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TLEP: a first step on a long vision for HEP

M. KoratzinosUniv. of Geneva

On behalf of the TLEP study groupAthens, 6 December 2013

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Contents• The physics case• Circular collider challenges• TLEP implementation• TLEP physics reach• TLEP design study

Acknowledgements: I am indebted to the whole TLEP community and especially R. Aleksan, A. Blondel, P. Janot, F. Zimmermann for liberal use of material

This talk would not have been complete without the comparison data with the ILC. I hope I have represented them accurately

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The physics case

• The energy scale of any new physics is already pushed to beyond a few hundreds of GeV and will probably be pushed to 1TeV or more with the next LHC run.

• In this scenario, Physics beyond the standard model is only accessible via loop corrections rather than direct observation of a (heavy) state.

• The sensitivity of precision measurements can be to energy scales far above what is directly accessible in current or next generation machines (LHC, ILC, CLIC)

• A clearer picture on this will emerge after the next LHC run.• Meaningful over-constraining of the standard model can only start

now that the Higgs sector is known and might lead to revealing weaknesses of the standard model

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Precision needed

• Higgs couplings: sensitivity to new physics

– Typical deviations of SM Higgs couplings: with |d| < 5%

Where is the energy scale for new physics (exact value of d depends on coupling and model)• Need at least a per-cent accuracy for a 5s observation if ΛNP = 1 TeV and a sub-per-cent

accuracy for multi-TeV New Physics scale

• Z pole measurements– Increase sensitivity to new physics by an order of magnitude need 100 times smaller

errors 10,000 more statistics• W and top mass determination

– Need to match the precision of direct measurements by improving by one order of magnitude

• (It is not clear that the ILC can deliver these accuracies)

2

NP

TeV 11

dSMHXX

HXX

gg

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Circular colliders

• In the next few slides I would like to overview the parameters that affect circular collider performance.

• I will then show what can reasonably be achieved in terms of luminosity.

• The following is not TLEP specific; it can apply to any circular machine (CEPC?)

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Major limitations

• The major limitations of circular colliders are:– Power consumption limitations that affect the

luminosity– Tunnel size limitations that affect the luminosity

and the energy reach– Beam-beam effect limitations that affect the

luminosity– Beamstrahlung limitations that affect beam

lifetimes (and ultimately luminosity)

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Energy reach

• In a circular collider the energy reach is a very steep function of the bending radius. To make a more quantitative plot, I have used the following assumptions:– RF gradient: 20MV/m– Dipole fill factor: 90% (LEP was 87%)

• I then plot the energy reach for a specific ratio of RF system length to the total length of the arcs

and

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Energy reach

Assumptions: 20mV/m, 90% dipole fill factor.What is plotted is the ratio of RF length to total arc length

LEP2 had a ratio of RF to total arc length of 2.2%

100 150 200 250 300 3500

2000

4000

6000

8000

10000

12000

14000

Energy reach

5% RF2% RF1% RF

beam energy (Gev)

bend

ing

radi

us (m

)

TLEP175 sits comfortably below the 1% line

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Luminosity of a circular collider

Luminosity of a circular collider is given by

Which can be transformed in terms of

and

to:

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Luminosity of a circular collider

The maximum luminosity is bound by the total power dissipated, the maximum achievable beam-beam parameter (the beam-beam limit), the bending radius, the beam energy, , and the hourglass effect (which is a function of σz and )

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Total power

• Luminosity is directly proportional to the total power loss of the machine due to synchrotron radiation.

• In our approach, it is the first parameter we fix in the design (the highest reasonable value)

• Power loss is fixed at 100MW for both beams (50MW per beam)

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Machine radius

• The bending radius of the collider also enters linearly in the luminosity formula

• The higher the dipole filling factor, the higher the performance

• [there is a small dependance on the maximum beam-beam parameter since smaller machines for the same beam energy can achieve higher beam-beam parameters]

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Beam-beam parameter

The maximum beam-beam parameter is a function of the damping decrement: where

Or, more conveniently:

The damping decrement is the fractional energy loss from one IP to the next.Therefore, for a specific machine, for 1IP is generally higher than for 2IPs

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Maximum beam-beam

• It is not trivial to predict what can be achieved in terms of beam-beam parameter at TLEP or other machines.

