The end of September marks the end of an era at Fermilab, with the shut down of the Tevatron after 28 years of operation at the frontiers of particle physics (CERN Courier March 2011 p5). The Tevatron’s far-reaching legacy spans particle physics, accelerator science and industry. The collider established Fermilab as a world leader in particle-physics research, a role that will be strengthened with a new set of facilities, programmes and projects in neutrino and rare-process physics, astroparticle physics and accelerator and detector technologies.
The Tevatron exceeded every expectation ever set for it. This remarkable machine achieved luminosities with antiprotons once considered impossible, reaching more than 4 × 1032 cm–2s–1 instantaneous luminosity and delivering more than 11 fb–1 of data to the two collider experiments, CDF and DØ. Such luminosity required the development of the world’s most intense, consistent source of antiprotons. The complex process of making, capturing, storing, cooling and colliding antiprotons stands as one of the great achievements by Fermilab’s accelerator team.
As the world’s first large superconducting accelerator, the Tevatron developed the technology that allowed later accelerators – including CERN’s LHC – to push beam energy and intensity even higher. But beyond its scientific contributions, an enduring legacy to mankind is the role it played in the development of the superconducting-wire industry. The construction of the accelerator required 135,000 lb of niobium-titanium-based superconducting wire and cable at a time when annual world production of these materials was only a few hundred pounds. Fermilab brought together scientists, engineers and manufacturers who developed a large-scale manufacturing capability that quickly found huge demand in another emerging field: MRI machines.
The life of the Tevatron is marked by historic discoveries that established the Standard Model. Tevatron experiments discovered the top quark, five B baryons and the Bc meson, and observed the first τ neutrino, direct CP violation in kaon decays, and single top production. The CDF and DØ experiments measured top-quark and W-boson masses, as well as di-boson production cross-sections. Limits placed by CDF and DØ on many new phenomena and the Higgs boson guide searches elsewhere – and continuing analysis of Tevatron data may yet reveal evidence for processes beyond our current understanding. Chris Quigg’s article in this issue gives further details on the Tevatron’s scientific legacy and results still to come (Long live the Tevatron).
As we bid farewell to the Tevatron, what’s next for Fermilab? Over the next decades, we will develop into the foremost laboratory for the study of neutrinos and rare processes – leading the world at the intensity frontier of particle physics.
Fermilab’s accelerator complex already produces the most intense high-energy beam of neutrinos in the world. Upgrades in 2012 will allow the NOνA experiment to push neutrino oscillation measurements even further. The Long-Baseline Neutrino Experiment, which will send neutrinos 1300 km from Fermilab to South Dakota, will be another leap forward in the quest to demystify the neutrino sector and search for the origins of a matter-dominated universe.
The cornerstone for Fermilab’s leadership at the intensity frontier will be a multimegawatt continuous-beam proton-accelerator facility known as Project X. This unique facility is ideal for neutrino studies and rare-process experiments using beams of muons and kaons; it will also produce copious quantities of rare nuclear isotopes for the study of fundamental symmetries. Coupled to the existing Main Injector synchrotron, Project X will deliver megawatt beams to the Long-Baseline Neutrino Experiment. A strong programme in rare processes is developing now at Fermilab with the muon-to-electron conversion and muon g-2 experiments. A strong foundation for Project X exists at Fermilab, with expertise in high-power beams, neutrino beamlines, and superconducting RF technology.
Project X’s rare-process physics programme is complementary to the LHC. If the LHC produces a host of new phenomena, then Project X experiments will help elucidate the physics behind them. Different models postulated to explain the new phenomena will have different consequences for very rare processes that will be measured with high accuracy using Project X. If no new phenomena are discovered at the LHC, the study of rare transitions at Project X may show effects beyond the direct reach of particle colliders. Project X could also serve as a foundation for the world’s first neutrino factory, or – even further in the future – as the front end of a muon collider.
In parallel with the development of its intensity frontier programme, Fermilab will remain a strong part of the LHC programme as the host US laboratory and a Tier-1 centre for the CMS experiment, as well as through participation in upgrades of the LHC accelerator and detectors. Fermilab will also continue to build on its legacy as the birthplace of the understanding of the deep connection between cosmological observations and particle physics. The Dark Energy Survey, which contains the Fermilab-built Dark Energy Camera, will see first light in 2012. Better detectors are in development for the Cryogenic Dark Matter Search, and the COUPP dark-matter search is now operating a 60 kg prototype at Fermilab.
As Fermilab’s staff and users say goodbye to the Tevatron, we look forward to working with the world community to address the field’s most critical and exciting questions at facilities in the US, at CERN and around the world.