DØ experiment

[8] The DØ experiment is an international collaboration that, at its peak, included about 650 physicists from 88 universities and national laboratories from 21 countries.

[9][10] It studied the collisions between the protons and antiprotons circulating in the Tevatron to test many aspects of the Standard Model of particle physics.

The DØ detector consisted of several nested subdetector groups surrounding the region where the beam protons and antiprotons collided.

[14] One of the early goals of the DØ experiment was to discover the top quark,[15] the last of the six constituents of matter predicted by the Standard Model of particle physics.

The DØ and CDF experiments both collected data for the search, but they used different observation and analysis techniques that allowed independent confirmation of one another's findings.

On February 24, 1995, DØ and CDF submitted research papers to Physical Review Letters describing the observation of top and antitop quark pairs produced via the strong interaction.

[17][18] [19] On March 4, 2009, the DØ and CDF collaborations both announced the discovery of the production of single top quarks via the weak interaction.

[20] Precision measurements of top quark properties such as mass, charge, decay modes, production characteristics, and polarization were reported in over one hundred publications.

"[21] In later years, one of the main physics goals of the DØ experiment was the search for the Higgs boson, which was predicted to exist by the Standard Model, but with an unknown mass.

[26] The techniques developed at the Tevatron for the Higgs boson searches served as a springboard for subsequent LHC analyses.

[27] The properties of the W and Z bosons that transmit the weak nuclear force are sensitive indicators of the internal consistency of the Standard Model.

This result has comparable precision to electron positron collider experiments at CERN and SLAC and helps to resolve a long-standing tension between those measurements.

[29] Although the B-factory experiments at KEK, SLAC and IHEP in Beijing and the LHCb experiment at CERN have dominated many aspects of the study of hadrons containing b- or c-quarks, DØ has made notable contributions using large samples containing all heavy flavor hadrons that can be seen through their decays to muons.

Examples were finally observed 40 years later in cases where the exotic meson contains the more distinctive heavy b- and c-quarks.

QCD makes quantitative predictions for the production of jets (collimated sprays of particles evolved from scattered quarks or gluons), photons and W or Z bosons.

These were surrounded by a second shell consisting of calorimeters that measured the energy of electrons, photons, and hadrons and identified "jets" of particles arising from scattered quarks and gluons.

The material in the solenoid augmented with lead sheets caused primary electrons and photons to begin a shower of secondary particles.

The active gaps contained liquid argon with a strong electric field applied to collect the ionization of traversing particles on finely segmented planes of copper electrodes.

The stainless steel vessels needed to contain the modules at liquid argon temperature (-190 C) were relatively thick, so scintillation detectors were inserted between central and end calorimeters to correct for energy lost in the cryostat walls.

A primary task for the calorimetry is identification of jets, the sprays of particles created as quarks and gluons escape from their collision point.

Jet identification and measurement of their directions and energies allow analyses to recreate the momenta of the underlying quarks and gluons in the primary collision.

The iron of the large central magnet was reclaimed from a NASA cyclotron built to simulate radiation damage in space.

Therefore, an intricate Data Acquisition (DAQ) system was implemented that determined which events were "interesting" enough to be written to tape and which could be thrown out.

The operation of the trigger system was a delicate balance between maximizing the number of events saved and minimizing the dead time incurred while collecting them.