On the use of Magnetically Coupled Resonant Snubbers to Mitigate the Electromagnetic Emission of Power Switching Circuits

This letter presents a novel solution to attenuate the electromagnetic emission of power switching circuits due to the resonance of the loop parasitic inductances with the parasitic capacitances of the power devices. A resonant snubber based on the magnetic coupling of a power parasitic loop causing unwanted oscillations with another one inserted at the printed circuit board level purposely and loaded by a dissipative element, is presented. A design method is proposed and used to damp the unwanted oscillations affecting the switching voltage and current in a prototype, which was specifically designed and fabricated to validate the proposed solution. The conducted emission delivered by such a prototype equipped with the resonant snubber, with an RC snubber, and without any snubber are compared

Measurement of the J/ψ cross section and polarization in CMS

This paper describes the measuremet of J/ψ inclusive, prompt and non-prompt cross section using the dimuon channel in the CMS experiment with the first 314 nb−1 of LHC data. An important contribution to the systematic uncertainty is given by the unknown polarization of the prompt J/ψ, in particular for what concerns the measurement of the detector acceptance. A complex framework for a measure of the prompt J/ψ polarization has been developed by the CMS collaboration and a measure of the angular parameters is foreseen in the close future. A brief description of the main issues of the polarization measurement is also given

Tracking results from LHC collisions at 900 GeV with CMS

At the end of 2009 LHC started to provide p-p collisions at a centerof-mass energy of 900 GeV. About 500 k collisions events have been recorded by the CMS experiment. This paper describes briefly the performance of the tracking and vertexing algorithms as obtained by the analysis of the first data using only mesurements in the inner silicon tracker of CMS. The reconstruction of the invariant mass of several resonant states and the precise determination of the primary and secondary vertex position are the best indication that the detector is ready to face the challenging physics program of CMS

Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV

The production of b jets in association with a Z/gamma* boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector. The inclusive cross section for Z/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.55) (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by PYTHIA.Comment: Submitted to the Journal of High Energy Physic

Experimental investigations on the tuning of active gate drivers under load current variations

Active Gate Drivers have gained of interest as they allow one to shape the switching waveforms finely, thus reducing overshoots and oscillations. However, when fast power switches are exploited, the tuning of such drivers is still challenging. This paper investigates the adjustment of gate current profile under load variations, which is a crucial issue when targeting practical applications. Indeed, a technique, based on the stretching of time intervals, is proposed and its effectiveness, in terms of undershoot reduction, is experimentally assessed

Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns

Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV

The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO

Compressed representation of a partially defined integer function over multiple arguments

In OLAP (OnLine Analitical Processing) data are analysed in an n-dimensional cube. The cube may be represented as a partially defined function over n arguments. Considering that often the function is not defined everywhere, we ask: is there a known way of representing the function or the points in which it is defined, in a more compact manner than the trivial one