physics at future colliders

Patrick Janot

Physics at Future Colliders Lecture 1

u An historical perspective (1964-2014): The need for precision and energy

u A strategy for the future: Towards the precision and energy frontier

u The short-term perspectives (2020-2030)

Lecture 2u The quest for precision (2030-2045): Linear or Circular ?u The energy frontier (2045-2060): Leptons or Hadrons ?

4-5 August 2014Physics at Future Colliders 1

Patrick Janot

Lecture 2


Mid-term perspectives (2030-2045)The quest for precision: Linear or Circular ?

Patrick Janot

Precision with e+e- colliders (1) Historically, e+e- colliders have been used for precision

measurementsu The accuracy of e+e- colliders led to predictions at higher scales

(mtop , mH , limits on NP) l And to unexpected discoveries (e.g., c quark, gluon, tau

lepton, …)


Circular ?

Linear ?FCC-ee, CEPC

ILC, CLIC

Patrick Janot

Precision with e+e- colliders (2) The European Strategy update in 2013 does not say

otherwise

u Electrons are not protons, i.e., do not interact strongly: no pile-up collisions

l Corollary #1: Final state is clean and cosy, triggering is easy (100% efficient)

l Corollary #2: No huge QCD cross section: All events are signal. u Electrons are leptons, i.e., elementary particles: no underlying

event l Corollary: Final state has known energy and momentum: (√s,

0, 0, 0)è E.g., can determine jet energies from jet directions and

conservation laws


A e+e- → HZ → qqbb candidate at LEP with ALEPH

Remember: A m+m- candidate event at LHC with CMS

- -

Patrick Janot

Precision with e+e- colliders (3) For 20 years, there was only one such project on the

marketu A 500 GeV e+e- linear collider, now called “ILC”, proposed in the

early 1990’s

l Why not a 500 GeV circular collider ?


Total length: 31 km

Patrick Janot

Linear or Circular ? (1) Why not a 500 GeV circular collider ?

u Synchrotron radiation in circular machinesl Energy lost per turn grows like , e.g., 3.5

GeV/turn at LEP2

è Must compensate with R and accelerating cavities

Cost grows like E4 too.

u A 500+ GeV e+e- collider can only be linear. Cost of a circular collider is prohibitive.

l “Up to a centre of mass energy of 350 GeV at least, a circular collider with superconducting accelerating cavities is the cheapest option”


~500 GeV

Author: Herwig Schopper(Former CERN DG)

Foreword: Rolf Heuer(Current CERN DG)

H. Schopper, private communication, 2014

Patrick Janot

Linear or Circular ? (2) Interest for circular collider projects grew up again

after first LHC resultsu The Higgs boson is light – LEP2 almost made it: only moderate √s

increase needed

l Need to go up to the top-pair threshold (~350 GeV) anyway to study the top quark

u There seems to be no heavy new physics below 500 GeVl The interest of √s = 500 GeV (and even 1 TeV) is now very

much debatedu Way out: study with unprecedented precision the Z, W, H and top

quarkè Highest luminosities at 91, 160, 240 and 350 GeV are

needed


LEP2

Patrick Janot

Linear or Circular ? (3) The ILC is designed for √s = 500 GeV

u It is supported by 20 years of R&D and innovationl With a complete technical design report delivered in 2013

è In principle, ready for construction as soon as decision is taken

u This machine has many technological challengesl A 24 km-long, high-gradient (31 MV/m), RF systeml A very low * b optics delivering small beam spot sizes at high

intensityè Never demonstrated to be achievable - ATF2 still

struggling l A positron source with no precedent

è Its performance cannot be verified before the construction is complete

l A green-field project

u It can deliver data to only one detector at a time

u It is in principle upgradeable to √s = 1 TeVl And possibly more : CLIC or Plasma acceleration in the same

tunnel (?)4-5 August 2014

Physics at Future Colliders 8

D. Schulte

Patrick Janot

Linear or Circular ? (4) The FCC-ee is designed to be a Z, W, H, and top factory

(√s = 90-400 GeV)u It is a project in its infancy

l Less than two years old

u This machine has at least as many technological challengesl A high-power (200 MW), high-gradient (15-20 MV/m), 1 km-