• LEP is a good yardstick to use• LEP achieved at 45GeV and run up to 0.08 at 100GeV

without reaching the beam-beam limit• Going up in energy increases the damping decrement

(and therefore )• Values between 0.05 and 0.1 should be achievable with

relative ease at future circular colliders. At beam energies of 120GeV or higher, higher values might be possible

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Beta* and hourglassWe are opting for a realistic β*y value of 1mm. σz beam sizes vary from 1mm to 3mm. In this range the hourglass effect is between 0.9 to 0.6

0.5 1 1.5 2 2.5 3 3.5 4 4.50.3

0.4

0.5

0.6

0.7

0.8

0.9

1

R for beta*_y of 1mm

sigma_z (mm)

redu

ction

fact

or

Self-consistent σz at different energies for TLEP

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Luminosity of a circular collider

0 50 100 150 200 2501.00E+33

1.00E+34

1.00E+35

1.00E+36

beam energy [GeV]

Lum

inos

ity [

cm−2

s−1]

Single IP luminosity of a circular collider of 9000m bending radius as a function of beam energy. • Power loss is

100MW. • ξy between 0.05

and 0.1. • β*y = 1mm. • =0.75

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Beamstrahlung

• Beamstrahlung is the interaction of an incoming electron with the collective electromagnetic field of the opposite bunch at an interaction point.

• Main effect at circular colliders is a single hard photon exchange taking the electron out of the momentum acceptance of the machine.

• If too many electrons are lost, beam lifetime is affected

• [the beamstrahlung effect at linear colliders is much larger and it increases the beam energy spread]

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Beamstrahlung (2)

• The beamstrahlung limitation was introduced by Telnov*

• It depends on where is the momentum acceptance, the beam sizes in x and z (note no dependence!) and is the number of electrons per bunch

• It has a γ2 dependence, so it is only important at high energies (>~120GeV per beam)

• It is mitigated by high momentum acceptance, small emittances and very flat beams

*: arXiv:1203.6563

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Beamstrahlung limitation

100 110 120 130 140 150 160 170 180 190 2001.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

TelnovTelnov tuned

beam energy (GeV)

beam

life

time

(sec

)

Plot on left is if we run with a value of the beam-beam parameter of 0.1Above ~180 GeV is difficult to run without opting for a more modest beam-beam parameter value (which would reduce the luminosity)

TLEP Latest parameter set, mom. acceptance 2.2%

Can even run at 250GeV with a beam-beam parameter of 0.05

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A specific implementation: TLEP• A study has been commissioned for an

80-km tunnel in the Geneva area.• For TLEP we fix the radius

(conservatively 9000m) the power (100MW) and try to have beams as flat at possible to reduce beamstrahlung.

• Our arc optics design (work in progress) conservatively uses a cell length of 50m, which still gives a horizontal emittance of 2nm at 120GeV

• We assume that we can achieve a horizontal to vertical emittance ratio of 500-1000 (LEP was 200)

LHC

Possible TLEP location

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Other tunnel diameters

• …but of course other tunnel diameters and locations are equally good

• Many other proposals floating, but I would like to mention the Circular Electron-Positron Collider in China (CEPC) – certainly the tunnel can be built more cheaply in China

• Performance scales with tunnel size, but in case no funds are available for a new tunnel, the LHC tunnel can be used after the end of the LHC physics programme (a project we call LEP3)

Patrick Janot

TLEP implementation At 350 GeV, beams lose 9 GeV / turn by synchrotron

radiationu Need 600 5-cell SC cavities @ 20 MV/m in CW mode

l Much less than ILC (8000 9-cell cavities@ 31 MV/m)l Length ~900 m, similar to LEP (7 MV/m)

u 200 kW/ cavity in CW : RF couplers are challengingl Heat extraction, shielding against radiation, …

Luminosity is achieved with small vertical beam size : sy ~ 100 nm

u A factor 30 smaller than at LEP2, but much more relaxed than ILC (6-8 nm)

l TLEP can deliver 1.3 × 1034 cm-2s-1 per collision point at √s = 350 GeV

Small beam lifetime due to Bhabha scattering (~ 15 min) + beamstrahlung

u Need efficient top-up injection

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BNL 5-cell 700 MHz cavity RF Coupler(ESS/SPL)

