418 research outputs found
High statistic measurement of the K- -> pi0 e- nu decay form-factors
The decay K- -> pi0 e- nu is studied using in-flight decays detected with the
ISTRA+ spectrometer. About 920K events are collected for the analysis. The
lambda+ slope parameter of the decay form-factor f+(t) in the linear
approximation (average slope) is measured: lambda+(lin)= 0.02774 +-
0.00047(stat) +- 0.00032(syst). The quadratic contribution to the form-factor
was estimated to be lambda'+ = 0.00084 +- 0.00027(stat) +- 0.00031(syst). The
linear slope, which has a meaning of df+(t)/dt|_{t=0} for this fit, is lambda+
= 0.02324 +- 0.00152(stat) +- 0.00032(syst). The limits on possible tensor and
scalar couplings are derived: f_{T}/f_{+}(0)=-0.012 +- 0.021(stat) +-
0.011$(syst), f_{S}/f_{+}(0)=-0.0037^{+0.0066}_{-0.0056}(stat) +- 0.0041(syst).Comment: 11 pages, 8 figures. Accepted by Phys.Lett.
Search for light pseudoscalar sgoldstino in K- decays
A search for the light pseudoscalar sgoldstino production in the three body
K- decay K-->pipi0P has been performed with the ISTRA+ detector exposed to the
25 GeV negative secondary beam of the U70 proton synchrotron. No signal is
seen. An upper limit for the branching ratio Br(K->pipi0P), at 90% confidence
level, is found to be around 9*10**-6 in the effective mass m(P) range from 0
till 200 MeV, excluding the region near m(pi0) where it degrades to 3.5*10**-5.Comment: 10 pages, LATEX, 8 EPS figures, revised version, to be published in
Phys.Lett.
Measurement of the Dalitz plot slope parameters for K- -> pi0 pi0 pi- decay using ISTRA+ detector
The Dalitz plot slope parameters g, h and k for the K- -> pi0 pi0 pi- decay
have been measured using in-flight decays detected with the ISTRA+ setup
operating in the 25 GeV negative secondary beam of the U-70 PS. About 252 K
events with four-momenta measured for the pi- and four involved photons were
used for the analysis. The values obtained g=0.627+/-0.004(stat)+/-0.010(syst),
h=0.046+/-0.004(stat)+/-0.012(syst), k=0.001+/-0.001(stat)+/-0.002(syst) are
consistent with the world averages dominated by K+ data, but have significantly
smaller errors.Comment: LaTeX, 10 pages, 8 eps-figures, update of IHEP 2002-1
High statistic study of the K- -> pi0 mu- nu decay
The decay K- -> pi0 mu- nu has been studied using in-flight decays detected
with the "ISTRA+" spectrometer. About 540K events were collected for the
analysis. The lambda+ and lambda0 slope parameters of the decay form-factors
f+(t), f0(t) have been measured : lambda+ = 0.0277+-0.0013 (stat)+-0.0009
(syst), lambda0 = 0.0183+-0.0011(stat)+-0.0006(syst), and
d(lambda0)/d(lambda+)=-0.348. The limits on the possible tensor and scalar
couplings have been derived: fT/f+(0)=-0.0007 +- 0.0071, fS/f+(0)=0.0017 +-
0.0014. No visible non-linearity in the form-factors have been observed.Comment: 11 pages, 8 EPS figures, accepted by Physics Letters
Influence of the Bilayer Thickness of Nanostructured Multilayer MoN/CrN Coating on Its Microstructure, Hardness, and Elemental Composition
Multilayer nanostructured coatings consisting of alternating MoN and CrN layers were obtained
by vacuum cathode evaporation under various conditions of deposition. The transition from micron sizes of
bilayers to the nanometer scale in the coatings under investigation leads to an increase in hardness from 15 to
35.5 GPa (with a layer thickness of about 35 nm). At the same time, when the number of bilayers in the coat-
ing decreases, the average Vickers hardness increases from 1267 HV0.05 to 3307 HV0.05. An increase in the
value of the potential supplied to the substrate from –20 to –150 V leads to the formation of growth textures
in coating layers with the [100] axis, and to an increase in the intensity of reflections with increasing bilayer
thickness. Elemental analysis carried out with the help of Rutherford backscattering, secondary ion mass
spectrometry and energy dispersion spectra showed a good separation of the MoN and CrN layers near the
surface of the coatings
Development of a Momentum Determined Electron Beam in the 1 -45 GeV Range
A beam line for electrons with energies in the range of 1 to 45 GeV, low
contamination of hadrons and muons and high intensity up to 10^6 per
accelerator spill at 27 GeV was setup at U70 accelerator in Protvino, Russia. A
beam tagging system based on drift chambers with 160 micron resolution was able
to measure relative electron beam momentum precisely. The resolution sigma_p p
was 0.13% at 45 GeV where multiple scattering is negligible. This test beam
setup provided the possibility to study properties of lead tungstate crystals
(PbWO_4) for the BTeV experiment at Fermilab.Comment: 12 pages, 8 figures; work done by the BTeV Electromagnetic
Calorimeter grou
High statistics study of the K- -> pi0 e- nu decay
The decay K- -> pi0 e- nu has been studied using in-flight decays detected
with the "ISTRA+" spectrometer working at the 25 GeV negative secondary beam of
the U-70 PS. About 550K events were used for the analysis. The lambda+
parameter of the vector form-factor has been measured: lambda+ = 0.0286 +-
0.0008 (stat) +- 0.0006(syst). The limits on the possible tensor and scalar
couplings have been obtained: f(T)/f+(0)=0.021 +0.064 -0.075 (stat) +-
0.026(syst) ; f(S)/f+(0)=0.002 +0.020 -0.022 (stat) +- 0.003(syst)Comment: LaTeX-2e, epsfig.sty, 10 pages, 7 figures in EPS forma
Relic Neutrino Absorption Spectroscopy
Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang
relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption
dips in the neutrino flux to be observed at Earth. The high-energy edges of
these dips are fixed, via the resonance energies, by the neutrino masses alone.
Their depths are determined by the cosmic neutrino background density, by the
cosmological parameters determining the expansion rate of the universe, and by
the large redshift history of the cosmic neutrino sources. We investigate the
possibility of determining the existence of the cosmic neutrino background
within the next decade from a measurement of these absorption dips in the
neutrino flux. As a by-product, we study the prospects to infer the absolute
neutrino mass scale. We find that, with the presently planned neutrino
detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant
energy regime above 10^{21} eV, relic neutrino absorption spectroscopy becomes
a realistic possibility. It requires, however, the existence of extremely
powerful neutrino sources, which should be opaque to nucleons and high-energy
photons to evade present constraints. Furthermore, the neutrino mass spectrum
must be quasi-degenerate to optimize the dip, which implies m_{nu} >~ 0.1 eV
for the lightest neutrino. With a second generation of neutrino detectors,
these demanding requirements can be relaxed considerably.Comment: 19 pages, 26 figures, REVTeX
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
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