long, RF systeml Loads of synchrotron radiation (100 MW) to deal withl A booster (for top up injection), and probably a double ring for

e+ and e-

l An optics with very low *b , and large momentum acceptancel Polarization (transverse and longitudinal ?)l Up to four experiments to serve l … and much more

u It is supported by 50 years of experience and progress with e+e- circular machines

l Most of the above challenges will be addressed at SuperKEKB as of 2015

è FCC-ee will have to build on this experience

u It is the first step towards a 100 TeV proton-proton collider


D. Schulte

Patrick Janot

Linear or Circular ? (5) Performance target for e+e- colliders

u Complementarityl Ultimate precision measurements with circular colliders (FCC-

ee)l Ultimate e+e- energies with linear colliders (CLIC)


CEPC (2 Ips)

Possible upgrades with dashed lines

D. Schulte

Patrick Janot

Precision Higgs physics at FCC-ee and ILC (1)

Dominant production processes for √s ≤ 500 GeV

u Effect of beam polarization (exercise)l Higgs-strahlung cross section multiplied by 1 - P-P+ - Ae × (P- -

P+)

l Boson fusion cross section multiplied by (1-P-) × (1+P+)


Higgs-strahlung Boson fusion

300

200

100

0200 250 300 350 400 450 500

FCC-ee ILC

√s (GeV)

Cro

ss s

ect

ion

(fb

)

Patrick Janot


Number of Higgs events expected / year

u The plan is to run ~5 years at each centre-of-mass energy, in order to

l Determine all Higgs couplings in a model-independent wayl Infer the Higgs total decay widthl Evaluate (or set limits on) the Higgs invisible or exotic decays

è Through the measurements of

with Y = b, c, g, W, Z, g, t, m , invisible


Lumi /year (ab-1) HZ WW

FCC-ee-H 2.4 480,000 12,000

ILC-250 0.075 20,000 750

FCC-ee-t 0.72 95,000 18,000

ILC-500 0.18 18,000 25,000

Patrick Janot


Reminder: Predicted Higgs branching fractions

u mH = 126 GeV is a very good place to be for precision

measurements !l All decay channels open and measurable – can test new

physics from many angles4-5 August 2014


Patrick Janot


Physics backgrounds are “small”u For example, at √s = 240 GeV

l “Green” cross sections decrease like 1/sè “Purple” cross sections increase slowly with s

u To be compared to


e+e- → qq, l+l-gg → qq, l+l-

m > 30 GeV e+e- → W+W- e+e- → Ze+e- e+e- → Wen e+e- → ZZ e+e- → Znn- - -

60 pb 30 pb 16 pb 3.8 pb 1.3 pb1.4 pb 32 fb

200 fb

Only one to two orders of magnitude smaller

u vs. 11 orders of magnitude in pp collisions

l Trigger is 100% efficient (no need for trigger with ILC – all crossings are recorded)

l All Higgs events are useful and exploitable

l Signal purity is large

Add e+e- → tt for √s > 340 GeV

-0.6 pb

Patrick Janot


Example: Model-independent measurement of sHZ and kZ

u The Higgs boson in HZ events is tagged by the presence of the Z → e+e-, m+m-

l Select events with a lepton pair (e+e-, m+m-) with mass compatible with mZ

l No requirement on the Higgs decays: measure sHZ × BR(Z→ e+e-, m+m-)

l Apply total energy-momentum conservation to determine the “recoil mass”

è mH2 = s + mZ

2 - 2√s (p+ + p-)

l Plot the recoil mass distribution – resolution proportional to momentum resolution

u Provides an absolute measurement of kZ and set required detector performance


Exercise !

ILD simulation

mH=125 GeV √s=240 GeVZH → l+l-X

Eve

nts

/ 0.