A. Blondel

F. Zimmermann

SuperKEKB: a TLEP demonstrator• SuperKEKB will be a TLEP demonstrator

• Beam commissioning starts early 2015• Some SuperKEKB parameters :

– Lifetime : 5 minutes• TLEP : 15 minutes

– b*y : 300 mm• TLEP : 1 mm

– sy : 50 nm• TLEP : ~100 nm

– ey/ex : 0.25%• TLEP : 0.20%-0.10%

– Positron production rate : 2.5 × 1012 / s• TLEP : < 1 × 1011 / s

– Off-momentum acceptance at IP : ±1.5%• TLEP : ±2.0 to ±2.5%

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Patrick Janot

TLEP Cost (Very Preliminary) Estimate Cost in billion CHF

As a self-standing project :

Same order of magnitude as LHC

As an add-on to the VHE-LHC project :

Very cost-effective : about 2-3 billion CHF

Cost per Higgs boson : 1 - 3 kCHF / Higgs

(ILC cost : 150 k$ / Higgs) [ NB : 1CHF ~ 1$ ]

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80-100 km tunnel

LEP/LHC

Bare tunnel 3.1 (1)

Services & Additional infrastructure (electricity, cooling, service cavern, RP, ventilation, access roads …)

1.0(

2)

RF system 0.9 (3)

Cryo system 0.2 (4)

Vacuum system & RP 0.5(

5)

Magnet system for collider & injector ring

0.8(

6)

Pre-injector complex SPS reinforcements

0.5

Total 7.0

Note: detector costs not included – count 0.5 per detector (LHC)

(1): J. Osborne, Amrup study, June 2012

(2): Extrapolation from LEP

(3): O. Brunner, detailed estimate, 7 May 2013

(4): F. Haug, 4th TLEP Days, 5 April 2013

(5): K. Oide : factor 2.5 higher than KEK, estimated for 80 km ring

(6): 24,000 magnets for collider & injector; cost per magnet 30 kCHF (LHeC);

Cost for the 80 km version : the 100 km version might be cheaper.

Absolutely Preliminary

Not endorsed by anybody

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Power consumption

TLEP 120 TLEP 175RF systems 173-185 MWcryogenics 10 MW 34 MWtop-up ring 3 MW 5 MWTotal RF 186-198 MW 212-224 MW

Power consumption TLEP 175RF including cryogenics 224MWcooling 5MWventilation 21MWmagnet systems 14MWgeneral services 20MWTotal ~280MW

Highest consumer is RF:

Total power consumption for 350GeV running:

IPAC13 TUPME040, arXiv:1305.6498 [physics.acc-ph]

Limited by Klystron CW efficiency of 65%. This is NOT aggressive and we hope to be able to do better after dedicated R&D

CERN 2010 power demand:• Full operation 220MW• Winter shutdown 50MW

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A note on power consumption

• TLEP is using ~280MW while in operation and probably ~80MW between physics fills. So for 1×107 sec of operation and 1×107 sec of stand-by mode, total electricity consumption is ~1TWh

• CERN is currently paying ~50CHF/MWh• TLEP yearly operation corresponds to ~50MHF/year• This should be seen in the context of the total

project cost (less than 1% of the total cost of the project goes per year to electricity consumption)

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TLEP parameter set TLEP Z TLEP W TLEP H TLEP t

Ebeam [GeV] 45 80 120 175circumf. [km] 80 80 80 80beam current [mA] 1180 124 24.3 5.4#bunches/beam 4400 600 80 12#e−/beam [1012] 1960 200 40.8 9.0horiz. emit. [nm] 30.8 9.4 9.4 10 vert. emit. [nm] 0.07 0.02 0.02 0.01bending rad. [km] 9.0 9.0 9.0 9.0κε 440 470 470 1000mom. c. αc [10−5] 9.0 2.0 1.0 1.0Ploss,SR/beam [MW] 50 50 50 50β∗

