5,298 research outputs found
System Tests of the ATLAS Pixel Detector
The innermost part of the ATLAS (A Toroidal LHC ApparatuS) experiment at the
LHC (Large Hadron Collider) will be a pixel detector, which is presently under
construction. Once installed into the experimental area, access will be
extremely limited. To ensure that the integrated detector assembly operates as
expected, a fraction of the detector which includes the power supplies and
monitoring system, the optical readout, and the pixel modules themselves, has
been assembled and operated in a laboratory setting for what we refer to as
system tests. Results from these tests are presented.Comment: 5 Pages, 9 Figures, to appear in Proceedings of the Eleventh Workshop
on Electronics for LHC and Future Experiment
An Unfamiliar Way to Generate the Hierarchy of Standard Model Fermion Masses
While the properties of the observed Higgs boson agree with the Standard
Model predictions, the hierarchy of fermion masses lacks an explanation within
the model. In this work, we propose a fresh approach to this problem, involving
a different Higgs doublet responsible for each quark mass. We construct a model
with a gauged, non-anomalous family symmetry that fixes which fermion
couples to which doublet with an Yukawa coupling. The
hierarchy of masses is generated by the hierarchy of vacuum expectation values
of the Higgs fields. The model generically predicts a light, weakly coupled
pseudoscalar. We verify that the model satisfies constraints from flavour
changing neutral currents, Higgs phenomenology and electroweak precision tests.Comment: 31 pages incl. reference
A convenient criterion under which Z_2-graded operators are Hamiltonian
We formulate a simple and convenient criterion under which skew-adjoint
Z_2-graded total differential operators are Hamiltonian, provided that their
images are closed under commutation in the Lie algebras of evolutionary vector
fields on the infinite jet spaces for vector bundles over smooth manifolds.Comment: J.Phys.Conf.Ser.: Mathematical and Physical Aspects of Symmetry.
Proc. 28th Int. colloq. on group-theoretical methods in Physics (July 26-30,
2010; Newcastle-upon-Tyne, UK), 6 pages (in press
Jacobi multipliers, non-local symmetries and nonlinear oscillators
Constants of motion, Lagrangians and Hamiltonians admitted by a family of
relevant nonlinear oscillators are derived using a geometric formalism. The
theory of the Jacobi last multiplier allows us to find Lagrangian descriptions
and constants of the motion. An application of the jet bundle formulation of
symmetries of differential equations is presented in the second part of the
paper. After a short review of the general formalism, the particular case of
non-local symmetries is studied in detail by making use of an extended
formalism. The theory is related to some results previously obtained by
Krasil'shchi, Vinogradov and coworkers. Finally the existence of non-local
symmetries for such two nonlinear oscillators is proved.Comment: 20 page
(Non)local Hamiltonian and symplectic structures, recursions, and hierarchies: a new approach and applications to the N=1 supersymmetric KdV equation
Using methods of math.DG/0304245 and [I.S.Krasil'shchik and P.H.M.Kersten,
Symmetries and recursion operators for classical and supersymmetric
differential equations, Kluwer, 2000], we accomplish an extensive study of the
N=1 supersymmetric Korteweg-de Vries equation. The results include: a
description of local and nonlocal Hamiltonian and symplectic structures, five
hierarchies of symmetries, the corresponding hierarchies of conservation laws,
recursion operators for symmetries and generating functions of conservation
laws. We stress that the main point of the paper is not just the results on
super-KdV equation itself, but merely exposition of the efficiency of the
geometrical approach and of the computational algorithms based on it.Comment: 16 pages, AMS-LaTeX, Xy-pic, dvi-file to be processed by dvips. v2:
nonessential improvements of exposition, title change
The Control System for a new Pixel Detector at the sLHC
For the upgrade of the LHC, the sLHC (super Large Hadron Collider), a new ATLAS Pixel Detector is planned, which will require a completely new control system. To reduce the material budget new power distribution schemes are under investigation, where the active power conversion is located inside the detector volume. Such a new power supply system will need new control strategies. Parts of the control must be located closer to the loads. The minimization of mass, the demand for less cables and the re-use of the outer existing services are the main restrictions to the design of the control system. The requirements of the DCS (Detector Control System) and a first concept will be presented. We will focus on a control chip which necessarily has to be implemented in the new system. A setup of discrete components has been built up to investigate and verify the chip’s requirements. We report on the status of the work
A new life for sterile neutrino dark matter after the pandemic
We propose a novel mechanism to generate sterile neutrinos in theearly Universe, by converting ordinary neutrinos in scatteringprocesses . After initial production byoscillations, this leads to an exponential growth in the abundance. Weshow that such a production regime naturally occurs for self-interacting, and that this opens up significant new parameter space where make up all of the observed dark matter. Our results provide strong motivationto further push the sensitivity of X-ray line searches, and to improve onconstraints from structure formation.<br
A new life for sterile neutrino dark matter after the pandemic
We propose a novel mechanism to generate sterile neutrinos in theearly Universe, by converting ordinary neutrinos in scatteringprocesses . After initial production byoscillations, this leads to an exponential growth in the abundance. Weshow that such a production regime naturally occurs for self-interacting, and that this opens up significant new parameter space where make up all of the observed dark matter. Our results provide strong motivationto further push the sensitivity of X-ray line searches, and to improve onconstraints from structure formation.<br
Variational Lie algebroids and homological evolutionary vector fields
We define Lie algebroids over infinite jet spaces and establish their
equivalent representation through homological evolutionary vector fields.Comment: Int. Workshop "Nonlinear Physics: Theory and Experiment VI"
(Gallipoli, Italy; June-July 2010). Published v3 = v2 minus typos, to appear
in: Theoret. and Mathem. Phys. (2011) Vol.167:3 (168:1), 18 page
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