2 G

eV

Patrick Janot


Repeat the search in all possible final statesu For all exclusive decays of the Higgs boson: measure sHZ × BR(H →

YY)l Including invisible decays, just tagged by the presence of the

lepton pair & mmiss

l For all decays of the Z (hadrons, taus, neutrinos) to increase statistics

u For the WW fusion mode (Hnn final state): measure sWW→H × BR(H → YY)


mH=125 GeV √s=240 GeV

ZH → qq bb, 0.25 ab-1 ZH → l+l- + nothing, 0.5 ab-1

BR(H → invis) = 100%

- -

Mbb (GeV)

Mmiss (GeV)

ILD simulationCMS simulation

-

Patrick Janot


Indirect determination of the total Higgs decay widthu From a counting of HZ events with H → ZZ at √s = 240 GeV : sHZ ×

BR(H → ZZ)

l sHZ is proportional to kZ2

l BR(H → ZZ) = G(H → ZZ) / GH is proportional to kZ2/GH

è sHZ × BR(H → ZZ) is proportional to kZ4 / GH

u In practice, also use the WW fusion process: WW → H l Measure cross section at √s ≥ 350 GeVl Use BR(H → bb, WW) measured at 240 GeV

è Better precision for GH


e+

e-

Z*

Z

H

Z*

Z

Final state with three Z’sAlmost background free

Measured with the Hl+l- final state (see slide 16)

Patrick Janot



The 10B$ ILC, 15 years1-10% precision

FCC-ee, 10 years0.1-1% precision

Grand summary u Results from a model-independent determination of the couplings

l Mostly from measurements of sHZ, sHZ×BR(H → YY), and GH

Patrick Janot

Coupling HL-LHC ILC FCC-ee

kW 2-5% 1.2% 0.19%

kZ 2-4% 1.0% 0.15%

kb 4-7% 1.7% 0.42%

kc – 2.8% 0.71%

kt 2-5% 2.4% 0.54%

km ~10% 91% 6.2%

kg 2-5% 8.4% 1.5%

kg 3-5% 2.3% 0.8%

kZg ~12% ? ?

BRinvis~10-15%? < 0.9% <

0.19%

GH ~50%? 5.0% 1.0%

kt 7-10% 14% 13% (*)

kH30-

50% ? 80% 80%(*)


Comparison with LHC


Sensitive to new physics at tree levelExpected effects < 5% / L2

NP

1% precision needed for LNP~1TeVSub-percent needed for LNP>1TeV

Sensitive to new physics in loops

Need higher energy to improve on LHC

Sensitive to light dark matter (sterile n, c, …)and to other exotic decays

(*) indirect

Model-independent results

Patrick Janot


Sensitivity to new physics (example)

u Compare the difference between the predictions of a few simple SUSY models and the SM for a few Higgs branching fractions

l With LHC, HL-LHC, ILC and FCC-ee expected precision

l With the current SM prediction uncertainties

u Basic messagesl The statistics proposed by the

FCC-ee are needed to distinguish these SUSY models from the Standard Model

l The SM theoretical uncertainties (dominated by QCD) must be reduced to match the experimental potential

è Feasible by FCC-ee / ILC timescales ?


FCC-ee

Patrick Janot

Precision electroweak physics at FCC-ee (1)

The FCC-ee goals in numbers (after commissioning)

u FCC-ee is the ultimate Z, W, Higgs and top factoryl 10 to 10,000 times the ILC targeted statistics at the same

energiesl 105 more Z’s and 104 more W’s than LEP1 and LEP2

è Potential statistical accuracies are mind-boggling !

u It is the tool of choice for precision electroweak physics


√s (GeV)

Running time FCC-ee Statistics ILC LEP

91 1 year 1012 (1013) Z decays (Tera Z) 109 (*) 2x10

7

161 1 year 108 WW pairs (Oku W) 106 (*) 4x104

240 5 years 2×106 HZ events (Mega Higgs) 105 –

350 5 years 2×106 top pairs (Mega Top) 2×105 –

(*) Estimate

Patrick Janot

The Z line-shape measurement with 1012 Zu Repeat the LEP1 programme every 15 minutes !

l Remember, after 5 years at LEP: Nn = 2.984 ± 0.008

GZ = 2495.2 ± 2.3 MeV

mZ = 91187.5 ± 2.1 MeV

Rl = 20.767 ± 0.025 aS = 0.1190 ± 0.0025

u Predicting accuracies with 300 times smaller statistical precision than at LEP is difficult

l Conservatively used LEP experience for systematics. This is just the start.

u Example: The uncertainty on EBEAM (1 MeV) was the dominant uncertainty on mZ, GZ

l Can we do significantly better at FCC-ee ?



