Multi-Moment Advection scheme for Vlasov simulations

We present a new numerical scheme for solving the advection equation and its application to Vlasov simulations. The scheme treats not only point values of a profile but also its zeroth to second order piecewise moments as dependent variables, for better conservation of the information entropy. We have developed one- and two-dimensional schemes and show that they provide quite accurate solutions within reasonable usage of computational resources compared to other existing schemes. The two-dimensional scheme can accurately solve the solid body rotation problem of a gaussian profile for more than hundred rotation periods with little numerical diffusion. This is crucially important for Vlasov simulations of magnetized plasmas. Applications of the one- and two-dimensional schemes to electrostatic and electromagnetic Vlasov simulations are presented with some benchmark tests.Comment: 52 pages, 18 figures, accepted for the publication in Journal of Computational Physic

Measurement of the QED Compton scattering cross section with the H1 detector at HERA

Mit Hilfe von im Jahre 1997 aufgezeichneten Daten des H1-Experiments wurde der doppelt differentielle Wirkungsquerschnitt von QED-Compton-Streuung beiHERA gemessen. Die Messung wurde in Intervallen der kinematischen Variablen xl und Q2l im Bereich 1.8 · 10-5 < xl < 1.8 · 10-3 und 2 GeV2 < Q2l < 86 GeV2durchgeführt. Die Ergebnisse werden benutzt, um Informationen über die Protonstrukturfunktion F2 im kinematischen Bereich von kleinen Virtualitäten desausgetauschten Photons Q2h bis zu 0.05 GeV2 und in einem breiten Bereich der Bjorkenschen Variablen xh zwischen ca. 10-4 und 0.5 zu gewinnen, also in einemnicht in inklusiver ep-Streuung bei HERA zugänglichen kinematischen Bereich. Außerdem wurde die Messung mit theoretischen Berechnungen in der kollinearenApproximation verglichen, in der das ausgetauschte Photon als Parton im Proton betrachtet wird. Es wurde gefunden, dass dieser Ansatz im Bereich inelastischerQED-Compton-Streuung zu signifikanten Diskrepanzen zwischen den vorhergesagten und den gemessenen Werten des Wirkungsquerschnittes führt.The double differential cross section of QED Compton scattering at HERA is measured using data collected in 1997 by the H1 experiment. The measurement iscarried out in bins of the kinematic variables xl and Q2l in the range 1.8 · 10-5 < xl < 1.8 · 10-3 and 2 GeV2 < Q2l < 86 GeV2. The results are used to gaininformation on the proton structure function F2 in the kinematic region of small virtualities of the exchanged photon Q2h down to 0.05 GeV2 and in a wide range ofthe Bjorken variable xh between approximately 10-4 and 0.5, a region which is not accessible in inclusive ep scattering at HERA. The measurement is alsoconfronted to theoretical calculations performed in the collinear approximation, in which the exchanged photon is treated as a parton of the proton. It is found thatthis approach leads to significant discrepancies between the predicted and the measured cross section values in the domain of inelastic QED Compton scattering

Measurement of the neutral current reaction at high Q2 in the H1 experiment at HERA II

This thesis presents inclusive ep double and single differential cross section measurements for neutral current deep inelastic scattering of longitudinally polarized leptons on protons as a function of the negative four-momentum transfer squared Q2 and the Bjorken variable x. The data were collected in the years 2003-2007 in the H1 experiment at HERA with positively and negatively longitudinally polarized lepton beams of 27 GeV and a proton beam of 920 GeV corresponding to the centre-of-mass energy of sqrt{s} = 319 GeV. The integrated luminosity is about 330 pb^{-1}. An overview of the phenomenology of the deep inelastic scattering is given and the experimental apparatus is described. The NC cross section measurement procedure is presented and discussed in details. The measured cross sections are used to investigate electroweak effects at high Q2. The proton structure function xF_3, sensitive to the valence quarks in the proton, is measured. The polarization effects sensitive to the chiral structure of neutral currents are investigated. The Standard Model predictions are found to be in a good agreement with the measurement

Measurement of the neutral current reaction at high Q2 in the H1 experiment at HERA II

This thesis presents inclusive ep double and single differential cross section measurements for neutral current deep inelastic scattering of longitudinally polarized leptons on protons as a function of the negative four-momentum transfer squared Q2 and the Bjorken variable x. The data were collected in the years 2003-2007 in the H1 experiment at HERA with positively and negatively longitudinally polarized lepton beams of 27 GeV and a proton beam of 920 GeV corresponding to the centre-of-mass energy of sqrt{s} = 319 GeV. The integrated luminosity is about 330 pb^{-1}. An overview of the phenomenology of the deep inelastic scattering is given and the experimental apparatus is described. The NC cross section measurement procedure is presented and discussed in details. The measured cross sections are used to investigate electroweak effects at high Q2. The proton structure function xF_3, sensitive to the valence quarks in the proton, is measured. The polarization effects sensitive to the chiral structure of neutral currents are investigated. The Standard Model predictions are found to be in a good agreement with the measurement

Highlights of the SLD Physics Program at the SLAC Linear Collider

Starting in 1989, and continuing through the 1990s, high-energy physics witnessed a flowering of precision measurements in general and tests of the standard model in particular, led by e+e- collider experiments operating at the Z0 resonance. Key contributions to this work came from the SLD collaboration at the SLAC Linear Collider. By exploiting the unique capabilities of this pioneering accelerator and the SLD detector, including a polarized electron beam, exceptionally small beam dimensions, and a CCD pixel vertex detector, SLD produced a broad array of electroweak, heavy-flavor, and QCD measurements. Many of these results are one of a kind or represent the world's standard in precision. This article reviews the highlights of the SLD physics program, with an eye toward associated advances in experimental technique, and the contribution of these measurements to our dramatically improved present understanding of the standard model and its possible extensions.Comment: To appear in 2001 Annual Review of Nuclear and Particle Science; 78 pages, 31 figures; A version with higher resolution figures can be seen at http://www.slac.stanford.edu/pubs/slacpubs/8000/slac-pub-8985.html; Second version incorporates minor changes to the tex