Summary of the 200×200 GeV μ+−μ− collider working group

We report the discussions and some preliminary results from the sessions of the 200×200 GeV μ+−μ− Collider working group. The physics motivation for such a ‘‘medium‐energy’’ collider is discussed. Possible parameters for such a system are described, and compared with higher‐energy systems. Relatively‐high luminosities (L∼1033 cm−2s−1) appear possible. Modifications of existing facilities to obtain medium‐energy μ+−μ− collisions are discussed. Other discussion topics (μ‐p colliders, low‐energy μ sources, etc.) are summarized.