Linear e e- Colliders Physics and Projects A De

Linear e+e- Colliders: Physics and Projects A. De Roeck B. CERN C. China-CERN Workshop on Coorperation in High Energy Physics Contents Recent LC history The ILC: a Te. V collider CLIC: a multi-Te. V collider Albert De Roeck (CERN) 1

Linear e+e- Colliders Since end of 2001 there seems to be a worldwide consensus (ECFA/HEPAP/Snowmass 2001…) The machine which will complement and extend the LHC best, and is closest to be realized, is a Linear e+e- Collider with a collision energy of at least 500 Ge. V PROJECTS: Te. V Colliders (cms energy up to 1 Te. V) Technology ~ready August’ 04 ITRP: NLC/GLC/TESLA ILC superconducting cavities Multi-Te. V Collider (cms energies in multi-Te. V range) advanced R&D CLIC (CERN + collaborators) Two Beam Acceleration Albert De Roeck (CERN) 2

The Physics case for Te. V-LC A collider with energy up to 1 Te. V, such as the ILC 1 - Electroweak Symmetry Breaking decipher mechanism for EWSB regardless of what it may be e. g. Higgs precision physics (mass, couplings, self-coupling) 2 - Hierarchy Problem (instability of SM against different scales) direct observations and virtual effects 3 – Dark Matter precision on supersymmetry DM matching future astrophysical experiments 4 – Precision Measurements mass of top-quark, W mass and couplings, weak mixing angle Results of studies from Europe, the Americas, Asia Albert De Roeck (CERN) 3

A LC is a Precision Instrument • Clean e+e- (polarized intial state, controllable s for hard scattering) • Detailed study of the properties of Higgs particles mass to 0. 03%, couplings to 1 -3%, spin & CP structure, total width (6%) factor 2 -5 better than LHC/measure couplings in model indep. way • Precision measurements of SUSY particles properties, i. e. slepton masses to better than 1%, if within reach • Precision measurements a la LEP (TGC’s, Top and W mass) • Large indirect sensitivity to new phenomena (eg WLWL scattering) A LC will play important role to disentangle the underlying new theory Albert De Roeck (CERN) 4

LC Physics Examples Understanding SUSY High accuracy of sparticle mass measurements relevant for reconstruction of SUSY breaking mechanism Dark Matter LC will accurately measure m and couplings, i. e. Higgsino/Wino/Bino content Essential input to cosmology & searches LC will make a prediction of DMh²~ 3% (SPS 1 a) A mismatch with WMAP/Planck would reveal extra sources of DM (Axions, heavy objects) Quantum level consistency: MH(direct)= MH(indirect)? sin 2 W~10 -5 (Giga. Z), MW ~ 6 Me. V (+theory progress) MH (indirect) ~ 5% 1/M Ge. V-1 Gaugino mass parameters G. Blair et al Albert De Roeck (CERN) 5

Generic Linear Collider J. P. Delahaye 30 -40 km All collider elements are challenging Lot of communalities between different LC designs Common work to which the CERN-CLIC contributes Hence, CERN is involved in LCs on a more general level Albert De Roeck (CERN) 6

LC Competing technologies (spring 2004) For the main e+e- linac Superconducting cavities Two beam acceleration Warm cavities Albert De Roeck (CERN) 7

Meanwhile: LC getting on the Roadmap Study groups of ACFA, ECFA, HEPAP The next large accelerator-based project of particle physics should be a linear collider US DOE Office of Science Future Facilities Plan: mid-term new facility for all US Office of Science Major Funding Agencies LC is first priority Regular meetings concerning LC ICFA (February 2004) reaffirms its conviction that the highest priority for a new machine for particle physics is a linear electron-positron collider with an initial energy of 500 Ge. V, extendible up to about 1 Te. V, with a significant period of concurrent running with the LHC LCWS 04 Paris (April 2004) publication of the document “understanding matter, space and time” by 2600 physicists, in support of a linear collider EUROTEV selected by EC 9 MEuro for R&D for a LC Very sizable community wants a e+e- Linear Collider Albert De Roeck (CERN) 8

