2,964 research outputs found
Dynamic aperture studies for the LHC version 4
The limitations of the dynamic aperture due to field errors of the super-conducting magnets is a notorious problem for the LHC. Given the large amount of independent studies performed by a sizeable research team it becomes necessary to define a common tracking strategy. The emphasis is placed on an elaborate on - and off - line processing of the tracking data making use of all tools presently available. To manage the very time-comsuming investigations our approach is two-fold: firstly we are maximising the computing power running optimised code on state of the art equipment which is continuously upgraded and secondly we speed up the studies by using reliable and automated early indicators for long-term losses. The procedure is exemplified with a series of tracking runs for the LHC version 4 at injection
LHC Dynamic Aperture Including the Beam-Beam Force
The LHC dynamic aperture in collision is constrained mainly by the beam-beam encounters, and by the field errors in the low-beta triplet quadrupoles. The nominal field errors were used and have been corrected with a local corrector scheme at each IP. The correction algorithm is explained, and the resulting dynamic aperture is shown. In the calculations, the effect of the crossing angle geometry, the beta-function, the bunch intensity and the pacman bunches on the dynamic aperture are studied. It is, however, also necessary to study how the unavoidable long range beam-beam encounters influence the dynamic aperture
The upgrade of GEO600
The German / British gravitational wave detector GEO 600 is in the process of
being upgraded. The upgrading process of GEO 600, called GEO-HF, will
concentrate on the improvement of the sensitivity for high frequency signals
and the demonstration of advanced technologies. In the years 2009 to 2011 the
detector will undergo a series of upgrade steps, which are described in this
paper.Comment: 9 pages, Amaldi 8 conference contributio
Quantum Collective QCD String Dynamics
The string breaking model of particle production is extended in order to help
explain the transverse momentum distribution in elementary collisions. Inspired
by an idea of Bialas', we treat the string using a collective coordinate
approach. This leads to a chromo-electric field strength which fluctuates, and
in turn implies that quarks are produced according to a thermal distribution.Comment: 6 pages. Presented at SQM 2006. Submitted to J. Phys. G for
publication in proceedings. Vers. 2: Minor revisions; final hadron spectrum
calculation include
Nonlinear optical properties of functionalized DNA
Third-order nonlinear optical properties of functionalized deoxyribonucleic acid (DNA) are studied by optical third harmonic generation at 1 0642 nm fundamental wavelength. The studies were performed on thin films of DNA-CTMA and DNA-CTMA doped with a charge transfer molecules DR1 and with a cobalt phthalocyanine. They show that DNA, similarly as synthetic polymers, can be used as matrix for highly active NLO chromophores
Beyond âignoranceâ: using the cultural stereotypes of Americans studying in the UK as a resource for learning and teaching about British culture
A course introducing British culture is a standard component of many study abroad programmes running in this country that are aimed at international students who will be spending a limited amount of time in the United Kingdom. However, it is not often acknowledged that such students possess a range of strong pre-conceptions about British culture and society prior to their arrival. Conventional teaching strategies assume student ignorance of the subject. However, an alternative approach which makes us of pre-arrival stereotypes can be more productive in terms of engaging students in active processes of comparative analysis of their new and existing knowledge. A case study of American student stereotypes of the British monarchy is presented and it is suggested that these can be used as the basis for refining student understanding of cultural politics in the United Kingdom. International students, therefore, should not be treated as being culturally ignorant of Britain in the sense of having no knowledge or opinions at all. Rather, it should be understood that they possess a culturally mediated state of subjectivity which I refer to as âignoranceâ and that this can become a valuable resource for teaching and learning
Renormalization approach to many-particle systems
This paper presents a renormalization approach to many-particle systems. By
starting from a bare Hamiltonian with an
unperturbed part and a perturbation ,we define an
effective Hamiltonian which has a band-diagonal shape with respect to the
eigenbasis of . This means that all transition matrix elements are
suppressed which have energy differences larger than a given cutoff
that is smaller than the cutoff of the original Hamiltonian. This
property resembles a recent flow equation approach on the basis of continuous
unitary transformations. For demonstration of the method we discuss an exact
solvable model, as well as the Anderson-lattice model where the well-known
quasiparticle behavior of heavy fermions is derived.Comment: 11 pages, final version, to be published in Phys. Rev.
Contributions of the SL Division to the Workshop on Beam-beam Effects at Fermilab, June 2001
This is a compilation of the papers and presentations contributed to the workshop on beam-beam effects, held from 25-28.6 2001 at Fermilab, Batavia, Illinois, US
Subtraction of test mass angular noise in the LISA Technology Package interferometer
We present recent sensitivity measurements of the LISA Technology Package
interferometer with articulated mirrors as test masses, actuated by
piezo-electric transducers. The required longitudinal displacement resolution
of 9 pm/sqrt[Hz] above 3 mHz has been demonstrated with an angular noise that
corresponds to the expected in on-orbit operation. The excess noise
contribution of this test mass jitter onto the sensitive displacement readout
was completely subtracted by fitting the angular interferometric data streams
to the longitudinal displacement measurement. Thus, this cross-coupling
constitutes no limitation to the required performance of the LISA Technology
Package interferometry.Comment: Applied Physics B - Lasers and Optics (2008
NLO properties of functionalized DNA thin films
In this paper we investigate the third-order nonlinear optical properties of spin deposited thin films of DNA-based complexes using the optical third harmonic generation (THG) technique at a fundamental wavelength of 1064Â nm. We found that the third-order susceptibility, Ï(3)(â 3Ï;Ï,Ï,Ï), of DNA-based films was about one order of magnitude larger than that of our reference, a pure silica slab. In thin films doped with 5% of the chromophore disperse red 1 (DR1), a two order of magnitude larger value of Ï(3)(â 3Ï;Ï,Ï,Ï) was observed
- âŠ