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Expanding the Physics Reach of a Linear Collider

NLC. Expanding the Physics Reach of a Linear Collider. Nan Phinney Line Drive Seminar Fermilab May 10, 2001. Some History. Gilman subpanel (1998): R&D toward an LC with L > 10 34 “initial capability of 1 TeV, extendible to 1.5 TeV” Higgs mass range was < 800 GeV

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Expanding the Physics Reach of a Linear Collider

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  1. NLC Expanding the Physics Reach of a Linear Collider Nan Phinney Line Drive Seminar Fermilab May 10, 2001

  2. Some History • Gilman subpanel (1998): • R&D toward an LC with L > 1034 • “initial capability of 1 TeV, extendible to 1.5 TeV” • Higgs mass range was < 800 GeV • Supersymmetry range was up to a few TeV • Emphasis on Energy: US HEP community had serious concerns that 1 TeV would not be enough • DESY, KEK, SLAC had proposals for 500 GeV LC with L = ~5 1033 and upgrade paths to ~1 Tev (1995 TRC) • The situation has changed! N. Phinney - Line Drive talk, 5/10/01

  3. LC Physics Program • Precision measurements of Higgs and SUSY parameters to understand the nature of EWSB and • to complement the LHC program • “The Case for a 500 GeV e+e- Linear Collider” , • American Linear Collider Working Group:hep-ex/0007022 • Emphasis on PRECISION has shifted concern from energy regime to luminosity • As long as there is a believable route to higher energy • LC version of the “no lose” theorem: • If No New Particles, • there are distinctive predictions for precision EW parameters that • LC has resolution to measure N. Phinney - Line Drive talk, 5/10/01

  4. Physics Case for the LC from P. Grannis Line Drive Talk Conjecture : Whatever causes EWSB, whether the SM Higgs alone or physics beyond the SM, the Linear Collider will see measureable effects at 500 GeV. cannot be proven rigorously! But there is a very strong plausibility that the LC will have a crucial role, no matter what the character of new physics is. Without the LC, we will not understand the new physics in enough depth, even though LHC should have made the first sightings of it. LEP/SLC made no discoveries; but LEP/SLC elucidation of the SM was an overwhelming success! LC should do the same for Beyond the Standard Model. N. Phinney - Line Drive talk, 5/10/01

  5. Push for Luminosity • Precision measurements require more Luminosity • TESLA L = 3.4 1034 @ 500 GeV • building on FFTB success to reduce σy 64 -> 5 nm • + longer bunch train, etc. • NLC/JLC L = 2.0 1034 @ 500 GeV • building on SLC experience and R&D success with structure tolerances to reduce emittance dilution • + more bunches, smaller bunch spacing, etc. • Design luminosity increased by factor 4-5 N. Phinney - Line Drive talk, 5/10/01

  6. Parameters • All designs have very small beam emittances and IP spot sizes measured in nanometers! N. Phinney - Line Drive talk, 5/10/01

  7. Are Luminosities Believable? • FFTB demonstrated required demagnification, cancellation of aberrations, tuning techniques • NLC damping rings similar to 3rd generation light sources • ALS @ LBNL has emittances similar to NLC • ATF @ KEK has achieved 10-11 vertical emittance (2 * NLC spec) • Key for NLC is emittance preservation in linac • FFTB achieved μm level beam based alignment using diagnostics close to NLC spec - mover step size 300 nm (want 50 nm), • BPM resolution 1 μm striplines, 40 nm rf cavity (want 300 nm) • NLC structure measurements already EXCEED spec • NLC and TESLA are both designed for high luminosity but neither design has much margin at these parameters N. Phinney - Line Drive talk, 5/10/01

  8. Final Focus Test Beam at SLAC FFTB IP FFTB demonstrated required demagnification for TeV LCs Measured vertical beam size of 70 nm N. Phinney - Line Drive talk, 5/10/01

  9. ATF Damping Ring at KEK Vertical emittance 10-11 measured with laser wire (~2 * NLC spec) N. Phinney - Line Drive talk, 5/10/01