Machine Parameters Table from ILC-Technical Review Comittee (2003) http: //www. slac. stanford. edu/xorg//ilc-trchome. html emmitance beam size luminosity Albert De Roeck (CERN) 9

ITRP Recommendation to ICFA/ILCSC ITRP Mission: select a technology for a machine up to 1 Te. V Conclusion at ICHEP Beijing August ‘ 04 Both technologies mature Select the cold technology to continue Note: technology selected, not a design Endorsed by ICFA/ILCSC call project the International Linear Collider ILC Roadmap Start Global Design Initiative/Effort (GDI/GDE): B. Barish Central team director 2006 Conceptual Design Report for Linear Collider >2007 Technical Design Report for a Linear Collider 2009/2010 Aim to be ready for construction. LHC results? Budget? First collisions earliest 2015 ILCSC = International Linear Collider Steering Committee 10 Albert De Roeck (CERN)

CLIC Compact LInear Collider CERN + 12 Albert De Roeck (CERN)

CLIC • An e+e- linear collider optimized for a cms energy of 3 Te. V with a luminosity of 1035 cm-2 s-1 • Aim: 3 Te. V complementing LHC/Te. V class LC and breaking new ground, with a final stage up to 5 Te. V • To achieve this with reasonable cost (less than ~35 km) and not to many active elements Comparison with ILC High accelerating gradient: ~ 150 MV/m TESLA 500 Ge. V 25 MV/m Two Beam Acceleration (TBA) 800 Ge. V 35 MV/m Future ILC study? : 44 MV/m High beamstrahlungs regime to reach high luminosity Challenging beam parameters and machine requirements (nm stability, strong final focus, 30 GHz accelerating structures) CLIC TBA to date the only known way to reach multi-Te. V • Test facilities CTF 2 (’ 96 -’ 02): 150 -193 MV/m in TBA (16 ns pulses) CTF 3 (’ 02 -’ 09): Test of drive beam, R 1’s/ R 2’s of TRC (2003) See J. P. Delahaye 13 Albert De Roeck (CERN)

CLIC: a Multi-Te. V Linear Collider Physics case for CLIC documented in CERN yellow report CERN-2004 -005 (June) and hep-ph/0412251 CERN: accelerate CLIC R&D support to evaluate the technology by 2009 with extra external contributions CLIC collaboration. FAQs: CLIC technology R&D O(5) years behind ILC R&D CLIC can operate from 90 Ge. V 3 (5) Te. V. 14 Albert De Roeck (CERN)

CLIC Parameters & Backgrounds CLIC 3 Te. V e+e- collider with a luminosity ~ 1035 cm-2 s-1 (1 ab-1/year) CLIC parameters old new CLIC operates in a regime of high beamstrahlung Time between 2 bunches = 0. 67 ns Expect large backgrounds # of photons/beam particle e+e- pair production events Muon backgrounds Neutrons Synchrotron radiation Expect distorted lumi spectrum 15 Albert De Roeck (CERN)

Resonance Production Resonance scans, e. g. a Z’ 1 ab-1 M/M ~ 10 -4 & / = 3. 10 -3 Degenerate resonances e. g. D-BESS model Can measure M down to 13 Ge. V Smeared lumi spectrum allows still for precision measurements 16 Albert De Roeck (CERN)

Higgs Production Cross section at 3 Te. V: Large cross section at low masses Large CLIC luminosity Large events statistics Keep large statistics also for highest Higgs masses Low mass Higgs: 400 000 Higgses/year 45 K/100 K for 0. 5/1 Te. V LC 17 Albert De Roeck (CERN)

Rare Higgs Decays: H Not easy to access at a 500 Ge. V collider g. H Also H bb for masses up to 220 Ge. V 18 Albert De Roeck (CERN)

