RWTH Aachen University
III. Physikalisches Institut
Laboratory Class Particle Physics (Master)

Experiment 17: D0 Experiment - Production und Decay of W Bosons

Walter Bender, Thomas Hebbeker , Thomas Kress, Carsten Magass, Arnd Meyer, Simon Nieswand, Maurice Stephan

This 'experiment' does not foresee to set up an experimental device nor to take data with an existing apparatus. The objective is the evaluation of data recorded in the years 2004 to 2006 with the D0 particle detector at the proton-antiproton collider Tevatron at FERMILAB near Chicago. This is a typical large scale particle physics project which annot be reproduced in a laboratory class, obviously. The analysis of huge amounts of experimental data is an important and typical activity of experimental particle physicists. This 'experiment' allows to make precise measurements of fundamental constants of nature.

The cross section for the process

is measured and the mass of the W boson, one of the mediator particles of the weak interactions is determined. In addition the electroweak mixing angle is derived from the measured W mass.

The data analysis is performed on Linux computers; a rudimentary knowledge of the Linux operating system is useful. To facilitate the coding of the analysis program (C++, ROOT package), examples and templates are provided, so that a basic knowledge of the C++ language is sufficient.


The diagram shows a "W event" (`red' electron plus `yellow' neutrino = missing energy) in the D0 detector. Shown is a cross section perpendicular to the beam axis.


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Last update 2018-07-04 Thomas Hebbeker











Literature (to be be read before the lab days) :
can be found in the manual (second page).

Example program (to be be studied before the lab days):

Introductions/Tutorials to Linux, C++ and ROOT:










Data and code

  • D0 data set d0.root (13 MB)

  • Monte Carlo data set (incl. tau background) mc_all.root (56 MB)

  • Example root tree ("Beispiel-Tree") bsptree.root

  • Example analysis program w_analyse.C