985 research outputs found
Aspects of Cooling at the TRIP Facility
The TriP facility at KVI is dedicated to provide short lived radioactive
isotopes at low kinetic energies to users. It comprised different cooling
schemes for a variety of energy ranges, from GeV down to the neV scale. The
isotopes are produced using beam of the AGOR cyclotron at KVI. They are
separated from the primary beam by a magnetic separator. A crucial part of such
a facility is the ability to stop and extract isotopes into a low energy
beamline which guides them to the experiment. In particular we are
investigating stopping in matter and buffer gases. After the extraction the
isotopes can be stored in neutral atoms or ion traps for experiments. Our
research includes precision studies of nuclear -decay through
- momentum correlations as well as searches for permanent electric
dipole moments in heavy atomic systems like radium. Such experiments offer a
large potential for discovering new physics.Comment: COOL05 Workshop, Galena, Il, USA, 18-23. Sept. 2005, 5 pages, 3
figure
Non-Standard Neutrino Interactions from a Triplet Seesaw Model
We investigate non-standard neutrino interactions (NSIs) in the triplet
seesaw model featuring non-trivial correlations between NSI parameters and
neutrino masses and mixing parameters. We show that sizable NSIs can be
generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus,
these NSIs could lead to quite significant signals of lepton flavor violating
decays such as \mu^- \to e^- \nu_e anti\nu_\mu and \mu^+ \to e^+ anti\nu_e
\nu_\mu at a future neutrino factory, effects adding to the uncertainty in
determination of the Earth matter density profile, as well as characteristic
patterns of the doubly charged Higgs decays observable at the Large Hadron
Collider.Comment: 4 pages, 3 figures and 1 table; v2: minor corrections, Sect. IV
revise
3-3-1 exotic quark search at CERN LEPII-LHC
The 3-3-1 electroweak model is the simplest chiral extension of the standard
model which predicts single and double charged bileptons and exotic quarks
carrying -4/3 and 5/3 units of the positron charge. In this paper we study the
possibilities of the production and decay of one of these exotic quarks at CERN
LEPII-LHC collider. For typical vector bilepton, exotic quark masses and mixing
angles we obtained between 20 and 750 events per year. Angular distributions
are also presented.Comment: 5 pages, RevTex 3.1, 9 eps figures, to appear in Phys. Rev.
Precise Measurement of Magnetic Field Gradients from Free Spin Precession Signals of He and Xe Magnetometers
We report on precise measurements of magnetic field gradients extracted from
transverse relaxation rates of precessing spin samples. The experimental
approach is based on the free precession of gaseous, nuclear spin polarized
He and Xe atoms in a spherical cell inside a magnetic guiding field
of about 400 nT using LT SQUIDs as low-noise magnetic flux detectors. The
transverse relaxation rates of both spin species are simultaneously monitored
as magnetic field gradients are varied. For transverse relaxation times
reaching 100 h, the residual longitudinal field gradient across the spin sample
could be deduced to be pT/cm. The method takes
advantage of the high signal-to-noise ratio with which the decaying spin
precession signal can be monitored that finally leads to the exceptional
accuracy to determine magnetic field gradients at the sub pT/cm scale
Studies of the limit order book around large price changes
We study the dynamics of the limit order book of liquid stocks after
experiencing large intra-day price changes. In the data we find large
variations in several microscopical measures, e.g., the volatility the bid-ask
spread, the bid-ask imbalance, the number of queuing limit orders, the activity
(number and volume) of limit orders placed and canceled, etc. The relaxation of
the quantities is generally very slow that can be described by a power law of
exponent . We introduce a numerical model in order to understand
the empirical results better. We find that with a zero intelligence deposition
model of the order flow the empirical results can be reproduced qualitatively.
