The 1984 Nobel Prize in Physics Goes to Carlo Rubbia and Simon Vm Der Meer: R

arrent Comments” EUGENE GARFIELD INSTITUTE FOR SCIENTIFIC INFORMATION* 3501 MARKET ST,, PHILADELPHIA, PA !9104 The 1984 Nobel Prize in Physics Goes to Carlo Rubbia and Simon vm der Meer: R. Bruce Merrifield Is Awarded the Chemistry Prize I Number 46 November 18, 1985 Last week we reviewed the 1984 Nobel Rubbia, van der Meer, and the hun- laureates in medicine: immunologists dreds of scientists and technicians at Niels K. Jerne, Georges J.F. Kohler, and CERN were seeking the ultimate confir- C6sar Milstein. 1 In this week’s essay the mation of what is known as the electro- prizewinners in physics and chemistry weak theory. Thk theory states that two are discussed. of the fundamental forces—electromag- The 1984 physics prize was shared by netism and the weak force-are actually Carlo Rubbia, Harvard University and facets of the same phenomenon. The the European Center for Nuclear Re- 1979 Nobel Prize in physics was shared search (CERN), Geneva, Switzerland, by Sheldon Glashow and Steven Wein- and Simon van der Meer, also of CERN. berg, Harvard, and Abdus Salam, Impe- The Nobel committee honored “their rial College of London, for their contri- decisive contributions.. which led to the butions to the eiectroweak theory. I dk- discovery of the field particles W and Z, cussed their work in my examination of communicators of the weak interac- the 1979 Nobel Iaureates.s tion. ”z The 1984 Nobel Prize in chemis- The daunting task facing the scientists try was awarded to R. Bruce Mertileld, at CERN was to find evidence of the sub- Rockefeller University, New York, for atomic exchange particles that commu- his development of a “simple and in- nicate the weak force. Theorists specu- genious” method for chemical synthesis lated that, in the same way that tiny par- on a solid matrix.J ticles of light called photons communi- Physics cate electromagnetism, the weak force is transmitted by another, related group of Rubbia and van der Meer were select- particles. These very dense communica- ed less than two years after the identifi- tors of the weak force-the so-called in- cation of the W and Z particles, a re- termediate vector bosons designated markably short period for recognition by W+, W –, and Z~had been predicted the Nobel committee. The scient~lc by Weinberg and Salam, independently achievement of these two physicists and of one another, in the late 1960s.6,7 The their colleagues culminated a half-cen- task of actually finding these particles tury of theory and experiments on the remained. Groups of scientists at CERN so-called “weak force. ” Along with grav- and at the National Accelerator Labora- ity, electromagnetism, and the “strong tory (Fermilab), Batavia, Illinois, had at- force” that binds together particles in tempted to release the W particle. But the atomic nucleus, the weak force is the particle accelerators at these facili- one of the four fundamental forces in the ties did not have enough power to pro- universe. The weak force is responsible duce particles of the mass that Weinberg for certain kinds of radioactive decay. It and Salam had predicted.a also controls the reactions that result in Rubbia proposed the use of a collider, the sun’s generation of energy.d which would smash together two coun- 432 ter-rotating beams—one composed of can be collided with the counter-rotat- protons, the other of antiprotons. The ing beam of protons. resulting collkions, according to Rubbia Another problem facing the scientists and his colleagues, would provide suffi- at CERN was detecting the effects of cient energy to reveal the W and Z parti- these proton-antiproton collisions. In cles. However, this idea presented for- 1978 Rubbia turned his efforts to the cre- midable obstacles. Rubbia had proposed ation of a detector in which the collision converting the existing accelerator at experiments would actually take place. Fermilab into a proton-antiproton col- This 2,000-ton device, named Under- lider, but his idea was rejected. He then ground Area 1 (UA 1), took three years took his plan to the European scientific and $20 million to build. 