How it works
CDF is one of two detectors positioned along the four-mile Tevatron accelerator ring. Physicists use the detector to study the array of particles and forces within the atom by recording data about collisions of protons and anti-protons in the machine. The 4,500-ton detector sits more than four stories tall and is composed of more than 1 million individual detector elements.
Beams of protons and antiprotons collide at the center of CDF at nearly the speed of light, creating flashes of energy that condense into particles that in turn decay into more stable particles. This volatile process replicates the conditions just after the big bang. The beams cross paths in the detector an average of 1.7 million times per second. When they cross, one or many pairs of protons and antiprotons can collide. Because mass is energy in a different form, the kinetic energy from the collision can convert briefly into massive particles heavier than the protons and antiprotons involved in the collision. For interesting events, the detectors record information necessary to evaluate the energy, momentum and electric charge of the emerging particles.
CDF measures particles with three layers of detectors. As particles pass through the innermost layers, made up of tracking detectors, they leave traces of energy that allow researchers to map their flight paths. CDF excels at tracking particle paths, using 7 layers of silicon positioned closely around the beam pipe, and a large “wire” chamber around the silicon that records up to 96 position measurements for each particle produced in the collision. By connecting the dots, the CDF scientists are able to very precisely determine the particle’s momentum, where it came from and where it was headed.
The second layers of the detectors consist of calorimeters, which measure the energy of showers of particles by absorbing them. CDF’s calorimeter for measuring the energies of particles that interact electromagnetically, such as electrons and photons, is made of 23 layers of lead and light-emitting plastic, and its calorimeter for particles that interact via the strong force, hadrons such as protons, neutrons, pions and kaons, is made of 23 layers of steel and plastic. The final layer of the detector is made up of muon detectors, which catch the signals of the muons that pass through the calorimeters, giving up only a fraction of their energy.
Questions for the Universe
The CDF collaboration consists of researchers from about 60 institutions in 15 countries. CDF members come from the world’s leading universities and laboratories. The collaboration consists of about 600 members, including about 100 graduate students and about 100 postdoctoral researchers. The collaboration membership splits almost evenly between U.S. participants and those from foreign laboratories and universities.
Physicists observed the first proton-antiproton collisions produced by the Tevatron on Oct. 13, 1985. Since then, researchers at the CDF and DZero experiments have used the Tevatron to study matter at ever smaller scales.
On March 2, 1995, physicists at CDF and DZero announced the discovery of the top quark. Researchers in both collaborations had statistically proven observation of the top quark in collisions at their detectors.
The top quark, which is as heavy as a gold atom but much smaller than a proton, was the last undiscovered quark of the six predicted to exist by current scientific theory. Scientists worldwide had sought the top quark since the discovery of the bottom quark at Fermilab through fixed-target experiments in 1977.
Both collaborations were subsequently able to measure the mass of the top quark to high precision. Particle physicists measure particle masses to verify the correctness and accuracy of their particle models. Knowing the value of the top quark mass has allowed physicists to zero in on the mass of the undiscovered Higgs boson, a crucial component of the theoretical framework of particle physics.
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