Beyond the God Particle Read Online Free Page A

(approximately). Particle physics had become big science. These were powerful accelerators that could be used to produce very energetic beams that went off to various fixed target experiments. With fancy upgrades, however, they could in principle be converted to colliders, and with head-on collisions they could produce and “discover” the W + , W – , Z 0 .
    In the late 1970s Fermilab embarked upon an ambitious and long-term goal of building the Tevatron, a machine that would collide protons with antiprotons 6 and that would ultimately become the world's first superconducting-magnet collider operating at the highest achievable energies for the four-mile circumference ring. CERN, on the other hand, took the bold decision to convert the SPS into a proton–antiproton collider to aggressively stalk the weak bosons, W + , W – , Z 0 , as quickly as possible. This was a risky gambit, but it paid off handsomely.
    The first proton–antiproton collisions at the CERN SPS were achieved just two years after the project was approved. Two large experiments at the SPS, named UA1 and UA2, started to search the collision debris for signs of weak interaction particles, and in 1983, CERN announced its discovery of the W + , W – , and Z 0 bosons. Carlo Rubbia and Simon van der Meer, the two key scientists behind the discovery and the SPS conversion into a collider, received the Nobel Prize in Physics within a year. Fermilab's Tevatron came online later. It should be noted, however, that throughout this period the Fermilab budget (in today's dollars) was about $300 million per year, while the CERN budget was more than $1 billion per year. Money may not buy happiness, but it does buy big science, quickly and effectively.

    Though scooped by the W + , W – , Z 0 boson discoveries at CERN, the two Tevatron experimental collaborations, known as D-Zero and CDF, successfully discovered the elusive top quark, the heaviest of all known Standard Model particles, in the mid 1990s. All that remained to find in the Standard Model was its missing link—the Higgs boson. As the Tevatron assumed the role of the world's highest-energy particle accelerator, CERN began to build a new kind of collider, and the physically largest one ever. The new machine was a collider of electrons and their antiparticles, positrons. This was called the “Large Electron–Positron Collider (LEP). 7
    It was thought that LEP might actually discover the Higgs boson, an ingredient of the Standard Model that had been hypothesized by theorist Steven Weinberg to provide the origin of the masses of all the particles. The optimism of a LEP discovery had sprung from certain popular theories that had argued the Higgs mass was actually less than that of the Z 0 boson. To achieve the required energies to make a Z 0 boson with the precision afforded by using electrons and positrons (see chapters 7 and 8 ), LEP had to be an enormous circular ring, housed underground in a deep tunnel. CERN therefore built a 27-kilometer (almost 17 miles) circumference circular tunnel, the construction of which ultimately proved decisive for a pathway to the LHC.
    The excavation of the LEP tunnel was Europe's largest civil-engineering project prior to the Channel Tunnel. The tunnel is actually tilted, with its high side under the Jura Mountains, and this presented enormous and somewhat unforeseen engineering challenges, particularly in controlling high-pressure water leaks from springs within the mountains that threatened nonstop and major flooding. Three tunnel-boring machines started excavating the tunnel in February 1985, and the ring was completed three years later.
    LEP did not find the quarry it had sought—the elusive Higgs boson. In a machine such as LEP the “signal-to-background” ratio for the Higgs boson would have been optimal for a discovery. Though many scientists expected the Higgs boson to be within LEP's reach and were disappointed at the Higgs boson's failure to emerge at LEP, the