Search results for "SPEED"

Long-term variability of the Be/X-ray binary EXO 2030+375

1998

We present a multi-wavelength study of the Be/X-ray binary system EXO 2030+375. We report that the Be companion is currently in a low-activity phase as indicated by the notable decrease of the infrared and optical emission. If this trend continues the source will lose its circumstellar envelope. Infrared spectroscopy in the IJHK bands is presented for the first time, along with optical and X-ray observations. These infrared spectra agree with the optical companion being an early-type (B0) main-sequence star. When active EXO 2030+375 shows an X-ray outburst at each periastron passage of the neutron star. In addition to the maximum X-ray luminosity displayed at orbital phase ∼0.0, we find a s…

Rare Z Decays and Neutrino Flavor Universality

2015

We study rare four-body decays of the Z-boson involving at least one neutrino and one charged lepton. Large destructive interferences make these decays very sensitive to the Z couplings to neutrinos. As the identified charged leptons can determine the neutrino flavors, these decays probe the universality of the Z couplings to neutrinos. The rare four-body processes could be accurately measured at future lepton colliders, leading to percent level precision.

Flux limits on ultra high energy neutrinos with AMANDA-B10

2005

Abstract Data taken during 1997 with the AMANDA-B10 detector are searched for a diffuse flux of neutrinos of all flavors with energies above 10 16  eV. At these energies the Earth is opaque to neutrinos, and thus neutrino induced events are concentrated at the horizon. The background are large muon bundles from down-going atmospheric air shower events. No excess events above the background expectation are observed and a neutrino flux following E −2 , with an equal mix of all flavors, is limited to E 2 Φ (10 15  eV  E 18  eV) ⩽ 0.99 × 10 −6  GeV cm −2  s −1  sr −1 at 90% confidence level. This is the most restrictive experimental bound placed by any neutrino detector at these energies. Bound…

Pair production of helicity-flipped neutrinos in supernovae.

1990

The emissivity was calculated for the pair production of helicity-flipped neutrinos, in a way that can be used in supernova calculations. Also presented are simple estimates which show that such process can act as an efficient energy-loss mechanism in the shocked supernova core, and this fact is used to extract neutrino mass limits from SN 1987A neutrino observations.

Observability of the Neutrino Charge Radius

2002

It is shown that the probe-independent charge radius of the neutrino is a physical observable; as such, it may be extracted from experiment, at least in principle. This is accomplished by expressing a set of experimental ${\ensuremath{\nu}}_{\ensuremath{\mu}}\mathrm{\text{\ensuremath{-}}}e$ cross sections in terms of the finite charge radius and two additional gauge- and renormalization-group-invariant quantities, corresponding to the electroweak effective charge and mixing angle.

Resurrection of large lepton number asymmetries from neutrino flavor oscillations

2016

We numerically solve the evolution equations of neutrino three-flavor density matrices, and show that, even if neutrino oscillations mix neutrino flavors, large lepton number asymmetries are still allowed in certain limits by Big Bang Nucleosynthesis (BBN).

A Monochromatic Neutrino Beam to Obtain U(e3) and the CP Phase

2007

The goal for future neutrino facilities is the determination of the [Ue3] mixing and CP violation in neutrino oscillations. This will require precision experiments with a very intense neutrino source. The future experiments such as T2K, NOVA and Double CHOOZ will measure the [Ue3] mixing. In order to explore CP violation, we present a novel method to create a monochromatic neutrino beam based on the recent discovery of nuclei that decay fast through electron capture in a superallowed Gamow-Teller transition. The boost of such radioactive ions will generate an intense monochromatic directional neutrino beam when decaying at high energy in a storage ring with long straight sections. We show t…

Neutrino Spin Oscillations in External Gravitational Fields

2007

Constraints on neutrino speed, weak equivalence principle violation, Lorentz invariance violation, and dual lensing from the first high-energy astrop…

2019

We derive stringent constraints on neutrino speed, weak equivalence principle violation, Lorentz invariance violation, and dual lensing from the first high-energy astrophysical neutrino source: TXS $0506+056$. Observation of neutrino (IceCube-170922A) and photons in a similar time frame and from the same direction is used to derive these limits. We describe ways in which these constraints can be further improved by orders of magnitude.

Neutrinos from the primary proton–proton fusion process in the Sun

2014

International audience; In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun's energy and contributing to the discovery of neutrino oscillations, those from proton-proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrin…