1 Future Colliders Why do we need them? And which one do we need? Albert De Roeck CERN VLHC

2 Future Machines Introduction –Restrict to machines at the high energy frontier …as a warm–up for the round table discussion Future Hadron Machines –LHC –SLHC –VLHC Future Lepton Machines –TeV e+e- LC Hot topic these days! –Multi-TeV e+e+ LC Others (neutrino factories, muon colliders) –Skip due lack of time…Apologies!

3 Physics case for new High Energy Machines Reminder: The Standard Model - tells us how but not why (contains 19 parameters!) 3 flavour families? Mass spectra? Hierarchy? - needs fine tuning of parameters to level of ! - has no connection with gravity - no unification of the forces at high energy If a Higgs field exists: - Supersymmetry - Extra space dimensions If there is no Higgs below ~ 700 GeV - Strong electroweak symmetry breaking around 1 TeV Other ideas: more gauge bosons/quark & lepton substructure, Little Higgs models… SM SUSY Understand the mechanism Electroweak Symmetry Breaking Discover physics beyond the Standard Model Most popular extensions these days See R. Barbieri

4 The Next Collider: LHC …and in a few years Dipoles arriving at CERN… Production of components well on track Some problems with the QRL/Cryogenics, but delay should be recovered Plan still for first collisions in 2007  Commissioning will take time (~months)  Luminosities at start will be low and then gradually move to cm 2 s -1

5 The CMS & ATLAS Experiments Major Challenge o Event pile up ~23 high lumi ~ readout channels o Size of 1 event bytes o Trigger selection Total Event Rate 40 MHz  100 Hz o Radiation, stability, calibration… CMS: ~2350 people/~159 institutes  Construction of the experiments progressing well (some problems; but being tackled)  Commissioning:in situ calibrations allignements, synchronization etc.  On schedule to be ready for physics by Maybe with some reduced acceptance

6 Physics Landscape by 2010? Hence the future begins in 2007 (2008) –Unless advanced by results from low energy experiments (g-2…), Tevatron, EGRET… LHC should have told us, say, by 2010 (with ~30 fb -1 ) –Whether a light (or heavy) Higgs exist..unveil the EWSB mechanism –Whether the world is or could be (low energy) supersymmetric –Whether we can produce dark matter in the lab –Whether there are more space time dimensions, micro-black holes… –Whether it is all different than what we thought –Whether there is nothing strikingly new found in its reach…unlikely! Theory  Either at least one Higgs exisits with mass below 1 TeV, or new phenomena (strong EWSB?) set on in the TeV region  New physics prefers the TeV scale (Hierarchy problem, fine tunning) but not fully guaranteed

< M higgs < 237 GeV  Light Higgs preferred by EW data  Light Higgs needed for SUSY (<135 GeV) Caution … some recent developments  Higgs + higher dimensional operators (  Higgs could be heavy)  Higgsless models in Extra Dimensions scenarios  EW fit criticism…  A light Higgs is not guaranteed Probability for m H combining direct and indirect information LHC: SM Higgs with 10 fb -1 ~1 good year of data taking What do we know about the Higgs?

8 LHC: low scale SUSY discovery Discovery reach 300 fb -1: TeV 30 fb -1 : 2 TeV already  If low scale SUSY: then large production of squarks/gluinos at the LHC  LSP responsible for dark matter? Comparison with WMAP to within 15%

9 Upgrades of the LHC J. Strait exercise: Not an “official” LHC plot If startup is as smooth as assumed here:  Around 2013: simple continuation becomes less exciting  Time for an upgrade? Possible lumi scenario

10 The LHC upgrade: SLHC Higher luminosity ~10 35 cm -2 s -1 (SLHC) –Needs changes in machine and particularly in the detectors  Start change to SLHC mode some time ?  Collect ~3000 fb -1 /experiment in 3-4 years data taking. Two options presently discussed/studied Higher energy? –LHC can reach  s = 15 TeV with present magnets (9T field) –  s of 28 (25) TeV needs ~17 (15) T magnets  R&D needed! Time to think of upgrading the machine if wanted in ~10 years 95% CL 14 TeV 300 fb TeV 3000 fb TeV 300 fb TeV 3000 fb -1  (TeV)  85 Extended search reach for both upgrades: Example Contact Interaction Scale LHC project report 626 hep-ph/

