1. US strategy and plans for future Lepton Colliders
David MacFarlane
Director, Particle Physics and Astrophysics
SLAC National Accelerator Laboratory
LCWS 2011 in Granada, Spain

2. Physics at the Terascale
The LHC will lead the way to energy frontier discoveries
At the threshold for discovery of new physics, and we expect to cross it momentarily…
LHC discoveries would establish energy scale & physics case for Lepton Collider as the next energy frontier machine
Lepton Collider is a precision instrument that would let us understand Terascale physics
Establish the mechanism for EWSB is indeed the Higgs boson
Establish the nature of physics beyond the SM, such as SUSY, extra dimensions
Establish that accelerator-produced Dark Matter candidate does indeed resolve the cosmological Dark Matter problem
Open up new windows for discovery at the precision frontier
US Strategy for Lepton Colldiers: LCWS2011

3. Three Lepton Colliders options
Advanced concept to mature design phase
ILC: TeV e+e- linear collider
Superconducting RF accelerating cavities
Technology demonstrated, ready to propose ~2012
Physics/Detectors well studied, R&D ready ~2012
CLIC: 3 TeV e+e- linear collider
Two beam acceleration with warm RF
R&D underway, but technical demonstrations needed
Machine and Detector CDR in 2011, TDR in ?
Pre-conceptual phase demonstrating technologies
Muon Collider: 3 TeV µ+µ- storage ring
Fermilab’s Muon Accelerator Proposal will address some of the basic unanswered R&D questions
Feasibility/conceptual design ~
Possible technical design & demonstrations in 2020’s
US Strategy for Lepton Colldiers: LCWS2011

4. US partnership in GDE managed ILC R&D goals
KEK
DESY
Cornell
Fermilab
KEK
US Strategy for Lepton Colldiers: LCWS2011 4

5. US collaboration on CLIC R&D
Successful R&D on normal conducting x-band structures at CERN/KEK/SLAC
Demonstrated structures with >100 MV/m (unloaded) gradient satisfying breakdown rate requirements
TD24
23 MeV beam acceleration
106 MV/m accelerating gradient
US Strategy for Lepton Colldiers: LCWS2011

6. Detector concept development for ILC & CLIC
Learning from ILC machine-detector background work
Smaller spots, higher energy, much more beamsstrahlung
Detector requirements being evaluated
ILD and SiD simulation & reconstruction frameworks used to jumpstart CLIC performance studies
Conducting critical R&D
Benchmarking physics performance
SiD
ILD
US Strategy for Lepton Colldiers: LCWS2011

7. Muon Collider Concept: Fermilab
US Strategy for Lepton Colldiers: LCWS2011

8. Long-term vision for the Fermilab site
Neutrinos with LBNE and then ProjectX as a powerful front end to a broad intensity frontier physics program which enables longer-term plans
Neutrino Factory
Muon Collider
US Strategy for Lepton Colldiers: LCWS2011

9. Muon Collider Challenges
Multi-MW proton target with long lifetime
Liquid Hg jet MERIT experiment demo up to 8 MW
RF cavities operating inside magnetic fields may provide a method for capturing and cooling
R&D program at Fermilab’s MuCool Test Area
Gas filled RF cavities in magnetic fields offer a possible shortcut
Need demonstration of 6D cooling by a factor of 106
4D MICE experiment in progress (demonstrate O(10%) by ~2014)
6D cooling experiment sometime after 2015
Need development of very high fields solenoids (>30T) for last stages of cooling (luminosity proportional to field)
Program started at several labs FNAL, BNL, LBNL
US Strategy for Lepton Colldiers: LCWS2011

10. Muon Collider Challenges
Muon collider requires substantial acceleration (few km)
Ideally would use ILC technology
Major wall plug power consumer (out of perhaps 160 MW total)
Need end-to-end system simulation to understand beam dynamics, ultimate losses, and emittances
Recent substantial progress with collider ring, optimized cooling channels and proton beam compression ring designs
Demonstration of LC precision physics capability with realistic detector, MDI, and backgrounds simulation
Will require detailed simulation and physics performance studies
First steps taken at workshop at Telluride, CO June 27-July 1
US Strategy for Lepton Colldiers: LCWS2011

