1.1 Overview of fermion properties . . . 4
1.2 Overview of boson masses . . . 5
5.1 Overview of thetight menu shower shapes . . . 39
6.1 Event yields for data and expectations (preselection) . . . 52
6.2 Event yields for data and expectations (final selection) . . . 52
7.1 Signal and background parameters in the template fit . . . 55
10.1 Multijet estimation forfe→γ . . . 72
10.2 Uncertainties on the electron-to-photon misidentification rate . . . 74
10.3 Expected yields for processes with an electron misidentified as a photon . . . 76
11.1 Overview of the differentt¯tγ background contributions . . . 82
11.2 Overview of systematic variations for backgroundt¯tγ contributions from brems-strahlung . . . 82
11.3 Uncertainties on the estimate of the multijet+γ background . . . 87
11.4 Expected yields for different background contributions in theW+jets CR . . . . 88
11.5 W+jets+γ yields in the signal region using different control regions (CRs) . . . . 90
11.6 Sources of uncertainties on theW+jets+γ yield in the signal region . . . 91
11.7 Expected yields for additional backgrounds with prompt photons . . . 92
11.8 Expected yields for background processes with prompt photons . . . 92
13.1 Result of the combined template fit . . . 104
13.2 Statistical and systematic uncertainties on the number oft¯tγ events . . . 105
Acknowledgements
First of all, I want to express my sincere gratitude to Prof. Dr. Arnulf Quadt, my thesis adviser, who was at the origin of my enthusiasm for particle physics in M¨unchen back in 2006. I want to thank him for the opportunity to join him and his group of motivated top quark physicists in G¨ottingen, for his trust in a t¯tγ measurement with early ATLAS data, and for his constant support in physics and non-physics matters. Moreover, I am particularly grateful for the op-portunities to stay, work and extend my knowledge at LAL and at CERN for extended periods during my time as a PhD student. I want to thank Jun.-Prof. Dr. Lucia Masetti that she kindly agreed to be the second referee of this thesis.
I am very grateful to Kevin Kr¨oninger for his excellent supervision and lots of efficient advice.
Not only was he open for discussions at any time, but also could nothing make him lose his calm. I want to sincerely thank Lisa Shabalina for the excellent supervision on top physics and Pixel matters during my time at CERN, and for her good mood regardless of conference stress.
Thanks to J¨org Meyer for tips and help on computing issues and especially for straightforward solutions when time was short. Special thanks to Kevin, Lisa, Andrea and J¨org for their attentive reading of the drafts of this thesis and their valuable comments.
I want to thank the ATLAS group at LAL, who cordially welcomed me in Orsay, and my colleagues from LAPP for the fruitful collaboration on the diphoton analysis. I want to express my special gratitude to Marumi Kado, from whom I learnt so much about photons, for a highly efficient and enjoyable time at LAL. I also want to thank the group of Prof. Dr. Ivor Fleck in Siegen for the great common effort for the HCP conference note.
Thanks to Ms Christa Wohlfahrt, Ms Bernadette Tyson, Ms Heidi Afshar, Heike Ahrens and Ms Gabriela Herbold for constant and constructive help with administrative issues. Special thanks to Lucie Hamdi for her patience with creatively filled travel forms.
I want to thank all my colleagues and friends at the II. Institute of Physics for the excellent atmosphere at and off work. Special thanks to Andrea, Anna, Boris, Daniel, Hans, Olaf and Stefan for distraction in form of football discussions, professional and office basketball, good movies and series, beer and sports.
Thanks to Andi, Andrea, George, Jarka, Johannes, Jonas, Katharina, Morten and Steffi for a great time at pont de Gremaz with kitchen discussions, ice-cream meetings, barbecues and hikes to the Reculet. Thanks to Marilla, Elina and the AOV for being my musical home in G¨ottingen and for a lot of superb rehearsals and concerts.
I am very grateful to my parents for their constant support – not only, but also – during my PhD time, and to Martin and Birgitta for valuable advice at any stage of my PhD thesis. Last but not least, I want to say thanks to my sister Marion and her husband Simon for support, distraction, conversations and eggs deluxe wherever and whenever needed.
Lebenslauf
Am 11.10.1982 wurde ich als Sohn des Oberstudienrates Christian Martin Erdmann und der In-strumentalp¨adagogin Katharina Erdmann in Bonn geboren. Nach dem Besuch der Grundschule besuchte ich das Evangelische Gymnasium in Meinerzhagen, wo ich im Juni 2002 das Abitur erhielt.
Anschließend leistete ich meinen Zivildienst in der evangelischen Tagungsst¨atte
”haus nord-helle“ in Valbert. Zum Wintersemester 2003/04 nahm ich das Physikstudium an der Ludwig-Maximilians-Universit¨at in M¨unchen auf. Im August 2005 erhielt ich dort das Vordiplom. Von September 2005 bis Mai 2006 studierte ich mit einem Erasmus-Stipendium an der Universit´e de Paris-Sud (Paris XI) in Orsay.
Im Anschluß an den Aufenthalt in Frankreich arbeitete ich f¨ur zwei Monate am Max-Planck-Institut f¨ur Physik in M¨unchen bei Prof. Dr. Arnulf Quadt (jetzt Universit¨at G¨ottingen) an der Entwicklung eines kinematischenχ2-Fitters zur Rekonstruktion semileptonischer Topquarkpaar-Ereignisse am ATLAS-Experiment.
Nach dem Ablegen der Diplompr¨ufungen begann ich meine Diplomarbeit, die ich am Max-Planck-Institut f¨ur Physik zur Analyse der hadronischen Kalibration des ATLAS-Endkappen-kalorimeters mit Teststrahl-Daten anfertigte. Die Gutachter der Arbeit waren Prof. Dr. Siegfried Bethke und Prof. Dr. Dorothee Schaile. Im Dezember 2008 erhielt ich das Diplom der Ludwig-Maximilians-Universit¨at M¨unchen mit dem Vermerk
”mit Auszeichnung bestanden“.
Im Januar 2009 nahm ich das Promotionsstudium an der Georg-August-Universit¨at G¨ottingen auf. Von Mai bis August 2010 arbeitete ich am Laboratoire de l’Acc´el´erateur Lin´eaire in Orsay bei Paris an der Messung des inklusiven Diphoton-Wirkungsquerschnittes am ATLAS-Experiment.
Im Anschluss an den Aufenthalt in Orsay war ich ein Jahr am CERN, wo ich auch Aufgaben f¨ur den Betrieb des ATLAS-Detektors ¨ubernahm. Nach meiner R¨uckkehr nach G¨ottingen wurden die Ergebnisse dert¯tγ-Analyse im November 2011 von der ATLAS-Kollaboration alsconference note ver¨offentlicht.
Ich bin deutscher Staatsangeh¨origer.
G¨ottingen, den 25.04.2012