1. 1 MOTIVAZIONI PER COLLIDER ADRONICI DOPO LLHC: DALLSLHC AL VLHC G.F. Giudice CERN R. Brock (EXP Fermilab) C. Hill (TH Fermilab) P. Sphicas (EXP Cern) G. Giudice (TH Cern) Padova, 19 Nov 2003

2. 2 LHC Well-motivated energy range Find the Higgs Find the physics ultimately responsible for EW breaking

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4. 4 300-450 MCHF (incluso 70 MCHF di Linac4, ma senza rivelatori); 500 MCHF per SPL ~ 2 GCHF

5. 5 A. De Roeck

6. 6 Qual e il futuro dei collider adronici dopo lLHC?

7. 7 VLHC Parameters

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11. 11 Stage-2 VLHC Conclusions The Stage 2 VLHC can reach 200 TeV and 2x10 34 or more in the 233 km tunnel. A large-circumference ring is a great advantage for the high-energy Stage-2 collider. A small-circumference high-energy VLHC may not be realistic. There is the need for magnet and vacuum R&D to demonstrate feasibility and to reduce cost. –This R&D will not be easy, will not be quick, and will not be cheap.

12. 12 VLHC Tunnel Cross Section

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15. 15 Underground Construction Three orientations chosen to get representative geological samples of sites near Fermilab. –South site samples many geologic strata and the Sandwich fault. –One north site is flat and goes through many strata. –Other north site is tipped to stay entirely within the Galena- Platteville dolomite, and is very deep. These are not selected sites – merely representative. –Cost of other sites can be built from data gained in these sites.

16. 16 LHC is the machine to study the scale of EW breaking NEW THEORY Desert, e.g. conventional susy need for precision New thresholds around 10 TeV need for energy increase to make next step of discoveries Multi-TeV linear collider? VLHC ? m < TeV measurements after LHC VLHC not meant to push new-physics limits by an order of magnitude, but to explore a well-motivated (after some LHC discoveries) energy region

17. 17 DESERT Connection with GUT, strings, quantum gravity Gauge-coupling unification Neutrino masses Suppression of proton decay and flavour violations Setup for cosmology (inflation, baryogenesis) NON DESERT Low-scale string theory,… Accelerated running, different sin 2 W R in bulk Different location of quarks and leptons in bulk Low-scale inflation, EW baryogenesis

18. 18 NON-DESERT SCENARIOS offer good motivations for explorations with a s ~ 100 TeV hadron collider Need to test the theory well above the EW breaking scale Existence of new thresholds in the 10 TeV region Not a systematic review, but some examples relevant to VLHC

19. 19 GRAVITY IN EXTRA DIMENSIONS Fundamental scale at SM Any short-distance scale < SM -1 explained by geometry FLAT Arkani Hamed-Dimopoulos-Dvali WARPED Randall-Sundrum

20. 20 H QUANTUM GRAVITY AT LHC Graviton emission Missing energy (flat) Resonances (warped) Contact interactions (loop dominates over tree if gravity is strong) Higgs-radion mixing G.G.- Rattazzi - Wells G.G. - Strumia

21. 21 These processes are based on linearized gravity valid at s <<M D ~TeV Suitable for LHC VLHC can extend limits, but the motivations are weak VLHC can probe the region s >>M D ~TeV (only marginal at LHC) independent test, crucial to verify gravitational nature of new physics

22. 22 TRANSPLANCKIAN REGIME Planck length quantum-gravity scale Schwarzschild radius classical gravity same regime

23. 23 b > R S Non-perturbative, but calculable for b>>R S (weak gravitational field) Gravitational scattering: two-jet signal at hadron colliders G.G.-Rattazzi-Wells

24. 24 b < R S Giddings-Thomas, Dimopoulos-Landsberg At b<R S, no longer calculable Strong indications for black-hole formation At the LHC, limited space for transplanckian region and quantum-gravity pollution At the VLHC, perfect conditions

25. 25 2-jets with large M inv and Black holes Jets + missing E T 2-leptons QUANTUM GRAVITY Semi-classical approximation Linearized gravity Transplanckian Cisplanckian VLHC LHC

26. 26 INVESTIGATING THE THEORY OF ELECTROWEAK BREAKING 10 5.6 9.2 9.7 4.6 7.3 6.1 4.3 4.5 3.2 6.4 9.3 5.0 12.4 LEP1 LEP2 MFV Bounds on LH LH > 5-10 TeV +

27. 27 SM 5-10 TeV Little hierarchy between SM and LH New physics at SM is weakly interacting No (sizable) tree-level contributions from new physics at SM Strongly-interacting physics can only occur at scales larger than LH

28. 28 t m H 2 = H H + t ~ PROBLEMA DELLA GERARCHIA controllo delle divergenze quadratiche alla massa dellHiggs SUPERSIMMETRIA:

29. 29 HIGGS AS PSEUDOGOLDSTONE BOSON Gauge, Yukawa and self-interaction are large non- derivative couplings Violate global symmetry and introduce quadratic div.

30. 30 A less ambitious programme: Explain only little hierarchy At SM new physics cancels one-loop power divergences LITTLE HIGGS Collective breaking: many (approximate) global symmetries preserve massless Goldstone boson 1 2 H 1 2 Arkani Hamed-Cohen-Georgi

31. 31 Realistic models are rather elaborate Effectively, new particles at the scale f ~ SM canceling (same-spin) SM one-loop divergences with couplings related by symmetry Typical spectrum: Vectorlike charge 2/3 quark Gauge bosons EW triplet + singlet Scalars (triplets ?) Arkani Hamed-Cohen-Georgi-Katz-Nelson-Gregoire-Wacker- Low-Skiba-Smith-Kaplan-Schmaltz-Terning…

32. 32 HIGGS AS EXTRA-DIM COMPONENT OF GAUGE FIELD A M = (A,A 5 ), A 5 A 5 + 5 forbids m 2 A 5 2 gaugeHiggs Higgs/gauge unification as graviton/photon unification in Kaluza-Klein Correct Higgs quantum numbers by projecting out unwanted states with orbifold Yukawa couplings, quartic couplings without reintroducing quadratic divergences Csaki-Grojean-Murayama Burdman-Nomura Scrucca-Serone-Silvestrini EW BROKEN BY BOUNDARY CONDITIONS? Csaki-Grojean- Murayama-Pilo- Terning

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34. 34 Calculable description of EW breaking with strong dynamics at 5-10 TeV New realizations of technicolour theories with new elements (extra dimensions, AdS/CFT correspondence) allowing some calculability Little hierarchy is satisfied LHC will discover weak physics at SM New strong-dynamics thresholds at LH within the reach of VLHC

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39. 39 The most important requirement for the survival of HEP is worldwide cooperation resulting in a global strategy based on a visionary science roadmap. Sell the science, not the instruments –Learn from the NASA strategy, in which the goals are truly large and visionary, and the instruments are missions along the way. The parameters and schedule for a VLHC will depend on the timing and location of all other large facilities. The global plan should recognize these couplings. If we ever want to build a VLHC, or any other very large facility, we need to have a vigorous R&D program now. –The R&D is very challenging, and the penalty for failure will be severe. P. Limon

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42. 42 Anni futuri cruciali per i nuovi progetti di alte energie La fisica fondamentale puo difendere con orgoglio la sua missione EXP Un grande progetto negli USA necessario per la fisica delle particelle R&D sui vari fronti deve proseguire TH Nuove strategie per capire la fisica della rottura EW In scenari non-desert, forti motivazioni per una nuova scala a ~ 10 TeV VLHC CONCLUSIONI

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