x [m] 0.5 0.5 0.5 1β∗

y [cm] 0.1 0.1 0.1 0.1σ∗

x [μm] 124 78 68 100σ∗

y [μm] 0.27 0.14 0.14 0.10hourglass Fhg 0.71 0.75 0.75 0.65ESR

loss/turn [GeV] 0.04 0.4 2.0 9.2VRF,tot [GV] 2 2 6 12dmax,RF [%] 4.0 5.5 9.4 4.9ξx/IP 0.07 0.10 0.10 0.10ξy/IP 0.07 0.10 0.10 0.10fs [kHz] 1.29 0.45 0.44 0.43Eacc [MV/m] 3 3 10 20eff. RF length [m] 600 600 600 600fRF [MHz] 700 700 700 700δSR

rms [%] 0.06 0.10 0.15 0.22σSR

z,rms [cm] 0.19 0.22 0.17 0.25 /IP[1032cm−2s−1] 5600 1600 480 130number of IPs 4 4 4 4 beam lifet. [min] 67 25 16 20

By definition, in a project like TLEP, from the moment a set of parameters is published it becomes obsolete and we now already have an improved set of parameters.The new parameter set contains improvements to our understanding, but does not change the big picture.

IPAC13 TUPME040, arXiv:1305.6498 [physics.acc-ph]

Too pessimistic! 2nm @120GeV or lower should he easy

Revised (taking into account BS) but similar

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Luminosity of TLEP

TLEP : Instantaneous lumi at each IP (for 4 IP’s) Instantaneous lumi summed over 4 IP’sZ, 2.1036

WW, 6.1035

HZ, 2.1035

tt , 5.1034

Why do we always quote 4 interaction points?• It is easier to extrapolate luminosity from the LEP experience.

Lumi of 2IPs is larger than half the lumi of 4IPs• According to a particle physicist: “give me an experimental cavern

and I guarantee you that it will be filled”

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Upgrade path

• TLEP offers the unique possibility to be followed by a 100TeV pp collider (VHE-LHC)

• Luminosity upgrade: a study will be launched to investigate if luminosity can be increased by a significant factor at high energies (240 and 250GeV ECM) by using a charge-compensated scheme of four colliding beams. We will aim to gain a factor of 10 (to be studied and verified)

The physics caseOur first paper treating exclusively the physics case will be published in JHEP shortly (submitted 23/9/2013): M.Bicer et el., “First Look at the Physics Case of TLEP” http://arxiv.org/abs/1308.6176 (130 authors)

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Author(s): M. Bicer, H. Duran Yildiz, I. Yildiz, G. Coignet, M. Delmastro, T. Alexopoulos, C. Grojean, S. Antusch, T. Sen, H.-J. He, K. Potamianos, S. Haug, A. Moreno, A. Heister, V. Sanz, G. Gomez-Ceballos, M. Klute, M. Zanetti, L.-T. Wang, M. Dam, C. Boehm, N. Glover, F. Krauss, A. Lenz, M. Syphers, C. Leonidopoulos, V. Ciulli, P. Lenzi, G. Sguazzoni, M. Antonelli, M. Boscolo, O. Frasciello, C. Milardi, G. Venanzoni, M. Zobov, J. van der Bij, M. de Gruttola, D.-W. Kim, M. Bachtis, A. Butterworth, C.Bernet, C. Botta, F. Carminati, A. David, D. d’Enterria, G. Ganis, B. Goddard, G. Giudice, P. Janot, J. M. Jowett, C. Lourenco, L. Malgeri, E. Meschi, F. Moortgat, P. Musella, J. A. Osborne, L. Perrozzi, M. Pierini, L. Rinolfi, A. de Roeck, J. Rojo, G. Roy, A. Sciaba, A. Valassi, C. S. Waaijer, J. Wenninger, H. Woehri, F. Zimmermann, A. Blondel, M. Koratzinos, P. Mermod, Y. Onel, R. Talman, E. Castaneda Miranda, E. Bulyak, D. Porsuk, D. Kovalskyi, S. Padhi, P. Faccioli, J. R. Ellis, M. Campanelli, Y. Bai, M. Chamizo, R. B. Appleby, H. Owen, H. Maury Cuna, C. Gracios, G. A. Munoz-Hernandez, L. Trentadue, E. Torrente-Lujan, S. Wang, D. Bertsche, A. Gramolin, V. Telnov, P. Petrov, P. Azzi, O. Nicrosini, F. Piccinini, G. Montagna, F. Kapusta, S. Laplace, W. da Silva, N. Gizani, N. Craig, T. Han, C. Luci, B. Mele, L. Silvestrini, M. Ciuchini, R. Cakir, R. Aleksan, F. Couderc, S. Ganjour, E. Lancon, E. Locci, P. Schwemling, M. Spiro, C. Tanguy, J. Zinn-Justin, S. Moretti, M. Kikuchi, H. Koiso, K. Ohmi, K. Oide, G. Pauletta, R. Ruiz de Austri, M. Gouzevitch, S. Chattopadhyay

