at a Neutrino Factory using realistic muon reconstruction
A Neutrino Factory producing an intense beam composed of nu_e(nubar_e) and
nubar_mu(nu_mu) from muon decays has been shown to have the greatest
sensitivity to the two currently unmeasured neutrino mixing parameters,
theta_13 and delta_CP . Using the `wrong-sign muon' signal to measure nu_e to
nu_mu(nubar_e to nubar_mu) oscillations in a 50 ktonne Magnetised Iron Neutrino
Detector (MIND) sensitivity to delta_CP could be maintained down to small
values of theta_13. However, the detector efficiencies used in previous studies
were calculated assuming perfect pattern recognition. In this paper, MIND is
re-assessed taking into account, for the first time, a realistic pattern
recognition for the muon candidate. Reoptimisation of the analysis utilises a
combination of methods, including a multivariate analysis similar to the one
used in MINOS, to maintain high efficiency while suppressing backgrounds,
ensuring that the signal selection efficiency and the background levels are
comparable or better than the ones in previous analyses
Spatial considerations for instructional development in a virtual environment
In this paper we discuss spatial considerations for instructional development in a virtual environment. For both the instructional developer and the student, the important spatial criteria are perspective, orientation, scale, level of visual detail, and granularity of simulation. Developing a representation that allows an instructional developer to specify spatial criteria and enables intelligent agents to reason about a given instructional problem is of paramount importance to the success of instruction delivered in a virtual environment, especially one that supports dynamic exploration or spans more than one scale of operation
Developing the Framed Standard Model
The framed standard model (FSM) suggested earlier, which incorporates the
Higgs field and 3 fermion generations as part of the framed gauge theory
structure, is here developed further to show that it gives both quarks and
leptons hierarchical masses and mixing matrices akin to what is experimentally
observed. Among its many distinguishing features which lead to the above
results are (i) the vacuum is degenerate under a global symmetry which
plays the role of fermion generations, (ii) the fermion mass matrix is
"universal", rank-one and rotates (changes its orientation in generation space)
with changing scale , (iii) the metric in generation space is
scale-dependent too, and in general non-flat, (iv) the theta-angle term in the
QCD action of topological origin gets transformed into the CP-violating phase
of the CKM matrix for quarks, thus offering at the same time a solution to the
strong CP problem.Comment: 53 Page
Three-Neutrino Oscillations of Atmospheric Neutrinos, theta13, Neutrino Mass Hierarchy and Iron Magnetized Detectors
We derive predictions for the Nadir angle (theta_n) dependence of the ratio
Nmu-/Nmu+ of the rates of the mu- and mu+ multi-GeV events, and for the mu- -
mu+ event rate asymmetry, A_{mu-mu+}=[Nmu- - Nmu+]/[Nmu- + Nmu+], in
iron-magnetized calorimeter detectors (MINOS, INO) in the case of 3-neutrino
oscillations of the atmospheric nu_mu and antinu_mu, driven by one neutrino
mass squared difference, |Delta m^2_{31}| >> Delta m^2_{21}. The asymmetry
A_{mu- mu+} (the ratio Nmu-/Nmu+) is shown to be particularly sensitive to the
Earth matter effects in the atmospheric neutrino oscillations, and thus to the
values of sin^2(theta13) and sin^2(theta23), theta13 and theta23 being the
neutrino mixing angles limited by the CHOOZ and Palo Verde experiments and that
responsible for the dominant atmospheric nu_mu -> nu_tau (antinu_mu ->
antinu_tau) oscillations. It is also very sensitive to the type of neutrino
mass spectrum which can be with normal (Delta m^2_{31}>0) or with inverted
(Delta m^2_{31} 0.50, sin^2(2
theta13)>0.06 and Delta m^2_{31}=(2-3) 10^{-3} eV^2, the Earth matter effects
produce a relative difference between the integrated asymmetries barA_{mu- mu+}
and barA^{2nu}_{mu- mu+}$ in the mantle (cos(theta_n)=0.30-0.84) and core
(cos(theta_n)=0.84-1.0) bins, which is bigger in absolute value than ~15%, can
reach the values of (30-35)%, and thus can be sufficiently large to be
observable. The sign of the indicated asymmetry difference is anticorrelated
