Intense muon sources have been discussed as a starting point for very high energy colliders and even more in recent years as a source of very intense and well-collimated neutrino beams. This working group should identify, but clearly distinguish, the main accelerator physics aspects of both the Muon Collider and the Neutrino Source. Even more, it is crucial to understand for the high energy physics community, how much a Neutrino Source represents a first step to a muon collider and what are the additional burdens. Given the variety of technologies that require R&D makes it necessary to have the group present a risk assessment of the various subcomponents, their R&D goals and the time scale on which the R&D could be realized. The more recent refocus of the collaboration towards Neutrino Sources should reflect in the main topics of the discussion. The different approaches: CERN, KEK-JAERI, and the Muon Collaboration (including the Fermilab and Brookhaven locations) should be compared in performance, risk and (if possible) schedule. A discussion on whether a Muon Cooling experiment is necessary and/or viable is absolutely required and should be presented by the group. For the Muon Colliders, the technical performance, especially for a low energy (Higgs collider) machine should be addressed. Technical performance (power consumption, risk assessment, luminosity etc ) should be compared to linear colliders in the same energy range. Input here will be required from the High Energy physicists to define the measure of performance for these two concepts (MC, LC). For the long-term R&D the advantages compared to electron-positron accelerators should be worked out and quantified as much as possible.

Organizing Committee Contacts: N. Holtkamp, T. Roser

Perform a survey of the present status as well as the vision of the future promises of the various electron-positron circular colliders. The colliders to be covered include those currently in operation, currently under construction, or envisioned as a possibility of the future, and in the US and abroad. Special emphasis should be placed on the clear identification of the beam physics limits and accelerator technology limits, and an examination of the extent that they have been addressed by past research or need to be addressed by futher research. Identify new and promising ideas even though they may need additional work. These issues should be addressed for all of the leading technical realizations of the circular electron-positron colliders. Finally, the group should summarize in a brief report (a few pages) the highest priority research topics for different techological realizations of circular electron-positron systems and give an approximate timetable for key R&D development. The group is also asked to provide comprehensive presentations to high-energy and accelerator physicists in plenary sessions during the Snowmass workshop.

Organizing Committee Contacts: A. Chao, J. Seeman

The linear collider group should give a vision of the potential of linear colliders both in the near and far term. Special emphasis should be placed on the clear identification of the beam physics limits and accelerator technology limits and an examination of the extent that they have been addressed by past research or need to be addressed by future research. These issues should be addressed for all the leading possible technical realizations of a Linear Collider. Finally, the Linear Collider group should summarize the highest priority research topics for different technological realizations of both the near term proposals and longer term concepts and give a rough time scale for key calculations, experiments or technology developments. In particular, we would like the linear collider group to pay special attention to the NLC/JLC design, the TESLA design for possible near term projects. For the longer term, the group should examine the upgradability of each design with extensions of the proposed technology. The group should also examine two-beam ideas as either an upgrade option or a stand alone technology for higher energy linear colliders.

Organizing Committee Contacts: N. Holtkamp, R. Ruth

A long-term goal of the US high energy physics program is to regain the energy frontier after the start of LHC operation. A very high energy, high luminosity hadron collider is the only sure way to accomplish this goal. The Working Group on Hadron Colliders should develop a vision and a long-term plan for the US hadron collider program. In particular, it should examine the physics and technology issues central to the design of very high energy, high luminosity hadron colliders and specify the most critical accelerator physics and engineering issues that determine the performance of the machine; identify the technology developments and accelerator physics experiments needed to prove the machine feasible, and evaluate and estimate the technological and physics limitations on ultimate energy and luminosity in hadron colliders.
The results of the recently completed VLHC study of a staged collider in a large-circumference tunnel should be evaluated and compared with other potential approaches to building and operating very large hadron colliders.
Finally, an R&D plan that will accomplish the goals set out above should be developed. This plan should prioritize the areas of technology R&D that will provide maximal benefit to a future VLHC in terms of performance and cost-effectiveness, and should include an estimated cost and schedule for the R&D.

Organizing Committee Contacts: G. Dugan, J. Strait

Perform a survey of the present status as well as the vision of the future promise of the various lepton-hadron colliders. The colliders to be covered include those currently in operation, currently under construction, or envisioned as a possibility for the future, and in the US and abroad. Special emphasis should be placed on the clear identification of the beam physics limits and accelerator technology limits and an examination of the extent that they have been addressed by past research or need to be addressed by further research. Identify new and promising ideas even though they may need additional work. These issues should be addressed for all of the leading technical realizations of the lepton-hadron colliders. Finally, the group should summarize in a brief report (a few pages) the highest priority research topics for different technological realizations of lepton-hadron systems and provide an approximate schedule for key R&D developments. The group is also asked to provide comprehensive presentations to high-energy and accelerator physicists in plenary sessions during the Snowmass workshop.

Organizing Committee Contacts: A. Chao, G. Dugan

Several present and future high energy physics facilities are based on high intensity secondary particle beams produced by high intensity proton beams.
The group is to perform a survey of the beam parameters of existing and planned multi GeV high intensity proton sources and compare with the requirements of high energy physics users of secondary beams. The group should then identify areas of accelerator R&D needed to achieve the required performance. This should include simulations, engineering and possibly beam experiments. the level of effort and time scale should also be considered.

Organizing Committee Contacts: T. Roser, J. Strait