Patrick Janot

TLEP : Possible Physics Programme

Higgs Factory mode at √s = 240 GeV: 5+ yearsu Higgs boson properties, WW and ZZ production.

l Periodic returns at the Z peak for detector and beam energy calibration

Top Threshold scan at √s ~ 350 GeV: 5+ yearsu Top quark mass, width, Yukawa coupling; top quark physics; more

Higgs boson studies.l Periodic returns at the Z peak for detector and beam energy

calibration Z resonance scan at √s ~ 91 GeV: 1-2 years

u Get 1012 Z decays @ 15 kHz/IP. Repeat the LEP1 Physics Programme every 15 minutes.

l Continuous transverse polarization of some bunches for precise Ebeam calibration

WW threshold scan at √s ~ 161 GeV: 1-2 yearsu Get 108 W decays; Measure the W mass; Precise W studies.

l Continuous transverse polarization of some bunches and returns to the Z peak.

Longitudinally polarized beams at √s = mZ: 1 yearu Get 1011 Z decays, and measure ALR, AFB

pol, etc.l Polarization wigglers, spin rotators

Luminosity, Energy, Polarization upgradesu If justified by scientific arguments (with respect to the upgrade to

VHE-LHC)

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Higgs: the situation today

The mass dependence of the couplings of the Higgs boson to fermions and gauge bosons, from a two-parameter fit (dashed line) to a combination of the CMS and ATLAS data. The dotted lines bound the 68% C.L. interval. The value of the coupling of the Higgs boson to the c quark shown in the figure is a prediction of the fit. The solid line corresponds to the Standard Model prediction

Patrick Janot

TLEP as a Mega-Higgs Factory (1)

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ILC-250 TLEP-240 ILC-350 TLEP-350

Lumi / 5 yrs 250 fb-1 10 ab-1 350 fb-1 2.6 ab-1

Beam Polarization 80%, 30% – 80%,30% –

# of HZ events 70,000 2,000,000 65,000 325,000

# of WW→H events 3,000 50,000 20,000 65,000

Z → nn

Z → All

Unpolarized cross sections PJ and G. Ganis

Patrick Janot

TLEP as a Mega-Higgs Factory (2)

Example : ee- → ZH → ll- + anything u Measure sHZ Summary of the

possible measurements : (TLEP : CMS Full Simulation + some extrapolations for cc, gg)

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ILC-250 TLEP-240sHZ 2.5% 0.4%

sHZ *BR(H→bb) 1.1% 0.2%sHZ *BR(H→cc) 7.4% 1.2%sHZ *BR(H→gg) 9.1% 1.4%

sHZ *BR(H→WW) 6.4% 0.9%

sHZ *BR(H→tt) 4.2% 0.8%sHZ *BR(H→ZZ) 19% 3.1%sHZ *BR(H→gg) 35% 3.0%sHZ *BR(H→mm) 100% 13%

GINV / GH < 1% < 0.2%mH 40 MeV 8 MeV

e+

e-

Z*

Z

H

e, m

e-, m-gHZZ

TLEP-2401 year1 detector

ILC TDRFrom P. Azzi et al.arXiV:1208.1662

Patrick Janot

Global fit of the Higgs couplings Model-independent fit

u NB : Theory uncertainties must be worked out.

