(with their full complement of orbi­ Four years later, the National Ac­ tal electrons), these conditions can FERMILAB celerator Laboratory/AEC Design be more difficult to explore. 20 years on Study Contract was signed, ap­ The importance of relativity is pointing Robert Wilson as Director measured by the mass increase of the new Laboratory. With the (gamma) factor, which approaches Its twentieth anniversary celebra­ 1967 selection of the Batavia site infinity as the velocity nears that of tions last December gave Fermilab near Chicago, and a construction light. Theoretical ideas say that the an opportunity to look back to its authorization of $250 million, collision rate between atoms would beginnings, look over its accom­ ground wa^ broken the following reach a plateau starting from gam­ plishments, and look ahead to the year. ma values of about 10, but even next two decades. Under the able leadership of Ro­ this modest level has been difficult In 1963, the Ramsey Panel had bert Wilson, it took just four years to reach with beams of neutral recommended the United States to complete the four-mile Main atoms. Atomic Energy Commission (AEC) Ring and ramp it to its 200 GeV One of the simplest atoms is po- to build a 200 GeV accelerator. design energy. With an eye to the sitronium - an artificial concoction These were early days for particle future, ambitious R&D work also of an electron and a positron physics (the discovery of the began on magnets for a possible circling round each other. In an at Brookhaven by Leon new superconducting accelerator. experiment at the 70 GeV proton Lederman, , and After returning $6.5 million dollars machine at the Soviet Institute for Melvin Schwartz was then only one to the United States Government, High Energy Physics at Serpukhov, year old) but were be­ the Laboratory was dedicated as near Moscow, one neutral pion de­ coming aware of the new horizons the Fermi National Accelerator Lab­ cay per billion yielded a fast mov­ that higher energies could bring, oratory, routinely providing 400 ing positronium atom, with a gam­ and US researchers applauded the GeV beams. ma factor between 800 and 2000. Ramsey Panel's idea. A new laboratory energy scale The interaction rate of these synthetic atoms was measured by massing them through a carbon foil 10 -15^- *d fraction of a micron thick. Taking all relativistic effects into account (under these conditions any intra- atomic positronium clock runs much slower than the actual flight time through the foil), the reaction cross-section of positronium atoms with carbon is found to be 16(+16- 6).10"19 cm2/atom. This does not contradict the theoretically ex­ pected value, but also does not rule out ultrarelativistic ionization or excitations which could considera­ bly increase the reaction rate.

Variation of total reaction rate (cross-sec­ tion) with kinetic energy (expressed in terms of the relativistic gamma factor) for the in­ teraction of positronium atoms with carbon, showing the theoretical expectation (solid line) and the data point from a Dubna/Ser- 10 "3 1 0 "2 10 "1 1 10 1 0 * 10 3 10 4 pukhov experiment investigating an ultrarela­ tivistic region (shaded). Previous experi­ 7-1 ments using hydrogen atoms were confined to much lower velocities (arrow).

CERN Courier, March 1989 15 Twenty years ago, a pristine shovel for groundbreaking at the future Fermi National Accelerator Laboratory was wielded by (left) Laboratory Director Robert Wilson, and by US Atomic Energy Commission Chairman Glenn Seaborg. was born when the 1000 GeV Te- vatron' was formally proposed by Wilson in 1975, but in the environ­ mentalist climate of the time, the name 'Energy Saver' was adopted for the 1977 proposal to the De­ partment of Energy (DOE). That same year, Leon Lederman was named Director following Wilson's dramatic resignation, and the dis­ covery of the upsilon particle by Lederman's Columbia/Fermi- lab/Stony Brook team showed that quarks come in at least five varie­ ties. Construction of the Energy Saver began in 1979, and work was well advanced when preparations to ex­ ploit the higher energy beams were launched with the Tevatron I scheme in 1981 and Tevatron II the following year. The new Energy Saver broke the Main Ring's 500 GeV record in 1983 when protons were acceler­ ated to 512 GeV. In the same year, construction of the Antiproton Source began as part of the Teva­ tron I plan to provide the US with a proton-antiproton collider to rival CERN's, which had begun opera­ tions in 1981. 1984 brought Fermilab and the world into a new higher energy do­ main with protons being acceler­ ated to 800 GeV. Less than a year later, the new Antiproton Source provided antiparticles for the Teva­ tron to supply 1.6 TeV collisions for the new CDF detector. A com­ prehensive programme of fixed-tar­ get physics with the upgraded Te­ vatron II facilities and an 800 GeV proton beam rounded out the phy­ sics programme. A prolific amount of fixed target data (May 1988, page 16) and re-

The Wilson Hall high-rise - centrepiece of Fermilab's striking architecture.

16 CERN Courier, March 1989 La societe C, A.E.N. (Costruzioni Apparecchiature Elettroniche Nucleari) et la societe A.E.M.M. (Atelier d'Electromecanique de Montsouris) sont heureuses de vous faire part de la naissance de leur filiale commune :

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CERN Courier, March 1989 17 Giant Read-Out Boards?

