F. Richard LAL

Recent update on the world-wide LC Project

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François Richard LAL/Orsay

9th Franco-Italian meeting on B physics at LAPP, Annecy February 18-19 2013

Introduction There exist a technically well established

scenario to build right away a LC (and its detectors) reaching up to ECM=1 TeV

There are solid physics arguments to believe that such a machine can achieve major physics results i.e. provide a decisive test of the SM

The main unknown, in the present international context, is whether our developed nations are willing to commit the large resources needed to build globally such a machine

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Process to build a world-wide LC At the end of LEP2 it was felt that the next project

should not only go well beyond LEP energy but also allow for X100 luminosity and beam polarization

500 GeV was considered as the minimal energy range to cover the light Higgs (ttH, ZHH) and the top program (couplings and mass measurement)

Accordingly a consensus (OECD meeting of Minister of science) emerged in 2004 to state that the next large collider after LHC should be an e+e- collider which should be a WORLD WIDE machine (TESLA, mainly led by Germany could not fly)

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The Present Situation Japan/Asia logically becomes the next contender given

that CERN is over-booked with LHC commitments It should be stressed that the commitment of Japan,

very cautious as usual, has recently gained momentum with strong support from politicians (including the new prime minister) and industry

Two sites are being officially studied The discovery at CERN of a ‘H-like’ candidate has

considerably boosted the process A window of opportunity for HEP that our

community is ready to exploitF. Richard 4

Erice and ILC (draft version) Gobalisation is emphasized There is a strong scientific case for an electron-positron

collider, complementary to the LHC, that can study the properties of the Higgs boson and other particles with unprecedented precision and whose energy can be upgraded. The Technical Design Report of the International Linear Collider(ILC) has been completed, with large European participation. The initiative from the Japanese particle physics community to host the ILC in Japan is most welcome, and European groups are eager to participate

Europe looks forward to a proposal from Japan to discuss a possible participation.

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WORLD MAP OF HEP

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2006

2012

The WW effort on ILC

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Physics aspects What could be our future? The present picture can be tentatively summarized by

saying that we can imagine 3 types of scenarios: 1 The present standard theory valid up to the Planck

scale (DM, Baryogenesis, EW phase transition ?) 1 cannot be known a priori and only very precise

measurements allow to ‘close’ the model (GigaZ, superB)

2 A SUSY scenario emerging at a TeV scale 2 is difficult to cover completely with LHC given the

possibility of light SUSY particles ~degenerate with the LSP while ILC offers cleaner techniques to deal with this

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Scenarios 3 A composite scenario with its various avatars

(Technicolor, extra dimensions, little Higgs…) 3 usually predicts new heavy bosons and quarks but

without the guarantee that they could be observed at LHC

We should therefore be prepared for a scenario where the new signals are not directly accessible to LHC in which case only precision measurements are left to indirectly predict the new phenomena as was the case in the past (W/Z masses, existence of 2nd and 3d generations, c mass, top mass, Higgs mass)

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Size of deviations After LHC results most scenarios predict small

deviations (<10%) and it will not be easy for LHC to indirectly demonstrate (>5 sd) the existence of phenomena beyond the SM and, moreover, to find a full set of EW observables to pin down the new theory to guide our choice of the next colliders 

This mission is clearly given to e+e- colliders (and b factories) which, in many instances, can extend the domain of vision to energy scales reaching beyond 10 TeV

I will illustrate this with Higgs and top precision measurements

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Higgs at ILC

250 GeV gHZZ 1% s>>b

CP (small admixture)

Spin 0 or 2 ?

Brinv <1%

BR(ccbar) 7%

≥ 500 GeV G(WW)+BR(WW) -> GT 6%

crucial to extract width in a model independent way ttH dgt/gt~5% H->2H d /l l~10-20% ongoing analysis (7 sd significance)

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Why so precise ?

ILC500 vs LHC 3000 fb-1

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M. Klute et al. http://arxiv.org/pdf/1301.1322.pdf

Top mass

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G. Degrassi et al arXiv:1205.6497

dMt<100 MeV dGt=22 MeV

Top couplings stt+ AFBt+Lepton helicity

slope with Pe-,e+=±0.8,∓0.3 provide 6 observable from which g/Z form factors are extracted separately

(g-2)t can be measured (~as/p) to 10%

CPV form factors are also accessible

These measurements allow to test extra dimensions up to 50TeV F. Richard 15

What can we expect in the next years ?

TDR for the 500 GeV machine : done with costing shown this month in Vancouver (ICFA meeting)

Global organization ILC+CLIC with one project leader under ICFA: done (L. Evans)

A worldwide political agreement, G20 type, is needed: the hidden sector that we cannot control

First step will be the Japanese expression of interest but, in my view, this can only happen with positive signs from the 2 other regions

It is essential that the community becomes aware of this aspect which conditions the future of our field

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Time scale Given the time scale, we need to launch the

ILC right now to be in phase with the next ‘energy frontier’ machine

To understand this last point, imagine that after ‘freezing’ the LC project (and therefore wasting the present effort, discouraging the Japanese offer and dispersing the community of physicist & engineers), we get stuck at LHC without any clear message indicating the parameters of the next machine…

