The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides work on the parameters of a 3-4 and 0.5 TeV center-of-mass (COM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (COM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from 1098-4402͞99͞2(8)͞081001(73)$15.00 © 1999 The American Physical Society 081001-1 PRST-AB 2 CHARLES M. ANKENBRANDT et al. 081001 (1999) a heavy-Z target and proceeding through the phase rotation and decay (p ! m n m ) channel, muon cooling, acceleration, storage in a collider ring, and the collider detector. We also present theoretical and experimental R&D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the research and development since the feasibility study of muon colliders presented at the Snowmass '96

Intense highly collimated neutrino beams, created from muon decays at high-energy muon colliders or storage rings, cause significant radiation problems even at very large distances from the machine. A recently developed weighted neutrino interaction generator permits detailed Monte Carlo simulations of the interactions of neutrinos and of their progeny with the MARS code. Special aspects of neutrino radiation dose evaluation are discussed. Dose distributions in a tissue-equivalent phantom are calculated when irradiated with 100 MeV to 10 TeV neutrino beams. Results are obtained for a bare phantom, one embedded in several shielding materials, and one located at various distances behind a shield. Neutrino radiation is investigated around muon storage rings serving as the basis for neutrino factories. The most challenging problem of offsite neutrino dose from muon colliders and storage rings is studied. The distance from the collider ring (up to 60 km) at which the expected dose rates equals prescribed annual dose limits is calculated for 0.5-4 TeV muon colliders and 30 and 50 GeV muon storage rings. Possible mitigation of neutrino radiation problems are discussed and investigated.

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Physical processes causing limited ( < -1%) energy loss to high-energy particles traversing bulk matter are examined and their cross sections cast in a form suitable for use in Monte Carlo transport calculations. Special attention is paid to scattering off edges. An algorithm is developed, based on the Fermi distribution of multiple Coulomb scattering, which generates first-passage distributions for escaping particles and more generally for transport of particles undergoing multiple scattering in the presence of an edge. Implementation of the various processes and of the edgescattering algorithm into a Monte Carlo code are briefly indicated. A sample of results obtained with this code is included. 3292

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