√s ~ 91 GeV

Patrick Janot


Measurement of the beam energy at LEPu Ultra-precise measurement unique to circular colliders (crucial for

mZ, GZ)


Electron with momentum p in a uniform vertical magnetic field B:

In real life, B non uniform, LEP ring not circular

The electrons get transversally polarized (i.e., their spin tends to align with B)

Slow process (~ 1 hour to get 10% polarization)

NB. Polarization can be kept in collision (was tried only once at LEP).

LEP L = 2pR = 27km

R

Bdipol

e

e-

p

E p = e B R = (e/2p) B L

To bemeasured

Patrick Janot


Measurement of the beam energy at LEP (cont’d)u The spin precesses around B with a frequency proportional to B

(Larmor precession)l Hence, the number of revolutions nS for each LEP turn is

proportional to BL (or Bdl)

u Resonant intrinsic precision of the method DEbeam<100 keV !

l However, mZ and GZ measured at LEP with a precision of 2.2 MeV …

è Extrapolation uncertainty from measurements performed w/o collisions


0

1 2

3

Bx

-Bx

e-

p

Bdipole

Bx: oscillating field with frequency nin one point of the ring

Vary n until Pol = 0 ( =n nS)

Resonant depolarization:beam2

2E

m

g

e

es

Patrick Janot


Measurement of the beam energy at the FCC-eeu LEP was colliding 4 bunches of e+ and e-; FCC-ee will have 10,000’s

of bunches.u Use ~100 “single” bunches to measure EBEAM with resonant

depolarizationl Each measurement gives 100 keV precision, with no

extrapolation uncertaintyè Examples of targeted accuracy

l Many opportunities for direct searches for new physics through rare decays

è 1012 (1013) Z, 1011 b, c or tFantastic potential that remains to be explored.


+ many asymmetries for sin2qW to 10-5 - 10-6

Observable

Measurement

Current precision

TLEP stat.

Possible syst. Challenge

mZ (MeV)

Lineshape 91187.5 ± 2.1 0.005 < 0.1 QED corr.

GZ (MeV)

Lineshape 2495.2 ± 2.3 0.008 < 0.1 QED corr.

Rl Peak20.767 ± 0.025

0.0001 < 0.001 Statistics

Rb Peak 0.21629 ± 0.00066

0.000003

< 0.00006

g → bb

Nn Peak2.984 ± 0.008

0.00004

< 0.004 Lumi meast

as(mZ) Rl0.1190 ± 0.0025

0.00001

0.0001 New Physics

mZ to < 100 keV!

Patrick Janot


E.g, search for heavy sterile neutrino in Z decays

u Number of events depend on mixing between N and n, and on mN


Z → Nni, with N → W*l or Z*nj

BAU

See-saw

4×106 Z decays

maybe achievable with1010 - 1013 Z decays?

Patrick Janot

Longitudinally polarized beams at √s = mZ: ALR measurement ?

u SLC demonstrated the feasibility of longitudinally polarized beams at linear colliders

l ILC design values: P- = 80% and P+ = 30% u FCC-ee would need a specific setup for this measurement

l Reduced luminosity (~1% of nominal) to avoid top-up injection (depolarizing)

l Wigglers to get transverse polarization faster (natural time: 15h for 5% polarization)

l Spin rotators on both sides of the detector(s) to get longitudinal fragmentation

u With 1010 Z (1% design, still a factor 10 more than ILC)

l Measurement of sin2qW to 2×10-6

è Added value to be weighed with the experimental challenge



Observable

MeasurementCurrent

precisionTLEP stat.

Possible syst.

Challenge

ALRZ peak,

polarized0.1514 ± 0.0022

0.000015

< 0.000015

Design Expt

Patrick Janot


Oku-W: 108 WW events at production threshold Measurement of the W mass Measurement of the number of neutrinos

with cross section at threshold (with single photon events)

u Will bring final answer to the current Nn deficit (sterile neutrinos ?) 4-5 August 2014


n

n-

Nn ~ s(e+e- → nng) / 2s(e+e- → m+m-g)-

Observable

MeasurementCurrent

precisionTLEP stat.

