Search results for "Measurement"
showing 10 items of 2918 documents
ELECTROWEAK THEORY AND THE NEUTRINO-MASS AND NEUTRINO-OSCILLATION QUESTIONS
2007
It is shown that both conjectures of neutrino mass and neutrino oscillation can be made really well-grounded within the Standard Model provided that one adopts a recent new version of the electroweak scheme spontaneously giving also a fundamental explanation for the so-called "maximal parity-violation" effect. A crucial role is played by the prediction of two distinct, scalar and pseudoscalar, replicas of (electron, muon, and tau) lepton numbers that could fully account for an actual non-coincidence between neutrino mass-eigenstates and gauge-eigenstates.
Neutrino masses and mixing in A(4) models with three Higgs doublets
2013
We study neutrino masses and mixing in the context of flavor models with A(4) symmetry, three scalar doublets in the triplet representation, and three lepton families. We show that there is no representation assignment that yields a dimension-5 mass operator consistent with experiment. We then consider a type-I seesaw with three heavy right-handed neutrinos, explaining in detail why it fails, and allowing us to show that agreement with the present neutrino oscillation data can be recovered with the inclusion of dimension-3 heavy neutrino mass terms that break softly the A(4) symmetry.
The Seesaw Scale vs Cosmology
2015
We will study the simplest extension of the Standard Model that can account for neutrino masses: the Type-I seesaw. The model introduces a New Physics scale, M, which is often assumed to be much larger than the electroweak scale. However, it is presently unconstrained and the light neutrino masses and mixing can be generated for any value of M above O(eV). Paying special attention to the contribution of the sterile states to Neff as a function of M, we will show that a large part of the M parameter space (8 orders of magnitude) can be excluded thanks to cosmological measurements. The implications for neutrinoless double beta decay will be discussed too.
Physics at new accelerators: Looking beyond the Standard Model
1993
Abstract Neutrino masses can have important implications in nuclear and particle physics, astrophysics and cosmology. Apart from the effects related to solar neutrinos, neutrino oscillations, dark matter, beta and double beta decays, massive neutrinos can also produce signals in the new accelerators. Here I focus on μ and τ number violating processes, very promising for muon and tau factories, as well as on the signatures associated with spontaneously broken R parity supersymmetry and neutral heavy leptons. These include the possibility of high rates for single chargino and neutralino production at LEP, LHC/SSC, as well as new signatures involving invisibly decaying Higgs bosons.
Neutrino magnetic moments and low-energy solar neutrino-electron scattering experiments
1998
The scattering of solar neutrinos on electrons is sensitive to the neutrino magnetic moments through an interference of electromagnetic and weak amplitudes in the cross section. We show that future low-energy solar neutrino experiments with good angular resolution can be sensitive to the resulting azimuthal asymmetries in event number and should provide useful information on non-standard neutrino properties such as magnetic moments. We compare asymmetries expected at HELLAZ (mainly pp neutrinos) with those at the Kamiokande and Super-Kamiokande experiments (Boron neutrinos), both for the case of Dirac and Majorana neutrinos and discuss the advantages of low energies. Potentially interesting…
Effects of sterile neutrinos on the ultrahigh-energy cosmic neutrino flux
2003
We investigate the effect of sterile neutrinos that are nearly degenerate with active ones on the flux of ultrahigh-energy cosmic ray neutrinos at earth. This offers a way to probe neutrino oscillations in the mass-squared range (10^{-16} eV^2 < ��m^2 < 10^{-11} eV^2) which maybe hard to detect by any other means. Taking into account the present experimental uncertainties of the active-active mixing angles and by allowing any values for the active-sterile mixing angles we find that the ratio of the electron and muon neutrino fluxes may change by -40 % to 70 % in comparison with the ratio in the absence of active-sterile mixing.
On the description of non-unitary neutrino mixing
2015
28 pages.- 8 figures.- typos corrected.- modified bounds on non-unitarity parameters.- new figs 3 and 4
Supernova Bounds on Majoron-emitting decays of light neutrinos
2000
Neutrino masses arising from the spontaneous violation of ungauged lepton-number are accompanied by a physical Goldstone boson, generically called Majoron. In the high-density supernova medium the effects of Majoron-emitting neutrino decays are important even if they are suppressed in vacuo by small neutrino masses and/or small off-diagonal couplings. We reconsider the influence of these decays on the neutrino signal of supernovae in the light of recent Super-Kamiokande data on solar and atmospheric neutrinos. We find that majoron-neutrino coupling constants in the range $3\times 10^{-7}\lsim g\lsim 2\times 10^{-5}$ or $g \gsim 3 \times 10^{-4}$ are excluded by the observation of SN1987A. T…
Nanoscale X-ray detectors based on individual CdS, SnO2 and ZnO nanowires
2021
Abstract The development of nanoscale X-ray sensors is of crucial importance to achieve higher spatial resolution in many X-ray-based techniques playing a key role in materials science, healthcare, and security. Here, we demonstrate X-ray detection using individual CdS, SnO 2 , and ZnO nanowires (NWs). The NWs were produced via vapor–liquid–solid technique and characterized using X-ray diffraction, scanning, and transmission electron microscopy . Electrical measurements were performed under ambient conditions while exposing two-terminal NW-based devices to X-rays generated by a conventional tungsten anode X-ray tube. Fast and stable nanoampere-range X-ray beam induced current (XBIC) in resp…
Observation of Bc+→J/ψD(*)K(*) decays
2017
A search for the decays B + c → J / ψ D ( * ) 0 K + and B + c → J / ψ D ( * ) + K * 0 is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb − 1 . The decays B + c → J / ψ D 0 K + and B + c → J / ψ D * 0 K + are observed for the first time, while first evidence is reported for the B + c → J / ψ D * + K * 0 and B + c → J / ψ D + K * 0 decays. The branching fractions of these decays are determined relative to the B + c → J / ψ π + decay. The B + c mass is measured, using the J / ψ D 0 K + final state, to be 6274.28 ± 1.40 ( stat ) ± 0.32 ( syst ) MeV / c 2 . This is the most precise single measurement of the B + c mass to date.