19,520 research outputs found
Optimizing momentum resolution with a new fitting method for silicon-strip detectors
A new fitting method is explored for momentum reconstruction of tracks in a
constant magnetic field for a silicon-strip tracker. Substantial increases of
momentum resolution respect to standard fit is obtained. The key point is the
use of a realistic probability distribution for each hit (heteroscedasticity).
Two different methods are used for the fits, the first method introduces an
effective variance for each hit, the second method implements the maximum
likelihood search. The tracker model is similar to the PAMELA tracker. Each
side, of the two sided of the PAMELA detectors, is simulated as momentum
reconstruction device. One of the two is similar to silicon micro-strip
detectors of large use in running experiments. Two different position
reconstructions are used for the standard fits, the -algorithm (the best
one) and the two-strip center of gravity. The gain obtained in momentum
resolution is measured as the virtual magnetic field and the virtual
signal-to-noise ratio required by the two standard fits to reach an overlap
with the best of two new methods. For the best side, the virtual magnetic field
must be increased 1.5 times respect to the real field to reach the overlap and
1.8 for the other. For the high noise side, the increases must be 1.8 and 2.0.
The signal-to-noise ratio has similar increases but only for the
-algorithm. The signal-to-noise ratio has no effect on the fits with the
center of gravity. Very important results are obtained if the number N of
detecting layers is increased, our methods provide a momentum resolution
growing linearly with N, much higher than standard fits that grow as the
.Comment: This article supersedes arXiv:1606.03051, 22 pages and 10 figure
Projective Modules of Finite Type and Monopoles over
We give a unifying description of all inequivalent vector bundles over the
2-dimensional sphere by constructing suitable global projectors via
equivariant maps. Each projector determines the projective module of finite
type of sections of the corresponding complex rank 1 vector bundle over .
The canonical connection is used to compute the
topological charges. Transposed projectors gives opposite values for the
charges, thus showing that transposition of projectors, although an isomorphism
in K-theory, is not the identity map. Also, we construct the partial isometry
yielding the equivalence between the tangent projector (which is trivial in
K-theory) and the real form of the charge 2 projector.Comment: 15 pages, Late
Examples of noncommutative instantons
These notes aim at a pedagogical introduction to recent work on deformation
of spaces and deformation of vector bundles over them, which are relevant both
in mathematics and in physics, notably monopole and instanton bundles.
We first decribe toric noncommutative manifolds (also known as isospectral
deformations) and give a detailed introduction to gauge theories on a toric
four-sphere. This includes a Yang-Mills action functional with associated
equations of motion and self-duality equations. We construct a particular class
of instanton solutions on a SU(2) bundle with a suitable use of twisted
conformal symmetries.
In the second part, we describe a different deformation of an instanton
bundle over the classical four-sphere by constructing a quantum group SU_q(2)
bundle on a sphere which is different from the toric one.Comment: 34 pages; AMS-Latex. v2: Several minor changes. Based on lectures
delivered at the 2005 Summer school on ``Geometric and Topological Methods
for Quantum Field Theory'', July 11-29 2005, Villa de Leyva, Colombi
Scattering Polarization in the Presence of Magnetic and Electric Fields
The polarization of radiation by scattering on an atom embedded in combined
external quadrupole electric and uniform magnetic fields is studied
theoretically. Limiting cases of scattering under Zeeman effect and Hanle
effect in weak magnetic fields are discussed. The theory is general enough to
handle scattering in intermediate magnetic fields (Hanle-Zeeman effect) and for
arbitrary orientation of magnetic field. The quadrupolar electric field
produces asymmetric line shifts and causes interesting level-crossing phenomena
either in the absence of an ambient magnetic field or in its presence. It is
shown that the quadrupolar electric field produces an additional depolarization
in the profiles and rotation of the plane of polarization in the
profile over and above that arising from magnetic field itself. This
characteristic may have a diagnostic potential to detect steady state and time
varying electric fields that surround radiating atoms in Solar atmospheric
layers.Comment: 41 pages, 6 figure
Global Analysis of an Expectations Augmented Evolutionary Dynamics
We consider a deterministic evolutionary model where players form expectations about future play. Players are not fully rational and have expectations that change over time in response to current payoffs and feedback from the past. We provide a complete characterization of the qualitative dynamics so induced for a two strategies population game, and relate our findings to standard evolutionary dynamics and equilibrium selection when agents have rational forward looking expectations.evolutionary games, dynamic systems, bounded rationality
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