8,226 research outputs found
The design of a very high-Q superconductor electromechanical clock
We discuss theoretically the properties of an electromechanical oscillator
whose operation is based upon the cyclic, quasi-conservative conversion between
gravitational potential, kinetic, and magnetic energies. The system consists of
a strong-pinning type-II superconductor square loop subjected to a constant
external force and to magnetic fields. The loop oscillates in the upright
position at a frequency that can be tuned in the range 10-1000 Hz, and has
induced in it a rectified electrical current. The emphasis of this paper is on
the evaluation of the major remaining source of losses in the oscillations. We
argue that such losses should be associated with the viscous vibration of
pinned flux lines in the superconductor Nb-Ti wire, provided the oscillator is
kept close to zero Kelvin, under high-vacuum, and the magnetic field is
sufficiently uniform. We discuss how other different sources of loss would
become negligible for such operational conditions, so that a very high quality
factor Q exceeding 10^(10) might in principle be reached by the oscillator. The
prospective utilization of such oscillator as a low-frequency high-Q clock is
analyzed.Since publication the ideas in this paper have been explored both by
the author and elsewhere, in applications covering Metrology, quantum systems,
and gravimetry.Comment: developments based upon this paper results are discussed. arXiv admin
note: substantial text overlap with arXiv:cond-mat/051076
Early Electroweak and Top Quark Physics with CMS
The Large Hadron Collider is an ideal place for precision measurements of the
properties of the electroweak gauge bosons W^\pm, Z^0, as well as of the top
quark. In this article, a few highlights of the prospects for performing such
measurements with the CMS detector are summarized, with an emphasis on the
first few 1/fb of data.Comment: 4 pages, to appear in the proceedings of DIS 2007, Munich, April 200
Diffractive DIS Cross Sections and Parton Distributions
Highlights are presented mainly from two recent measurements of the
diffractive Deep Inelastic Scattering cross section at HERA. In the first, the
process is studied by tagging the leading final state proton. In
the second, events of this type are selected by requiring a large rapidity gap
devoid of hadronic activity in the proton direction. The two measurements are
compared in detail and the kinematic dependences are interpreted within the
framework of a factorisable diffractive exchange. Diffractive parton
distributions are determined from a next-to-leading order QCD analysis of the
large rapidity gap data, which can be applied to the prediction of diffractive
processes, also at the TEVATRON and the LHC.Comment: to appear in the proceedings of the 33rd Intl. Conference on High
Energy Physics, ICHEP 2006 (Moscow, July 2006
Weak order for the discretization of the stochastic heat equation driven by impulsive noise
Considering a linear parabolic stochastic partial differential equation
driven by impulsive space time noise, dX_t+AX_t dt= Q^{1/2}dZ_t, X_0=x_0\in H,
t\in [0,T], we approximate the distribution of X_T. (Z_t)_{t\in[0,T]} is an
impulsive cylindrical process and Q describes the spatial covariance structure
of the noise; Tr(A^{-\alpha})0 and A^\beta Q is bounded
for some \beta\in(\alpha-1,\alpha]. A discretization
(X_h^n)_{n\in\{0,1,...,N\}} is defined via the finite element method in space
(parameter h>0) and a \theta-method in time (parameter \Delta t=T/N). For
\phi\in C^2_b(H;R) we show an integral representation for the error
|E\phi(X^N_h)-E\phi(X_T)| and prove that
|E\phi(X^N_h)-E\phi(X_T)|=O(h^{2\gamma}+(\Delta t)^{\gamma}) where
\gamma<1-\alpha+\beta.Comment: 29 pages; Section 1 extended, new results in Appendix
Status and Commissioning of the CMS Experiment
After a brief overview of the Compact Muon Solenoid (CMS) experiment, the
status of construction and installation is described in the first part of the
note. The second part of the document is devoted to a discussion of the general
commissioning strategy of the CMS experiment, with a particular emphasis on
trigger, calibration and alignment. Aspects of b-physics, as well as examples
for early physics with CMS are also presented. CMS will be ready for data
taking in time for the first collisions in the Large Hadron Collider (LHC) at
CERN in late 2007.Comment: Talks given at the 11th Intl. Conference on B-Physics at Hadron
Machines BEAUTY 2006, Oxford (UK), September 200
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