Possible syst.

Challenge

mw (MeV) Threshold scan 80385 ± 15 0.3 < 0.5 QED Corr.

NnRadiative returnse+e-→gZ, Z→nn, ll

2.92 ± 0.052.984 ± 0.008

0.001 < 0.001 ?

as(mW) Bhad = (Ghad/Gtot)W

Bhad = 67.41 ± 0.27

0.00018

< 0.0001 CKM Matrix

mW to < 500 keV!

Patrick Janot


Mega-top: a million tt events at thresholdu Measure top quark mass and width

l From cross section at threshold10 x the ILC statisticsNo beamstrahlung systematics

u Measure the top Yukawa coupling


Observable

MeasurementCurrent

precisionTLEP stat.

Possible syst.

Challenge

mtop (MeV)

Threshold scan 173200 ± 900 10 10QCD (~40

MeV)

Gtop (MeV) Threshold scan ? 12 ? as(mZ)

ltop Threshold scanm = 2.5 ±

1.0513% ? as(mZ)

FCC-ee

-

mtop to 10 MeV!

Patrick Janot


Comparison with potential precision measurements at linear colliders

u Beam energy measurement (compton back-scattering, spectrometer) to ~10-4

l mZ and mW not measured to better than 5-10 MeV at ILC

è In absence of new physics, the (mtop, mW) plot would look like this

u Constraints on new physics ?4-5 August 2014

Physics at Future Colliders

SM with m H

= 126 GeV

Without mZ@FCC-ee, the SM line would have a 2.2 MeV width

30

Patrick Janot


Higher-dimensional operators as relic of new physics ?u Possible corrections to the standard model


Sensitivity to Weakly-coupled NP

LEP constraints: LNP > 10 TeV

After FCC-ee: LNP > 100 TeV ?

Patrick Janot


Theoretical uncertaintiesu Today’s measurements of mZ, mtop, mH, aQED(mZ) and aS(mZ) and lead

to the predictions

l First uncertainty is parametric, and arises from experimental uncertainties

è Will need to reduce uncertainties on mZ, mtop, aQED and aS by a factor 10

mZ, mtop, and aS will be addressed by FCC-ee measurements

Need to find ways to improve aQED (experimentally and theoretically)

l Second uncertainty comes from the lack of higher-order electroweak corrections

è Will need order of magnitude improvement here tooè Requires a new generation of electroweak calculations to

higher ordersBeyond the state of the art today …But within reach on the time scale required by FCC-ee

è Until recently, theory efforts were motivated by the precision needed by ILC

The FCC-ee brings an entirely renewed ambition towards better results


Patrick Janot

Precision with e+e- colliders: Summary

The small mass of the Higgs boson allows two options to be contemplated

u A 250 – 500 GeV linear collider: ILC (possibly CLIC at low energy)u A 90-400 GeV circular collider: FCC-ee (also CEPC at √s = 240 GeV)

Precision measurements at the EW scale are sensitive to new physics

u To potentially very high scales (up to ~100 TeV with FCC-ee)u To potentially very small couplings (sterile neutrinos, dark matter,

…)l Through a study of the Z, W, H, and top properties with

unprecedented statistics

Both options will be technologically / politically / financially challenging

u But can potentially be ready for collisions in the 2030’sl Go through the slides again to form a personal opinion – at this

level.

Access to the high-energy frontier is essential to evaluate these options

u The likelihood of new physics below 1 TeV has reduced considerably with LHC Run1

l An new evaluation will have to be made after LHC Run2


Patrick Janot

Lecture 2, cont’d


Long-term perspectives (2045-2060)The energy frontier: Leptons or Hadrons ?

