نتایج جستجو برای: neutron decay
تعداد نتایج: 117888 فیلتر نتایج به سال:
A new technique to measure the lifetime � of a neutron-radioactive nucleus that decays in-flight via neutron emission is presented and demonstrated utilizing MonteCarlo simulations. The method is based on the production of the neutron-unbound nucleus in a target, which at the same time slows down the produced nucleus and the residual nucleus after (multi-) neutron emission. The spectrum of the ...
In the neutron-rich internal shocks model for Gamma-ray Burts (GRBs), the Lorentz factors (LFs) of ions shells are variable, so are the LFs of accompanying neutron shells. For slow neutron shells with a typical LF ∼ tens, the typical β−decay radius reads Rβ,s ∼ several× 10cm, which is much larger than the typical internal shocks radius ∼ 10cm, so their impact on the internal shocks may be unimp...
The Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory with an anticipated start-up in early 2006, will provide the most intense pulsed beams of cold neutrons in the world. At a projected power of 1.4 MW, the time averaged fluxes and fluences of the SNS will approach those of high flux reactors. One of the flight paths on the cold, coupled moderator w...
In the neutron-rich internal shocks model for Gamma-ray Burts (GRBs), the Lorentz factors (LFs) of ions shells are variable, so are the LFs of accompanying neutron shells. For slow neutron shells with a typical LF ∼ tens, the typical β−decay radius reads Rβ,s ∼ several× 10cm, which is much larger than the typical internal shocks radius ∼ 10cm, so their impact on the internal shocks may be unimp...
The FINUDA experiment at DAΦNE, Frascati, has found evidence for the neutron-rich hypernucleus ΛH studying (π , π−) pairs in coincidence from the K− stop+ 6Li→ 6 ΛH+π + production reaction followed by ΛH→ 6He+π− weak decay. The production rate of ΛH undergoing this two-body π − decay has been found to be (2.9 ± 2.0) · 10−6/K− stop. Its binding energy has been evaluated to be BΛ(ΛH) = (4.0 ± 1.1...
The hypothesis that ultra-high energy (& 1019 eV) cosmic rays (UHECRs) are accelerated by gamma-ray burst (GRB) blast waves is assumed to be correct. Implications of this assumption are then derived for the external shock model of gamma-ray bursts. The evolving synchrotron radiation spectrum in GRB blast waves provides target photons for the photomeson production of neutrinos and neutrons. Deca...
Motivated by neutron scattering experiments, we investigate the decay of the fidelity with which a wave packet is reconstructed by a perfect time-reversal operation performed after a phase-space displacement. In the semiclassical limit, we show that the decay rate is generically given by the Lyapunov exponent of the classical dynamics. For small displacements, we additionally show that, followi...
We present two-dimensional simulations for the cooling of neutron stars with strong magnetic fields (B ≥ 1013 G). We study how the cooling curves are influenced by magnetic field decay. We show that the Joule heating effects are very large and in some cases control the thermal evolution. We characterize the temperature anisotropy induced by the magnetic field and predict the surface temperature...
The Apollo and Galileo missions provided unambiguous evidence that the Sun is iron-rich. New experimental measurements and theoretical studies are now needed to build a framework for understanding the source of solar luminosity, neutrinos and mono-isotopic hydrogen coming from the Sun. Specifically, measurements are needed of the low energy (E 0.782 MeV) anti-neutrinos that would be produced if...
The UCNA experiment is designed to measure the neutron decay beta asymmetry (the "A" parameter) to very high precision (<0.5%), using the ultracold neutron (UCN) source at the Los Alamos National Lab. After a successful commissioning run in 2007, data were taken in 2008 which will lead to a 1% measurement of A. In this talk, I will discuss major improvements we made in 2008, and report the stat...
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