  10. Structure Design Issues Precision wakefield measurements agree well with model prediction Fabrication achieved frequency errors < 1 Mhz (tolerance 5 Mhz) Structure BPM achieved < 1 m centroid resolution (tol. 20 m) N. Phinney - Line Drive talk, 5/10/01

  11. Ground Motion Tightest tolerance is on stability of final quads - < 1 nm Measurements at various sites show integrated high frequency ground motion @ nm level except at HERA (x 20) Diffusive motion is also 20 x higher at HERA TESLA depends on intra-train IP feedback to compensate Quiet sites are suitable for NLC with adequate stabilization feedback Hz N. Phinney - Line Drive talk, 5/10/01

  12. Low Energy Measurements • Corollary of “No Lose” Theorem • If no Higgs or Supersymmetry at TeV scale, then precision measurements at Z, W-pair, etc. become a path to see new physics • TESLA & NLC/JLC had forseen Z-pole calibration • at limited luminosity ~ 1032 but not Giga-Z runs • TESLA requires high E e- for e+ production • yield drops below Ecm ~ 300 Gev • NLC/JLC have softer fall-off • limit is apertures for collimation, masking, magnets N. Phinney - Line Drive talk, 5/10/01

  13. TESLA @ Low Energy • For Z pole, TESLA plans to use 1st 50 GeV of linac for production e- & extract into bypass line • To make e+, a 2nd gun would feed last 200 GeV > target • W-pair or Higgs might require E upgrade to 35 MV/m for e+ yield and e- beam energy together • Bypass & 2nd gun not in baseline Blue assume bypass line & nominal e+ I quick estimate courtesy of N. Walker, DESY N. Phinney - Line Drive talk, 5/10/01

  14. Linac and bypass NLC @ Low Energy • NLC needs a bypass line for low E to avoid wakefields from beam passing through unpowered structures • Primary IR not designed for highest Luminosity low E operation - use 2nd IR or modify first • Bypass & 2nd IR are in baseline for 2nd IR N. Phinney - Line Drive talk, 5/10/01

  15. IR Choices TESLA has possibility of 2nd IR with 34 mrad crossing angle (forgg?) Baseline has 1 IR ZDR NLC design had symmetric IR layout both with 20 mrad angle Baseline had tunnel for 2nd IR but no beamline JLC design similar with 16 mrad crossing angle N. Phinney - Line Drive talk, 5/10/01

  16. TESLA Layout N. Phinney - Line Drive talk, 5/10/01

  17. NLC Layout - 2 IRs • Many discussions with HEP physics community • @ LC Physics meetings, • esp. @ FNAL in Jan 2001 • US HEP physicists want 2 IRs to broaden physics program cost of 2nd IR ~ 150M$ • Hi/Lo energy IR scheme redesigned for • future expansion, • energy flexibility • Linacs point at high E IR 30 km N. Phinney - Line Drive talk, 5/10/01

  18. NLC High/Low E IRs NLC IR layout inspired by new compact FF design which can support 2.5 Tev in ~ 700 m (CLIC @ 1.5 Tev 3 km) Symmetric IR layout: Big Bend generated crossing angle and provided muon suppression but it was long (expensive) and limited energy range With short FF, muons had line of sight to detector Asymmetric IR layout: High E IR beamline has minimal bending to allow for upgrades to 3-5 TeV collisions! Low E IR with larger crossing angle for gg L* = ~4 meters to ease detector integration FF designs easily span ~ factor of 4 in E but not factor of 10 some tricks possible to extend range up or down N. Phinney - Line Drive talk, 5/10/01

  19. NLC Luminosity Scaling with Energy High E IR - 0.25-1 TeV Low E IR - 90-500 GeV Luminosity increases linearly with energy at High and Low E IRs Above maximum design energy, L drops due to synchrotron radiation emittance growth Below E range, L drops due to aberrations & limited apertures, depends on collimation details Can extend high E range by changing geometry to soften bend angle N. Phinney - Line Drive talk, 5/10/01