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M. Bachtis

Coupling gZ gW gb gc gg gt gm gg BRexo

TLEP-240 0.16% 0.85

% 0.88% 1.0% 1.1% 0.94% 6.4% 1.7% 0.48%

TLEP-350 0.15% 0.19

% 0.42% 0.71% 0.80% 0.54% 6.2% 1.5% 0.45%

ILC-350 0.9% 0.5% 2.4% 3.8% 4.4% 2.9% 45% 14.5% 2.9%

1.0%

Snowmass 2013

Patrick Janot

TLEP as a Mega-Top Factory Scanning the tt threshold at √s ~ 350 GeV

u Effect of beamstrahlung on E_beam at TLEP is small compared to Linear Colliders

Luminosity E Spectrum Effect on top threshold

u No need to measure the luminosity spectrum @ TLEP reduced mtop uncertaintyu Slightly larger cross section @ TLEPu Beam energy calibration from e+e- → WW and mW ; as from Z and W leptonic decays.u Still need to work on theoretical predictions (40 MeV uncertainty on mtop)

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TLEP

ILC

TLEP,

Lumi / 5 years # top pairs Dmtop DGtop Dltop/ltop

TLEP 4 × 650 fb-1 1,000,000 10 MeV 12 MeV 13%ILC 350 fb-1 100,000 30 MeV 35 MeV 40%

-

Stat. only

M. Zanetti

Expected sensitivity for TLEP (full study to be done) and ILC

Patrick Janot

TLEP as a Tera-Z and Oku-W Factory (1) TLEP repeats the LEP1 physics programme every 15

minutesu Added value: Transverse polarization up to the WW threshold

(LEP: up to 60GeV)l Exquisite beam energy determination with resonant

depolarizationè Up to 5 keV precision – unique at circular ee- colliders

u Measure mZ, mW, GZ, … with unbeatable accuracy

u Measure the number of neutrinosl From the peak cross section at the Z pole – Luminosity

measurement is a challengel From radiative returns to the Z from the WW threshold – e+e-

→ gnn

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Z lineshape, asymetries WW threshold scan New Physics in loops ?

-

No beamstrahlungis a clear advantage

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This is a unique part of the TLEP programme. It is also very challenging for the accelerator (intensity, longitudinal polarization), experiments (rate) and Theory

Measurements with Tera-Zu Caution : TLEP will have 5×104 more Zs than LEP - Predicting achievable accuracies with 250

times smaller statistical precision is difficultu The study is just beginning : errors might get better with increasing understandingu Much more to do at the Z peak e.g., asymmetries, flavour physics (>1011 b, > 1011 c, > 1010 t),

rare Z decays, … Measurements with Oku-W

u Caution : TLEP will have 5×106 more W than LEP at the WW threshold -Predicting achievable accuracies with 1000 times smaller statistical precision is difficult

u Much more W physics to do at the WW threshold and above e.g., GW, lW, rare W decays, diboson couplings, …

Measurement with longitudinal polarizationu One year data taking with luminosity reduced to 20% of nominal (requires spin rotators)

l 40% beam longitudinal polarization assumed – NB: LEP kept polarization in collisions - hardware needed is challenging

TLEP as a Tera-Z and Oku-W Factory (2)

NB: ILC limited to a factor > 30 larger errors

Patrick Janot

EWSB Precision tests at TLEP: Teaser

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TLEPTLEP

ILC m H=1

26 G

eV

Warning : indicative only.Complete study being done

Very stringent SM closure test.Sensitivity to weakly-interacting BSM Physics at a scale > 10 TeV

TLEP Design Study: provisional Structure

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26 Working Groups: Accelerator / Experiment / Phenomenology

Soon to be replaced by an official structure in the framework of FCC

TLEP Design Study: People

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• 295 subscribers from 23 countries (+CERN)– Distribution reflects the level of awareness in the different countries

• 4 physicists from Greece: subscribe at http://tlep.web.cern.ch !

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The two pillars: pp and e+e-mandate is to deliver full CDR for both machineswith an extended cost review

Michael Benedikt

The combination of TLEP and the VHE-LHC offers, for a great cost effectiveness, the best precision and the best search reach of all options presently on the market.