Physics at Future Colliders

FCC (100 km)[Future Circular Colliders]Ultimate goal: FCC-hh (100 TeV)[Access to highest energies]

CLIC (50km)e+e- at 0.5 - 3 TeV

HE-LHC (27 km)pp collisions at 33 TeV)

ILC (50km)e+e- at 1 TeV

Patrick Janot

Higgs physics at high energy (1) Production in e+e- collisions

u Improve the precision on all couplings through vector-boson

fusionl See slide 18 – FCC-ee precision still standing out

u Access to direct ttH coupling and Higgs self coupling measurements

l Only possible at high energy4-5 August 2014


H

H

e+

e-

Z

Z

Patrick Janot

Higgs physics at high energy (2) Production in pp collisions

Large cross section increase with √s


Process 14 TeV 33 TeV100 TeV

gg → ttH

0.62 pb 4.5 pb× 7.3

37.8 pb× 61

gg → HH

33.8 fb 206 fb× 6.1

1.41 pb× 42

FCC-hh

lt 4% 14% 4% 2% 4% < 4% 3% < 1%

Patrick Janot

WW scattering at high energy Why WW scattering (and Higgs pair production) ?

u In the SM, Z and H exchange diagrams diverge, but exactly cancel each other

l Anomalous couplings, as relics of new physics, would have dramatic effects

è Total WW scattering / Higgs pair cross section diverge with m4

WW,HH


Precision on a and b

~30% at HL-LHC

~30% with CLIC 3 TeV

~1% with FCC-hh 100 TeV

NB. “a” can be measured with 0.1% (1%) precision with FCC-e (ILC)

Patrick Janot

Supersymmetry at high energy (1) Production in e+e-

collisionsu If the spectrum is light

enoughl CLIC can produce a whole

bunch of new particles with masses below 1.5 TeV

l And measure the masses with sub-per-cent precision

u Unique opportunity to probe the supersymmetry breaking mechanism

4-5 August 2014Physics at Future Colliders 38Example: Heavy Higgses

Patrick Janot

Supersymmetry at high energy (2) Production in pp collisions

u If the spectrum is heavier (as hinted at by the so-far negative LHC searches)

l Higher energy will be neededè Example: gluino discovery reach ~ 11 TeV at FCC-hh (5 TeV

at HE-LHC)

è Discovery reach of stop searchesUp to 3 TeV with HE-LHCUp to 6 TeV with FCC-hh


Patrick Janot

Other exotica at high energy (1) Example: Searches for new bosons (Z’)

u FCC-hh directly sensitive up to mZ’ ~ 30-35 TeV (vs. 1.5 TeV for CLIC)

l By looking for di-lepton resonancesu CLIC 3-TeV indirectly sensitive up to mZ’ ~ 15-20 TeV

l By looking for deviations in the dilepton mass distribution at high mass


Patrick Janot

Other exotica at high energy (2) 14 TeV (300 fb-1) → 100 TeV (3 ab-1) with pp collisions

u Rule of thumb: a factor 5 in mass reach from LHC to FCC-hh


Patrick Janot

Rare decays and precision measurements

E.g., at FCC-hh, 10 ab-1 at 100 TeV implyu 1010 Higgs bosons = 104 today’s statistics, 104 FCC-ee statistics

l More precision measurementsl Rare decays, FCNC probes, e.g., H→em …

u 1012 top quarks = 5×104 today’s statistics, 106 FCC-ee statisticsl Rare decays, FCNC probes, e.g., t→cZ, cHl CP violationl 1012 W and 1012 b from top decaysl 1011 t from t → W → t

è Rare decays, e.g., t → 3 , , m mg CP violation …l BSM decays : any interesting channels to consider ?

è Example: Majorana neutrino search in top decays


Patrick Janot

Detector challenges at FCC-hh (1) Detectors will be a formidable challenge, well beyond

HL-LHCu 171 in-time pile-up events with 25 ns bunch spacing, bunch length

5 cml High-granularity calorimetry, tracking and vertexing required

u Reduced to 35 in-time pile-up events with 5 ns bunch spacingl Ultra fast detectors required (out-of time pile-up)

u Large longitudinal event boostl Enhanced coverage at large rapidity required (with tracking

and calorimetry)è Also need for forward-jet tagging in boson fusion

productionu Zs, Ws, Higgses, tops, will also be boosted

l Again, high-granularity detectors needed

u Very energetic charged particlesl Precise momentum measurement up to 10 TeV require large

coil and trackeru Very energetic jets

l Energy containment require thicker calorimeter4-5 August 2014Physics at Future Colliders 43

Bigger, thicker, faster, clever detectors

Patrick Janot

Detector challenges at FCC-hh (2) Bigger, thicker, faster, clever …

u Example : long solenoid (6T) + dipoles (2T) + return yoke (a la CMS)

l + shield coil (3T) to avoid 120 kt yoke !

