Recent results of the searches for Supersymmetry in final states with one or two leptons at CMS are presented. Many Supersymmetry scenarios, including the Constrained Minimal Supersymmetric extension of the Standard Model (CMSSM), predict a substantial amount of events containing leptons, while the largest fraction of Standard Model background events -which are QCD interactions -gets strongly reduced by requiring isolated leptons. The analyzed data was taken in 2011 and corresponds to an integrated luminosity of approximately L = 1 fb −1 . The center-of-mass energy of the pp collisions was √ s = 7 TeV.

The behaviour of fine-mesh vacuum phototetrodes and phototriodes (VPTs) in an axial magnetic field of (0 ÷ 4)T has been investigated. The measured VPT parameters are: fine-mesh cell dimensions, the photocathode sensitivity and its homogenity, the gain in zero and 4T magnetic field at tilt angles corresponding to the rapidity range of CMS ECAL Endcap 1.479 ÷ 3.0 and excess noise factor. Measurements have been performed on 21 and 30 mm diameter photodetectors with different fine-mesh structures: 30, 60 and 100 lines per mm under different types of photocathode illumination by green LED. Phototriodes with 30 or 60 lines per mm and an external diameter of 21 mm are found to be the best candidates for the CMS environment with the initial size of PWO crystals proposed to be used in the Endcap, by comparison with phototetrodes. They provide a gain of the order of 6 ÷ 8 in 4T magnetic field and an excess noise factor of 2 under full photocathode illumination.To be submitted to Nucl. Instr. and Meth.

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