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TLEP: a first step on a long vision for HEP. M. Koratzinos Univ. of Geneva On behalf of the TLEP study group Athens, 6 December 2013. C ontents. The physics case Circular collider challenges TLEP implementation TLEP physics reach TLEP design study.

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Tlep a first step on a long vision for hep

TLEP: a first step on a long vision for HEP

M. Koratzinos

Univ. of Geneva

On behalf of the TLEP study group

Athens, 6 December 2013

C ontents

  • 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

The physics case
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

Precision needed
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 TeVand 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)

Circular colliders
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?)

Major limitations
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)

Energy reach
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


Energy reach1
Energy reach

Assumptions: 20mV/m, 90% dipole fill factor.

What is plotted is the ratio of RF length to total arc length

TLEP175 sits comfortably below the 1% line

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

Luminosity of a circular collider
Luminosity of a circular collider

Luminosity of a circular collider is given by

Which can be transformed in terms of



Luminosity of a circular collider1
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 σzand )

Total power
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)

Machine radius
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]

Beam beam parameter
Beam-beam parameter

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


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

Maximum beam beam
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

Beta and hourglass
Beta* and hourglass

We 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

Self-consistentσz at different energies for TLEP

L uminosity of a circular collider
Luminosity of a circular collider

  • 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


  • 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]

Beamstrahlung 2
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

Beamstrahlung limitation
Beamstrahlung limitation

Plot on left is if we run with a value of the beam-beam parameter of 0.1

Above ~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

A specific implementation tlep
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)


Possible TLEP location

Other tunnel diameters
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)

Tlep implementation
TLEP implementation

  • At 350 GeV, beams lose 9 GeV / turn by synchrotron radiation

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

      • Much less than ILC(8000 9-cell cavities@ 31 MV/m)

      • Length ~900 m, similar to LEP (7 MV/m)

    • 200 kW/ cavity in CW : RF couplers are challenging

      • Heat extraction, shielding against radiation, …

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

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

      • 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

    • Need efficient top-up injection

BNL 5-cell 700 MHz cavity

RF Coupler


A. Blondel

F. Zimmermann

Superkekb a tlep demonstrator
SuperKEKB: a TLEP demonstrator

  • SuperKEKBwill 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%

  • Tlep cost very preliminary estimate
    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$ ]

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

    Absolutely Preliminary

    Not endorsed by anybody

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


    (1): J. Osborne, Amrupstudy, June 2012

    (2): Extrapolation from LEP

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

    80-100 km tunnel

    (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);

    Power consumption
    Power consumption

    Highest consumer is RF:

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

    Total power consumption for 350GeV running:

    • CERN 2010 power demand:

    • Full operation 220MW

    • Winter shutdown 50MW

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

    A note on power consumption
    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)

    Tlep parameter set
    TLEP parameter set

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

    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.

    Revised (taking into account BS) but similar

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

    Luminosity of tlep
    Luminosity of TLEP

    TLEP : Instantaneous lumi at each IP (for 4 IP’s)

    Instantaneous lumi summed over 4 IP’s

    Z, 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”

    Upgrade path
    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 case1
    The physics case

    Our 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” authors)

    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. CastanedaMiranda, 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

    Tlep possible physics programme
    TLEP : Possible Physics Programme

    • Higgs Factory mode at √s = 240 GeV: 5+ years

      • Higgs boson properties, WW and ZZ production.

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

    • Top Threshold scan at √s ~ 350 GeV: 5+ years

      • Top quark mass, width, Yukawa coupling; top quark physics; more Higgs boson studies.

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

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

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

        • Continuous transverse polarization of some bunches for precise Ebeam calibration

    • WW threshold scan at √s ~ 161 GeV: 1-2 years

      • Get 108 W decays; Measure the W mass; Precise W studies.

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

    • Longitudinally polarized beams at √s = mZ: 1 year

      • Get 1011 Z decays, and measure ALR, AFBpol, etc.

        • Polarization wigglers, spin rotators

    • Luminosity, Energy, Polarization upgrades

      • If justified by scientific arguments (with respect to the upgrade to VHE-LHC)

    Higgs the situation today
    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

    Tlep as a mega higgs factory 1
    TLEP as a Mega-Higgs Factory (1)

    Unpolarized cross sections

    PJ and G. Ganis

    Z → All

    Z → nn

    Tlep as a mega higgs factory 2
    TLEP as a Mega-Higgs Factory (2)

    • Example : e+e- → ZH → l+l- + anything

      • Measure sHZSummary of the possible measurements :

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



    From P. Azzi et al.




    e-, m-



    • gHZZ

    e+, m+


    1 year

    1 detector

    Global fit of the higgs couplings
    Global fit of the Higgs couplings

    • Model-independent fit

      • NB : Theory uncertainties must be worked out.

    M. Bachtis


    Snowmass 2013

    Tlep as a mega top factory
    TLEP as a Mega-Top Factory


    • Scanning the tt threshold at √s ~ 350 GeV

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

        Luminosity E Spectrum Effect on top threshold

      • No need to measure the luminosity spectrum @ TLEP reduced mtopuncertainty

      • Slightly larger cross section @ TLEP

      • Beam energy calibration from e+e-→ WW and mW; as from Z and W leptonic decays.