Higgs Potential: e+e- HH Precision on HHH for 5 ab-1 for Higgs masses in the range m. H = 120 Ge. V m. H = 140 Ge. V m. H = 180 Ge. V m. H = 240 Ge. V 3 Te. V Can improve further by using spin information and polarization (factor 1. 7)? precision ~ 6 -8% 19 Albert De Roeck (CERN)

Heavy Higgs (MSSM) LHC: Plot for 5 discovery 3 Te. V CLIC H, A detectable up to ~ 1. 2 Te. V 20 Albert De Roeck (CERN)

Supersymmetry (Battaglia at al hep-ph/0306219) # sparticles that can be detected Higher mass precision at LC vs LHC Mass measurements to O(1%) for smuons 21 Albert De Roeck (CERN)

Precision Measurements Taking into account backgrounds, lumi spectrum, detector… E. g. : Contact interactions: Sensitivity to scales up to 100 -800 Te. V 22 Albert De Roeck (CERN)

Precision Measurements A light Higgs implies that the Standard Model cannot be stable up to the GUT or Planck scale (1019 Ge. V) The effective potential blows up, due to heavy top quark mass Allowed corridor but needs strong fine-tuning… Hambye Riesselmann The electroweak vacuum is unstable to corrections from scales >> v= 246 Ge. V New physics must show up before 100 -1000 Te. V 23 Albert De Roeck (CERN)

Summary: Physics at CLIC Experimental conditions at CLIC are more challenging than at LEP, or ILC Physics studies for CLIC have included the effects of the detector, and backgrounds e. g e+e- pairs and events. Benchmark studies show that CLIC will allow for precision measurements in the Te. V range CLIC has a very large physics potential, reach beyond that of the LHC. 24 Albert De Roeck (CERN)

Detector To exploit the full physics potential excellent detectors will be needed International R&D for ILC for key detector components vertex tracking calorimeter Detector R&D effort will be needed for CLIC as well E. g. Bunch spacing at CLIC= 0. 67 nsec 25 Albert De Roeck (CERN)

Tracking Technologies 3 D Silicon Amorphous Silicon Time stamping will be important O(ns) Macro-pixels? Radiation however not a big issue ~ 5 1010 neutrons/cm-2/year Detector R&D will be required!! 26 Albert De Roeck (CERN)

Calorimetry Importance of good energy resolution (e. g via energy flow) Interesting developments in Te. V-class LC working groups e. g. compact 3 D EM calorimeters, or “digital” hadronic calorimeters Detailed simulation studies of key processes required R&D accordingly afterwards 27 Albert De Roeck (CERN)

CLIC Physics Studies Topics for possible contributions to the CLIC physics study • New & more detailed studies on physics processes – Some processes to be completed, new processes, other backgrounds • Little Higgs Models, Split SUSY, Higgsless ED models… • Detector optimization – Study so far uses a somewhat adapted TESLA detector • Initiate/link with detector R&D – If we want to be ready to know how to built a detector for CLIC (tracker, calorimeter, timestamping) • Study other options for CLIC ? I. e. lower energy ‘start up’ options – – – ep option ( p, A options) Cliche ( factory) Z factory? Higgs factory Compare with Te. V class collider (0. 5 -1 Te. V) Full energy and e option for CLIC 28 Albert De Roeck (CERN)

Summary • LC physics and accelerator community has a lot of momentum • ILC design starting to take shape – Machine to produce a CDR soon – All regions actively involved in its preparation • ILC Roadmap aims for a decision/start construction around 2009 – First LHC data should be available by then – These data will be the referee and motivator for the most optimum next machine to be built • CLIC multi-Te. V study aims at proof of feasibility/CDR by ~2009 – Has to be ready in case LHC indicates a multi-Te. V machine is required. • CLIC has an attractive physics program that can cover the range from the Z-pole (90 Ge. V) up to the multi-Te. V range • Opportunities to join the CLIC physics (& Detector) studies 29 Albert De Roeck (CERN)

Backup Slides 30 Albert De Roeck (CERN)

