256 research outputs found
Modeling of electron emission processes accompanying Radon--decays within electrostatic spectrometers
Electrostatic spectrometers utilized in high-resolution beta-spectroscopy
studies such as in the Karlsruhe Tritium Neutrino (KATRIN) experiment have to
operate with a background level of less than 10^(-2) counts per second. This
limit can be exceeded by even a small number of Rn-219 or Rn-220 atoms being
emanated into the volume and undergoing alpha-decay there. In this paper we
present a detailed model of the underlying background-generating processes via
electron emission by internal conversion, shake-off and relaxation processes in
the atomic shells of the Po-215 and Po-216 daughters. The model yields electron
energy spectra up to 400 keV and electron multiplicities of up to 20 which are
compared to experimental data.Comment: 7 figure
Higgs triplet effects in purely leptonic processes
We consider the effect of complex Higgs triplets on purely leptonic processes
and survey the experimental constraints on the mass and couplings of their
single and double charge members. Present day experiments tolerate values of
the Yukawa couplings of these scalars at the level of the standard electroweak
gauge couplings. We show that the proposed measurement of the ratio
R_{LCD}=\sigma (\nu_{\mu}e)/ [\sigma (\bb\nu_{\mu}e) + \sigma (\nu_e e )]
would allow to explore a large region of the parameter space inaccessible to
the usual ratio R=\sigma (\nu_{\mu}e)/\sigma (\bb\nu_{\mu}e).Comment: 14 pages, LaTeX, Three figures included using uufiles. A postscript
version is available at ftp://ftp.ifae.es/preprint/ft/uabft378.p
The Search for Neutrino Oscillations numubar->nuebar with KARMEN
The neutrino experiment KARMEN is situated at the beam stop neutrino source
ISIS. It provides numu's, nue's and numubar's in equal intensities from the pi+
mu+ decay at rest (DAR). The oscillation channel numub->nueb is investigated in
the appearance mode with a 56t liquid scintillation calorimeter at a mean
distance of 17.7m from the nu source looking for p(nue,e+)n reactions. The
cosmic induced background for this oscillation search could be reduced by a
factor of 40 due to an additional veto counter installed in 1996. In the data
collected through 1997 and 1998 no potential oscillation event was observed.
Using a unified approach to small signals this leads to an upper limit for the
mixing angle of sin**2(2t) < 1.3x10^{-3} (90%CL) at large Dm**2. The excluded
area in (sin**2(2t),Dm**2) covers almost entirely the favored region defined by
the LSND numub->nueb evidence.Comment: Proceedings Contribution to Neutrino98 in Takayama, Japan, June 4-9,
1998; 13 pages, including 4 figure
Modelling of gas dynamical properties of the KATRIN tritium source and implications for the neutrino mass measurement
The KATRIN experiment aims to measure the effective mass of the electron
antineutrino from the analysis of electron spectra stemming from the beta-decay
of molecular tritium with a sensitivity of 200 meV. Therefore, a daily
throughput of about 40 g of gaseous tritium is circulated in a windowless
source section. An accurate description of the gas flow through this section is
of fundamental importance for the neutrino mass measurement as it significantly
influences the generation and transport of beta-decay electrons through the
experimental setup. In this paper we present a comprehensive model consisting
of calculations of rarefied gas flow through the different components of the
source section ranging from viscous to free molecular flow. By connecting these
simulations with a number of experimentally determined operational parameters
the gas model can be refreshed regularly according to the measured operating
conditions. In this work, measurement and modelling uncertainties are
quantified with regard to their implications for the neutrino mass measurement.
We find that the systematic uncertainties related to the description of gas
flow are represented by eV,
and that the gas model is ready to be used in the analysis of upcoming KATRIN
data.Comment: 28 pages, 13 figure
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