Results 1 - 10 of 16071
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[en] It is shown that quantum systems of identical particles can be treated as different when they are in well-differentiated states. This simplifying assumption allows for the consideration of quantum systems isolated from the rest of the universe and justifies many intuitive statements about identical systems. However, it is shown that this simplification may lead to wrong results in the calculation of the entropy
[en] Data at √s = 35 GeV from the e+e- collider PETRA has been analysed using information from the high precision vertex detector to determine the average lifetime of b flavoured hadrons. The B lifetime was measured using the average signed impact parameter of high PT muon tracks, which is related to the lifetime in a way which can be determined by Monte Carlo studies. The result was τB 1.32 ± 0.45 ± 0.14 ps, which is in good agreement with other measurements and with the world average. The b quark forward-backward asymmetry was also estimated using the b enriched data sample and was found to be -0.33± 0.27, again in good agreement with other measurements. A study of muon identification using DELPHI detector components is also presented. Data taken during a beam test of the electromagnetic and hadronic calorimeters and muon chambers were analysed to evaluate the efficiency of the muon chambers, and the ability of the hadron calorimeter to distinguish between muon and pion signals. The muon tag from the hadron calorimeter was shown to be valuable in suppressing the hadronic punchthrough background to the muon signal. Muon identification criteria were devised which could be used in analysis for the selection of muon candidate tracks, and the results were used to estimate the pion punchthrough background to the signal of the Higgs boson in the channel Zo → Ho μ+μ-. (author)
[en] The techniques used for the particle identification are reviewed: time-of-flight method, identification by pulse discrimination, E-ΔE telescope, magnetic beam bending jointly with a position sensitive detector. The essential conditions to which a semiconducting material must satisfy to be usable as a γ ray detector are also recalled. The performance of various materials are compared: silicon, germanium, cadmium telluride, gallium arsenide, mercuric iodide, and diamond
[fr]On passe en revue les techniques utilisees pour l'identification des particules: methode du temps de vol, identification par discrimination des impulsions utilisation de telescope E-ΔE, et utilisation d'une deflexion magnetique associee a un detecteur de position. On rappelle egalement les conditions essentielles auxquelles doit satisfaire un materiau semiconducteur pour pouvoir etre utilise comme detecteur de rayonnement γ. On compare les performances des differents materiaux connus: silicium, germanium, tellurure de cadmium, arseniure de gallium, iodure mercurique, diamant
[en] At studying particle interactions we often have no particle identification. In this case the task of defining the true channel arises. One of the important numerical instruments which is used to determine the true channel of a reaction is the procedure of 'kinematical fitting', which for each of the tested combinations calculates the value of the functional χ"2 (⩾ 0). In this work it is proposed to use the obtained χ"2 -values to attribute a specific weight to every combination. Thus, in the proposed method all combinations (with their weight) which were successfully fitted take part in the forming of channels of a reaction. The Kolmogorov criterion that has been applied to χ"2-distributions, obtained with two described methods, gives a better agreement between the experimental distributions and theoretical ones when the weight method is used.
[ru]При изучении взаимодействия частиц нередко отсутствует идентификация вторичных частиц, тогда возникает задача определения конкретного канала реакции. Одним из действенных численных инструментов, который используется для определения канала реакции, является процедура кинематического фитирования, которая каждой из испытываемых комбинаций ставит в соответствие значение функционала χ"2 (⩾ 0). В настоящей работе предлагается по полученным величинам χ"2 определенным образом приписывать комбинациям некоторый вес. Таким образом, по предлагаемой методике в формировании каналов реакции участвуют (с весом) все комбинации, прошедшие процедуру фитирования. Критерий Колмогорова, примененный к распределениям χ"2, полученным по двум методикам, показывает лучшее согласие экспериментальных распределений с теоретическими при использовании метода установки весов.
[en] The properties of the G(1590) meson recently discovered at the Institute of High Energy Physics are analyzed by using a model based on the assumption that the interaction between hadrons is carried by their confined components (by the virton spinor and vector fields). The available experimental data support the assertion that the G(1590) meson is a scalar gluonium
[en] A detailed report on the time development of the charges induced by SQS is presented. The signals from a multicathode coaxial detector were integrated through gates from 150 ns down to 10 ns. The ratio of the charges induced on opposite cathode pads relative to the streamer direction is about 2, down to the shortest gate widths used; the charges collected are large, e.g. 2-3 pC at 20 ns. The angular distribution of the streamers shows a well defined correlation with the direction of arrival of the primary electrons, which is stronger for the smallest gate widths. (orig.)