Showing papers by "Gregor Herten published in 2007"
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TL;DR: The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities.
Abstract: The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC.
55 citations
01 Aug 2007
49 citations
TL;DR: In this article, the W-pair production cross sections at 10 different centre-of-mass energies were used to determine the W boson branching fractions, which were found to be consistent with lepton universality of the charged current interaction.
Abstract: From a total data sample of 701.1 pb-1 recorded with e+e- centre-of-mass energies of \(\sqrt{s} =\)161–209 GeV with the OPAL detector at LEP, 11693 W-pair candidate events are selected. These data are used to obtain measurements of the W-pair production cross sections at 10 different centre-of-mass energies. The ratio of the measured cross sections to the standard model expectation is found to be: \({\text{data}}/{{\text{SM}}} = 1.002\pm0.011 ({\text{stat.}}) \pm0.007 ({\text{syst.}}) \pm0.005 ({\text{theory}})\), where the uncertainties are statistical, experimental systematics and theory systematics respectively. The data are used to determine the W boson branching fractions, which are found to be consistent with lepton universality of the charged current interaction. Assuming lepton universality, the branching ratio to hadrons is determined to be 67.41±0.37(stat.)±0.23(syst.)%, from which the CKM matrix element |Vcs| is determined to be 0.969±0.017(stat.)±0.012(syst.). The differential cross section as a function of the W- production angle is measured for the qqeν and qqμν final states. The results described in this paper are consistent with the expectations from the standard model.
23 citations
TL;DR: In this paper, a study of Bose-Einstein correlations in pairs of identically charged pions produced in e+e- annihilations at the Z0 peak has been performed for the first time assuming a non-static emitting source.
Abstract: A study of Bose–Einstein correlations in pairs of identically charged pions produced in e+e- annihilations at the Z0 peak has been performed for the first time assuming a non-static emitting source. The results are based on the high statistics data obtained with the OPAL detector at LEP. The correlation functions have been analyzed in intervals of the average pair transverse momentum and of the pair rapidity, in order to study possible correlations between the pion production points and their momenta (position–momentum correlations). The Yano–Koonin and the Bertsch–Pratt parameterizations have been fitted to the measured correlation functions to estimate the geometrical parameters of the source as well as the velocity of the source elements with respect to the overall centre-of-mass frame. The source rapidity is found to scale approximately with the pair rapidity, and both the longitudinal and transverse source dimensions are found to decrease for increasing average pair transverse momenta.
13 citations
TL;DR: In this article, the OPAL detector at LEP has been used to measure the production of charged hadrons in the collisions of quasi-real photons (e(+)e(-) + X) at energies from 183 to 209 GeV, and the differential cross-sections as a function of the transverse momentum and the pseudorapidity of the hadrons are compared to theoretical calculations of up to next-to-leading order (NLO) in the strong coupling constant alpha(s).
7 citations
TL;DR: In this article, the authors describe a topological search for an invisibly decaying Higgs boson, H, produced via the Bjorken process (e(+)e(-)-> HZ).
Abstract: This paper describes a topological search for an invisibly decaying Higgs boson, H, produced via the Bjorken process (e(+)e(-)-> HZ). The analysis is based on data recorded using the OPAL detector at LEP at centre-of-mass energies from 183 to 209 GeV corresponding to a total integrated luminosity of 629 pb(-1). In the analysis only hadronic decays of the Z boson are considered. A scan over Higgs boson masses from 1 to 120 GeV and decay widths from 1 to 3000 GeV revealed no indication for a signal in the data. From a likelihood ratio of expected signal and standard model background we determine upper limits on cross-section times branching ratio to an invisible final state. For moderate Higgs boson decay widths, these range from about 0.07 pb (M-H=60 GeV) to 0.57 pb (M-H=114 GeV). For decay widths above 200 GeV the upper limits are of the order of 0.15 pb. The results can be interpreted in general scenarios predicting a large invisible decay width of the Higgs boson. As an example we interpret the results in the so-called stealthy Higgs scenario. The limits from this analysis exclude a large part of the parameter range of this scenario experimentally accessible at LEP 2.
5 citations