Discovery of Single Top Quark Production by Dag Gillberg

By Dag Gillberg

This unique, impressive thesis provides the 1st discovery of unmarried most sensible quark creation and records one of many flagship measurements of the D0 test, a collaboration of greater than six hundred particle physicists from worldwide. It describes the 1st commentary of a actual method often called “single best quark production,” which were hunted for greater than 10 years earlier than its eventual discovery in 2009.

This thesis describes, intimately, an leading edge strategy of utilizing Boosted choice timber, a machine-learning strategy, to watch the tiny unmarried best sign inside of an another way overwhelming history. the ultimate consequence used to be released in August 2009 in actual evaluation Letters, the main prestigious magazine within the box of experimental particle physics. It was once additional made an “editor’s selection” in that booklet and used to be highlighted within the magazine Physics as some of the most attention-grabbing and demanding effects released in all of physics at that time.

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3 ZpT Reweighting In the Z+jets samples, the Z pT spectrum generated by ALPGEN does not quite agree with the next-to-leading order theory prediction. To account for this, a weight depending on the true Z pT and the jet multiplicity is assigned to the event [12]. 4 Electron Identification Efficiencies Each event with an isolated electron is scaled by a factor that accounts for the differences in electron cluster finding and identification efficiency between data and Monte Carlo. The scale factor is divided into two parts: preselection and post– preselection.

Muons only deposit a small amount of energy in the calorimeter, and neutrinos no energy at all. Some energy will also be deposited in poorly instrumented regions and hence give no or little signal. This absence of measured energy results in a momentum imbalance in the transverse plane. This imbalance is called the missing transverse energy, E 6 T: The basic unit of the DØ calorimeters is a calorimeter cell. Such a cell consists of an absorber plate (U, Cu or Fe) followed by a gap filled with liquid argon.

Instead, each background needs to be probed for its individual distinguishing features. In order to identify these, and to correctly evaluate the amounts of signal and background in the dataset, it is necessary to create an accurate signal and background model. This chapter explains the analysis strategy and describes the dataset used, the selection criteria applied, and the momentous task of modeling the signal and all background processes in the data. 1 Strategy As explained in Sect. 3, single top quarks decay to a W boson and a b quark almost 100% of the time.

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