11 Some Examples with Increased Luminosity If no Higgs, expect strong V L V L scattering (resonant or non-resonant) Maybe difficult for LHC (eg. perhaps only 3-5  effect for WW scattering with 100 fb -1 ) q q q q VLVL VLVL VLVL VLVL Heavy Higgs observable region increased by ~100 GeV. MSSM Heavy Higgs reach 3000 fb -1 /5  3000fb -1 /95% CL

12 LHC Upgrades  Extend the LHC discovery mass range by 25-30% (SUSY,Z’,,EDs)  Higgs self-coupling (20-30%)  Rear decays: H ,  Z, top decays…  Improved Higgs coupling ratios,… In general: SLHC looks like giving a good physics return for modest cost.  Get the maximum out of the (by then) existing machine  Will extend the LHC mass range by factor 1.5  Is generally more powerful than a luminosity upgrade  Needs a new machine, magnet& machine R&D, and will not be cheap  It will be a challenge for the experiments!  Needs detector R&D starting now Tracking, electronics, trigger,endcaps,…  CMS and ATLAS started working groups  Aim: be ready around 2013 The LHC luminosity upgrade to cm -2 s -1 An LHC energy upgrade to  s ~ 28 TeV

13 VLHC: Very Large Hadron Collider Tunnel of 233 km (E.G could be somewhere near FNAL) Stage 1: 40 TeV collider with “cheap” 2T field magnets L=10 34 cm -2 s -1 Stage 2: 200 TeV collider with superconducting magnets. L= cm -2 s -1 Magnet & Vacuum R&D required (and ongoing) Detectors with good tracking up to 10 TeV (increase B,L), calorimeter coverage |  | up to 6-7, good linearity up to 10 TeV, harsh forward radiation

14 Why a VLHC? Probe directly the region TeV Unlike for the TeV scale, no clear preference today for specifc energy- scale in the multi-10 TeV region. However indirect evidence for New Physics at TeV could emerge from LHC and first LC  compelling arguments for a direct exploration of this range. eg. if M H ~ 115 GeV  New physics at  < GeV  A VLHC can probe directly a large part of this range The importance and role of such a machine can be appreciated better after LHC(/LC) data will be fully understood  revisite during the next decade Effective potential blow-up Unstable EW vacuum Hambye-Riesselmann

15 Linear Colliders CERN: CLIC Two-Beam acceleration scheme to reach >3TeV with 150 MV/m Europe USA Japan TESLA/NLC/GLC: 90 GeV  1 TeV with MV/m 33 km GLC International collaborations

16 Machine Parameters International LC scope document  500 GeV upgradeable to ~1 TeV,  500 fb -1 in 4 years  2 interaction regions,  80% electron polarization  Energy flexibility between √s = GeV  Future: possibility of γγ, e-e-, e+ polarization, Giga –Z  TeV e+e- Linear Collider Table from ILC-TRC (2003)

17 Warm/Cold Technologies  International Technology Recommendation Panel (ITRP) to make a recommendation on the technology choice  Next ITRP meeting: Korea August (Tomorrow) ??Perhaps a decision announced at ICHEP04 in Beijing?? Warm: NLC/GLC Cold: TESLA CLIC beam structure similar to the warm case Choice has impact on detector R&D/choice (e.g. time stamping…) We can built at most one collider: which technology to choose?

18 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: LC is first priority mid-term new facility for all US Office of Science Major Funding Agencies 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 GeV, extendible up to about 1 TeV, with a significant period of concurrent running with the LHC LCWS04 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 LC is Moving Forward Strongly! Very sizable community wants a e+e- Linear Collider

19 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 W L W L scattering) LC will very likely play important role to disentangle the underlying new theory

20 LC: Few More 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  DM h²~ 3% (SPS1a)  A mismatch with WMAP/Planck would reveal extra sources of DM (Axions, heavy objects)  Quantum level consistency: M H (direct)= M H (indirect)?  sin 2  W ~10 -5 (GigaZ),  M W ~ 6 MeV (+theory progress)   M H (indirect) ~ 5% 1/M GeV -1 G. Blair et al ‘WMAP’ 7 % LHC ~15 % ‘Planck’ ~2 % LC ~3 % F. Richard/SPS1a Gaugino mass parameters