      • Still need to work on theoretical predictions (40 MeV uncertainty on mtop)

    M. Zanetti




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

    Stat. only

    Tlep as a tera z and oku w factory 1
    TLEP as a Tera-Z and Oku-W Factory (1)

    • TLEP repeats the LEP1 physics programme every 15 minutes

      • Added value: Transverse polarization up to the WW threshold (LEP: up to 60GeV)

        • Exquisite beam energy determination with resonant depolarization

          • Up to 5 keV precision – unique at circular e+e- colliders

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

      • Measure the number of neutrinos

        • From the peak cross section at the Z pole – Luminosity measurement is a challenge

        • From radiative returns to the Z from the WW threshold – e+e- → gnn

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


    No beamstrahlung

    is a clear advantage

    Tlep a first step on a long vision for hep

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

    • 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-Z

      • Caution : TLEP will have 5×104 more Zsthan LEP - Predicting achievable accuracies with 250 times smaller statistical precision is difficult

      • The study is just beginning : errors might get better with increasing understanding

      • Much more to do at the Zpeak e.g., asymmetries, flavour physics (>1011b, > 1011 c, > 1010 t), rare Z decays, …

    • Measurements with Oku-W

      • 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

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

    • Measurement with longitudinal polarization

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

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

    NB: ILC limited to a factor > 30 larger errors

    Ewsb precision tests at tlep teaser
    EWSB Precision tests at TLEP: Teaser

    Warning : indicative only.

    Complete study being done

    mH=126 GeV




    Very stringent SM closure test.

    Sensitivity to weakly-interacting

    BSM Physics at a scale > 10 TeV

    Tlep design study provisional structure
    TLEP Design Study: provisional Structure

    26 Working Groups: Accelerator / Experiment / Phenomenology

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

    Tlep design study people
    TLEP Design Study: People


    • 295 subscribers from 23 countries (+CERN)

      • Distribution reflects the level of awareness in the different countries

        • 4 physicists from Greece: subscribe at !

    Tlep a first step on a long vision for hep



    The twopillars: pp and e+e-

    mandate is to deliver full CDR for both machines

    with an extendedcostreview

    Tlep a first step on a long vision for hep

    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 presentlyon the market.

    First look at The Physics Case of TLEP

    arXiv:1308.6176v2 [hep-ex] 22 Sep 2013

    Tlep and fcc in the news
    TLEP and FCC in the news

    FCC front-page news in the CERN bulletin:

    Tlep and fcc in the news ii
    TLEP and FCC in the news II

    …meanwhile in the same issue:

    Our web page
    Our web page


    • Last event : Sixth TLEP workshop 16-18 October 2013

    • Joint VHE-LHC + TLEP kick-off meeting 12-15February 2014


    • 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.

    Thank you


    Thank you


    • 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

    *: arXiv:1203.6563



    • 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


    • 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

    Beamstrahlung energy dependence
    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

    European strategy r ecommendations
    European Strategy recommendations

    • High-priority large-scale scientific activities

      • Second-highest priority, recommendation #2

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

    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 energyfrontier 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-positron

    machine 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 e+e-machine (TLEP) reaching energies up to 350 GeV with high luminosity.

    The tlep tunnel
    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

    Global fit of the higgs couplings 2
    Global fit of the Higgs couplings (2)

    • Model-dependent (seven-parameter) fit a-la-LHC

      • Assume no exotic Higgs decays, and kc = kt

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

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

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

      • Much theoretical progress is needed to reduce accordingly theory uncertainties

    HL-LHC : One experiment only

    … CMS Scenario 1

    CMS Scenario 2

    CMS, July 13

    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)

    Tlep as a mega higgs factory 3
    TLEP as a Mega-Higgs Factory (3)

    • Determination of the total width

      • From the number of HZ events and of ZZZ events at √s = 240 GeV

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




    Note : mm collider

    DGH/GH ~ 5%

    Higgs physics with s 350 gev 1
    Higgs Physics with √s > 350 GeV ? (1)

    • Signal cross sections in e+e- collisions

    • Measurements at higher energy

      • √s > 350 GeV does not do much for couplings to c, b, g, Z, W, g, m and Gtot. (slide 15)

        • Invisible width best done at √s = 240 GeV

      • The ttH coupling benefits from higher energy

        • TLEP 350 : 13%

        • ILC 500 : 14% ; ILC 1 TeV : ~4% ; CLIC : ~4%

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

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




    Higgs physics with s 350 gev 2
    Higgs Physics with √s > 350 GeV ? (2)

    • Measurements at higher energy (cont’d)

      • 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

    • Summary

      • For the study of H(126), the case for e+e- collisions above 350 GeV is not compelling.

        • Astronger motivation will exist if a new particle found (or inferrred) at LHC

          • IF e+e- collisions can bring substantial new information about it

    J. Wells et al.


    Snowmass, Aug 13


      • 0.5 ab-13 ab-11 ab-1 3 ab-12 ab-1 3 ab-1