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Search Results: 1 - 10 of 51435 matches for " CMS.;Silva "
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Recent results on Top quark Physics with the ATLAS and CMS experiments
Pedro Silva,for the ATLAS Collaboration,for the CMS Collaboration
Physics , 2012,
Abstract: An overview of the most recent results on top quark physics obtained using proton-proton collision data collected with the ATLAS and the CMS experiments at 7 TeV center-of-mass energy is given. Measurements for inclusive and differential top quark pair or single top quark production in different final states are reviewed. Top properties such as W helicity in top decays, electric charge, charge asymmetry and spin correlations of top quark pairs, among others have also been measured by the LHC experiments. All the measurements are found to be consistent with the Standard Model predictions with a good level of accuracy. The latest results in the measurement of the top quark mass at the LHC are also presented and discussed.
Reproductive cycle of Macrobrachium amazonicum females (Crustacea, Palaemonidae)
Sampaio, CMS.;Silva, RR.;Santos, JA.;Sales, SP.;
Brazilian Journal of Biology , 2007, DOI: 10.1590/S1519-69842007000300022
Abstract: macrobrachium amazonicum is considered a favorite brazilian species of freshwater prawn for cultivation as a result of its quick development and because it is easy to maintain in captivity. the aim of this work is to describe the sexual cycle stages and determine maturation age of the female m. amazonicum, which was collected monthly from june, 2002 to may, 2003 in the jaguaribe river, itai?aba, ceará. a monthly sample of water was also collected to determine the following parameters: temperature, dissolved oxygen, ph and salinity. a monthly sample of females was selected among the individuals caught, to determine the total weight (wt), carapace length (lc) and abdomen+telson length (la+t) and to register the number of non-ovigerous females (nof) and ovigerous females (of). determining ovarian maturation stages of m. amazonicum was done in a laboratory by observing macroscopic characters such as coloring, size, location and appearance of ovarians examined by transparent carapace. the first maturation age was determined from the relative frequency of the total length (lt) of young and adult females. the environmental parameters of the jaguaribe river did not hold any influence in the number of individuals collected. a total of 1,337 prawns were sampled, 513 males (38.4%) and 824 females (61.6%). the proportion between males and females in the studied population was of 1:1.6. among the collected females, 492 (50.7%) did not carry eggs in their abdomens (nof) and 332 (40.3%) carried eggs in their abdomens (of). there was no record of intact females. non-ovigerous females with mature ovaries were recorded throughout all the months of collection. the female ovaries were classified as immature (im), rudimentary (ru), intermediary (in) and mature (m). m. amazonicum females reach their first sexual maturity between 4.5 and 5.5 cm of total length.
Performance of the CMS Hadron Calorimeter with Cosmic Ray Muons and LHC Beam Data
CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03012
Abstract: The CMS Hadron Calorimeter in the barrel, endcap and forward regions is fully commissioned. Cosmic ray data were taken with and without magnetic field at the surface hall and after installation in the experimental hall, hundred meters underground. Various measurements were also performed during the few days of beam in the LHC in September 2008. Calibration parameters were extracted, and the energy response of the HCAL determined from test beam data has been checked.
Performance of the CMS Level-1 Trigger during Commissioning with Cosmic Ray Muons
CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03002
Abstract: The CMS Level-1 trigger was used to select cosmic ray muons and LHC beam events during data-taking runs in 2008, and to estimate the level of detector noise. This paper describes the trigger components used, the algorithms that were executed, and the trigger synchronisation. Using data from extended cosmic ray runs, the muon, electron/photon, and jet triggers have been validated, and their performance evaluated. Efficiencies were found to be high, resolutions were found to be good, and rates as expected.
Commissioning and Performance of the CMS Pixel Tracker with Cosmic Ray Muons
CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03007
Abstract: The pixel detector of the Compact Muon Solenoid experiment consists of three barrel layers and two disks for each endcap. The detector was installed in summer 2008, commissioned with charge injections, and operated in the 3.8 T magnetic field during cosmic ray data taking. This paper reports on the first running experience and presents results on the pixel tracker performance, which are found to be in line with the design specifications of this detector. The transverse impact parameter resolution measured in a sample of high momentum muons is 18 microns.
Alignment of the CMS Muon System with Cosmic-Ray and Beam-Halo Muons
CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03020
Abstract: The CMS muon system has been aligned using cosmic-ray muons collected in 2008 and beam-halo muons from the 2008 LHC circulating beam tests. After alignment, the resolution of the most sensitive coordinate is 80 microns for the relative positions of superlayers in the same barrel chamber and 270 microns for the relative positions of endcap chambers in the same ring structure. The resolution on the position of the central barrel chambers relative to the tracker is comprised between two extreme estimates, 200 and 700 microns, provided by two complementary studies. With minor modifications, the alignment procedures can be applied using muons from LHC collisions, leading to additional significant improvements.
Identification and Filtering of Uncharacteristic Noise in the CMS Hadron Calorimeter
The CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03014
Abstract: Commissioning studies of the CMS hadron calorimeter have identified sporadic uncharacteristic noise and a small number of malfunctioning calorimeter channels. Algorithms have been developed to identify and address these problems in the data. The methods have been tested on cosmic ray muon data, calorimeter noise data, and single beam data collected with CMS in 2008. The noise rejection algorithms can be applied to LHC collision data at the trigger level or in the offline analysis. The application of the algorithms at the trigger level is shown to remove 90% of noise events with fake missing transverse energy above 100 GeV, which is sufficient for the CMS physics trigger operation.
Aligning the CMS Muon Chambers with the Muon Alignment System during an Extended Cosmic Ray Run
CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03019
Abstract: The alignment system for the muon spectrometer of the CMS detector comprises three independent subsystems of optical and analog position sensors. It aligns muon chambers with respect to each other and to the central silicon tracker. System commissioning at full magnetic field began in 2008 during an extended cosmic ray run. The system succeeded in tracking muon detector movements of up to 18 mm and rotations of several milliradians under magnetic forces. Depending on coordinate and subsystem, the system achieved chamber alignment precisions of 140-350 microns and 30-200 microradians, close to the precision requirements of the experiment. Systematic errors on absolute positions are estimated to be 340-590 microns based on comparisons with independent photogrammetry measurements.
Time Reconstruction and Performance of the CMS Electromagnetic Calorimeter
CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03011
Abstract: The resolution and the linearity of time measurements made with the CMS electromagnetic calorimeter are studied with samples of data from test beam electrons, cosmic rays, and beam-produced muons. The resulting time resolution measured by lead tungstate crystals is better than 100 ps for energy deposits larger than 10 GeV. Crystal-to-crystal synchronization with a precision of 500 ps is performed using muons produced with the first LHC beams in 2008.
Performance Study of the CMS Barrel Resistive Plate Chambers with Cosmic Rays
CMS Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/5/03/T03017
Abstract: In October and November 2008, the CMS collaboration conducted a programme of cosmic ray data taking, which has recorded about 270 million events. The Resistive Plate Chamber system, which is part of the CMS muon detection system, was successfully operated in the full barrel. More than 98% of the channels were operational during the exercise with typical detection efficiency of 90%. In this paper, the performance of the detector during these dedicated runs is reported.
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