11. Fermilab-led Muon Accelerator Program (MAP)
Fermilab set up a joint organization incorporating previous Neutrino Factory NFMCC Muon Collider MCTF efforts
MAP proposal developed, reviewing and endorsed by DOE/HEP, including project management plan
Mission is to develop and demonstrate the concepts and critical technologies to produce, capture, condition, accelerate, and store intense beams for NF and MC
Goal is to permit HEP to make an informed choice of the optimal path to a energy frontier MC or NF
Develop and manage a coherent national R&D program in a multi-institutional framework with a Program Director and suitable oversight
Annual cost ~10M$ now  ~15 M$ requested FY12-FY16
US Strategy for Lepton Colldiers: LCWS2011

12. MAP R&D plan in development
Execute multi-year R&D program to:
Develop a feasible concept for a Muon Collider
Participate in NF Initial Design Study to produce an RDR
Carry out basic R&D aspects elements of a Muon Collider
Participate in systems tests of 4D and 6D cooling at MICE and with a “6D” bench test (no beams)
US Strategy for Lepton Colldiers: LCWS2011

13. Engaging the broader Community
“…To review the physics case for a Muon Collider, accelerator R&D progress, the outstanding challenges, future plans, and opportunities for new and existing groups to participate in the R&D. “
US Strategy for Lepton Colldiers: LCWS2011

14. Informing future directions on Lepton Colliders
Machine questions beyond R&D efforts
What is the maximum energy required? Does the physics case lie within the range of ILC, or does it need CLIC or MuC?
What range of energies/luminosities is needed? Need to run at lower energies for Higgs, top, low-mass SUSY? Are threshold scans needed for precision measurements?
Does beam energy spread matter for the physics?
Is beam polarization essential?
Detector questions beyond R&D efforts
Can the detector do physics in the machine’s environment?
Is detector performance adequate for the precision physics goals?
How critical is full solid angle coverage?
US Strategy for Lepton Colldiers: LCWS2011

15. Coordinating a Common Process in the US
HEP labs are working with the US community to develop a plan for coordinated study of physics and detectors at lepton colliders
Establish the physics capability of each lepton collider option
Provide feedback to machine designs to optimize physics reach
Establish detector requirements at each collider, accounting for the very different machine environments
Facilitate development of suitable detector concepts, exploiting existing software frameworks for simulation and benchmarking
Coordinate and guide the necessary physics studies and detector R&D needed to establish concept viability
Compare the physics potential of all the options on an equal footing.
US Strategy for Lepton Colldiers: LCWS2011

16. US Lepton Collider Framework
Goal:
Establish the physics capability for energy frontier lepton colliders
LCF would coordinate studies needed to reach that goal
Define and compare the physics potential for Lepton Colliders with a common benchmarks and simulation tools
Evaluate machine backgrounds and their impact on physics capabilities
Provide feedback to the machine designs
Support developing detector concepts for Lepton Colliders
Provide a common simulation framework
Establish a list of critical R&D required
Coordinate Lepton Collider related detector R&D as part of a national generic R&D program
US Strategy for Lepton Colldiers: LCWS2011

17. Recent ALCPG meeting in Oregon
March 19-23, 2011
US hosting LCWS 2012 meeting in Arlington, TX
US Strategy for Lepton Colldiers: LCWS2011

18. American Linear Collider Physics Group
ALCPG was formed in 2002 to advance preparation for an experimental program at an electron-positron linear collider
ALCPG leadership has spurred:
Studies of critical physics processes with full simulation
Understanding of detector requirements, including the machine-detector interface
Development of integrated detector concepts with international collaboration, essential to assessment of physics performance
Promotion of prioritized detector R&D program funded by government agencies
Organization of periodic workshops with international participation, coordinated with accelerator community
The ALCPG is the North American part of a global effort working closely with Europe and Asia colleagues
US Strategy for Lepton Colldiers: LCWS2011

