Electron reconstruction and research of anomalous couplings in pp->ZZ->4l with the CMS detector at LHC

by Dr David Sabes (LLR - Ecole Polytechnique)

Friday 18 Jan 2013, 14:00 → 15:00 Europe/Brussels

Large seminar room (IIHE (ULB-VUB))

abstract: This seminar will cover the work I did during my PhD in the CMS collaboration at LHC using data from 2010 and 2011 pp collisions. The electron reconstruction is essential for the study of many decay channels like the H→ZZ→4l, or the one considered in this presentation: ZZ→4l. Therefore the optimisation of electron reconstruction algorithms in CMS will be introduced and the electron reconstruction efficiency measurement will be presented.The 4l leptons invariant mass can be affected by energy loss due to final state radiations. A recovery algorithm can correct 4.2% of ZZ→4μ events. Finally the research of anomalous triple gauge couplings (ATGCs) will be presented: neutral trilinear couplings are forbidden in Standard Model but can be introduced using an effective Lagrangian with new couplings terms f4Z and f5Z in the ZZZ case. ATGCs generally generate an increase of the ZZ cross-section production and some distortions in the ZZ mass spectrum or Z kinematical distributions. A pure selection of ZZ→4l events has been established. A search for ATGCs thanks to a reponderation method using the shape of the invariant mass of the 4-leptons system has been performed. Limits on ZZZ ATGCs are set at 95% confidence level: -0.0116< f4Z <0.0116 and -0.0119< f5Z <0.0119.