Search
Results
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Numerical simulations with two flavours of twisted-mass Wilson quarks and DBW2 gauge action
(2006)The European Physical Journal CDiscretisation errors in two-flavour lattice QCD with Wilson quarks and DBW2 gauge action are investigated by comparing numerical simulation data at two values of the bare gauge coupling. Both non-zero- and zero-twisted-mass values are considered. The results, including also data from simulations using the Wilson plaquette gauge action, are compared to next-to-leading order chiral perturbation theory formulas.Journal Article -
Searching for evolutions from pure states into mixed states with entangled neutral kaons
(2004)The European Physical Journal CEntangled two-quantum states may be a sensitive probe for a loss of quantum coherence due to apparent violations of quantum mechanics, e.g. as caused by gravitation. We show that there exists a modest experiment sensitive to any one of the nine phenomenological parameters which describe decoherence in the neutral kaon system.Journal Article -
Search for single top quark production in ep collisions at HERA
(2004)The European Physical Journal CA search for single top quark production is performed in e±p collisions at HERA. The search exploits data corresponding to an integrated luminosity of 118.3 pb-1. A model for the anomalous production of top quarks in a flavour changing neutral current process involving a tuγ coupling is investigated. Decays of top quarks into a b quark and a W boson are considered in the leptonic and the hadronic decay channels of the W. Both a cut-based ...Journal Article -
Measurement of beauty production at HERA using events with muons and jets
(2005)The European Physical Journal CA measurement of the beauty production cross section in ep collisions at a centre-of-mass energy of 319 GeV is presented. The data were collected with the H1 detector at the HERA collider in the years 1999-2000. Events are selected by requiring the presence of jets and muons in the final state. Both the long lifetime and the large mass of b-flavoured hadrons are exploited to identify events containing beauty quarks. Differential cross ...Journal Article -
Inclusive dijet production at low Bjorken-x in deep inelastic scattering
(2004)The European Physical Journal CDijet production in deep inelastic ep scattering is investigated in the region of low values of the Bjorken-variable x (10-4 < x < 10-2) and low photon virtualities Q 2 (5 < Q 2 < 100 GeV2). The measured dijet cross sections are compared with perturbative QCD calculations in next-to-leading order. For most dijet variables studied, these calculations can provide a reasonable description of the data over the full phase space region covered, ...Journal Article -
Measurement of prompt photon cross sections in photoproduction at HERA
(2005)The European Physical Journal CResults are presented on the photoproduction of isolated prompt photons, inclusively and associated with jets, in the γp center of mass energy range 142 < W < 266 GeV. The cross sections are measured for the transverse momentum range of the photons 5<EγT<10 GeV and for associated jets with E T jet > 4.5 GeV. They are measured differentially as a function of EγT,EjetT, the pseudorapidities ηγ and ηjet and estimators of the momentum fractions ...Journal Article -
Fermion pair production in e+e- collisions at 189-209 GeV and constraints on physics beyond the standard model
(2007)The European Physical Journal CCross sections, angular distributions and forward-backward asymmetries are presented, of two-fermion events produced in e+e- collisions at centre-of-mass energies from 189 to 209 GeV at LEP, measured with the ALEPH detector. Results for e+e-, μ+μ-, τ+τ-, qq̄, bb̄ and cc̄ production are in agreement with the standard model predictions. Constraints are set on scenarios of new physics such as four-fermion contact interactions, leptoquarks, ...Journal Article -
Study of spin and decay-plane correlations of W bosons in the e(+) e(-)-> W+W- process at LEP
(2005)The European Physical Journal CData collected at LEP at centre-of-mass energies s√=189−209 GeV are used to study correlations of the spin of W bosons using e+e−→W+W−→\ensuremathℓνqq¯ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in e+e−→W+W−→\ensuremathℓνqq¯ and e+e−→W+W−→\ensuremathqq¯qq¯ events. Decay-plane correlations are measured to be ...Journal Article -
Results from the ICARUS T600 module
(2004)The European Physical Journal CWe have studied the μ decay energy spectrum from a sample of stopping μ events acquired during the test run of the ICARUS T600 prototype. This detector allows the spatial reconstruction of the events with fine granularity, hence the precise measurement of the μ range and dE/dx with high sampling rate. This information is used to compute the correction factors needed for the calorimetric reconstruction. The Michel ρ parameter is then ...Journal Article -
Measurement of F-2(c(c)over-bar) and F-2(b(b)over-bar) at high Q(2) using the H1 vertex detector at HERA
(2005)The European Physical Journal CMeasurements are presented of inclusive charm and beauty cross sections in e + p collisions at HERA for values of photon virtuality Q 2 > 150 GeV2 and of inelasticity 0.1 < y < 0.7. The charm and beauty fractions are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. The data are divided into four regions in Q 2 and Bjorken x, and values ...Journal Article