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Studies on the top quark mass measurement in the all-hadronic t¯t decay channel with ATLAS [Elektronische Ressource] / Paola Giovannini. Gutachter: Siegfried Bethke ; Stephan Paul. Betreuer: Siegfried Bethke

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Published 01 January 2011
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¨ ¨TECHNISCHE UNIVERSITAT MUNCHEN
PHYSIK-DEPARTMENT
Studies on the top quark mass
measurement in the all-hadronic
tt decay channel with ATLAS
Dissertation
von
Paola Giovannini
¨MAX-PLANK-INSTITUT FUR PHYSIK
WERNER-HEISENBERG-INSTITUT¨ ¨TECHNISCHE UNIVERSITAT MUNCHEN
Max-Planck-Institut fu¨r Physik
(Werner-Heisenberg-Institut)
Studies on the top quark mass
measurement in the all-hadronic
tt decay channel with ATLAS
Paola Giovannini
Vollstandiger Abdruck der von der Fakultat fur Physik¨ ¨ ¨
der Technischen Universit¨at Mu¨nchen
zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.
Vorsitzender: Univ.-Prof. Dr. A.J. Buras
Prufer der Dissertation: 1. Hon.-Prof. Dr. S. Bethke¨
2. Univ.-Prof. Dr. St. Paul
Die Dissertation wurde am 05.05.2011
bei der Technischen Universita¨t Mu¨nchen eingereicht und
durch die Fakult¨at fu¨r Physik am 04.07.2011 angenommen.Finirai per trovarla la Via
se hai il coraggio di perderti.
T.TerzaniAbstract
Prospects for measuring the top quark mass in thett all-hadronic chan-
nel with the ATLAS detector are investigated. A robust analysis is develo-

−1ped on Monte Carlo simulations at s = 10 TeV, considering 200 pb of
integrated luminosity. The event selection is based on a set of topological
variables and on two b-tagged jets. The top quark mass is measured by a
2χ fitting procedure on the reconstructed invariant mass distribution and
the fit result is corrected for missing b-jet energy calibration. With a top
MCquark mass ofm = 172.5 GeV as input to the simulation, the proposedt
method yields to a result ofm = 173.4±2.1| ±7.3| GeV for a typicalt stat sys
pseudo-experiment. The main contribution to the systematic error comes
from the jet energy scale uncertainty. Studies on the performance of the jet
calibration method used, called Local Hadron Calibration, are performed
both with Monte Carlo simulations and with first ATLAS data collected

for pp collisions at s =900 GeV.
iAcknowledgements
Theresearch presented inthisthesiswascarried outattheMPI forPhysics inMunich.
Working at MPI was an incredibly enriching experience. I could join the IMPRS grad-
uate school, which gave me the opportunity to be in close contact with the other MPI
graduate students and to follow a very interesting programme of lectures and training
courses. At the same time, this work was partially supported by the European Com-
mission, through the ARTEMIS Research Training Network (contract number MRTN-
CT-2006-035657). By being part of the ARTEMIS network I could meet scientists
outside my home institute and collaborate with them. Moreover I could participate
in international schools and in dedicated training events. I am very grateful for these
opportunities of scientific and personal growth, which led to the completion of this
PhD thesis. Among all the people that made this possible, I would like to especially
thank a few.
Iwould like tothankmy Supervisor, Prof. Dr.Siegfried Bethke, forhaving followed
the development of my work very closely and for having helped me in taking the right
direction in difficult moments.
I wish to thank my day-to-day Supervisor, Dr. Sven Menke, for having shared with
me his innovative insight into physics. I very much appreciated our discussions, where
I felt my point of view was always taken into deep consideration. I also cannot forget
the many situations where he helped me with some magic computing potion, thanks!
I am grateful to Dr. Richard Nisius for his participation to the Advisory Panel
meetings. I felt that he always tried to give the best suggestions for my career and for
the quality of the thesis.
I would like to thank Dr. Giorgio Cortiana for having given me a lot of ideas and
explanations on top physics. His experience with the top all-hadronic phenomenology
was very precious to me.
I wish to thank all the ATLAS-HEC group members for their constant support. In
particular I would like to thank Dr. Teresa Barillari for her warm welcome in Munich
iiiiv ACKNOWLEDGEMENTS
and for her careful reading of the thesis.
I am very grateful to my officemates Gennady and Andreas for the very enjoyable
time spent together. I owe a lot to Genna for all the times he helped me out of
computing and calorimeter problems with patience and care. I would like to thank
Andi for his collaboration on the top mass analysis and for all our discussions on
physics, on philosophy or on economics, which widened my horizons. I also would like
to thank him a lot for all the times he helped me with settling down in Germany.
But mainly I would like to thank them both for having always been friends to me ...
especially during the last year when it became much harder!
Finally I would like to thank all the MPI colleagues for making my staying at the
institute so pleasant. In particular a big thanks goes to Sophio for being such a good
friend, she introduced me most of the people and places that I know in Munich! I
would also like to thank Silke and Maike for having involved me in the organization of
the various MPI public outreach events, collaborating with them was really interesting
and enjoyable.
This work would not have been possible without my family and friends behind the
scenes. I want to thank my mum for her unconditional support during these years. I
know they have been hard for her, but she always stood at my side.
A big thanks goesas well to my cousin Raffyfor her vital and enthusiastic support,
which reached me even from so far away!
I want to thank my friends Mary and Rita for having encouraged me to look for
the Unknown Island at the beginning of this journey. Thanks for having brought me
here, for having come to visit at any occasion and for having kept listening to me as if
we never lived apart a single day.
I’m happy now, because I’m not alone any longer in my journey. I want to thank
Edo for having chosen to be part of this and of what will come.