The Physics Case for the International Linear Collider

1. The Physics Case for the International Linear Collider Brian Foster (Oxford & GDE) Научная сессия-конференция секции ядерной физики ОФНРАН "Физика фундаментальных взаимодействий" Протвино, 22-25 декабря, 2008

2. Lessons from history Global Design Effort

3. Why e+e-? • Simple particles. • Well defined E, J • E can be scanned precisely • Particles produced ~ democratically. • Final states fully reconstructible. Global Design Effort

4. Why a linear collider? • Because radiated synchrotron-radiation power goes like m-4,circular e+e- colliders bigger than LEP are uneconomical. • The ILC is a linear collider – thus there is no synchrotron radiation produced in bending e+e- in a circular orbit. The challenges stem from this – in circular machines, the beams pass through each other many times/second, giving many chances for interaction. In ILC, they pass through each other once and then are dumped. • The only way to restore the luminosity is to crush the beams to a tiny volume so that 1 pass gives the interaction probability that many passes gives less dense bunches. Also requires 1 pass acceleration => high gradient & power efficiency. Global Design Effort

5. Why a linear collider? ILC • TINY BEAMS • High gradient. Global Design Effort

6. Outline Physics Case • Physics case rests on three legs: known phenomena that ILC will definitely study - e.g. top quark; • the Higgs: • for which there is • very strong • indirect evidence • new particles, • for which there is very • strong theoretical • prejudice Global Design Effort

7. Outline Physics Case • Physics case rests on three legs: known phenomena that ILC will definitely study - e.g. top quark; • the Higgs: • for which there is • very strong • indirect evidence • new particles, • for which there is very • strong theoretical • prejudice Global Design Effort

8. Outline Physics Case • Physics case rests on three legs: known phenomena that ILC will definitely study - e.g. top quark; • the Higgs: • for which there is • very strong • indirect evidence • new particles, • for which there is very • strong theoretical • prejudice Global Design Effort

9. New phenomena @ ILC • If SUSY exists, we need to know which of many varieties Nature has chosen. • This requires LHC+ILC – LHC cannot do it on its own. Global Design Effort

10. SUSY @ ILC 200 3000 500 1000 • If SUSY exists, typical production cross section spectra look like this: Global Design Effort

11. Superstrings @ ILC • If SUSY exists, do Superstrings and can we see any evidence for them? • Only at ILC can precision measurements of Higgs couplings tell us number, shape and size of extra dimensions. Global Design Effort

12. Superstrings @ ILC • If SUSY exists, do Superstrings and can we see any evidence for them? • ILC’s precision measurements of particle spectra can show up patterns that are smoking guns for strings. Global Design Effort

13. Dark Matter @ ILC • What can ILC tell us about Dark Matter? • The ILC can distinguish between various model reference points with SUSY spectra much better than LHC. • ggThe ILC can distinguish between various • model reference points with SUSY spectra • much better than LHC. Global Design Effort

14. But what if….. • There is no Higgs….. • The high precision of e+e- means that ILC is sensitive to phenomena far above its CM energy because of quantum corrections – as LEP proved. • So that, e.g. if there turns out to be no Higgs, ILC is sensitive via measuring form factors in 6-fermion final states to new strong interactions with scales as high as 4 TeV. Global Design Effort

15. Higgs at ILC • Many “little Higgs” models have extra light pseudoscalars. • Such things ideally suited to investigation by the ILC. Global Design Effort

16. But what if….. • There is SUSY but the mass scale is very large? • Something must appear at ILC energies or SUSY can’t do its job – most likely charginos. • Once again precision comes to rescue – chargino decay sensitive to the heavier fermions & polarisation & energy dependence give additional handles. Global Design Effort

17. But what if…. • There is a SM Higgs but “nothing” else…. • Well the ILC is THE Higgs machine. Many models with Higgs + heavies - e.g. little Higgs + T parity affect the ttZ coupling via mixing. • ILC precision necessary to distinguish such models Global Design Effort

18. But what if…. • All new physics is at 10 TeV…. • l+l- final states very sensitive to virtual effects - up to mass scales of 100 TeV. • ILC precision can see various forms of extra dimensional effects. Global Design Effort

19. So why not build ILC now? • There is no physics reason to wait for LHC. Even if there is nothing at all new - including no Higgs - @ LHC, the ILC is the only way forward. Indeed the idea that we will have clear physics messages from LHC by 2012 is somewhat optimistic. • However, we will wait until 2012 for LHC results - for political reasons. Success of the LHC project essential for credibility of field - & exciting discoveries there will be crest of wave on which ILC could ride. Global Design Effort

