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MOTIVAZIONI PER COLLIDER ADRONICI DOPO L’LHC: DALL’SLHC 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

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LHC

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22222

2

2 GeV200TeV

4228

3

SM

tHZWSMF

H mmmmG

m

Well-motivated energy range

• Find the Higgs

• Find the physics ultimately responsible for EW breaking

TeVSM

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300-450 MCHF (incluso 70 MCHF di Linac4, ma senza rivelatori); 500 MCHF per SPL

~ 2 GCHF

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A. De Roeck

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Qual e’ il futuro dei collider adronici dopo l’LHC?

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VLHC ParametersStage 1 Stage 2

Total Circumference (km) 233 233

Center-of-Mass Energy (TeV) 40 200

Number of interaction regions 2 2

Peak luminosity (cm-2s-1) 1 x 1034 2.0 x 1034

Dipole field at collision energy (T) 2 11.2

Average arc bend radius (km) 35.0 35.0

Initial Number of Protons per Bunch 2.6 x 1010 5.4 x 109

Bunch Spacing (ns) 18.8 18.8

* at collision (m) 0.3 0.5

Free space in the interaction region (m) ± 20 ± 30

Interactions per bunch crossing at Lpeak 21 55

Debris power per IR (kW) 6 94

Synchrotron radiation power (W/m/beam) 0.03 5.7

Average power use (MW) for collider ring 25 100

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Stage-2 VLHC Conclusions

• The Stage 2 VLHC can reach 200 TeV and 2x1034 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.

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VLHC Tunnel Cross Section

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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.

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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

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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 sin2W

• R in bulk

• Different location of quarks and leptons in bulk

• Low-scale inflation, EW baryogenesis

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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

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GRAVITY IN EXTRA DIMENSIONS

GRAVITY IN EXTRA DIMENSIONSFundamental scale at SM

Any short-distance scale < SM

-1 explained by geometry

42/12/ DMRM DPl

KRPl eMM 5

FLAT Arkani Hamed-Dimopoulos-Dvali

WARPED Randall-Sundrum

20H

QUANTUM GRAVITY AT LHCQUANTUM GRAVITY AT LHC

Graviton emissionMissing energy (flat)

Resonances (warped)

TT

4

1

252

1ff

Contact interactions (loop dominates over tree if gravity is strong)

Higgs-radion mixing

G.G.- Rattazzi - Wells

G.G. - Strumia

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These processes are based on linearized gravity valid at √s <<MD ~TeV

• Suitable for LHC

• VLHC can extend limits, but the motivations are weak

VLHC can probe the region √s >>MD~TeV

(only marginal at LHC)

independent test, crucial to verify gravitational nature of new physics

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TRANSPLANCKIAN REGIME

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1

3

c

GDP

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1

3

1

1

2

3

2

81

c

sGR DS

Planck length quantum-gravity scale

PSD

PS

RM

R

:slimit kian transplanc

:0 limit classical

Schwarzschild radius

classical gravity

same regime

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b > RS

Non-perturbative, but calculable for b>>RS (weak gravitational field)

Gravitational scattering: two-jet signal at hadron colliders

G.G.-Rattazzi-Wells

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b < RSGiddings-Thomas, Dimopoulos-Landsberg

At b<RS, 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

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2-jets with large Minv and Black holes

Jets + missing ET 2-leptons

QUANTUM GRAVITY

Semi-classical approximation

Linearized gravity

Transplanckian

Cisplanckian

VLHC

LHC

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INVESTIGATING THE THEORY OF ELECTROWEAK BREAKING

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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

FqdH

qq

bbee

ee

LLHDiH

HDH

BWHH

LuudR

uuL

aa

2

55

2

2

1

LEP1

LEP2

MFV

Bounds on LH

LH > 5-10 TeV

+

O2LH

1L

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SM<1 TeV, LH>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

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22222

2

2 GeV200TeV

4228

3

SM

tHZWSMF

H mmmmG

m

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t

mH2 =

H H+

t~

2

2

2

22

~ln2

~3

t

ttF

m

mmG

PROBLEMA DELLA GERARCHIA controllo delle divergenze quadratiche alla massa dell’Higgs

SUPERSIMMETRIA:

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HIGGS AS PSEUDOGOLDSTONE BOSON

HIGGS AS PSEUDOGOLDSTONE BOSON

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/

forbids

symmetry realizedlinearly -Non

:

2

hmahh

ae

fef

ia

fi

Gauge, Yukawa and self-interaction are large non-derivative couplings

Violate global symmetry and introduce quadratic div.

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A less ambitious programme:

Explain only little hierarchy

At SM new physics cancels one-loop power divergences

LITTLE HIGGSLITTLE HIGGS

LH

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4

22

222

2

TeV10 loops Two

TeV loop One

SMFSM

FH

F

SMSMSMF

H

mGm

Gm

Gm

Gm

“Collective breaking”: many (approximate) global symmetries preserve massless Goldstone bosonℒ1ℒ

2

H2

222

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Hm

ℒ1 ℒ2

Arkani Hamed-Cohen-Georgi

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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…

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HIGGS AS EXTRA-DIM COMPONENT OF GAUGE FIELD

AM = (A,A5), A5 A5 +∂5 forbids m2A52

gauge HiggsHiggs/gauge unification as graviton/photon unification in Kaluza-Klein

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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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

KKMgN

sRgg

sgN

T

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2500

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96

2

1

192

23 Unitarity

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• 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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• 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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