Preparatory ‘Pre-lab’ Proposed for ILC

by Matthew Chalmers, editor,

On September 10, the International Committee for Future Accelerators (ICFA) announced the structure and members of a new organizational team to prepare a “pre-laboratory” for an International Linear Collider (ILC) in Japan. The ILC International Development Team (ILC-IDT), which consists of an executive board and three working groups—governing the pre-lab setup, accelerator, physics and detectors—aims to complete the preparatory phase for the pre-lab on a timescale of around 1.5 years.

The aim of the pre-lab is to prepare the ILC project, should it be approved, for construction. It is based on a memorandum of understanding among participating national and regional laboratories, rather than intergovernmental agreements, explains chair of the ILC-IDT executive board, Tatsuya Nakada of École Polytechnique Fédérale de Lausanne. “The ILC-IDT is preparing a proposal for the organizational and operational framework of the pre-lab, which will have a central office in Japan hosted by the KEK laboratory,” says Nakada. “In parallel to our activities, we hope that the effort by our Japanese colleagues will result in a positive move by the Japanese government that is equally essential for establishing the pre-laboratory.”

In June, the Linear Collider Board and Linear Collider Collaboration, which were established by ICFA in 2013 to promote the case for an electron–positron linear collider and its detectors as a worldwide collaborative project, reached the end of their terms in view of ICFA’s decision to set up the ILC-IDT.

The ILC has been on the table for almost two decades. Shortly after the discovery of the Higgs boson in 2012, the Japanese high-energy physics community proposed to host the estimated $7 billion project, with Japan’s prime minister at that time, Yoshihiko Noda, stressing the importance of establishing an international framework. In 2018 ICFA backed the ILC as a Higgs factory operating at a center-of-mass energy of 250 GeV – half the energy set out five years earlier in the ILC’s technical design report.

Higgs factory

An electron–positron Higgs factory is the highest-priority next collider, concluded the 2020 update of the European strategy for particle physics (ESPPU). The ESPPU recommended that Europe, together with its international partners, explore the feasibility of a future hadron collider at CERN at the energy frontier with an electron–positron Higgs factory as a possible first stage, noting that the timely realization of the ILC in Japan “would be compatible with this strategy”. Two further proposals exist: the Compact Linear Collider at CERN and the Circular Electron–Positron Collider in China. While the ILC is the most technically ready Higgs-factory proposal (see p35), physicists are still awaiting a concrete decision about its future.

In March 2019 Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT) expressed “continued interest” in the ILC, but announced that it had “not yet reached declaration” for hosting the project, arguing that it required further discussion in formal academic decision-making processes. In February KEK submitted an application for the ILC project to be considered in the MEXT 2020 roadmap for large-scale research projects. KEK withdrew the application the following month, announcing the move in September following the establishment of the ILC-IDT.

“The ministry will keep an eye on discussions by the international research community while exchanging opinions with government authorities in the US and Europe,” said Koichi Hagiuda, Japanese minister of education, culture, sports, science and technology, at a press conference on September 11.

Steinar Stapnes of CERN, who is a member of the ILC-IDT executive board representing Europe, says that clear support from the Japanese government is needed for the ILC pre-lab. “The overall project size is much larger than the usual science projects being considered in these processes and it is difficult to see how it could be funded within the normal MEXT budget for large-scale science,” he says. “During the pre-lab phase, intergovernmental discussions and negotiation about the share of funding and responsibilities for the ILC construction need to take place and hopefully converge.”