ILC NewsLine
ILC detectors in the making

François Richard

Jim Brau

Hitoshi Yamamoto

The experiments will be the centre piece of the future ILC. The detectors will not only physically sit right in the middle of the machine - all the physics will revolve around them as well. Sub-detector R&D and test-beam studies are aimed today at developing these experiments. Within the Worldwide Study, physicists are imagining and studying complete ILC detectors. They are designing detector concepts for the ILC. Presently, the concept teams' membership overlaps the sub-detector R&D collaborations. In a few years, competitive detector collaborations will be formed. By then, the detector concepts will have evolved into mature ILC detectors which can be built.

The main goal of developing these concepts now is to begin to work through details of detector integration, to evaluate the physics performance of an integrated system of all the detector subsystems, and to enable an evaluation of the cost of a complete detector. By combining the many elements such as tracking, calorimetry and magnetic fields, into an achievable working detector design, it is possible to reach the required feasibility, performance and cost evaluations. Many of the international collaborations for sub-detector R&D presently work independently of the concepts, and are contributing to more than one concept.

The ILC detector calorimeters will have to reach extreme precision on the particle jet energy measurement. Knowing this energy is crucial to understand which kinds of events were produced at one e+ e- interaction point. To solve this problem, two kinds of solutions are now being studied. Three of the four ILC detector concepts use a particle flow algorithm enabled by ultra-granular calorimeters. Such calorimeters will make it possible to reconstruct each individual particle of a given jet, including neutral particles. The newer '4th concept' uses the principle of compensation. It is aiming to read the particles energies independently of their nature (photons, electrons, hadrons…). The concepts were originally developed in specific regions: the Silicon Detector (SiD) in North America, the Global Large Detector (GLD) in Asia and the Large Detector Concept (LDC) in Europe. Now, the four concept memberships are regionally broader and physicists from around the world are contributing to all of the studies.

The International Organising Committee of the Worldwide Study of Physics and Detectors for Future Linear e+e- Colliders (WWSOC), co-chaired by by Jim Brau (University of Oregon), François Richard (LAL Orsay) and Hitoshi Yamamoto (Tohoku University) coordinates the ILC concept detectors activities. They organise the "International Workshops on Linear Colliders" (LCWS) and support regional ones. They also form dedicated panels. The R&D panel reviewed worldwide ILC R&D detector activities and made a list of the missing R&D areas. The Detector Concept Report (DCR) panel is writing a document which will be published alongside the ILC Reference Design Report. This document will consist of a physics section, a description of the detector concepts, an average cost estimate for an ILC detector, a review of the ongoing R&D and the priorities and also a machine detector interface section. The WWS helps coordinate the work of the three regional studies: the European (ECFA) Study, the North American (ALCPG) Study and the Asian (ACFA) Study. "Finally, with the Detector Concept Report, we will check that the ILC detector price is not concept-dependant", said François Richard "And we are confident that it will be so."

In principle, additional concepts might emerge after the Detector Concept Report. To be considered, a new concept team will have to produce a document which will include a complete description of the detector with simulated performances, descriptions of the crucial R&D and machine detector interface studies. In the DCR, the global performances and global cost will be presented. Also an "average" detector will be described in sub-detectors chapters (in which the conceptual differences will be detailed). "Concept detectors will turn to probably only two final detectors at the ILC startup," said Hitoshi Yamamoto. "The detector studies will undergo some form of reorganisation". In order to validate a detector concept in the future, a detailed Technical Design Report (TDR) will have to be produced. It will require large resources in manpower, equipment and studies to achieve a full study of a realistic prototype of each sub-detector. "Significant efforts have already been devoted to developing the detector concepts," said Jim Brau. "In order to bring experiments to the maturity needed by the end of the decade, the efforts will need to expand greatly. Meanwhile, we strive to make each active concept effort a global enterprise." The start-up for such detector Technical Design Reports has not been decided yet. "The construction of the ILC machine and the ILC detectors are at the same order of timescale." said Richard. "Therefore, the detector roadmap should logically stay close to the machine roadmap".

In future issues, ILC NewsLine will report successively on each of the four detector concepts, starting with the Global Large Detector next week.

-- Perrine Royole-Degieux