Search results for "Speed"
showing 10 items of 876 documents
Hunt for θ13with LENA
2012
In a hunt for by far missing neutrino mixing angle ?13 the accelerator experiments have recently indicated non-zero value and the dedicated reactor neutrino experiments are moving towards the data-taking phase to confirm that. The small effect of ?13 to the neutrino oscillation probabilities can be also complementarily probed using artificially made source of mono-chromatic neutrinos with low energies originated from electron capture processes. Due to the small energy of neutrino and tiny interaction cross section, and the expected scale of ?13 support the use of large liquid scintillation detector. In this work, the estimated sensitivities for measurement of mixing angle ?13 is presented i…
Testing the Standard Model and beyond with the LENA proposal
2014
We discuss the possibility of a precision measurement of the electroweak mixing angle and a probe for new physics in the leptonic process of neutrino electron scattering. In the new physics schemes we explore the case of non standard neutrino interactions (NSI). The LENA proposal, currently under discussion, considers a large detector and the use of an articial, 51 Cr, radioactive neutrino source with of 5 MCi intensity. We also discuss the possible use of the solar neutrino
An experimental study of double-to-single-loop transition in stirred vessels
1999
The velocity characteristics of the flows in a fully baffled vessel of diameter T = 290 mm stirred by a Rushton impeller of diameter D = T/3 were investigated by means of laser-Doppler anemometry measurements. The effects of clearance and rotational speed on the flow patterns in the vessel were studied. It was found that at impeller clearances from the bottom of the vessel (C) around 0.2 T the characteristic double-loop flow pattern undergoes a transition to a single-loop one with the impeller stream direction becoming partly axial and being inclined at around 25 to 30° to the horizontal. The impeller stream inclination varied with radial distance from the impeller, as well as with angular …
Generation of radiative knots in a randomly pulsed protostellar jet
2009
HH objects are characterized by a complex knotty morphology detected mainly along the axis of protostellar jets in a wide range of bands. Evidence of interactions between knots formed in different epochs have been found, suggesting that jets may result from the ejection of plasma blobs from the source. We aim at investigating the physical mechanism leading to the irregular knotty structure observed in jets in different bands and the complex interactions occurring among blobs of plasma ejected from the stellar source. We perform 2D axisymmetric HD simulations of a randomly ejected pulsed jet. The jet consists of a train of blobs which ram with supersonic speed into the ambient medium. The in…
The X-ray emission mechanism in the protostellar jet HH 154
2004
We study the mechanism causing the X-ray emission recently detected in protostellar jets, by performing a detailed modeling of the interaction between a supersonic jet originating from a young stellar object and the ambient medium, for various values of density contrast, ν, between the ambient density and the jet, and of Mach number, M; radiative losses and thermal conduction have been taken into account. Here we report a representative case which reproduces, without any ad hoc assumption, the characteristics of the X-ray emission recently observed in the protostellar jet HH 154. We find that the X-ray emission originates from a localized blob, consistent with observations, which moves with…
X-rays from protostellar jets: emission from continuous flows
2006
Recently X-ray emission from protostellar jets has been detected with both XMM-Newton and Chandra satellites, but the physical mechanism which can give rise to this emission is still unclear. We performed an extensive exploration of a wide space of the main parameters influencing the jet/ambient interaction. Aims include: 1) to constrain the jet/ambient interaction regimes leading to the X-ray emission observed in Herbig-Haro objects in terms of the emission by a shock forming at the interaction front between a continuous supersonic jet and the surrounding medium; 2) to derive detailed predictions to be compared with optical and X-ray observations of protostellar jets; 3) to get insight int…
On the Origin of the X-Ray Emission in Protostellar Jets Close to the Launching Site
2019
Observations of stellar jets show evidence of X-ray emitting shocks close to the launching site. In some cases, the shocked features appear to be stationary (e.g. HH 154 and DG Tau). We aim at investigating the origin of X-ray emission and the effect of perturbations in X-ray emitting stationary shocks in stellar jets. We performed a set of 2.5-dimensional MHD numerical simulations modelling supersonic pulsed jets ramming into a magnetized medium, exploring different parameters for the model. We consider two cases: a jet less dense than the ambient medium (HH 154), and a jet denser than the ambient (DG Tau). In both cases, we found that the jet is collimated by the magnetic field forming a …
Test of relativistic time dilation with fast optical atomic clocks at different velocities
2007
Time dilation is one of the most fascinating aspects of special relativity as it abolishes the notion of absolute time. It was first observed experimentally by Ives and Stilwell in 1938 using the Doppler effect. Here we report on a method, based on fast optical atomic clocks with large, but different Lorentz boosts, that tests relativistic time dilation with unprecedented precision. The approach combines ion storage and cooling with optical frequency counting using a frequency comb. 7Li+ ions are prepared at 6.4% and 3.0% of the speed of light in a storage ring, and their time is read with an accuracy of 2×10−10 using laser saturation spectroscopy. The comparison of the Doppler shifts yield…
Test of Time Dilation Using StoredLi+Ions as Clocks at Relativistic Speed
2014
We present the concluding result from an Ives-Stilwell-type time dilation experiment using 7Li+ ions confined at a velocity of β=v/c=0.338 in the storage ring ESR at Darmstadt. A Λ-type three-level system within the hyperfine structure of the 7Li+3S1 →3P2 line is driven by two laser beams aligned parallel and antiparallel relative to the ion beam. The lasers' Doppler shifted frequencies required for resonance are measured with an accuracy of <4×10(-9) using optical-optical double resonance spectroscopy. This allows us to verify the special relativity relation between the time dilation factor γ and the velocity β, γ√1-β2=1 to within ±2.3×10(-9) at this velocity. The result, which is singled …
Digital simulation of wind field velocity
1998
Abstract In this paper some computational aspects on the generation procedure of n -variate wind velocity vectors are discussed in detail. Decompositions of the power spectral density matrix are also discussed showing the physical significance of eigenquantities of this matrix.