Giving credit to the first linear collider.

Abstract

The first of the three well-done articles on the high-energy physics community's effort to realize a world-wide consortium to build the World Linear Collider accelerator project (“Collision course with reality,” News Focus, Adrian Cho, 21 Feb., p. [1168][1]) makes one error of fact. It says, “The proposed electron-positron accelerator would be unlike any ever built.” This is not so. To start a $5-billion project without having fully tested out the fundamental accelerator physics issues would make us even crazier than the author implies that we are. The first linear collider (SLC), built at the Stanford Linear Accelerator Center (SLAC), began operation at energies up to 95 GeV in 1987. The critical issue for this new kind of accelerator was the ability to make what were then regarded as impossibly small beams stably collide with each other. It took some time to understand new accelerator physics problems and learn how to operate this machine. Many of the physicists involved in the new design competition discussed in the article took part in that work. The world accelerator physics community accepted the possibility of a very-high-energy collider when the SLC bettered its original beam size design goals, routinely operating for experiments with beams at the collision point of 0.5 by 1.0 μm. The article by Charles Seife (“Why physicists long for the straight and narrow,” News Focus, 21 Feb., p. [1171][2]) asserts that the Large Electron-Positron Collider (LEP) at CERN and the Tevatron at the Fermi National Accelerator Laboratory (FNAL) “filled in the details of the Standard Model.” In fact, the SLC delivered beams for the Mark II and SLD detectors. The linear collider makes it relatively straightforward to deliver polarized electron beams, and SLD used polarization asymmetries to make the most precise determination of the weak interaction “Weinberg” angle. The unique operating environment of the SLC permitted micrometer level reconstruction of the tracks of short-lived particles. The polarization and precision vertex reconstruction led to measurements more precise in some cases than comparable results from the combined four LEP detectors with their 30-times-larger sample of Z decays. For, example, the most stringent constraint on the Standard Model Higgs boson mass is due to the SLC/SLD program. Today's international competition between technologies and for a home site is the natural evolution of what has been an enormously productive international collaboration in the R&D phase of collider design. Since the late 1980s, SLAC, KEK, DESY, and FNAL have cooperated in building and operating facilities to test key concepts of an advanced linear collider. The collaborative R&D ensured that everyone was part of the determination of the feasibility and of setting the parameters of a future facility. It has worked beautifully and has sped up development. The present rivalry is a natural consequence of having to choose a site, and it will turn again to collaboration when a site is chosen. # Response {#article-title-2} Certainly in size, complexity, and expense, the proposed linear collider would be unlike anything that has come (to completion) before. However, as Baltay, Breidenbach, and Richter rightly point out, the SLC deserves recognition both as the first linear collider and for its scientific achievements. [1]: /lookup/doi/10.1126/science.299.5610.1168 [2]: /lookup/doi/10.1126/science.299.5610.1171