  20. Options under Study Options offer Broader physics program ($) Simultaneous operation: interleaved pulses to both IRs, possibly different energies Sequential operation (baseline): pulses to 1 detector for weeks/months 180 hz: Injector and up to 250 Gev of Linac @ 180 hz split between IRs - 60/120, 90/90, 180 Issues: Simultaneous operation requires separate collimators 180 hz requires new Damping rings, better klystron cooling Status: Compatible layout, continue to explore, understand costs N. Phinney - Line Drive talk, 5/10/01

  21. High/Low E IR Layout Issues: IR separation for vibration isolation (LIGO limit > 100 m) Support for 2 energies, simultaneous ops Low E IR can tolerate more bending but bend angle limits maximum energy Separate tunnels: Cleanest solution but most $ - 2.5 km from end of main linac Separate collimators point only at 1 IR to simplify radiation/access Shared tunnel (partial): 1.2 km line to 2nd IR after collimation Both IRs use same collimators or separate lines in same tunnel (later) All collimators point at High E IR Bend 25 mrad to allow 1 TeV upgrade N. Phinney - Line Drive talk, 5/10/01

  22. FF2 27mrad Coll2+Bends 52mrad Coll1 FF1 Separate Tunnel Layout Separate Collimation systems, Dx=100m 100 m separation inspired by LIGO requirement for vibration sources N. Phinney - Line Drive talk, 5/10/01

  23. 80 60 40 Coll FF2 25mrad Coll Bend 20 Stretch 0 FF1 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500 -20 -40 -60 Beam Delivery 2 IR Layout One Collimation Tunnel per Side, Dx=25m Dz = 440m Layout requires ~500 m stretch Stretch used asymmetricallyto provide longitudinal separation N. Phinney - Line Drive talk, 5/10/01

  24. Overall Site Layout Anamorphic drawing Linac angle causes ~120 m transverse offset of low E ends with respect to IP N. Phinney - Line Drive talk, 5/10/01

  25. Route to 1 TeV TESLA baseline has RF @ 23 MV/m installed in full tunnel length to reach 250 GeV/beam Upgrade path to 800 GeV is to replace cavities in all modules with 35 MV/m cavities+ upgrade cryogenics, power sources NLC/JLC baseline has RF @ 70 MV/m installed in half of tunnel length to reach 250 GeV/beam Bypass line takes beam from last RF to end of Linac Upgrade path to 1 TeV is to install RF in 2nd half of Linac Full tunnel allows flexibility in energy upgrade steps to match funding & physics interest N. Phinney - Line Drive talk, 5/10/01

  26. Gradient Status • TESLA Single cell cavities have reached > 40 MV/m • 9 cell cavities have reached > 30 MV/m • TTF modules “have operated reliably at 15 MV/m” •  Goal 23.4 MV/m @ 500 GeV and 35 MV/m @ 800 Gev • X-Band Single cell cavities have reached 150-200 MV/m • Short structures have run as high as 90-140 MV/m recent results discussed later • NLCTA has operated reliably at 40-45 MV/m (1.8 m long) • Goal 70 MV/m for 1 Tev from TDR N. Phinney - Line Drive talk, 5/10/01

  27. TESLA Test Facility N. Phinney - Line Drive talk, 5/10/01

  28. NLC Test Accelerator Operated since 1996 N. Phinney - Line Drive talk, 5/10/01

  29. Impact of NLC Gradient Issue Total project cost relatively insensitive to gradient NLC Linac cost is tradeoff between length (1/gradient) and power ( gradient) Several alternatives possible: ZDR/TESLA approach: 500 GeV in full tunnel length cost ~ equal now, expensive later for 1 TeV Brute force: 50 MV/m in longer tunnel (21 km/linac) cost increases by ~0.5B (less power required) 70 MV/m with short structures: either standing wave or RDDS designs cost increases by 1-200M N. Phinney - Line Drive talk, 5/10/01

  30. 1st Low Group Velocity Test Structure DS2S: Last 52 Cells of a 206 cell 1.8 m long structure run for >1000 hrs at NLCTA Group Velocity Varies from 5% to 3% c Processed > 1500 hours @50-70 Mv/m No damage seen after initial processing duringfirst 250 hours Average Gradient (MV/m) Switched from 50 ns to 250 ns Pulse Length Time with RF On at 60 Hz (hours) N. Phinney - Line Drive talk, 5/10/01

