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The electron-positron linear collider project stems from the Japanese High Energy Committee's recommendation made back in 1986 as the post-TRISTAN program for energy-frontier physics. Following the recommendation a 5-years R&D program was set up to address key issues in basic component technologies and to formulate the project as a whole. The R&D program crystallized into the first project design in 1992 which elucidated physics prospects and novel detector concepts matching the opportunities, and outlined the accelerator complex including its application to X-ray laser production.

The basic physics that motivated the project is intact and the principal guideline shown there for the project promotion remains unchanged or even enforced especially in the necessity for further internationalization of the project. In this respect, the 1997 endorsement of the JLC as one of the major future facilities in the Asia-Pacific region is a remarkable milestone made by the Asian Committee for Future Accelerators (ACFA) and was an important step towards its realization in this region. The inter-regional cooperation also became more important than ever, which is reflected in recent close cooperation with European and North American regions to promote R&D's for the JLC facility which is, in its first stage, to cover center of mass energies up to about 500 GeV with a luminosity in the $ 10^{34} {\rm cm}^{-2} {\rm sec}^{-1}$ range.

The JLC, being an unprecedentedly high luminosity e+e- collider, is capable of producing more than 0.5 million light Higgs bosons, if any, and top quarks, for sure, within 5-6 years, and naturally serves as a Higgs and top factory. In addition it has a remarkable physics potential as a W and Z factory equipped with highly polarized beams and a two-orders of magnitude higher luminosity than those of existing facilities. Precision study of these particles at the JLC is a crucial step to establish the standard model and will pave the way to go beyond it.

In response to the ACFA statement of the linear collider project, a study group, Joint Linear Collider Physics and Detector Working Group, has been set up under ACFA. The charge of the working group is to elucidate physics scenario and experimental feasibilities.

The working group has been subdivided, according to physics topics and detector components and many institutions in Asia are participating in various subgroups, expanding their research activities at home institutes. The subgroup activities in different part of Asia are discussed and exchanged over Internet and have been summarized annually at a series of ACFA workshops.

Taking into account the scale of and the worldwide interests in linear collider projects, it is highly desirable that actual studies be carried out in a more global scope in spite of the regional nature of ACFA's initiative. In this respect, it should also be noted that, although the body of the JLC project promotion lies in Asia, there have always been active participants from Europe and North America in the framework of the inter-regional cooperation. Reciprocally Asian colleagues have been contributing to the workshops of the other regions, and all of these regional activities are reported and discussed at a series of worldwide linear collider workshops.

This report is a result from the past few years of the working groups' activities, and is intended to bring back and further enforce the importance of the physics that motivates the project, as well as to detail the technical feasibility of the experimentation that is involved in it.

The report is organized in the following format: in Chapter 1, we first detail the mission imposed upon the working group, and overview physics prospects and the detector model. We then list up basic sets of parameters of the JLC machine, on which all the studies are based. The subsequent chapters are grouped into three parts. First two of them are for physics and detectors, which are subdivided, according to the subgroups formation, and devoted to summaries of subgroups' activities. The last chapter describes optional experiments using $\gamma\gamma/e^-\gamma/e^-e^-$ collisions.

We are convinced that the JLC is a reasonable next step for the Asian high energy physics community well motivated by our present knowledge of particle physics. We have been integrating outcomes from the accelerator, physics, and detector studies to realize the project in Asia through healthy collaboration among Asian laboratories and universities.

We are willing to host this challenging large-scale inter-regional facility in the 21st century and we believe the project would be a model case for the promotion of accelerator-based science in Asia.

next up previous contents
Next: Contents Up: Particle Physics Experiments at Previous: List of Authors
ACFA Linear Collider Working Group