The End of the Tevatron

By John Conway | January 10, 2011 2:48 pm

It’s the beginning of the end for the Tevatron at Fermilab. In the fall, the Department of Energy’s High Energy Physics Advisory Panel recommended that the Tevatron be funded to run for three years beyond the planned end in September of 2011, largely in order to provide additional information in the search for the Higgs boson. The recommendation was contingent on there being new funds, about 5% above current levels, in order to staff and operate the machine and the experiments. But in a letter to day to the chair of HEPAP, the head of the Office of Science at the Department of Energy, William Brinkman, wrote that “Unfortunately, the current budgetary climate is very challenging, and additional funding has not been identified. Therefore…operation of the Tevatron will end in FY2011, as originally scheduled.”

The dream for a superconducting proton synchrotron at Fermilab goes back to at least 1976, when it began to become clear that the interesting mass range to explore in order to understand the weak interaction would be around 100 GeV. The lab was engaged in a wide range of fixed target experiments, using the Fermilab Main Ring proton synchrotron as its workhorse, and in 1977 the b (or bottom) quark was discovered there. This meant there had to be a top quark, as well as very massive (80-100 GeV) W and Z bosons.

But Europe pulled ahead – it already had the Super Proton Synchrotron, and plans to convert it into a proton-antiproton collider. Whoever did so first would have the energy to produce W’s and Z’s directly, and nail down their masses. And maybe, whoever managed to create the first high energy proton-antiproton collider would be able to find the top quark, whose mass could be, well, just about anything above the b quark mass of 5 GeV, but probably at least 20 GeV.

Fermilab designed a new generation of superconducting magnets to operate at 3 Tesla, and began construction of the new ring, then dubbed the Saver (short for Energy Saver, since Energy Doubler, the initial name, sounded too expensive). At the same time CERN developed its antiproton source and the techniques for cooling the antiproton bunches for injection to the new SppS, the Super Proton-Antiproton Synchrotron (there’s a bar over the second p).

CERN won the race for the W and Z. In early 1983, not long after commissioning the new complex, handfuls of these massive carriers of the weak force were observed by the UA1 experiment, and confirmed by UA2. Carlo Rubbia, who lead UA1, and Simon van der Meer, who designed the antiproton source, shared the Nobel the next year. Would the top quark soon follow?

But in late 1983, the Fermilab Saver turned on, running extracted proton beams to the new raft of fixed target experiments awaiting them. My graduate thesis experiment, E615, was among them, and I count it among some of the most thrilling science moments in my career to have had my face plastered to the viewer of an oscilloscope, eyes dark-adapted, waiting for the first pulses from the counters in our experiment to tell me the secondary pion beam had arrived to us. The chain of injectors, a thousand new superconducting magnets, RF kickers, beam separators…it all worked! There were the pions! We went on, over the next year or so, to collect tons (for us) of data on the structure of the pion, still the best measurement to date.

UA1 and UA2 continued on, and CERN commenced deep tunnel drilling for LEP, the Large Electron Positron collider, slated to begin in 1988. It was designed to directly produce thousands of Z bosons by colliding electrons and positrons (antielectrons), and measure the Z as precisely as posible. At SLAC at Stanford, construction was underway to build the SLC, the SLAC Linear Collider, which would challenge LEP in the race for the Z. The age of the great colliders was in full blossom.

Fermilab commissioned its antiproton source in 1985 and 1986, and began collisions, redubbing the machine the Tevatron, as the ultimate goal was to reach 1 TeV per beam of energy – a trillion volts! The first engineering run was 800 GeV per beam, and much work remained to be done to get the beam intensity high enough to produce useful numbers of W’s and Z’s and surpass the SppS results.

SLC and LEP began operating in 1989 (a year late for LEP) but the Mark II experiment at the SLAC and the four (!) LEP experiments immediately made two important discoveries. First, by measuring the Z production rate, there appeared to be only three species of neutrino to which the Z could decay. This meant a fourth generation of quarks and leptons did not appear to be ready to be discovered. The second important SLC/LEP discovery was that the top quark must be rather massive, 150 GeV or more. This put it out of range of the electron positron machines, and meant that the top could be discovered soon at the Tevatron, if it could collide enough protons and antiprotons.