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18 CERN Courier, March 1989 cord antiproton production rates (December 1988, page 9) were early dividends from the Tevatron Upgrading investment. But Fermilab is more than a With its Tevatron collider and have been looked at in some de­ world centre for high energy phy­ fixed target programmes well tail. Even higher energies could sics. Thanks to the vision of found­ into their stride, Fermilab could be reached by replacing both the ing director Robert Wilson, its idyl­ raise its sights and aim for high­ existing main ring and the super­ lic site and imaginative architecture er collision rates and more in­ conducting Tevatron with higher continually thrill and inspire visitors, tense fixed target beams. field superconducting magnets, whether scientists or the curious Initial work is already under­ similar to those piling up for the public. New buildings like the Muon way to revamp the linac injector HERA electron-proton collider at Laboratory and the Feynman Com­ (September 1988, page 16) to the German DESY Laboratory in puting Center have continued the provide more protons. To furth­ Hamburg. tradition. The unfenced 6,800 acre er boost the collision rate, The big advantage of a pro- site is a paradise of natural beauty measures include improvements ton-antiproton (or any particle- and a haven of environmental inter­ to the antiproton source and antiparticle) collider is that the est, the scene of ambitious pro­ beam cooling, stronger quadru- contrarotating beams can be jects to restore the Mid-West prai­ poles to squeeze the colliding held in the same ring. However rie to its former state, and home to beams closer together, more proton antimatter is not easy to a large herd of buffalo. stored bunches, and electrostat­ handle, and in any push for high­ The vision behind Fermilab was ic beam separation. In addition, er collision rates there comes a captured in Director Lederman's improved Tevatron cryogenics stage when it is more cost ef­ testimony before a Congressional could push operating levels high­ fective to aim instead for a two Science and Technology Sub-Com­ er and make the machine live up ring solution providing proton- mittee on Energy Development in to its name. proton collisions. The original 1984. 'High energy physics pays To push collider performance main ring could be replaced by a hack because it enhances our cul­ still higher calls for more ambi­ smaller 150 GeV ring nearby, ture, contributes to human dignity, tious schemes. A 20 GeV pro­ leaving space above the Teva­ broadens our view of the evolution ton superbooster injecting into tron for a second superconduct­ of the universe and our own posi­ the existing main ring, and a ing ring. tion in it. Some will tell you that so­ new antiproton 'depository' ciety profits because we set stan­ dards for applied science, we re­ cruit young people into science by the seduction of and quarks and black holes. All this is true, but what is also true is that the predecessors of today's high energy physicists changed the world, and there is no reason to believe that what we do now, ab­ stract and remote as it may seem, will not have major effects on the lives of our children's children.'

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20 CERN Courier, March 1989 Peter Hasenfratz - mass limits for the long- awaited but still unseen Higgs particle.

('top') quark. Ideas of a new MEETING strongly coupled phase of quantum Lattice 88 electrodynamics were aired by John Kogut of Illinois. The calculation of particle The forty-year dream of under­ masses is one of the main lattice standing the properties of the theory goals, the contribution of iti­ strongly interacting particles from nerant 'sea' quarks being the most first principles is now approaching difficult to include. A 'quenched' reality. approximation with valence quarks (QCD - the field theory of the only, ignoring sea effects, is not quark and constituents of expected to give the right answer, strongly interacting particles) was but it is still important to see what initially handicapped by the severe happens before embarking on the limitations of the conventional (per­ full calculation. turbation) approach in this picture, Progress with the quenched ap­ but Ken Wilson's inventions of lat­ proximation was covered by Enzo tice gauge theory and renormaliza- Marinari of Rome. High statistics tion group methods opened new calculations by a special-purpose doors, making calculations of computer using improved calcula- masses and other particle proper­ tional methods say the proton is sive parallel array of nodes. ties possible. about 1.4 times heavier than the The better understanding of Lattice gauge theory became a rho meson, compared to the actual (particles containing major industry around 1980, when value of 1.22. rather than quarks) was Monte Carlo methods were intro­ New improved algorithms were pointed out by Andreas Kronfeld of duced, and the first prototype cal­ reviewed by Don Weingarten of Fermilab. Two years ago, confu­ culations yielded qualitatively rea- IBM, Yorktown Heights, and Steph­ sion reigned in this area and there pnable results. The promising de- en Adler of the Institute for Ad­ was no unanimity even on basic »elopments over the past year vanced Study, Princeton. Progress questions. Improved methods of were highlighted at the 1988 Sym­ has been most spectacular in gaug­ calculating masses have posium on Lattice Field Theory - ing the effects of sea quarks, with helped to clarify the situation, the Lattice 88 - held at Fermilab. new Monte Carlo algorithms being consensus being that the spin 2, Peter Hasenfratz of Bern sum­ about 10,000 times faster than positive parity glueball is about 1.5 marized recent lattice work on the their predecessors. times heavier than its spin zero mass limits of the so-far unseen Hardware too has seen compar­ counterpart. Higgs particle (responsible for able improvements. The special Pierre van Baal of CERN summar­ mass in the standard electroweak purpose machines under construc­ ized recent analytic work on the model). It has long been known tion at various institutions around spectrum of a pure glue theory. In that simple Higgs theory breaks the world are roughly 10,000 times addition to being very beautiful, down if the Higgs is heavier than more powerful than the VAXes this work has been accurately veri­ about 1 TeV. Recent lattice work used for the original calculations fied by Monte Carlo methods, so has even brought the limit down to seven years ago. Norman Christ of increasing confidence in the numer­ about 600 - 700 GeV and made it Columbia described machines ex­ ical approach. more general. According to these isting or under construction at Co­ The physics of QCD at high tem­ calculations, no Higgs below this lumbia, IBM, Rome, Fermilab, Cal- peratures and densities - interest­ level means some new physics tech, and Tsukuba, and in industry. ing for heavy ion physics, astro­ beyond the . Some of these borrow ideas from physics, and cosmology - has pro­ Julius Kuti of San Diego outlined the approach pioneered by the Co­ vided the first accurate, reliable si­ further lattice applications in the el­ lumbia group and now in wide­ mulation result - the transition ectroweak sector, including bounds spread use for lattice calculations - temperature at which quarks are on the mass of the missing sixth fast floating point chips on a mas­ unlocked from their conventional

CERN Courier, March 1989 21