486 research outputs found
Strong CP, Up-Quark Mass, and the Randall-Sundrum Microscope
In the Randall-Sundrum model, setting the ratio of up and down quark masses
, relevant to the strong CP problem, does not require chiral
symmetry or fine-tuning, due to exponential bulk fermion profiles. We point out
that such geometric suppression of the mass of a fermion magnifies the masses
of its corresponding Kaluza-Klein (KK) states. In this sense, these KK states
act as "microscopes" for probing light quark and lepton masses. In simple
realizations, this hypothesis can be testable at future colliders, like the
LHC, by measuring the spectrum of level-1 KK fermions. The microscope can then
provide an experimental test for the vanishing of in the ultraviolet,
independently of non-perturbative determinations, by lattice simulations or
other means, at hadronic scales. We also briefly comment on application of our
microscope idea to other fermions, such as the electron and neutrinos.Comment: 7 pages. New discussions and references added. Main previous
conclusions unchange
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
A Population of Teraelectronvolt Pulsar Wind Nebulae in the H.E.S.S. Galactic Plane Survey
The most numerous source class that emerged from the H.E.S.S. Galactic Plane
Survey are Pulsar Wind Nebulae (PWNe). The 2013 reanalysis of this survey,
undertaken after almost 10 years of observations, provides us with the most
sensitive and most complete census of gamma-ray PWNe to date. In addition to a
uniform analysis of spectral and morphological parameters, for the first time
also flux upper limits for energetic young pulsars were extracted from the
data. We present a discussion of the correlation between energetic pulsars and
TeV objects, and their respective properties. We will put the results in
context with the current theoretical understanding of PWNe and evaluate the
plausibility of previously non-established PWN candidates.Comment: 4 pages, 5 figures. In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil
Spectrometer-related background processes and their suppression in the KATRIN experiment
Die direkte Neutrinomassenbestimmung aus dem Tritium-Beta-Zerfall mit dem KATRIN-Experiment erfordert eine niedrige Untergrundzählrate. Die Arbeit beschreibt Entwurf und Optimierung eines komplexen, doppellagigen Drahtelektrodensystems für das KATRIN-Hauptspektrometer zur elektrostatischen Abschirmung der wichtigsten Untergrundkomponente. Ebenso können Fallen für geladene Teilchen zur Untergrundrate beitragen. Eine Methode zur periodischen Fallenentleerung wurde in dieser Arbeit experimentell untersucht. Im Testaufbau wurden mittels einer UV-Leuchtdiode Photoelektronen erzeugt. Dabei wurde gezeigt, dass sich eine schnell pulsbare Photoelektronenquelle mit schmaler Energieverteilung verbunden mit Flugzeitmessungen zur Charakterisierung der Spektrometereigenschaften nutzen lässt. Zusätzlich kann die Winkelverteilung der Elektronen durch geeignete Wahl der elektromagnetischen Felder gesteuert werden. Ein Prototyp einer solchen winkelselektiven Photoelektronenquelle wurde getestet. Zu dieser Arbeit ist ein ergänzender Artikel in der Zeitschrift "New Journal of Physics" erschienen; vgl. http://www.iop.org/EJ/abstract/1367-2630/11/6/063018The direct determination of the neutrino mass scale from tritium
beta-decay with the KATRIN experiment requires a very low background
level. This work describes the design and optimization of a complex
two-layer wire electrode system for the KATRIN main spectrometer with
the purpose of suppressing a major background source. Furthermore,
charged particles stored in electromagnetic traps in the setup can cause
additional background. In a test setup, a method to periodically empty
such traps was tested. Photoelectrons created with a UV LED were used to
fill the trap. This work demonstrates that such a fast-pulsed
photoelectron source with a narrow energy spread can, in combination
with time-of-flight measurements, serve as a valuable tool for the
characterization of the spectrometer. An appropriate setting of
electromagnetic fields allows angular selectivity of the photoelectrons,
as shown in tests with a prototype
The KATRIN Experiment
The KArlsruhe TRitium Neutrino mass experiment, KATRIN, aims to search for
the mass of the electron neutrino with a sensitivity of 0.2 eV/c^2 (90% C.L.)
and a detection limit of 0.35 eV/c^2 (5 sigma). Both a positive or a negative
result will have far reaching implications for cosmology and the standard model
of particle physics and will give new input for astroparticle physics and
cosmology. The major components of KATRIN are being set up at the Karlsruhe
Institut of Technology in Karlsruhe, Germany, and test measurements of the
individual components have started. Data taking with tritium is scheduled to
start in 2012.Comment: 3 pages, 1 figure, proceedings of the TAUP 2009 International
Conference on Topics in Astroparticle and Underground Physics, to be
published in Journal of Physics, Conference Serie
-Decay Spectrum, Response Function and Statistical Model for Neutrino Mass Measurements with the KATRIN Experiment
The objective of the Karlsruhe Tritium Neutrino (KATRIN) experiment is to
determine the effective electron neutrino mass with an
unprecedented sensitivity of (90\% C.L.) by precision electron
spectroscopy close to the endpoint of the decay of tritium. We present
a consistent theoretical description of the electron energy spectrum in
the endpoint region, an accurate model of the apparatus response function, and
the statistical approaches suited to interpret and analyze tritium
decay data observed with KATRIN with the envisaged precision. In addition to
providing detailed analytical expressions for all formulae used in the
presented model framework with the necessary detail of derivation, we discuss
and quantify the impact of theoretical and experimental corrections on the
measured . Finally, we outline the statistical methods for
parameter inference and the construction of confidence intervals that are
appropriate for a neutrino mass measurement with KATRIN. In this context, we
briefly discuss the choice of the energy analysis interval and the
distribution of measuring time within that range.Comment: 27 pages, 22 figures, 2 table
A UV LED-based fast-pulsed photoelectron source for time-of-flight studies
We report on spectroscopy and time-of-flight measurements using an 18 keV
fast-pulsed photoelectron source of adjustable intensity, ranging from single
photoelectrons per pulse to 5 photoelectrons per microsecond at pulse
repetition rates of up to 10 kHz. Short pulses between 40 ns and 40
microseconds in length were produced by switching light emitting diodes with
central output wavelengths of 265 nm and 257 nm, in the deep ultraviolet (or
UV-C) regime, at kHz frequencies. Such photoelectron sources can be useful
calibration devices for testing the properties of high-resolution electrostatic
spectrometers, like the ones used in current neutrino mass searches.Comment: 16 pages, 11 figure
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