Multi-Te. V collider • Machine Detector Interface related issues to keep in mind if one plans for a facility that can be upgraded to a multi-Te. V collider in future – Crossing angle needed of ~20 mrad (multi-bunch kink stability) – Present design: Long collimator syst. and final focus (2. 5 km each side) – Energy collimators most important. Fast kicker solution not applicable. Maybe rotating collimators … – Gentle bending to reduce SR & beam spot growth construct the linacs already under an angle of ~ 20 mrad – Internal geometry differences of the collimation system and final focus, allow for enough space in the tunnels (O(m)) 31 Albert De Roeck (CERN)

ITRP Recommendation to ICFA/ILCSC ITRP Mission: select a technology R&D to support both technologies becomes too demanding on resources Conclusion at ICHEP Beijing August ‘ 04 Both technologies mature Select the cold technology to continue Some arguments in favor of cold Note: technology selected, not a design Endorsed by ICFA/ILCSC call project the International Linear Collider ILCSC = International Linear Collider Steering Committee 32 Albert De Roeck (CERN)

ILC Parameters & options Several years of intense physics studies have led to: • Baseline Linear Collider – Minimum energy of 500 Ge. V, with int. luminosity of 500 fb-1 in the first 4 years – Scan energies between from LEP 2 till new energy range: 200 -500 Ge. V with a luminosity ~ s. Switch over should be quick (max 10% of data taking time) – Beam energy stability and precision should 0. 1% or better. – Electron beam polarization with at least 80% – Two interaction regions should be planned for – Should allow for calibration running at the Z ( s = 90 Ge. V) – Upgrade: Energy upgrade up to ~ 1 Te. V with high luminosity should be planned • Options beyond the baseline: enhance the physics reach – – – Running as an e-e- collider Running as a e or collider Polarization of the positron beam Running at Z 0 with a luminosity of several 1033 cm-2 s-1 (Giga. Z) Running at WW mass threshold with a luminosity of a few times 10 33 cm-2 s 33 Albert De Roeck (CERN)

LC Time Scales ILCSC Road Map R. Heuer LCWS 04 2004 Technology recommendation (done) 2005 Start Global Design Initiative/Effort (GDI/GDE): central team director job as been offered a few days ago 2005 Conceptual Design Report for Linear Collider 2006 Start Global Design Organization (GDI/GDO) 2007 Technical Design Report for a Linear Collider 2008 Site selection 2009/2010 Construction could start (if budget approved) First collisions > 2015? 34 Albert De Roeck (CERN)

Higgs: Strength of a multi-Te. V collider • Precision measurements of the quantum numbers and properties of Higgs particles, for large Higgs mass range • Study of Heavy Higgses (e. g. MSSM H, A, H ) • Rare Higgs decays, even for light Higgs • Higgs self coupling over a wide range of Higgs masses • Study of the CP properties of the Higgs… 35 Albert De Roeck (CERN)

Higgs Potential Reconstruct shape of the Higgs potential to complete the study of the Higgs profile and to obtain a direct proof of the EW symmetry breaking mechanism Measure the triple (quartic) couplings process 36 Albert De Roeck (CERN)

Higgs Production Cross section at 3 Te. V: Large cross section at low masses Large CLIC luminosity Large events statistics Keep large statistics also for highest Higgs masses Low mass Higgs: 400 000 Higgses/year 45 K/100 K for 0. 5/1 Te. V LC 37 Albert De Roeck (CERN)

Higgs: Strength of a multi-Te. V collider • Precision measurements of the quantum numbers and properties of Higgs particles, for large Higgs mass range • Study of Heavy Higgses (e. g. MSSM H, A, H ) • Rare Higgs decays, even for light Higgs • Higgs self coupling over a wide range of Higgs masses • Study of the CP properties of the Higgs… 38 Albert De Roeck (CERN)

Results: e+e- HH Precision on HHH for 5 ab-1 for Higgs masses in the range m. H = 120 Ge. V m. H = 140 Ge. V m. H = 180 Ge. V m. H = 240 Ge. V 3 Te. V Can improve by factor 1. 7 if both beams are polarized 39 Albert De Roeck (CERN)