While Europe put its hopes of discovery in the electron positron machine, the US community was already building the biggest machine of all, the Superconducting Supercollider, or SSC, in Waxahachie, Texas. This mammoth proton-proton collider with 54 miles of superconducting magnets would begin operation in 1999 at an energy 20 times that of the Tevatron. “Throw deep” was Ronald Reagan’s exhortation to the physicists when presented with the project, and deep they threw. Too deep perhaps – by 1993, the cost of the project had grown too rapidly, and, in a cost-cutting mood not unlike the present day, in October of that year the US Congress killed the project, which had spent about $2 billion, and dug almost 15 miles of tunnel (now backfilled).

The demise of the SSC was a serious blow to the US high energy community, and left one option for staying on the high energy frontier: an enhanced Tevatron complex. But it took another half decade after the LEP startup to amass the data sample necessary to get the first glimpse of top-antitop production in the CDF and D0 experiments at Fermilab. In early 1995, during “Run 1” of the Tevatron, both experiments announced the discovery of excess production of events consistent with that expected from top production. The mass of the top turned out to be a whopping 175 GeV. Pinning it down, and also measuring the mass of the W would answer the ultimate question: where is the Higgs boson lurking? Can it be seen at the Tevatron? Or would LEP2, with ever-increasing energy in the late 1990’s, get it first? Or would the Large Hadron Collider, scheduled to begin colliding protons in the LEP tunnel at CERN in 2004, be the first to see it?

Fermilab completed construction of the new Main Injector and Antiproton Recycler as the millennium turned, and cast its eye upon the Higgs boson. The two new additions to the Fermilab accelerator complex would allow a huge increase in the beam intensities, possibly enough to produce the very weakly interacting Higgs. I helped lead a study which, in late 2000, published the prediction: it would take somewhere around 15 inverse femtobarns of integrated luminosity, plus major upgrades to the experiments, to find the Higgs boson, at least the vanilla Standard Model one.

LEP2, in late 2000, was facing its own imminent shutdown to make way for the LHC, having reached 206 GeV energy and a sensitivity to a Higgs boson of at least 114.5 GeV, but had no evidence for the Higgs boson. The accelerator and detectors began to be removed the next year, 2001, just as the Tevatron began Run 2.

The first years of Run 2 at the Tevatron were plagued by problems, some due to the then-aging infrastructure, some from the years of downtime since 1996, and some due the fact that, well, colliding matter and antimatter in large quantities is just damned hard to do. There was a learning curve, and by 2003 the lab was on track to meet the design goals for the collider. Large new samples began to roll in, and physics papers began to roll out. But getting to even 10 inverse femtobarns before the LHC turned on seemed to be a receding hope.

The LHC was having difficulties of its own. The plan to operate in 2004, became 2005, then 2006. A somewhat snide plot of the projected start date as a function of time showed that the machine would start in late 2008.

Which it did. But then, as faithful readers of CV know, the LHC had its rather spectacular failure triggered by a faulty magnet interconnect, and propagated by a detection/avoidance system that failed to detect the condition and was insufficient to avoid the massive boil-off of six tons of liquid helium. The resulting damage took a year and 35 million Euros to repair.

In these years, the Tevatron marched on, reaching its first inverse femtobarn by mid 2005, then setting new records almost routinely in the following years. The huge new sample provided a treasure trove for us data-starved particle hunters. And it became clear that with the slow turn-on of the LHC, the Tevatron had a chance, albeit a slim one, to discover the Higgs or some other new physics before the LHC. And so in 2009 the run of the Tevatron was extended until late 2011. The machine has kept running, kept improving, and we now hope to have 10 fb-1 by the time we shut down.