19. US Strategy for Lepton Colldiers: LCWS2011
Next steps in US
Need an ALCPG-like organization to advance a broader agenda for energy frontier Lepton-Collider physics
Will likely reconstitute ALCPG to assume the same functions for a broader set of energy frontier options
Would like to see it recognized by LCSGA, DPF, and DOE in this broader role
Need a common simulation tool to underpin physics studies
Fermilab and SLAC will submit a joint proposal to DOE to enhance LCSim capabilities and provide community support
Detector R&D needs will emerge from these studies
LC framework group could coordinate detector R&D proposals as part of national generic R&D program
US Strategy for Lepton Colldiers: LCWS2011

20. Global direction post 2012 discussed by the ILCSC
Proposed adiabatic transition to post-2013 linear collider organization
Organization will speak for a unified linear collider facility
Will converge to a single linear collider proposal based on LHC physics data
Steering committee successor organization to the current ILCSC
Membership and mandate should be reviewed by ICFA
Most of the relevant organizations are already represented in the current ILCSC
ICFA
“ILCSC” equivalent
Linear Collider Director
“GDE”
“CLIC”
Detectors/
Physics
US interface:
ART for ILC R&D
ALCPG for detectors/physics
US Strategy for Lepton Colldiers: LCWS2011

21. The future of ART – US Steering Group
ILC not the highest priority in a US funding climate with significant challenges for the future direction of HEP
US ILC community recommendation to DOE/HEP:
Maintain the Americas Regional Team (ART) concept for accelerator R&D and Project Management type activities
Continue virtual laboratory model, where the ART Director reaches agreement with participating laboratories regarding tasks
ART Director reports to the LCO for policy & technical guidance, while responsible to US funding agencies for US R&D outcomes
DOE/HEP encourages this direction and will likely charge the ART for prepare a budget for the period
Preliminary discussions range from $15M-$18M per year, down by about a factor of two from recent years
US Strategy for Lepton Colldiers: LCWS2011

22. US Strategy for Lepton Colldiers: LCWS2011
ART Strategy for FY2012
FY2012 still not enacted by Congress
Current guidance suggests a $22M investment
ART priorities for FY2012 are:
Support the GDE TDR effort – maintain the key core personnel who will produce the TDR at a level consistent with the TDR work load.
Continue with (baseline) SRF technology development – cavity production looks OK but cryomodules are not really proven yet and klystron cluster R&D is not finished.
Continue with baseline technology where necessary – e.g. positrons
Remaining R&D activities
US Strategy for Lepton Colldiers: LCWS2011

23. Possible ART R&D plan for post 2012
Physics case may suggest a higher energy SRF based LC with a cost no more than the current 500 GeV design
Since ~80% of the total cost is tied up in CFS & Main linac, focus would be higher gradients & value engineering
Possible directions for such a future R&D program at US facilities:
Gradient enhancement through evolutionary R&D (new shapes, superstructures, ...) at JLAB & Cornell or fundamental R&D (coatings, materials, ...) at ANL, JLAB and possibly Fermilab.  
Value engineering studies mainly pursued through Fermilab
Continue to pursue cryomodule system tests at Fermilab (Project X phase II synergy)
US Strategy for Lepton Colldiers: LCWS2011

24. US Strategy for Lepton Colldiers: LCWS2011
Summary
Physics landscape may change substantially in near-term, with possible new Terascale discoveries at the LHC
Discoveries would define the physics case for a lepton collider as a precision instrument to elucidate the nature of the new physics
US also focusing on intensity frontier opportunities such as LBNE and ProjectX (DOE Intensity Frontier Workshop this fall)
US capital investments will be very limited in present fiscal climate
US pursuing R&D for three lepton collider options in different states of readiness
ILC: engineering design ready after 2012 for energies up to ~1 TeV
CLIC: may be ready to build by late in the decade for energies up to ~3 TeV (although energy costs are large)
Muon Collider: small footprint & capable of multi-TeV, but significant R&D required and physics performance not yet established
US Strategy for Lepton Colldiers: LCWS2011