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Detectors The proposed detectors, ILD & SiD, have required a

formidable R&D effort again only conceivable as a world-wide organisation

Typically ~CMS type but with much more ambitious performances made possible with the ‘friendly’ environment of ILC: e.g. a TPC detector becomes possible, thin Si detectors <20%X0 in from ECAL, very thin µvertex detectors close by (<2cm) to the interaction point etc…

2 of them scientifically highly desirable and efforts with machine experts have resulted in a realistic push pull set up

~same detectors for CLIC with special features

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Some features Multijet topologies like tt ttH and ZHH demand high performance

detectors far beyond LEP2: Full coverage for tracking (including tagging) , calorimetry, µ/e

identification Resolution on jets ~3% e.g. for W/Z separation PFLOW method requiring high granularity of calorimetry and large

BR² (B in SiD R in ILD) Excellent momentum resolution for recoil mass in Z->µµ(ee)+H Sophisticated b/c tagging capabilities (b charge determination for

AFBt and AFBb) Luminosity and polarization at the 0.1% level All of these features are necessary and optimized at variance

between SiD and ILD

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sE/E = 0.6/ÖE sE/E = 0.3/ÖE

Construction aspects Cost drivers are mainly the magnet (+return yoke) and

calorimetry CMS allows a safe extrapolation of the magnet while

realistic calorimetry prototypes are being developed Typical cost is ~500 M$/detector including MY (will be

delivered soon) but not the R&D part ~10% of the cost of the machine but of strategical

importance: Some experts even think that the time of construction will be conditioned by our ability to construct the detectors

When ? The answer given at Krakow is: before 2030 F. Richard 20

Conclusions The worldwide community has been preparing for

a LC since many years and is ready for a timely decision

The impact of the ‘H-like’ candidate discovery should be used to trigger this decision

Japan is expressing strong interest to build ILC in a worldwide framework (Japan cannot do it alone)

The future of our field would be strongly reinforced if this happens and therefore we should do our best to make it happen

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F. Richard

BACK UPS

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ILD overviewReturn Yoke

Coil

Forward components(QD0 magnet – FCals)

HCal

ECal

TPC

Beam line

VTXSITFTD

ETD

SET

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ILC 500 GeV (RDR 2006)

Components 4.15 B

CF 2.47 B

SummaryRDR Costs

Total Value Cost$4.65B Shared

+$1.67B Host

+17 106 manhours

(in-house labor)

Impact parameter resolutionImpact parameter resolution

ILC

Belle ATLAS

LHCb

Alice

Jet energy resolution

Jet Energy (GeV)

Jet

En

erg

y R

eso

luti

on

s/E

jet (%

)

PFA simulationE 13 26 39 52 65 78 91 104117130143156169182195208221234247

-4.16333634234434E-17

0.05

0.1

0.15

0.2

0.25

0.3

ILC goal

ATLAS simulationH1 measured

ALEPH measured

CDF measured

DREAM measured

Invisible width

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http://arxiv.org/ftp/hep-ph/papers/0703/0703173.pdf

ILC250/500 vs LHC 3000 fb-1

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M. Klute et al. http://arxiv.org/pdf/1301.1322.pdf

ILD DBD

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GigaZ

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Composite Higgs

F. RichardG. Giudice et al hep-ph/0703164 31

Discrimination between models

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P. Doublet, PhD-Thesis

An other observable In the rest system of the top quark the lepton angular

distribution is given by:

where alep=1 l=1 for tR and -1 for tL (NB: helicities)

The angle qhel is measured in the rest frame of the top quark with the z axis defined by the direction of motion of the top quark in the laboratory

It is easy to reconstruct qhel at a LC Can be done with b jets (ab=-0.4) which are sensitive

to tbW anomalous couplings F. Richard 33

1 cos1

cos 2f hel

hel

d

d

The top mass For many years LC studies have shown that a

threshold scan can provide a top mass with <100 MeV accuracy (including theory)

LC can also measure very precisely mt and Gt (~20 MeV) as a fit to an invariant mass distribution but theorists cannot relate easily this measurement to a well defined quantity to deduce the EW parameter

LHC will suffer from this problem and it is proposed to use other observables (xsection, gluon radiation)

-> Not clear that an error <1 GeV can be reached when one includes theory uncertainties

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What is needed ? The evolution of l in the Higgs potential towards the high

energy scale is controlled by mt and as As noted by several authors with mh=126 GeV l tends to

come very close to the stability limit (0) at high energy which may have some interesting cosmological consequences

mH=126 GeV was ‘predicted’ assuming SM+gravity valid up to arbitrary energies also implying l(Planck)=0 arXiv:0912.0208 M. Shaposnikov & C. Wetterich

To assess such ideas one will ultimately need an unambiguous (QCD) and precise (<200 MeV) determination of mt which seems to require a LC

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F2A form factor One has:

One can construct CPV observables with optimized sensitivity (W.Bernreuther et al hep-ph/9511256 & 9602273)

Example:

Where where one uses the direction of the anti-top and of the positron coming from the top. One then defines a CP image of this observable O- (replace the first vector by –kt the second by –le- and draw the difference O+ - O-. The quality of the estimator depends on the dispersion of this distribution.

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1 5 1 2 5 22ttZ Z Z Z Z

V A V At

q qie F F F F

m

Ret e

O k l z

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TOTAL 1650

Japan http://www.policycouncil.jp/en/pdf/prop02/2nd_recommendations.pdf

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