First look at The Physics Case of TLEP arXiv:1308.6176v2 [hep-ex] 22 Sep 2013

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TLEP and FCC in the newsFCC front-page news in the CERN bulletin:

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TLEP and FCC in the news II…meanwhile in the same issue:

Our web page• http://tlep.web.cern.ch

• Last event : Sixth TLEP workshop 16-18 October 2013 http://indico.cern.ch/conferenceDisplay.py?ovw=True&confId=25771

• Joint VHE-LHC + TLEP kick-off meeting 12-15 February 201447

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Conclusions

• TLEP is a 3-in-1 package:– It is a powerful Higgs factory– It is a high-intensity EW parameter buster– It offers the path to a 100TeV pp collider

• TLEP is based on solid technology and offers little risk, has a price tag which is expensive but not out of reach, has reasonable consumption, offers multiple interaction points and might even have an upgrade potential.

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THANK YOUend

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Extra slides

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Beamstrahlung• I am using the approach of Telnov throughout*• The energy spectrum of emitted photons during a collision of

two intense bunches (usual bremstrahlung formula) is characterized by a critical energy

• Where ρ is the radius of curvature of the affected electron which depends on the field he sees

• And the maximum field can be approximated by

𝐸𝑐=ħ3 γ 0

3𝑐2 ρ

ρ=γ 0𝑚𝑐2

𝑒𝐵

𝐵𝑚𝑎𝑥=2𝑒𝑁 𝑏

𝜎𝑥𝜎 𝑧 *: arXiv:1203.6563

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Beamstrahlung

• So, the critical energy turns out to be

for the maximum field (it would be smaller for a smaller field)Telnov’s approximation:

• 10% of electrons see maximum field•90% of electrons see zero field

𝐸𝑐=𝐸0

3𝑟𝑒❑2 γ 0 𝑁𝑏

α 𝜎 𝑥𝜎𝑧

constants

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Beamstrahlung

• Electrons are lost if they emit a gamma with an energy larger than the momentum acceptance, η:

• We define or otherwise • The number of photons with

• So we see that η can directly be traded off by • Going up in energy aggravates the effect

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Beamstrahlung energy dependence

• For a specific ring, power consumption, emittances and ξ:

• Number of particles per bunch scales with gamma:

• And u scales with γ2. This produces a steep drop in lifetime with increased energy

𝑁 𝑏=𝜉 𝑦2𝜋𝛾𝜎 𝑥𝜎 𝑦

𝑟 𝑒𝛽∗𝑦❑

European Strategy recommendations

• High-priority large-scale scientific activities – Second-highest priority, recommendation #2

• Excerpt from the CERN Council deliberation document (22-Mar-2013)

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d) To stay at the forefront of particle physics, Europe needs to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next Strategy update, when physics results from the LHC running at 14 TeV will be available.

CERN should undertake design studies for accelerator projects in a global context, with emphasis on proton-proton and electron-positron high-energy frontier machines. These design studies should be coupled to a vigorous accelerator R&D programme, including high-field magnets and high-gradient accelerating structures, in collaboration with national institutes, laboratories and universities worldwide.

The two most promising lines of development towards the new high energy frontier after the LHC are proton-proton and electron-positron colliders. Focused design studies are required in both fields, together with vigorous accelerator R&D supported by adequate resources and driven by collaborations involving CERN and national institutes, universities and laboratories worldwide. The Compact Linear Collider (CLIC) is an electron-positronmachine based on a novel two-beam acceleration technique, which could, in stages, reach a centre-of-mass energy up to 3 TeV. A Conceptual Design Report for CLIC has already been prepared. Possible proton-proton machines of higher energy than the LHC include HE-LHC, roughly doubling the centre-of-mass energy in the present tunnel, and VHE-LHC, aimed at reaching up to 100 TeV in a new circular 80km tunnel. A large tunnel such as this could also host a circular ee- machine (TLEP) reaching energies up to 350 GeV with high luminosity.

