Tomorrow is the last day on duty. For twenty-six years the Tevatron collider, the four-mile-long accelerator of the Fermi laboratory in Batavia (IL), has provided the CDF and DZERO experiments with proton-antiproton collisions at 1.8 and then 1.96 Tera-electron-Volts, allowing the investigation of fundamental physics at the highest available energy.I received today a very nice video which commemorates the Tevatron collider. The video was produced by a colleague, Rob Snihur, together with an artist friend of his, Maria Scileppi. I hope you like it! A text is also available on Maria's site.
The Tevatron September 21st 2011 from Maria Scileppi on Vimeo.
Going back to the three decades of Tevatron operations, we must remember that dozens of burning questions have been addressed, and ticked off the list. Below I make a short summary, trying to explain what is their significance. Of course, there is more to know about all of these, because in Science you never really exhaust a topic, you only deepen your understanding and knowledge; but the amount of insight and information that is contained in the over 550 physics papers produced by CDF, and over 400 by DZERO (I await for somebody to provide me with a more precise number in this latter case -400 looks about right since DZERO started data taking in 1992, but is only a guess) is really immense.
So here's a first bid of a list, which is certainly grossly incomplete -I invite you to add items to it, by commenting in the thread below. In no particular order:
- Is there a sixth quark ? YES. The top quark was discovered in 1995, after a chase which lasted 17 years and involved a dozen particle physics experiments. Physicists knew the top quark had to exist, because its presence made itself felt in a number of ancillary measurements, plus the theory made little sense without it; yet finding it was a crucial verification of the Standard Model. Incidentally, I wrote a very accessible two-part post on the history of the top quark search and discovery here (part I) and here (part II), will be happy if you read it.
- What is the top quark mass ? 173.2+-0.9 GeV. This incredibly precise result (the uncertainty being by now of the same order of magnitude of the limit with which you can ever measure the mass of a coloured body) helps constraining the yet unknown value of the Higgs boson mass, and is an important input in Supersymmetry model building, since depending on its value the mass of sparticles varies significantly.
- What is the oscillation frequency of Bs mesons ? 17.77+-0.12/ps. The mechanism of Bs oscillations is the door to a whole new area of investigations of the physics of these interesting particles, which hides CP violation effects, and could be sensitive to new physics effects in a number of ways.
- Is Supersymmetry around the corner ? NO. When the Tevatron collider started operations, many believed that supersymmetric particles would pop out of the collisions in big numbers. Nothing like that has happened, but this failed discovery is an advancement of Science in its own right. Of course, the LHC experiments are now incurring in the same fate...
- What is the W boson mass ? 80420+-31 MeV. This is the most precise result of the world, beating if only by little the LEP II dedicated measurements. The W mass is one of the most sensitive parameters to the Higgs boson mass, and an improvement of this number is still in the air (the CDF collaboration might produce an update soon).
- Are there new quarks ? NO. A fourth-generation quark has been sought by CDF and DZERO for two decades, but none has appeared. Of course, a fourth generation of quarks would mess up quite a few things (among them, the Higgs boson would be produced in much higher numbers, and this has been recently ruled out). However, nobody can really be sure that higher-mass quarks do not exist. Some mechanism might keep them from interfering with lower-energy measurements...
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