The document discusses plans for establishing the future of linear colliders through workshops at Snowmass in 2001 and technical reviews in Europe and Japan. It outlines the charge for various working groups at Snowmass to compile the physics case for an initial 500 GeV linear collider and evaluate the need for higher energies. It also notes that the US linear collider group should focus on making the strongest possible physics case for the LC within the community to support its consideration as the next major facility.

1. Linear Collider Workshop – Charge Johns Hopkins University P. Grannis March 19, 2001 The coming months will be crucial for establishing a future for the Linear Collider … In the US: “Linear Collider Physics Resource Book for Snowmass01” Snowmass workshop HEPAP Subpanel In Europe: TESLA design report (Colloquium at DESY Mar. 23-24) (see talk of Ties Behnke) In Japan: Work on cost, milestones is ongoing for 2003 design rept? Globally: Expect technical review/comparison of proposed machines, costs, technical risks, upgradability; Start early 2002? ICFA umbrella

3. Snowmass 2001 EWSB Flavor Hi Scale AstroPart QCD  SR/  Coll ee Circular ee Linear Had. Collider Fixed Tgt AstroPart dets HEP & technology The Matrix … connections between Physics and Experimental Approaches groups

6. What should the North American Linear Collider group be doing? In past, the LC group activities have been devoted to developing the physics case for a linear collider, in conjunction with physicists in Europe and Asia. Enough attention to detector issues has been given to define the primary features of a LC detector and approximate cost. Recently, more attention has been focussed on the case for a first stage at up to 500 GeV. This meeting comes at a transition time, as accelerator proposals become better defined and we enter the era of evaluating machines, working toward approval by governments, international cooperation arrangements. In the US, the HEP community has not yet articulated its support for the LC; our chief focus now should be to make the case for the LC within the physics community as fairly and as completely as possible. Only with a recommendation from the community that the LC is the right next choice can we address the case with other branches of science, the government, and international partners. It will be hard enough even if we are unanimous!

7. The future of the American Linear Collider working group The American LC group has been in operation since 1995. Many physics studies have been performed and reported in numerous workshops. Detector studies and rather generic detector designs developed for the purpose of defining scope (with a conscious attempt to avoid usurping the role of eventual LC detector collaborations). Since 1998, we’ve had an international coordinating group for European, Asian and American activities; this group serves also as the advisory body for the series of International LC Workshops. In late 2000, ICFA agreed that an international technical review panel should be formed – evaluate LC designs from point of view of design parameters, technical risks, cost, R&D needs on a comparative basis. Is it time to bring the regional physics and detector working groups together more closely, and operate them as a merged single group? Doing so would underscore the existence of an integrated international community that we foresee doing the experiments at whichever LC may be built. There may be an opportunity now, with the ECFA/DESY study completion of its Physics and Detector technical design report.

8. Book on Physics at the Linear Collider and Detector Issues The book should be of real importance for the Snowmass Workshop, and for the discussions prior to Snowmass at various workshops, universities and Laboratories. The TESLA TDR – Detector and Physics sections – will be of importance for Snowmass. We need it soon, and its not at all there yet! Plug in and get this document in order. (see M. Peskin talk) This should be a major theme at this workshop. Addressing the concerns of our colleagues is, at this time, more important than most of the specific physics/detector studies that one could do. It is also imperative that each of us be able to present a cogent case for the physics of the linear collider, defend its first phase operation at about 500 GeV, and to place the LC in context with other initiatives .

9. Some questions that need addressing We should frame the questions that Snowmass groups can work on. People appreciate the validity of the LC better through doing studies than reading reports! These questions should emerge naturally from the ‘Orange Book’, and we should develop the list of them this week. More generally, our colleagues have many concerns that influence their view of the Linear Collider as the appropriate next step for the US to take. We need to listen and take these seriously -- and provide thoughtful input to these concerns. In what follows, I give some of the questions that I hear from the sceptics (some are interrelated). We need to have sensible answers to these. (See J. Jaros’ talk)

10. Some examples for further studies 1. Study on  t from the F-B asymmetry in tt 2. Study of g ttH Yukawa coupling from tt cross section 3. How can one probe CP violation from top production at threshold? 4 Can one improve m top resolution for tt production above threshold (use m eff ?) 5. Study the anomalous top couplings at some fixed positron polarization (including zero); what is the utility of positron polarization here? These are specific topics for LC working group study taken from reading of the top quark chapter: There will be similar lists from the other chapters

16. This Meeting The main jobs are: Prepare as honest and compelling a case for the community to evaluate Linear Colliders as we can make. Get that book out! Start to think more globally about where we need to go. Review the recent studies, and formulate the questions for the next round of physics and detector studies.