20. So why not build ILC now? • LHC results will of course be vital for us in many ways - the full range of theories can only be explored by LHC & ILC working together; LHC results WILL be essential to work out the upgrade path for the ILC beyond 500 GeV – or whether an upgrade makes no sense and we should wait for CLIC, or some other bright idea. Global Design Effort

21. ILC Detectors • The simplicity of the final state, the possibility of full reconstruction, with unprecedented HQ & L id via vertex tagging implies that ILC detectors must be state-of-the-art and beyond to utilise fully the potential of the ILC. • The challenges are very different to those of the LHC detectors, but in some areas just as great. In particular the vertex detector and calorimeter need substantial R&D. • Since Lumi shared at ILC, necessity for 2 detectors must be carefully justified. Global Design Effort

22. Vertex Detection • Flavour tagging of jets crucial. Require excellent VXD with CCD resolution but much faster readout. Many technologies being developed including pipelined CCDs, which promise required performance and speed. Global Design Effort

23. Calorimetry • Very high precision & granularity calorimetry essential. • Physics requires t polarisation measurement. Global Design Effort

24. Calorimetry 60%/√E 30%/ √E • Very high precision & granularity calorimetry essential. • High precision calorimetry can effectively double lumi. Global Design Effort

25. Detector Concepts - ILD Global Design Effort

26. Detector Concepts – 4th • Pixel Vertex (PX) 5-micron pixels • Drift chamber with He gas and • cluster counting. • Crystal dual-readout ECAL • Triple-readout fiber HCAL: scintillation/Cerenkov/neutron (new) • Muon dual-solenoid geometry (new), with ATLAS drift tubes. • Russian involvement in LoI. Global Design Effort

27. Detectors compared Global Design Effort

28. Detector assembly • CMS assembly approach: • Assembled on the surface in parallel with underground work • Allows pre-commissioning before lowering • Lowering using dedicated heavy lifting equipment • Potential for big time saving • Reduces size of required underground hall Global Design Effort

29. Experiments- structure Global Design Effort

30. Experiments - structure • Research Director and his structures now becoming very active: Global Design Effort

31. Experiments - review Global Design Effort

32. ILC as world project • In January 2004 the Science Ministers of the OECD met in Paris and, following the detailed work of a GSF Consultative Group on particle physics that produced a road Map,agreed a statement on the Linear Collider: Ministers “acknowledged the importance of ensuring access to large-scale research infrastructure and the importance of the long-term vitality of high-energy physics. They noted the worldwide consensus of the scientific community, which has chosen an electron-positron linear collider as the next accelerator-based facility to complement and expand on the discoveries that are likely to emerge from the Large Hadron Collider currently being built at CERN. They agreed that the planning and implementation of such a large, multi-year project should be carried out on a global basis, and should involve consultations among not just scientists, but also representatives of science funding agencies from interested countries. Accordingly, Ministers endorsed the statement prepared by the OECD Global Science Forum Consultative Group on High-Energy Physics (see Appendix).” Global Design Effort

33. ILC as world project • CERN Council Strategy states: “It is fundamental to complement the results of the LHC with measurements at a linear collider. In the energy range of 0.5 to 1 TeV, the ILC, based on superconducting technology, will provide an unique scientific opportunity at the energy frontier.” • EPP2020 (US blue-riband panel) states: ““Hosting the ILC will inspire students, attract talented scientists from throughout the world, create a suite of high technology jobs and strengthen national leadership in science & technology.” Global Design Effort

34. Russia & ILC • There is long-standing Russian involvement in GDE and its organs, in the experiments and in variety of technical aspects of machine design. • There are many aspects of the work where Russian institutes have enormous expertise directly of relevance to the ongoing project. We need to find ways to tap into this expertise. • Russian site proposal @ Dubna is very important initiative with some unique aspects. • More on all this in Marc’s talk. Global Design Effort

35. Outlook & Conclusions • The physics case for the ILC is as strong as it has ever been; its status as the next major project of choice for the international particle physics community has not changed. • Strengthening of interest from several countries, including China and India. The expertise and personnel of Russia is vital. • Clear roadmap and great progress in both machine and detectors. The next few years, and LHC results, will be both critical and very exciting. Global Design Effort

36. Backup slides Global Design Effort

37. Backup slides Global Design Effort

38. Backup slides Global Design Effort