11Designed es- community and CERN. There, the idea sentially as a series of boxes within box- was approved. In 1978 the tremendous es, UA 1 comprised an intricate collec- effort began to convert CERNS four- tion of sensing devices and processors mile, underground Super Proton Syn- that enabled the scientists to detect the chrotrons into a proton-antiproton col- fleeting presence of the W and Z parti- lider. cles in the midst of all the particles creat- One of the most serious problems was ed in the collision of the two beams. An the production and storage of antipro- immensely complicated device, UA 1 set tons inside the collider. Antiprotons do new standards for detectors in collidlng- not exist in ordinary matter and must be beam experiments. A second, somewhat produced in h~gh-energy particle colh simpler detector, UA2, was added as a sions.z Accumulating the necessary mil- backup.z lions of antiprotons and regulating their Collision experiments began in 1981, passage around the collider was a key ex- but much of the key data were taken perimental problem. Rubbia turned to a from collider runs late the next year. Af- CERN colleague, Sirnon van der Meer. ter examining information from millions In 1968 van der Meer had written a of collision “events,” the scientists fo- paper (not published until 1972) that de- cused their attention on a handful of col- scribed “stochastic cooling”—a method lisions that seemed significant. Analysis for increasing the density of a beam of of the data showed signs of the predicted protons.g Work began at CERN to adapt “signature” of the W particle: a single van der Meer’s technique to the accumu- electron shooting off at a wide angle lation of an unprecedented quantity of from the colliding beams. Measure- antiprotons. ments of the energy expended during The efforts of van der Meer and his these collisions-the so-called “missing coworkers led to the construction of the energy’’-pointed to the existence of an- Antiproton Accumulator, a storage ring other signature particle, a neutrino. ThM 154 feet in diameter in which millions of all-but-invisible particle veered off from newly created antiprotons are “cooled” the collision in the opposite direction into a dense beam. Inside the ring, sen- with force equal to that of the electron. sors detect deviations in the individual Calculations showed that the mass of the orbits of the antiprotons, and, in mil- W particle was equivalent to that pre- lionths of a second, an electronic signal dicted by theoretical models. Rubbia’s is flashed across the chord of the circle UA1 group announced the discovery of to intercept and tighten the beam of an- the W particle in 1983, closely followed tiprotons as it races around the ring. by the UA2 group. 12.13The discovery of Both the beam and the correcting signal the Z particle came a few months lat- travel near the speed of light. 10The pro- er.14,15 cess is repeated millions of times until, after approximately 24 hours, enough Rubbia antiprotons have been accumulated to Rubbia was born in Gorizia, Italy, in be fed into the larger ring, where they 1934 and attended the University of Piss. 433 His graduate work in physics was com- our forthcoming study of the most-cited pleted at Columbia University, New 1983 articles in the physical sciences. York. In 1961 Rubbia returned to Eu- The most-cited paper, “Observation rope to join CERN. 16Since 1970 he has of new-particle production by high-en- divided his time between CERN, where ergy neutrinos and antineutrinos,” has he is senior physicist, and Harvard Uni- received over 300 citations since its pub- versit y, where he is a professor of phys- lication in 1975.17 Another highly cited ics. paper is “Small-angle proton-proton Using the Science Citation Index” elastic scattering at very high energies (SCF ), w have determined Rubbia’s (460 GeVz < s < 2900 GeVz),” pub- most-cited works for the period 1955- fished in 1972. la The work has been cited 1984. The list is based on ISI@’s internal 249 times. “all-author” data, since Rubbia does not Table 1 lists some of the 1S1 research appear as first author in any of the pa- fronts in which works by Rubbia, van pers. The fifth most-cited work is the der Meer, and colleagues are core docu- Physics Letters B paper in which Rubbia ments. The fronts cover 10 years of re- and colleagues announced the discovery search in high-energy particle physics. of the W particle. 12Although only two Some of these papers appear regularly in years old, this paper has already been our annual inventory of research fronts. cited over 170 times—a dramatic dem- A 1974 paper from Physical Revie w Let- onstration of its immediacy and impact. ters, for example, “Observation of mu- The bimonthly SCIS show that the paper onless neutrino-induced inelastic inter- also was cited in 56 publications in the actions, “ 1’3is core to six fronts, covering first six months of 1985. Also highly cited the years 1974 to 1980. is the paper by Rubbia and colleagues Three of the research fronts in Table 1 that discusses the identification of the Z appear in Figure 1, which presents the particle. 14This work has been cited over Klgher level map of cluster #83-0021, 160 times in the two years since publica- “Gauge theory of quark interactions and tion—and over 80 times in the first half jet production in high-energy collisions of 1985.

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