1,717 research outputs found
Classifying LEP Data with Support Vector Algorithms
We have studied the application of different classification algorithms in the
analysis of simulated high energy physics data. Whereas Neural Network
algorithms have become a standard tool for data analysis, the performance of
other classifiers such as Support Vector Machines has not yet been tested in
this environment. We chose two different problems to compare the performance of
a Support Vector Machine and a Neural Net trained with back-propagation:
tagging events of the type e+e- -> ccbar and the identification of muons
produced in multihadronic e+e- annihilation events.Comment: 7 pages, 4 figures, submitted to proceedings of AIHENP99, Crete,
April 199
On the coupling of massless particles to scalar fields
It is investigated if massless particles can couple to scalar fields in a
special relativistic theory with classical particles. The only possible obvious
theory which is invariant under Lorentz transformations and reparametrization
of the affine parameter leads to trivial trajectories (straight lines) for the
massless case, and also the investigation of the massless limit of the massive
theory shows that there is no influence of the scalar field on the limiting
trajectories.
On the other hand, in contrast to this result, it is shown that massive
particles are influenced by the scalar field in this theory even in the
ultra-relativistic limit.Comment: 9 pages, no figures, uses titlepage.sty, LaTeX 2.09 file, submitted
to International Journal of Theoretical Physic
Determination of the Weak Axial Vector Coupling from a Measurement of the Beta-Asymmetry Parameter A in Neutron Beta Decay
We report on a new measurement of the neutron beta-asymmetry parameter
with the instrument \perkeo. Main advancements are the high neutron
polarization of from a novel arrangement of super mirror
polarizers and reduced background from improvements in beam line and shielding.
Leading corrections were thus reduced by a factor of 4, pushing them below the
level of statistical error and resulting in a significant reduction of
systematic uncertainty compared to our previous experiments. From the result
, we derive the ratio of the axial-vector to the vector
coupling constant Comment: 5 pages, 4 figure
Measurement of the Neutrino Asymmetry Parameter B in Neutron Decay
A new measurement of the neutrino asymmetry parameter B in neutron decay, the
angular correlation between neutron spin and anti-neutrino momentum, is
presented. The result, B=0.9802(50), agrees with the Standard Model expectation
and earlier measurements, and permits improved tests on ``new physics'' in
neutron decay.Comment: 4 pages, 2 figures; v2: revised PRL versio
Experimental study of ultracold neutron production in pressurized superfluid helium
We have investigated experimentally the pressure dependence of the production
of ultracold neutrons (UCN) in superfluid helium in the range from saturated
vapor pressure to 20bar. A neutron velocity selector allowed the separation of
underlying single-phonon and multiphonon pro- cesses by varying the incident
cold neutron (CN) wavelength in the range from 3.5 to 10{\AA}. The predicted
pressure dependence of UCN production derived from inelastic neutron scattering
data was confirmed for the single-phonon excitation. For multiphonon based UCN
production we found no significant dependence on pressure whereas calculations
from inelastic neutron scattering data predict an increase of 43(6)% at 20bar
relative to saturated vapor pressure. From our data we conclude that applying
pressure to superfluid helium does not increase the overall UCN production rate
at a typical CN guide.Comment: 18 pages, 8 figures Version accepted for publication in PR
Width of the QCD transition in a Polyakov-loop DSE model
We consider the pseudocritical temperatures for the chiral and deconfinement
transitions within a Polyakov-loop Dyson-Schwinger equation approach which
employs a nonlocal rank-2 separable model for the effective gluon propagator.
These pseudocritical temperatures differ by a factor of two when the quark and
gluon sectors are considered separately, but get synchronized and become
coincident when their coupling is switched on. The coupling of the
Polyakov-loop to the chiral quark dynamics narrows the temperature region of
the QCD transition in which chiral symmetry and deconfinement is established.
We investigate the effect of rescaling the parameter T_0 in the Polyakov-loop
potential on the QCD transition for both the logarithmic and polynomial forms
of the potential. While the critical temperatures vary in a similar way, the
width of the transition is stronger affected for the logarithmic potential. For
this potential the character of the transition changes from crossover to a
first order one when T_0 < 210 MeV, but it remains crossover in the whole range
of relevant T_0 values for the polynomial form.Comment: 10 pages, 6 figures, results for polynomial form of Polyakov-loop
potential included, references added, final version to appear in Phys. Rev.
Performance requirements analysis for payload delivery from a space station
Operations conducted from a space station in low Earth orbit which have different constraints and opportunities than those conducted from direct Earth launch were examined. While a space station relieves many size and performance constraints on the space shuttle, the space station's inertial orbit has different launch window constraints from those associated with customary Earth launches which reflect upon upper stage capability. A performance requirements analysis was developed to provide a reference source of parametric data, and specific case solutions and upper stage sizing trade to assist potential space station users and space station and upper stage developers assess the impacts of a space station on missions of interest
The D coefficient in neutron beta decay in effective field theory
In this paper we explore the time-reversal-odd triple-correlation coefficient
in neutron beta decay, the so-called "D coefficient", using heavy-baryon
effective field theory with photon degrees of freedom. We find that this
framework allows us to reproduce the known results for the contribution which
comes from final-state interactions, and also to discuss higher-order
corrections. In particular we are able to show that in the heavy-baryon limit
all electromagnetic contributions vanish. By calculating the leading correction
to the known result, we give a final expression which is accurate to better
than 1%. Hence we extend downwards the range over which the D coefficient could
be used to explore time-violation from new physics.Comment: 12c pages, 3 eps figures Version accepted for publication in Physics
Letters B; minor changes of wordin
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