The lifecycle of a particle collider
The Tevatron’s impending shut down has upset many, but is there really anything to be angry about?
If you’re like me, you’re inescapably drawn to the comments sections of online articles. You finish reading a story and your eyes start to drift down, down, down to the sometimes comical, oftentimes infuriating opinions of fellow news-gobblers. The next thing you know, a half-hour has passed, as if you’ve somehow jumped through time, and you’re left wondering: “How did I get sucked into that nonsense?”
But every once in a while, the online community will get the cogs in your brain turning. This was certainly the case when I read through readers’ reactions to the recent news regarding the Tevatron particle collider at Fermilab in Illinois.
In January, the U.S. Department of Energy pulled the plug on the collider, despite the High Energy Physics Advisory Panel’s recommendation that the Tevatron run through 2014. The department couldn’t justify the collider’s annual $35 million cost of operation, particularly since the European Organization for Nuclear Research’s (CERN) Large Hadron Collider is already surpassing the Tevatron in particle-collision energies. The Tevatron will be shut down this September.
You’d expect most people either to feel apathetic towards the collider or to think its projects are a waste of money. But surprisingly, the majority of people commenting on the news online shared feelings of grief and anger. “The United States spends $190 million A DAY in Afghanistan. This shutdown is a complete disgrace,” wrote commenter Dave on Science 2.0’s article about the Tevatron’s demise. Other people worried that the U.S will fall behind in basic research and possibly lose brilliant scientists to other countries. On ScienceNews’ story, Archie Whitehill remarked, “We are becoming a second rate country when we curtail funding of research…”
But should the upcoming close of the Tevatron really upset the public? Is this a disgrace, or does the Department of Energy’s decision fall in line with the typical lifecycle of a particle collider?
Across the globe, scientists have created over two-dozen particle colliders since the first came online in the 1960s at Italy’s National Institute of Nuclear Physics. While different in design and ability, the colliders all have the same purpose: to help physicists understand the fundamental nature of matter and energy. By smashing together certain particles — like protons and antiprotons — at very high velocities, scientists create rare and sometimes previously unobserved particles, filling the gaps in our knowledge. “We are trying to understand the world we live in, starting with the smallest of the small,” said Rob Roser, a physicist with the Tevatron’s Collider Detector at Fermilab.
Scientists begin collider experiments by sending two particle beams in opposite directions around large, ringed tracks, which are buried deep underground to shield people from the radiation produced by collisions. Just as NASA uses the gravitational energy from planets to speed up their space shuttles (the slingshot effect), physicists use the magnetic energy from powerful magnets to accelerate particles to near light speed. Once the particles acquire enough speed and energy, scientists collide the beams.
Rare particles created from the collisions decay into better-known objects in a fraction of a second. Physicists never actually “see” the new particles. “We look at the remnants of the collisions and work backwards, much like police officers coming onto the scene of a car accident,” explained Roser.
The Tevatron collided its first beam in 1985, and since then has been “fantastically successful,” said Roser. In 1995, scientists used it to find the last undiscovered quark: the top quark. Quarks, which are some of the smallest known particles, combine in various ways to form your everyday proton or neutron. The Tevatron also holds the record for the most precise measurement of the mass of the W boson, a particle that supplies the weak force with, well, force, enabling some types of particle decay. Currently, the Tevatron is searching for the Higgs boson, the “God particle” thought to give mass to all matter in the universe.
Unfortunately for the Tevatron, so is the Large Hadron Collider (LHC). Although the Tevatron has been collecting data for years, scientists expect that LHC will discover the particle first because LHC produces more energetic collisions (the Higgs boson is theorized to exist on its own only at very high energies).
In early April, the Tevatron made headlines when a mysterious “bump” popped up in its data. Some physicists say it could be version of the famed Higgs boson or it may even be a particle not predicted by the current model of physics. But the anomaly is likely just a statistical fluke. Whatever the case, the find may be too late to save the particle collider.
“The Tevatron enabled us to study a lot of phenomena,” said Hong Ma, a Brookhaven National Laboratory physicist, who is working on one of LHC’s experiments. “But as usual, every time we learn something more from an accelerator, we plan to build a new one.”
History shows that this is all too true. In the late 1970s, Brookhaven, located in Long Island, New York, began constructing ISABELLE (Intersecting Storage Accelerator, plus “belle”), a particle accelerator intended to discover the W boson. But in 1983, CERN’s Super Proton Synchrotron found it first. “Basically, Brookhaven got scooped by CERN,” said Brookhaven physicist Les Bland. The Department of Energy cancelled ISABELLE that same year.
Although ISABELLE died prematurely, CERN’s success prompted a new collider, the Relativistic Heavy Ion Collider (RHIC), to rise from ISABELLE’s ashes like the mythical phoenix (interestingly, RHIC has a detector named PHENIX). Constructed partially from the skeletal remains of ISABELLE, RHIC went online in 2000. “It really is remarkable that the government has the foresight to say that there is a need for basic research,” commented Bland, who works at RHIC.
Will the government now have the foresight to build a new machine from Tevatron’s remains? Fermilab scientists are hopeful.
While it appears that the U.S. is leaving collider experiments up to European facilities, it’s not backing out of particle physics completely — it’s just focusing on the “intensity frontier” instead. Smashing together particle beams is a successful method to study high-energy physics, but scientists can also learn much by creating high-density (intense) beams containing trillions of particles.
To create these high-density beams, Fermilab has proposed Project X in a bid to breathe new life into the Tevatron’s old parts, just as RHIC did for ISABELLE. (Similarly, LHC also revitalized its predecessor, the Large Electron-Positron Collider — it seems that atom smashers really do have an afterlife.) If Congress approves Fermilab’s budget plans this year, Project X will go online in 2019. With Project X, Fermilab will be able to extend current research into neutrinos — ghostlike particles that are difficult to detect because they pass through most matter with little interaction.
Despite the plans for Project X, Roser is still disappointed that Fermilab will lose the distinction it’s held in high-energy physics for the last 25 years. But, he said, “every machine has a natural lifetime.” Ma at Brookhaven echoes Roser’s sentiments: “Like any good thing, there is always an end.”
Tevatron’s end shouldn’t cause the public any distress. The United States’ brightest physicists won’t be defecting to other countries en masse, nor will the country lose its competitive edge in high-energy physics. Project X promises to forge a new path into neutrino research, and the U.S. is keeping in the high-energy physics game by actually backing LHC experiments more than any other single country, according to Ma. “LHC wouldn’t be as it is without the United States’ money and physicists,” he said.
It seems the shutdown of the Tevatron is just part of the cycle of life for particle colliders. Like all technology, particle colliders are born, they are useful for a time, and then they die when something better comes along. Sometimes their organs are salvaged for other experiments, and other times their bones support new colliders. Recycle and repeat. Recycle and repeat.