This suggests that the slow relaxations might not be results of agents'
strategic behaviour. Studying the difference between the exponents found
empirically and numerically helps us to better identify the role of strategic
behaviour in the phenomena.Comment: 19 pages, 7 figure
Production of Radioactive Nuclides in Inverse Reaction Kinematics
Efficient production of short-lived radioactive isotopes in inverse reaction
kinematics is an important technique for various applications. It is
particularly interesting when the isotope of interest is only a few nucleons
away from a stable isotope. In this article production via charge exchange and
stripping reactions in combination with a magnetic separator is explored. The
relation between the separator transmission efficiency, the production yield,
and the choice of beam energy is discussed. The results of some exploratory
experiments will be presented.Comment: 10 pages, 4 figures, to be submitted to Nucl. Instr. and Met
Spontaneous Symmetry Breaking in Two-Channel Asymmetric Exclusion Processes with Narrow Entrances
Multi-particle non-equilibrium dynamics in two-channel asymmetric exclusion
processes with narrow entrances is investigated theoretically. Particles move
on two parallel lattices in opposite directions without changing them, while
the channels are coupled only at the boundaries. A particle cannot enter the
corresponding lane if the exit site of the other lane is occupied. Stationary
phase diagrams, particle currents and densities are calculated in a mean-field
approximation. It is shown that there are four stationary phases in the system,
with two of them exhibiting spontaneous symmetry breaking phenomena. Extensive
Monte Carlo computer simulations confirm qualitatively our predictions,
although the phase boundaries and stationary properties deviate from the
mean-field results. Computer simulations indicate that several dynamic and
phase properties of the system have a strong size dependency, and one of the
stationary phases predicted by the mean-field theory disappears in the
thermodynamic limit.Comment: 13 page
First Test of Lorentz Invariance in the Weak Decay of Polarized Nuclei
A new test of Lorentz invariance in the weak interactions has been made by
searching for variations in the decay rate of spin-polarized 20Na nuclei. This
test is unique to Gamow-Teller transitions, as was shown in the framework of a
recently developed theory that assumes a Lorentz symmetry breaking background
field of tensor nature. The nuclear spins were polarized in the up and down
direction, putting a limit on the amplitude of sidereal variations of the form
|(\Gamma_{up} - \Gamma_{down})| / (\Gamma_{up} + \Gamma_{down}) < 3 * 10^{-3}.
This measurement shows a possible route toward a more detailed testing of
Lorentz symmetry in weak interactions.Comment: 11 pages, 6 figure
Evidence of triggered star formation in G327.3-0.6. Dust-continuum mapping of an infrared dark cloud with P-ArT\'eMiS
Aims. Expanding HII regions and propagating shocks are common in the
environment of young high-mass star-forming complexes. They can compress a
pre-existing molecular cloud and trigger the formation of dense cores. We
investigate whether these phenomena can explain the formation of high-mass
protostars within an infrared dark cloud located at the position of G327.3-0.6
in the Galactic plane, in between two large infrared bubbles and two HII
regions. Methods: The region of G327.3-0.6 was imaged at 450 ? m with the CEA
P-ArT\'eMiS bolometer array on the Atacama Pathfinder EXperiment telescope in
Chile. APEX/LABOCA and APEX-2A, and Spitzer/IRAC and MIPS archives data were
used in this study. Results: Ten massive cores were detected in the P-ArT\'eMiS
image, embedded within the infrared dark cloud seen in absorption at both 8 and
24 ?m. Their luminosities and masses indicate that they form high-mass stars.
The kinematical study of the region suggests that the infrared bubbles expand
toward the infrared dark cloud. Conclusions: Under the influence of expanding
bubbles, star formation occurs in the infrared dark areas at the border of HII
regions and infrared bubbles.Comment: 4 page
Dynamical Gauge Symmetry Breaking in Extension of the Standard Model
We study the extension of the Standard model with a
strong U(1) coupling. We argue that current experiments limit this coupling to
be relatively large. The model is dynamically broken to the Standard model at the scale of a few TeV with all the extra gauge bosons
and the exotic quarks acquiring masses much larger than the scale of
electroweak symmetry breaking. Furthermore we find that the model leads to
large dynamical mass of the top quark and hence also breaks the electroweak
gauge symmetry. It therefore leads to large dynamical effects within the
Standard model and can partially replace the Higgs interactions.Comment: 4 pages, revtex, no figures; revised version predicting realistic
mass spectru
- …