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

Study of sequential semileptonic decays of b hadrons produced at the Tevatron

We present a study of rates and kinematical properties of lepton pairs contained in central jets with transverse energy E_T > 15 GeV that are produced at the Fermilab Tevatron collider. We compare the data to a QCD prediction based on the HERWIG and QQ Monte Carlo generator programs.We find that the data are poorly described by the simulation, in which sequential semileptonic decays of single b quarks (b --> l c X with c --> l s X) are the major source of such lepton pairs.Comment: 25 pages, 8 figures. Some typos were fixed in the text and bibliography. Submitted to Phys. Rev.

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

Phenomenological study of the atypical heavy flavor production observed at the Fermilab Tevatron

We address known discrepancies between the heavy flavor properties of jets produced at the Tevatron collider and the prediction of conventional-QCD simulations. In this study, we entertain the possibility that these effects are real and due to new physics. We show that all anomalies can be simultaneously fitted by postulating the additional pair production of light bottom squarks with a 100% semileptonic branching fraction.Comment: 30 pages, 13 figures, 3 tables. Submitted to Phys. Rev.

Effective one-body dynamics in multiple-quantum NMR experiments

A suitable NMR experiment in a one-dimensional dipolar coupled spin system allows one to reduce the natural many-body dynamics into effective one-body dynamics. We verify this in a polycrystalline sample of hydroxyapatite (HAp) by monitoring the excitation of NMR many-body superposition states: the multiple-quantum coherences. The observed effective one-dimensionality of HAp relies on the quasi 1d structure of the dipolar coupled network that, as we show here, is dynamically enhanced by the quantum Zeno effect. Decoherence is also probed through a Loschmidt echo experiment, where the time reversal is implemented on the double-quantum Hamiltonian, I_{i,+}I_{j,+} + I_{i,-}I_{j,-}. We contrast the decoherence of adamantane, a standard 3d system, with that of HAp. While the first shows an abrupt Fermi-type decay, HAp presents a smooth exponential law.Comment: 8 pages, 6 figure

A New Mirroring Circuit for Power MOS Current Sensing Highly Immune to EMI

This paper deals with the monitoring of power transistor current subjected to radio-frequency interference. In particular, a new current sensor with no connection to the power transistor drain and with improved performance with respect to the existing current-sensing schemes is presented. The operation of the above mentioned current sensor is discussed referring to time-domain computer simulations. The susceptibility of the proposed circuit to radio-frequency interference is evaluated through time-domain computer simulations and the results are compared with those obtained for a conventional integrated current sensor