  31. 2nd Low Group Velocity Test Structures • Tested two additional structures with 5% group velocity like DS2S structure - performed like DS2S • Rapid processing to 60 MV/m • Ran between65 and 75 MV/m for 500 hoursbefore removal to test other potentially higher gradient structures Trip rate per hour Processing history Gradient (MV/m) Gradient (MV/m) Time (hours) N. Phinney - Line Drive talk, 5/10/01

  32. Standing Wave Structure LLNL has built 2 SW structures - now in NLCTA for testing 15 cells, 194 mm long Center feed 14 MW input yields 70 MV/m Simulations indicate less power delivered to damage structures Potential to reach gradient ~ 100 MV/m N. Phinney - Line Drive talk, 5/10/01

  33. Path Beyond 1 TeV TESLA could extend another 30 km to reach ~1.5 TeV Linac costs are ~ 60% of total project @ 500 Gev + issues of relocating IRs, etc. NLC/JLC could reach 1.5 TeV in same tunnel length @ ~ 100 MV/m Injector and beam delivery sized for 1.5 TeV Upgrade path to 1 TeV is to install RF in 2nd half of Linac Full tunnel allows flexibility in energy upgrade steps to match funding & physics interest N. Phinney - Line Drive talk, 5/10/01

  34. Multi-TeV Issues - Energy • Two issues: energy (cost effective) and luminosity • Too expensive with current technology • 5 TeV linac would be 12B$ with NLC or 35B DM TESLA technology • Need improvements in rf systems, e.g. multi-beam klystrons, active pulse compression, or two-beam accelerator • Need high gradients to keep length reasonable: • At 35 MV/m (TESLA max gradient), 3 TeV linac would be 110 km • Optimum gradient for NLC rf system is roughly 70 MV/m • CLIC 3 TeV design assumes 190 MV/m High gradient normal conducting rf required for multi-TeV collider to get factor 4 to 5 in cost reduction  Small bunch spacing and IP crossing angle required N. Phinney - Line Drive talk, 5/10/01

  35. Multi-TeV Issues - Luminosity • High luminosity requires very small beam emittances and small spots –CLIC 3 TeV design specifies 5x smaller eX and 2x eY • CLIC injection complex similar to present NLC but more difficult: (high performance damping rings; multiple stages bunch compression; high current sources) • CLIC linac emittance preservation requires tolerances roughly 5x tighter than NLC with more complex correction algorithms (NLC tolerances roughly 5x tighter than demonstrated at FFTB) • Must learn to operate this generation before moving to a multi-TeV collider • NLC injector, linac, beam delivery and rf systems will all teach essential lessons • Difficult to gain the needed experience at TESLA (this is an advantage as well as a disadvantage) N. Phinney - Line Drive talk, 5/10/01

  36. Issues for HEP • The US community must decide: • If you believe that a linear collider should be constructed • What initial energy and luminosity are needed and how important is the upgrade to higher energy • Whether you want a linear collider as the next US facility • The linear collider is the only possibility for an energy frontier machine in the next  20 years N. Phinney - Line Drive talk, 5/10/01

  37. Scenarios for a Linear Collider • If you want a 500 GeV LC without a route to 1 TeV and higher energies  probably choose TESLA • The cheapest 500 GeV-only collider is probably the S-band collider suggested by Gus Voss years ago • If you want to maintain a route to 1 TeV and higher energies  probably choose NLC • NLC teaches us much of what we need to know to pursue CLIC or another multi-TeV linear collider • TESLA could be built at DESY or US (Fermilab?) • DESY site could not support NLC or CLIC • Japanese want a normal conducting collider in Asia N. Phinney - Line Drive talk, 5/10/01

  38. Summary • Two linear collider options available for 500 GeV cms TESLA and NLC • Different challenges and • Different connections to the future • German government is reviewing the TESLA proposal • ICFA is sponsoring a technology comparison this year • European and Asian HEP communities are very interested • Big question: does the US want to participate and if so do you want the linear collider in the US? N. Phinney - Line Drive talk, 5/10/01

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