Will the Tevatron experiments see the SM Higgs boson before the LHC? It is looking quite doubtful, but there is some chance the run will end with a tantalizing excess. How long will it take the LHC? With the new data collected last year, only a tiny fraction of the Tevatron sample but at much higher energy, we are beginning to see the physics power of the new machine, and I owe you all a lot of posts on the picture beginning to emerge. But the Higgs boson could turn out to be at the hardest-to-discover mass of all at the LHC, around 120 GeV, in which case the LHC will almost certainly need to run well beyond the end of 2012 to get enough data. It may take as much as 10 inverse femtobarns at the LHC to see it at the golden five-sigma level. But of course we’ll get excited a long time before that.

And we know that the Higgs boson cannot be the one of the Standard Model, right? More on that tantalizing prospect later. (And three years ago from the Tevatron.)

CATEGORIZED UNDER: News, Science, Technology, Top Posts
  • Sili

    What would it cost to keep the experiment going? Anyone we can beg for money, if we promise to put their name on the press conference?

    Google™ is proud to present: The Higgs!

  • Wil

    How about Apple? They could call it the i-boson.

  • Anonymous_Snowboarder

    While certainly informative, how long have you had this obituary prepared? And you left out the ‘survived by’ section :(

    Sigh.. well hopefully somebody will go bang on Gates or Google’s door before turning the lights off.

  • Tom

    Honestly, this sucks. WFIRST now this..Frontier physics in the US is no more..

  • John

    Anonymous: I wrote it all today. Really.

    Sili: we asked Sergey Brin, not sure if we got an answer yet. Also really. Sergey?

    I guess if there was a “message” in the post, it’s that the back-and-forth between the US and Europe (and Japan – left out Tristan and the B factory…) has been going on for some time. Europe has the lead now, and for a long while to come. Will the US do something greater than the LHC in the future, in this field? We can certainly afford it, for a tiny fraction of the cost of the military…it’s ultimately a value judgement.

  • Dave

    We spend $190 million A DAY in Afghanistan.

  • Concerned citizen

    You know, it really irks me that an adminstrative official makes a (strong word censored by myself) decision and physicists are willing to accept it. When will you (strong word censored by myself) physicists understand that Congress sets the budget. This is a gambit, leadership in DOE is cutting something that has a strong possibility of being restored by public outcry, thus preserving less popular programs. I would highly recommend that you get out there and start a letter and phone campaign. The end of tevatron is the end of physics for the U.S. and we are basically ceding our future to foreign interests. The shame.

  • Vladimir Kalitvianski

    I wonder – will it be possible in the future to analyze the collected data via a pattern somewhat different from the standard model one?

    I mean, currently in the SM we have gauge fields which are initially decoupled from each other by construction, and this gives a not so brilliant initial approximation for permanently coupled things (bare instead of dressed particles). Maybe in the future we will be able to advance a different construction, with free quasi-particles instead of free particles, and we will need experimental data to compare its predictions.

  • Michael Aye

    > The resulting damage took a year and 35 million Euros to repair.

    Should that not be:
    “The resulting damage AND the required upgrade to avoid further damage like this took a year and 35 million Euros to repair.”?

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  • Arthur F. Arthursson

    I believe Holger Bech Nielsen´s theory from 2009 is correct – God is intervening from the future (when?) and preventing Higgs Boson (“The God Particle”) from being found which would create a huge black hole into which the entire universe would disappear. HE is stopping the Tevatron funds and HE caused the damage at LHC. Glory onto Him for preventing Doomsday!

  • Low Math, Meekly Interacting

    I hate to say it, but increased funding for HEP in the US will probably have to rely on some cynical, if not disingenuous, self-promotion that gains access to a slice of the Defense pie. This is where, distasteful and ethically dubious as it is, HEP theorists and experimentalists could possibly accomplish more by learning to be better politicians.

    The DOD really has spent millions of taxpayer dollars studying antigravity propulsion, FTL drives, and antimatter weapons. Let that fact sink in for a few minutes, and then see if you could pull a white paper out of your backside describing a more plausible military application for “atom smasher” technology. I bet it wouldn’t be all that difficult. You don’t have to actually think that your proposal has a snowball’s chance on Betelgeuse of yielding a deployable weapon. Do you think many engineers working for defense contractors believed for one moment that orbital laser canons would give us an effective shield against even a single cargo of MIRVs launched on a Soviet ICBM? Didn’t stop them from chomping down the pork anyway.