21 What if no new particles in LC range? M top =175 GeV 100 fb -1 per point  Precision measurements of the top quark, e.g top mass! Compare m W and sin 2  eff experimental accuracy with theoretical prediction  theoretical consistency! Top mass uncertainty is a limiting factor ~ similar to theoretical HO uncertainties, 5x better than exp. precision  Precision indirect measurements (TGCs, Z’, strong EWSB...) e.g Compares indirect (LC) Z’ searches with direct LHC Note: some indirect searches also possible at the LHC e.g. Z KK indirect sensitivity up to TeV for SLHC LC has large reach for indirect measurements

22 LHC/LC Complementarity  The complementarity of the LHC and LC results has been studied by a working group and has produced a huge document (>450 pages, G. Weiglein principal editor, finishing stage…)  Working group contains members from LHC and LC community + theorists  Most meetings at CERN (one in the US) Conclusion: lot to gain for analysis of BOTH machines if there is a substantial overlap in running time. Example: at LHC masses of the measured particles are strongly correlated with the mass of the lightest neutralino Largely improve LHC mass measurements when LC  1 0 value is used sleptons squarkssbottom LSP  1 11 11

23 ILCSC Road Map 2004 technology recommendation (confirmed by ITRP) Establish Global Design Initiative / Effort (GDI/E) 2005 CDR for Collider (incl. first cost estimate) 2007 TDR for Collider 2008 site selection 2009/2010 construction could start (if budget approved) LC Time Scales LC the first real “global machine” in HEP? R. Heuer LCWS04 First collisions in 2015?

24 CLIC: a Multi-TeV Linear Collider  Two beam acceleration presently only feasible way to reach multi-TeV region  Principle demonstrated with CTF2 CLIC: aim for 3 TeV (5 TeV) LC  CERN: accelerate CLIC R&D support to evaluate the technology by 2009/2010 with extra external contributions  CLIC collaboration. FAQs:  CLIC technology O(5-6) years behind TeV class LCs  CLIC can operate from 90 GeV  3 (5) TeV. Physics case for CLIC documented in a new CERN yellow report CERN (June)

25 CLIC: Examples of the Large Reach E.g.: Contact interactions: Sensitivity to scales up to TeV (1 year of data) E.g. Supersymmetry # sparticles that can be detected Expect higher precision at LC vs LHC Eur.Phys. J C (2004)

26 Summary: Indicative Physics Reach Don’t forget: (much) better precision at an e+e- machine Units are TeV (except W L W L reach)  Ldt correspond to 1 year of running at nominal luminosity for 1 experiment † indirect reach (from precision measurements) PROCESS LHC SLHC VLHC VLHC LC LC 14 TeV 14 TeV 28 TeV 40 TeV 200 TeV 0.8 TeV 5 TeV 100 fb fb fb fb fb fb fb -1 Squarks W L W L 2  4  4.5  7  18  6  30  Z’ † 30 † Extra-dim (  =2) † † q*  compositeness TGC (  ) Ellis, Gianotti, ADR hep-ex/ few updates

27 Conclusion LHC will be the next high energy collider –It will unveil the EWSB mechanism –It will probe the TeV scale for new physics SHLC (luminosity upgrade) will give good return for a modest investment VLHC is still for the far future A LC will be the next proposed machine/it will complement LHC perfectly –A LC collider is a precision instrument –LC community has built up large momentum –TESLA and NLC/GLC technologies essentially ready  choice? –Construction could start around 2009/2010  collisions in 2015? –CLIC (3 TeV) aims to demonstrate feasibility of the technology by 2009/2010 Is 500 (1000) GeV the optimal energy reach for the machine? Will certainly be addressed in the light of the LHC data by 2009/2010 In any case: exciting times ahead !!

28 Example: Point K Squarks: TeV Gluino: 2.5 TeV Can discover the squarks at the LHC but cannot really study them signal Inclusive: M eff > 4000 GeV S/B = 500/100 (3000 fb -1 ) Exclusive channel qq  1 0  1 0 qq S/B =120/30 (3000 fb -1 ) Measurements become possible P t >700 GeV & E t miss >600 GeV P t of the hardest jet ~~

29 Examples of possible scenarios for a VLHC