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Future Colliders Why do we need them?

And which one do we need?

Albert De Roeck CERN

VLHC

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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!

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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 10-30 ! - has no connection with gravity - no unification of the forces at high energy

If a Higgs field exists: - Supersymmetry - Extra space dimensionsIf there is no Higgs below ~ 700 GeV - Strong electroweak symmetry breaking around 1 TeVOther ideas: more gauge bosons/quark & lepton substructure,Little Higgs models…

SM

SUSY

Understand the mechanism Electroweak Symmetry BreakingDiscover physics beyond the Standard Model

Most popular extensions these days

See R. Barbieri

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The Next Collider: LHC

…and in a few years

Dipoles arriving at CERN…

Production of components well on trackSome 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 0.5-2.1033cm2 s-1

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The CMS & ATLAS Experiments

Major Challengeo Event pile up ~23 evts/bx @ high lumi ~100 000 000 readout channelso Size of 1 event 1 000 000 byteso Trigger selection Total Event Rate 40 MHz 100 Hzo 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 2007. Maybe with some reduced acceptance

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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

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114.4 < Mhiggs < 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 formH 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?

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LHC: low scale SUSY discovery

Discovery reach 300 fb-1: 2.5-3 TeV30 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%

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Upgrades of the LHCJ. Strait exercise:Not an “official” LHC plot

If startup is as smooth as assumed here:Around 2013: simple continuation becomes less excitingTime for an upgrade?

Possible lumi scenario

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The LHC upgrade: SLHC

•Higher luminosity ~1035cm-2 s-1 (SLHC)–Needs changes in machine and particularly in the detectors Start change to SLHC mode some time 2013-2016? 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-1 14 TeV 3000 fb-1 28 TeV 300 fb-1 28 TeV 3000 fb-1

(TeV) 40 60 60 85

Extended search reach for both upgrades: Example Contact Interaction Scale

LHC project report 626hep-ph/0204087

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Some Examples with Increased Luminosity

If no Higgs, expect strong VLVL scattering (resonant or non-resonant) Maybe difficult for LHC (eg. perhaps only3-5 effect for WW scattering with 100 fb-1)

q

q

q

q

VLVL

VL

VL

Heavy Higgs observable region increased by ~100 GeV.

MSSM Heavy Higgs reach

3000 fb-1/5

3000fb-1/95% CL

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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 1035 cm-2s-1

An LHC energy upgrade to s ~ 28 TeV

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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=1034cm-2 s-1

Stage 2: 200 TeV collider with superconducting magnets. L=2.1034cm-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

http://vlhc.org

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Why a VLHC?

• Probe directly the region 10-100 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 10-100 TeV could emerge from LHC and first LC compelling arguments for a direct exploration of this range.

• eg. if MH ~ 115 GeV New physics at < 105-106 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

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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 35-70 MV/m

33 km

GLC Internationalcollaborations

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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 = 90-500 GeV Future: possibility of γγ, e-e-, e+ polarization, Giga –Z TeV e+e- Linear Collider

Table from ILC-TRC (2003)

http://www.slac.stanford.edu/xorg//ilc-trc/ilc-trchome.html

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Warm/Cold Technologies

International Technology Recommendation Panel (ITRP) to make a recommendation on the technology choice Next ITRP meeting: Korea 11-13 August (Tomorrow) ??Perhaps a decision announced at ICHEP04 in Beijing??

Warm: NLC/GLCCold: TESLA

CLIC beam structure similar to the warmcase

Choice has impact on detector R&D/choice(e.g. time stamping…)

We can built at most one collider: which technology to choose?

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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 “understandingmatter, 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

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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)LC will very likely play important role to disentangle the underlying new theory

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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 DMh²~ 3% (SPS1a) A mismatch with WMAP/Planck would reveal extra sources of DM (Axions, heavy objects) Quantum level consistency: MH(direct)=

MH(indirect)?

sin2W~10-5 (GigaZ), MW ~ 6 MeV (+theory progress) MH (indirect) ~ 5%

1/M GeV-1

G. Blair et al

‘WMAP’ 7 %

LHC ~15 %

‘Planck’ ~2 %

LC ~3 %

F. Richard/SPS1a

Gaugino mass parameters

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What if no new particles in LC range?

Mtop=175 GeV100 fb-1 per point

Precision measurements of the top quark, e.g top mass!Compare mW and sin2eff experimental accuracy withtheoretical 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 LHCNote: some indirect searches also possible at the LHCe.g. ZKK indirect sensitivity up to 15-20 TeV for SLHC

LC has large reach for indirect measurements

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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 asubstantial 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 whenLC 1

0 value is used

sleptons squarks sbottom

LSP 1 11

http://www.ipp.dur.ac.uk/~georg/lhclc/

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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?

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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-2004-005 (June)

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CLIC: Examples of the Large Reach

E.g.: Contact interactions:Sensitivity to scales up to 100-400 TeV (1 year of data)

E.g. Supersymmetry# sparticles that can be detectedExpect higher precision at LC vs LHC

Eur.Phys. J C33 273 (2004)

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Summary: Indicative Physics Reach

Don’t forget: (much) better precision at an e+e- machine

Units are TeV (except WLWL 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-1 1000 fb-1 100 fb-1 100 fb-1 100 fb-1 500 fb-1 1000 fb-1

Squarks 2.5 3 4 5 20 0.4 2.5 WLWL 2 4 4.5 7 18 6 30Z’ 5 6 8 11 35 8† 30† Extra-dim (=2) 9 12 15 25 65 5-8.5† 30-55†

q* 6.5 7.5 9.5 13 75 0.8 5compositeness 30 40 40 50 100 100 400TGC () 0.0014 0.0006 0.0008 0.0003 0.0004 0.00008

Ellis, Gianotti, ADRhep-ex/0112004+ few updates

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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 2009/2010In any case: exciting times ahead !!