    Is it really so immoral to hoodwink the contemptible people drawing the pursestrings closed on “big science”, just so they can make symbolic sacrifices on the Altar of Austerity while they continue to cut taxes for the wealthiest corporations and CEOs? I think not.

  • Ian

    Well the argument being made is that science is important so that society can advance… which is natively a matter that includes defense. So why shouldn’t science get part of the defense budget for basic research?

    It did until the Mansfield Amendment of 1973, which restricted defense research to projects with direct military application. The motivation for this amendment was to ensure that with troops at war in Vietnam, all funding would go towards research more likely to be of direct benefit.

    The Air Force, for instance, actually had a 16 year period of support for general relativity research, and organized what was probably the first gravitational radiation conference.

    The Mansfield amendment was understandable in the political climate of the time, but I think is certainly outdated, and detrimental, now.

    A few references, if anyone is interested.
    Air Force reference:

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  • John

    Concerned citizen (#7): You raise an interesting point. Congress does indeed set the budget, but it’s a complex process involving the administration, advisory groups, and so on. Though there were good physics reasons to keep going, and those of us pursuing the physics supported it, we also know that Fermilab needs to build a new post-Tevatron future, and it’s already been delayed a bit by the present extension. I don’t think we really want Congress dictating science policy, or doing something like making a Tevatron earmark. The science community has a lot to say about scientific priorities, and in this case there was a full-court press within the community and up the chain, but the decision rested ultimately with the DOE Office of Science, where, this year, it’s clearly a zero-sum game (or negative-sum game!)

  • VP

    “But Europe pulled ahead – it already had the Super Proton Synchrotron, ….” I would not put it this way. Europe did not pull ahead, Fermilab just dropped the ball. The p-bar p collider idea was born in the U.S. (Peter McIntyre) but failed to get enough traction at Fermilab. Bob Wilson was obsessed with the “energy doubler/saver” and never paid much attention to the collider, although, as I remember , they did send an engineer to Novosibirsk to learn about electron cooling. Perhaps correctly the conclusion was that it wouldn’t work. Rubia/CERN took it much more seriously and the breakthrough was made by Van der Meer who did not “design the antiproton source” but invented the stochastic cooling which made it all possible.
    Now about yesterday’s decision; people who have been working hard and producing great physics are not going to like this but I believe that this is a blessing in disguise. It will allow Fermilab to concentrate in their future, something, I’m afraid, they have not been able to do since Leon Lederman started talking about the desertron.

  • Chris

    Here’s for hoping for the Muon collider.

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  • Concerned citizen

    John, understand but if DOE works like any of the other depts, the decision probably came down to a 25 yr old kid who may be trained as an accountant (if you’re lucky) but probably an english, history, journalism or political science major who worked on Sen. X’s campaingn, thinks physics is “neat”, but there really should be better graphics on the ppt slide…what does a “tevatron” look like anyway?

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  • Anonymous_Snowboarder

    John – Its sad that Tev won’t reach the necessary integrated luminosity to assure (probably) a Higgs discovery but I suppose we should also be considering the delay that life extension would cause in other projects such as NOvA.

    Also, does the ‘closing of the Tevatron’ really mean closing and a big garage sale, or is it possible that other experiments may make use of of it, for ihigh intensity proton beams for instance?

    And if there will be a garage sale, what are the plans? what happens with the magents, etc?

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  • Sili

    And if there will be a garage sale, what are the plans? what happens with the magents, etc?

    I’d love to get one for my fridge, but I don’t think I can take the shipping and handling.

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  • Dr Hoo

    I was one of those foolish people that built Fermilab, from bubble chambers to to collider detectors. It is a massive failure of investment to throw away. We have nothing left to build on for the future. Yet the theives of Wall Street get bonuses large enough to not only keep Fermilab runing, but build a couple more labs like it. Why does mindless greed outway making the future better? No one can build anything with out having a good foundation to put that thing on. Physics is the foundation of everything, and that is what we have thrown away to feed Wall Street. Since Wall Street makes nothing, tha will be our future.

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