Thermodynamics and collapse of self-gravitating Brownian particles in D dimensions

We address the thermodynamics (equilibrium density profiles, phase diagram, instability analysis...) and the collapse of a self-gravitating gas of Brownian particles in D dimensions, in both canonical and microcanonical ensembles. In the canonical ensemble, we derive the analytic form of the density scaling profile which decays as f(x)=x^{-\alpha}, with alpha=2. In the microcanonical ensemble, we show that f decays as f(x)=x^{-\alpha_{max}}, where \alpha_{max} is a non-trivial exponent. We derive exact expansions for alpha_{max} and f in the limit of large D. Finally, we solve the problem in D=2, which displays rather rich and peculiar features

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Production of a non-stoichiometric Nb-Ti HSLA steel by thermomechanical processing on a steckel mill

Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM (R) software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525-550 degrees C/550-600 degrees C/600-650 degrees C/650-700 degrees C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600-650 degrees C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values

On the differences between high-energy proton and pion showers and their signals in a non-compensating calorimeter

We present the results of experimental studies of hadron showers in a copper/quartz-fiber calorimeter, based on the detection of Cherenkov light. These studies show that there are very significant differences between the signals from protons and pions at the same energies. In the energy range between 200 and 375GeV, where these studies were performed, the calorimeter's response to protons was typically 10% smaller than the response to pions. On the other hand, the energy resolution was about 25% better for protons. In addition, the protons had a Gaussian line shape, whereas the pion response curve was asymmetric. These differences can be understood from the requirements of baryon number conservation in the shower development. They are expected to be present in any non-compensating calorimeter, to a degree determined by the e/h value. © 1998 Elsevier Science B.V. All rights reserved.Comisión Interministerial de Ciencia y Tecnología: AEN96-2051-E CERN Russian Foundation for Basic Research 95-02-04815 Országos Tudományos Kutatási Alapprogramok: T 016823 TBAG1590 International Foundation for Science: M82000, M82300We would like to thank our colleagues from CMS, and in particular J. Bourotte and M. Haguenauer, who made the described beam tests possible. We are grateful to N. Doble, who provided us with particle beams of excellent quality. This project was carried out with financial support from CERN, the US Department of Energy, RMKI-KFKI (Hungary, OTKA grant T 016823), the Scientific and Technical Research Council of Turkey (TÜBITAK, grant TBAG1590), CICYT (Spain, grant AEN96-2051-E), the International Science Foundation (grants M82000 and M82300), the State Committee of the Russian Federation for Science and Technologies, and the Russian Research Foundation (grant 95-02-04815)

Test beam of a quartz-fibre calorimeter prototype with a passive front section

We present test-beam data analysis of a quartzfibre calorimeter prototype composed of a single active section with a passive absorber in front of it. The partial suppression of the electromagnetic showers leads to the equalization of the response to electrons and pions for a given depth of this passive section. Results are compared with the Monte-Carlo expectations.Russian Foundation for Basic Research Ministry of Education and Science of the Russian Federation Comisión Interministerial de Ciencia y Tecnología: AEN96-205 1-E Országos Tudományos Kutatási Alapprogramok: T 0 16823 95-02-04815 CERN M82300, 82000This project was carried out with financial support from CERN, the US Departmento f Energy, RMKI-KFKI (Hungary, OTKA grant T 0 16823),T UBITAK (Turkey), CICYT (Spain, grant AEN96-205 1-E), the InternationalS cience Foundation (grantsM 82000 and M82300), the Ministry of the Russian Federation for Science and Technology, and the Russian Research Foundation (grant 95-02-04815)