Exercise: How do the fields add up ?


Experimental cavern and maintenance scenario

Patrick Janot

Conclusions of the second lecture (1)

The discovery of H(125) brought new light on the next large machine

u There are now many ideas around for the what is the best path to follow

l With thorough and precise measurements of the known particles

l With a thorough exploration of the TeV scaleè To uniquely address the key questions of our field

A whole set of new discoveries may be waiting for us at LHC@14 TeV

u … or it may be decades before the next big discoveryl Meanwhile, the LHC will set the scene for precision physics

and rare decay searches

Future options will need a long time to materializeu None of the options is cheap (from ~5 B$ to 20 B$)

l Clear and global planning and funding are probably neededè Criteria for choice include

Scientific potentialCost, funing availability, sociology Technological maturity


Patrick Janot


Two very ambitious visions for the futureu PLAN A


ILC

500 GeVSC 1.3 GHzklystrons31.5 MV/m31 km

ILC

1 TeVSC 1.3 GHzKlystrons45 MV/m?50 km

CLIC

3 TeVdrive beamNC 12 GHz100 MV/m50 km

Precision studies of Higgs and top

10 B$, 2030 ?

Energy Frontier20 B$, 2060 ?ttH (HHH) couplings

+10B$, 2045 ?

≥ 50 years of e+e- (e-e-, gg) collisions up to √s ~ 3 TeV

Plasma acceleration?> 1 GV/m4 km

Patrick Janot


Two very ambitious visions for the future (cont’d)u PLAN B


PSBPS (0.6 km)SPS (6.9 km)

FCC-ee (80-100 km, e+e-, √s from 90 to ~400 GeV)

FCC-hh (pp, up to 100 TeV c.m.)

Precision studies of Z, W, H, top3-5 B$, 2035 ?

ttH, HHH couplingsEnergy Frontier20 B$, 2055 ?

& e± (50-175 GeV) – p (50 TeV) collisions (FCC-he)

≥ 50 years of e+e-, pp and ep collisions at highest energies

LHCHL-LHC

LEP (26.7 km)

Patrick Janot


Two very ambitious visions for the future (cont’d)u Both visions have different, but solid, technological maturity

l The linear collider vision is the most advanced from the design point-of-view

è Many test facilities have proven the acceleration technology to work

But the associated risk is still quite high (final focus, positron source, …)

l The circular collider vision is much youngerè But is strongly backed up by 50 years of experience, by

historical successesAnd by projects that will prove its feasibility

(SuperKEKB, HL-LHC)

u The scientific case is obviousl Precision studies for new physics with small couplingsl Energy frontier for new physics at high mass and large

couplings

u My own impressionl Beyond the LHC Run2, the combination of FCC-ee and FCC-hh

offers, for a great cost/infrastructure effectiveness, the best precision and the best search reach

u This impression will have to be reviewed after the LHC Run2 and 5 years of FCC study


Patrick Janot


Beyond these two visions, the R&D for the far future must not stop

u Muon colliders, and even more sou Plasma wakefield acceleration

l Might be the only way to collide leptons at the highest energies (> 5 TeV)

è For acceptable construction and operation costs (?)u Other, even more innovative, ideas are obviously needed

l You have the opportunity to become key players for the future of our field

The journey towards the future of HEP will probably be long and tortuous

u You can make it enjoyable for yourself:l Always keep your passion for sciencel Apply healthy practical common sensel And follow your dreams !


physics at future colliders

Documents

gev e e collider

gev e e linear collider

gev circular collider

e e hz qqbb candidate

circular collider projects

circular machinesenergy

future colliderslecture

future colliders4