Electron reconstruction in simulated Pb + Pb events in CMS

Acknowledgments First of all I would like to thank professor Gunther Roland for supervising my thesis and, most of all, the guidance and training during the two years in which I stayed in this group. I would also like to thank Yen-jie Lee, who gave me a lot of advice on the possible ways to progress on the study. Finally I would like to thank my advisor, professor Wit Busza, and everyone who helps me with my studies at MIT and made the undergraduate studies here a pleasant experience.