CERN Accelerating science

Thesis
Report number	LYCEN–T-2009-40
Title	Contribution à la calibration des photons par les désintégrations radiatives $Z --> \nu\nu\gamma$, dans l'expérience CMS au LHC (CERN)
Translation of title	Contribution to the gamma calibration by the radiative decay $Z-->\nu\nu\gamma$, in the CMS experiment at LHC (CERN)
Author(s)	Bâty, Clément (Lyon, IPN)
Publication	250.
Thesis note	PhD : Lyon U. : 2009
Thesis supervisor(s)	Gascon-Shotkin, S
Note	presented 26 Nov 2009
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; CMS
Keywords	Radiative decay
Abstract	The LHC has started, since november 2009 taking data. This started a new era of discovery in particle physics. The CMS detector is one of the main experiment at the LHC (CERN). One goal of this experiment is the Higgs's boson discovery, that can be related to the electroweak symmetry breaking. After a contextual replacement of the LHC and CMS within the nowdays's particle physics, I will explain the whole chain allowing to go from the physical event to the nal analysis, in order to extract the reconstructed particles and the informations allowing, at the end, the discovery of new particles like the Higgs's boson. A rst part of my works was about the measurement and the study of the acquisition electronics's gains-ratios. This work aimed to have a precise measurement of the photons energy on the whole available energy band (35 MeV -> 1.7 TeV). In particular, my works were upon the validation of the dierent calibration methods for the VFE acquisition cards within the detector. A second part of my work was about the way that one have to generate the physics events avoiding double-counting between photons coming from matrix-element generators and those coming from parton-shower algorithms. In collaboration with phenomenologists physicists, an anti-double-counting veto have been created. At last, the nal part of my results was about the way the radiative decay of the Z° neutral electroweak gauge boson allow, by the selection of certied photons, the extraction of the photons energy scale inside the electromagnetical calorimeter of CMS.

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