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Particles and interactions

Particles and interactions

Fermilab boss unveils financial plan for Tevatron extension

22 Sep 2010
Pier Oddone has a plan for keeping Tevatron alive

Fermilab director Pier Oddone has unveiled a financial plan that would let his lab run the Tevatron collider for an additional three years. The plan involves delaying two upcoming experiments – the NOvA neutrino study and the Mu2e muon experiment – and using $25m per year in freed-up funds to help keep the collider running. The Tevatron machine, which collides protons and antiprotons, was due to shut down in September 2011.

Oddone’s plan is, however, not guaranteed because the lab will first have to find an additional $35m per year for the three-year extension. That money can only come from the US Department of Energy (DOE) and will need the blessing of President Obama and the US Congress.

“Securing the additional resources involves several steps and considerable uncertainty,” writes Oddone on the Fermilab website. “We could get a ‘no’ that is final at any point along these steps, but a ‘yes’ will be final only when Congress appropriates the funds.”

According to Oddone, Fermilab is already in discussions with the DOE, which will in turn be seeking advice from its High Energy Physics Advisory Panel (HEPAP). “Assuming that the advice is positive, we will not have any solid information until the president announces the FY12 budget in February 2011,” says Oddone.

Extension problems

Plans to extend Tevatron have been bandied about for some time and Oddone’s public comments on the issue had been lukewarm in recent weeks. Now, however, Oddone appears to have accepted the recommendation made last month by Fermilab’s Physics Advisory Committee (PAC), which strongly endorsed a three-year extension to 2014. While acknowledging the Tevatron’s “remaining promise for the future”, Oddone had called the non-binding recommendation “very problematic for us”, because an extension could hinder the lab’s transition towards projects on the so-called intensity frontier.

One such project is NOvA, which is designed to study neutrinos produced when a 700 kW beam of protons from Fermilab’s Main Injector accelerator collides with a graphite target. If the Tevatron is still running when NOvA starts in 2013, the available beam power would drop to about 400 kW, thereby sharply reducing the amount of data NOvA collects in its first 18 months.

However, the PAC concluded that this “would not mean robbing NOvA of a discovery”, says committee member and University of Rochester particle physicist Regina Demina, adding that competitors like Japan’s T2K are already better placed to make early progress in the field.

Two experiments better than one

Still, a delay for NOvA would be a blow to the neutrino community, says David Wark, a physicist at Imperial College London who is part of theT2K collaboration. “Of course, I would like T2K to make any discoveries first, but from a broader perspective it is critical to have multiple complementary experiments,” he says. T2K spokesperson Takashi Kobayashi agrees, noting that NOvA will be able to measure some things – such as which flavour of neutrino is lightest and which is heaviest – that T2K cannot.

A similar argument could, however, be made for the Tevatron and its competitor, CERN’s Large Hadron Collider (LHC). If the Higgs boson is heavier than about 140 GeV, it is more likely to decay into pairs of W or Z bosons, and the LHC should be able to detect this signal easily in the debris of proton–proton collisions. A lighter Higgs is more likely to decay into pairs of b-quarks, which would favour the Tevatron.

Extending the Tevatron would also affect the Mu2e experiment, which will create a beam of muons. The particles will be captured in atomic orbits in a foil target, where some may decay to an electron without the production of neutrinos. Such neutrino-less muon decay has never been seen in the lab and its discovery could point towards new theories of particles physics beyond the Standard Model.

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