Italy axes flavor-physics facility

A 27 November 2012 decision by the Italian government not to fund SuperB effectively killed the asymmetric-energy electron–positron collider that was to be built near Rome. Designated a flagship project by the Italian government just two years earlier, SuperB was canceled because its estimated cost grew from about €650 million (roughly $860 million) to nearly €1 billion and its schedule slipped by about three years. Ground had not yet been broken for SuperB.

The loss to science is likely to be small because of the similar Belle II experiment under construction at SuperKEKB in Japan. Both colliders were designed to produce large quantities of B mesons, D mesons, and tau leptons to study rare decays and to test mixing and CP violation among mesons bearing the charm quark.

One feature that would have been unique to SuperB was a polarized electron beam, says Caltech’s David Hitlin, a member of the SuperB team. “That opens up a number of improved studies of tau decays, such as searches for charged lepton flavor violation and measurements of electroweak parameters.” Such measurements can be made in Japan, he admits, “but SuperB could have done them better.”

A significant advance to come out of SuperB R&D is the combination of low emittance with the so-called “crab waist” focus technique to achieve higher luminosity for a given accelerator current. Elements of that approach, which was developed by Pantaleo Raimondi when he was at Italy’s National Institute for Nuclear Physics (INFN), are being incorporated into Belle II.

Although Belle II and a proposed upgrade to the Large Hadron Collider Beauty experiment at CERN “offer opportunities to pursue the search for new physics in heavy quarks and leptons,” says LHCb collaboration member Marina Artuso of Syracuse University, cancellation of the SuperB experiment “makes the high-energy physics community sad.” Still, she recalls her own experience working on BTeV at Fermilab, before it was canceled in 2005: “Nothing is worse than a project that lingers for years and does not come to a positive conclusion.” Such limbo is especially difficult for young people, she says, “who may be trapped in an uncertain future where they cannot really choose a different avenue of research.”

Members of the LHCb and Belle II experiments hope the axing of SuperB removes uncertainties for funding agencies in other countries that may have been torn between investing in their projects or in SuperB.

Fernando Ferroni, president of the INFN, says his institute will decide soon how to reallocate the €250 million that was committed to SuperB. As possibilities, he points to a tau–charm factory that would “retain most of the work” done for the project and still “give access to flavor physics but running at lower energy” and to an accelerator laboratory that would combine photon science and elementary particle physics research.