56

CERN medium term plan

57

The TLEP tunnel

• Standard size tunnel boring machines dictate a larger tunnel size of 5.6m diameter (LHC: 3.8m)

• Maximize boring in ‘molasse’ (soft stone)• 80km design necessitates a bypass tunnel to avoid very deep

shafts at points 4 and 5• A larger tunnel might actually be cheaper• This is only the beginning of the geological study

Patrick Janot

Global fit of the Higgs couplings (2)

Model-dependent (seven-parameter) fit a-la-LHCu Assume no exotic Higgs decays, and kc = kt

u Quantitative added value from ILC – wrt HL-LHC – does not stick out clearly.

l In contrast, sub-per-cent TLEP potential is striking for all couplings

è Only TLEP is sensitive to (multi-)TeV new physics with Higgs measurements

u Much theoretical progress is needed to reduce accordingly theory uncertainties

58

HL-LHC : One experiment only… CMS Scenario 1 CMS Scenario 2

In bold, theory uncertainty are assumed to be divided by a factor 2,experimental uncertainties are assumed to scale with 1/√L,and analysis performance are assumed to be identical as today(HL-LHC : One experiment only)

CMS, July 13

Patrick Janot

TLEP as a Mega-Higgs Factory (3)

Determination of the total widthu From the number of HZ events and of ZZZ events at √s = 240 GeV

u From the bbnn final state at √s = 350 GeV (and 240 GeV)

59

n

n-

GH from: ILC TLEPHZ →ZZZ@ 240 20% 3.2%

WW→H@240 12% 2.4%

WW→H@350 7% 1.2%

Combined 5.8% 1.0%Note : mm collider

DGH/GH ~ 5%

Patrick Janot

Higgs Physics with √s > 350 GeV ? (1)

Signal cross sections in ee- collisions

Measurements at higher energyu √s > 350 GeV does not do much for couplings to c, b, g, Z, W, g, m

and Gtot. (slide 15)l Invisible width best done at √s = 240 GeV

u The ttH coupling benefits from higher energyl TLEP 350 : 13%l ILC 500 : 14% ; ILC 1 TeV : ~4% ; CLIC : ~4%

u The HL-LHC will already do the measurement with 5% precision (and improving)

l Sub-per-cent precision will need the ultimate pp machine at 100 TeV : VHE-LHC 60

H

H

+

Patrick Janot

Higgs Physics with √s > 350 GeV ? (2)

Measurements at higher energy (cont’d)u Higgs tri-linear self coupling l very difficult for all machines

Particularly difficult for √s < 2-3 TeV

Few per-cent precision will need VHE-LHC

Summaryu For the study of H(126), the case for ee- collisions above 350 GeV

is not compelling.l A stronger motivation will exist if a new particle found (or

inferrred) at LHCè IF ee- collisions can bring substantial new information

about it

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ILC500, HL-LHC ILC1TeV, HE-LHC CLIC3TeV, VHE-LHC 0.5 ab-1 3 ab-1 1 ab-1 3 ab-1 2 ab-1 3 ab-1

J. Wells et al.arXiV:1305.6397

Snowmass, Aug 13

62

EW parameter summaryQuantity Physics Present

precision

TLEPStat errors

Possible TLEPSyst. Errors

TLEP key Challenge

Alain Blondel, Snowmass on Minnesota, 2 August 2013

MZ (keV) Input 91187500 2100

Z Line shape scan 5 keV <100 keV E_cal QED corrections

GZ (keV) D (T)(no D!)

2495200 2300

Z Line shape scan 8 keV <100 keV E_cal QED corrections

Rl s , db 20.767 0.025 Z Peak 0.0001 <0.001 Statistics QED corrections

NnPMNS Unitarity sterile n’s 2.984 0.008 Z Peak 0.00008 <0.004 Bhabha scat.

NnPMNS Unitarity sterile n’s

2.92 0.05 

(g+Z_inv)

(g+Z ll)0.001(161 GeV) <0.001 Statistics  

Rb db 0.21629 0.00066 Z Peak 0.000003 <0.000060 Statistics

, small IPHemisphere correlations

ALRD, e3 ,D(T, S )

0.15140.0022

Z peak, polarized 0.000015 <0.000015

4 bunch scheme, > 2exp

Design experiment

MW

MeV/c2D, e3 , e2, D(T, S, U)

80385 ± 15

Threshold (161 GeV) 0.3 MeV <0.5 MeV E_cal &

Statistics QED corections

mtop

MeV/c2Input 173200

± 900Threshold scan 10 MeV <10MeV E_cal &

StatisticsTheory interpretation 40MeV?