International Cooperation
 
At various facilities in the Asian region, there have been significant progresses in high energy physics and synchrotron radiation experiments. In addition, many researchers from ACFA member nations are actively participating in large-scale experiments such as those at KEKB/PEP-II,Tevatron, HERA, and LHC. The Asian physics community has grown significantly and has thus set a firm enough foundation for further bigger projects.
 
The linear collider has a facet which can serve as a new means for materials science. The ultra-low- emittance beam essential for the JLC is also an indispensable element of the next-generation, coherent x-ray source. Therefore it is very important to collaborate with the materials science community in ACFA to efficiently and effectively promote accelerator science.
 
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. Now 62 institutions in Asia are participating in various subgroups, expanding their research activities at their home institutes. The subgroup activities in different part of Asia are discussed over Internet and have been summarized annually at series of ACFA workshops.
 

ACFA Workshop at Korea University

The first workshop was held at Tsinghua University in Beijing (1998), followed by one at Korea University in Seoul (1999), and then one at Taiwan University in Taipei (2000). Thanks to the hospitality and thoughtfulness of the hosts, all of these meetings were very enjoyable and fruitful.
 
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 there have always been a few participants from Europe and the U.S.A. in the framework of the inter-regional cooperation. Reciprocally, Asian colleagues have been contributing to the workshops of the other regions. All of these regional activities are reported and discussed at a series of worldwide linear collider workshops.
 
The JLC is a reasonable next step for the Asian high energy physics community well motivated by our present knowledge of particle physics. KEK has been integrating outcomes from the accelerator, physics, and detector studies to realize the project in Asia through a healthy collaboration with Asian laboratories and universities. The inter-regional cooperation has become more active in time and has helped further promote the project.
 
KEK, being one of the most active major high energy physics laboratories in the world, is willing to host this challenging large-scale inter-regional facility in the 21st century. The JLC project would provide a good model case for the promotion of accelerator-based science in Asia.
 
For details please see http://acfahep.kek.jp/