958 resultados para CMS. CERN


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A study of proton-proton collisions in which two b hadrons are produced in association with a Z boson is reported. The collisions were recorded at a centre-of-mass energy of 7TeV with the CMS detector at the LHC, for an integrated luminosity of 5:2 fb-1. The b hadrons are identified by means of displaced secondary vertices, without the use of reconstructed jets, permitting the study of b-hadron pair production at small angular separation. Differential cross sections are presented as a function of the angular separation of the b hadrons and the Z boson. In addition, inclusive measurements are presented. For both the inclusive and differential studies, different ranges of Z boson momentum are considered, and each measurement is compared to the predictions from different event generators at leading-order and next-to-leading-order accuracy. Copyright CERN.

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Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Electrotécnica Ramo de Automação e Electrónica Industrial

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The purpose of the work was to realize a high-speed digital data transfer system for RPC muon chambers in the CMS experiment on CERN’s new LHC accelerator. This large scale system took many years and many stages of prototyping to develop, and required the participation of tens of people. The system interfaces to Frontend Boards (FEB) at the 200,000-channel detector and to the trigger and readout electronics in the control room of the experiment. The distance between these two is about 80 metres and the speed required for the optic links was pushing the limits of available technology when the project was started. Here, as in many other aspects of the design, it was assumed that the features of readily available commercial components would develop in the course of the design work, just as they did. By choosing a high speed it was possible to multiplex the data from some the chambers into the same fibres to reduce the number of links needed. Further reduction was achieved by employing zero suppression and data compression, and a total of only 660 optical links were needed. Another requirement, which conflicted somewhat with choosing the components a late as possible was that the design needed to be radiation tolerant to an ionizing dose of 100 Gy and to a have a moderate tolerance to Single Event Effects (SEEs). This required some radiation test campaigns, and eventually led to ASICs being chosen for some of the critical parts. The system was made to be as reconfigurable as possible. The reconfiguration needs to be done from a distance as the electronics is not accessible except for some short and rare service breaks once the accelerator starts running. Therefore reconfigurable logic is extensively used, and the firmware development for the FPGAs constituted a sizable part of the work. Some special techniques needed to be used there too, to achieve the required radiation tolerance. The system has been demonstrated to work in several laboratory and beam tests, and now we are waiting to see it in action when the LHC will start running in the autumn 2008.

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La presente investigación analiza los alcances y las limitaciones de cinco proyectos de Educación para la Paz desarrollados en la Escuela Normal Superior de San Juan Nepomuceno-Montes de María, en la prevención del reclutamiento y la utilización de niños, niñas y jóvenes por parte de grupos armados al margen de la ley. En ese sentido, se describe y explica de qué manera las estrategias pedagógicas orientadas hacia la enseñanza de derechos humanos, memoria histórica y resolución no violenta de conflictos pueden disminuir el riesgo de reclutamiento. Estos propósitos se resolvieron gracias a una revisión sistemática de documentos académicos e informes institucionales que se referían al objeto de estudio, y por medio del trabajo de campo realizado en San Juan Nepomuceno.

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Tras analizar y evaluar la argumentación jurídica efectuada por el Tribunal del CIADI respecto del caso CMS vs. Argentina, se aprecia que tal argumentación descansa sobre la errada concepción de que en el caso no existían aspectos que afecten derechos humanos. En realidad se trataba de un caso difícil, en materia de derechos sociales, que no podía ser resuelto por la simple aplicación de las reglas específicas del sistema (subsunción), como erróneamente lo hizo el Tribunal del CIADI, pues necesariamente debía acudirse al procedimiento de la ponderación. Si se acude a la ponderación se podrá constatar que existen dos principios aplicables, cada uno de los cuales lleva a una solución incompatible con la del otro: por un lado, la protección del derecho a la seguridad jurídica del inversionista extranjero, que exige un respeto a los derechos pactados contractual y legalmente, y, por otro, el de la protección al derecho a la vivienda, que exige una congelación en las tarifas de servicios básicos esenciales, entre ellos del transporte y distribución del gas. En este caso el segundo prevalece sobre el primero.

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During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm−3 s−1, and growth rates between 2 and 37 nm h−1. The corresponding H2SO4 concentrations were typically around 106 cm−3 or less. The experimentally-measured formation rates and H2SO4 concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1 _C).

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Guidance for University of Reading staff wishing to add CentAUR publication lists to CMS web pages: staff profile page; department page; standard page. Log in with University of Reading (staff) username and password when prompted.

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The complete understanding of the basic constituents of hadrons and the hadronic dynamics at high energies are two of the main challenges for the theory of strong interactions. In particular, the existence of intrinsic heavy quark components in the hadron wave function must be confirmed (or disproved). In this paper we propose a new mechanism for the production of D-mesons at forward rapidities based on the Color Glass Condensate (CGC) formalism and demonstrate that the resulting transverse momentum spectra are strongly dependent on the behavior of the charm distribution at large Bjorken x. Our results show clearly that the hypothesis of intrinsic charm can be tested in pp and p(d)A collisions at RHIC and LHC. (C) 2010 Elsevier B.V. All rights reserved.

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Arbetet behandlar säkerhetstestning av webbapplikationer och CMS plattformen EPiServer. För att Know IT Dalarna ska kunna fortsätta leverera säkra webblösningar efterfrågar de en säkerhetsanalys över plattformen EPiServer men även över sina egenutvecklade applikationer. Syftet med arbetet var att höja säkerheten kring Know ITs webbaserade projekt och samtidigt göra utvecklarna mer medvetna om säkerheten vid utvecklingsfasen. Resultatet var att EPiServer som plattformen tillhandahåller en fullgod säkerhet. De direkta brister som identifierades var upp till antingen Know IT eller kunden att åtgärda och ansvaret lades på den som hade hand om driften av webbplatsen. Säkerhetstesterna som utfördes var bland annat tester emot åtkomsthantering, avlyssningsattacker, lösenordsattacker, SQL-injections och XSS-attacker.För att förenkla säkerhetstestningen skapades en checklista innehållandes steg för steg för att göra en grundläggande säkerhetstestning. Den innehöll även rekommendationer till Know IT Dalarna på områden som ska belysas och undersökas i framtiden. Checklistan kan användas av utvecklarna för att säkerställa att ett pågående projekt håller en bra nivå säkerhetsmässigt. Listan måste i framtiden uppdateras och hållas i fas med den ständiga tekniska utvecklingen som sker på området.