with the sign of Delta m^2_{31}. An observation of the Earth matter effects in
the Nadir angle distribution of the asymmetry A_{mu- mu+} (ratio Nmu-/Nmu+)
would clearly indicate that sin^2(2 theta13)>0.06 and sin^2(theta23)>0.50, and
would lead to the determination of the sign of Delta m^2_{31}.Comment: 27 pages, 9 figure
Increased Medial Temporal Tau Positron Emission Tomography Uptake in the Absence of Amyloid-β Positivity
IMPORTANCE: An increased tau positron emission tomography (PET) signal in the medial temporal lobe (MTL) has been observed in older individuals in the absence of amyloid-β (Aβ) pathology. Little is known about the longitudinal course of this condition, and its association with Alzheimer disease (AD) remains unclear. OBJECTIVE: To study the pathologic and clinical course of older individuals with PET-evidenced MTL tau deposition (TMTL+) in the absence of Aβ pathology (A-), and the association of this condition with the AD continuum. DESIGN, SETTING, AND PARTICIPANTS: A multicentric, observational, longitudinal cohort study was conducted using pooled data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), Harvard Aging Brain Study (HABS), and the AVID-A05 study, collected between July 2, 2015, and August 23, 2021. Participants in the ADNI, HABS, and AVID-A05 studies (N = 1093) with varying degrees of cognitive performance were deemed eligible if they had available tau PET, Aβ PET, and magnetic resonance imaging scans at baseline. Of these, 128 participants did not meet inclusion criteria based on Aβ PET and tau PET biomarker profiles (A+ TMTL-). EXPOSURES: Tau and Aβ PET, magnetic resonance imaging, cerebrospinal fluid biomarkers, and cognitive assessments. MAIN OUTCOMES AND MEASURES: Cross-sectional and longitudinal measures for tau and Aβ PET, cortical atrophy, cognitive scores, and core AD cerebrospinal fluid biomarkers (Aβ42/40 and tau phosphorylated at threonine 181 p-tau181 available in a subset). RESULTS: Among the 965 individuals included in the study, 503 were women (52.1%) and the mean (SD) age was 73.9 (8.1) years. A total of 51% of A- individuals and 78% of A+ participants had increased tau PET signal in the entorhinal cortex (TMTL+) compared with healthy younger (aged <39 years) controls. Compared with A- TMTL-, A- TMTL+ participants showed statistically significant, albeit moderate, longitudinal (mean [SD], 1.83 [0.84] years) tau PET increases that were largely limited to the temporal lobe, whereas those with A+ TMTL+ showed faster and more cortically widespread tau PET increases. In contrast to participants with A+ TMTL+, those with A- TMTL+ did not show any noticeable Aβ accumulation over follow-up (mean [SD], 2.36 [0.76] years). Complementary cerebrospinal fluid analysis confirmed longitudinal p-tau181 increases in A- TMTL+ in the absence of increased Aβ accumulation. Participants with A- TMTL+ had accelerated MTL atrophy, whereas those with A+ TMTL+ showed accelerated atrophy in widespread temporoparietal brain regions. Increased MTL tau PET uptake in A- individuals was associated with cognitive decline, but at a significantly slower rate compared with A+ TMTL+. CONCLUSIONS AND RELEVANCE: In this study, individuals with A- TMTL+ exhibited progressive tau accumulation and neurodegeneration, but these processes were comparably slow, remained largely restricted to the MTL, were associated with only subtle changes in global cognitive performance, and were not accompanied by detectable accumulation of Aβ biomarkers. These data suggest that individuals with A- TMTL+ are not on a pathologic trajectory toward AD
Testable Deviation from Exact Tribimaximal Mixing
A simple relation U_{MNS}=V_{CKM}^\dagger U_{TB} between the lepton and quark
mixing matrices (U_{MNS} and V_{CKM}) is speculated under an ansatz that
U_{MNS} becomes an exact tribimaximal mixing U_{TB} in a limit V_{CKM}={\bf 1}.
By using the observed CKM mixing parameters, possible values of neutrino
oscillation parameters are estimated: \sin^2 \theta_{13}=0.024-0.028, \sin^2
2\theta_{23}=0.94-0.95 and \tan^2 \theta_{12}=0.24-1.00 depending on phase
conventions of U_{TB}. Those values are testable soon by precision measurements
in neutrino oscillation experiments.Comment: 8 pages, 3 figures, version to appear in Phys.Lett.
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