The ILC Project
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The ILC Project Karsten Buesser DESY Hamburg Corfu Summer School 06.09.2013 „I hear the roar of a big machine....“ The Sisters of Mercy Programme • Introduction - The International Linear Collider • ILC Accelerator Design • ILC Detectors • Global Context • Outlook Introduction Discovery of a New Boson at 125 GeV 7.2 Mass of the observed boson 27 -1 -1 CMS s = 7 TeV, L = 5.1 fb s = 8 TeV, L = 5.3 fb 0 µ 10 10 (*) 1 ATLAS 2011 - 2012 ± 1σ ATLAS 2011 - 2012 (a) H → ZZ → 4l 1 -1 ± 2σ 1σ -1 s = 7 TeV: ∫Ldt = 4.6-4.8 fb -1 Local p 10 10 -1 Observed s = 8 TeV: ∫Ldt = 5.8-5.9 fb 2σ Bkg. Expected -2 -2 10 2 σ 10 1 10-3 3σ 3 σ -3 -4 10 95% Limit CL on 10 -5 -1 4 σ -4 10 s = 7 TeV: ∫Ldt = 4.8 fb 10 4σ 10-6 s = 8 TeV: ∫Ldt = 5.8 fb-1 Local p-value -5 10-1 (a) CLs Limits 10-7 5 σ 10 0 200 300 400 500 0 10110 115 120 125 130 135 140 145 150 1 -6 (b) H → γγ 10 10-1 5 1 -2 σ -1 Local p 10 2 σ Local p -7 10 10-3 10 3 σ 10-2 2 σ 10-4 -8 10-3 10 10-5 Sig. Expected 4 σ 3 σ -6 10-4 -9 10 Observed 6σ -7 5 σ -5 10 10 10 4 σ s = 7 TeV: ∫Ldt = 4.8 fb-1 Combined10-8 obs. -10 10-6 s = 8 TeV: ∫Ldt = 5.9 fb-1 10 Expected10-9 for SM H (b) 6 σ 10-7 5 σ 10-10 -11 s = 7 ) TeV 0 10110 115 120 125 130 135 140 145 150 µ 2 (*) 10 H → γγ + H → ZZ (c) H → WW → lνlν s = 8 TeV 1 1.5 7σ -1 -12 10 10 Local p 2 σ 116 118 1201 122 124 126 128 130 10-2 10-3 0.5 3 σ mH (GeV) 10-4 4 σ 0 -5 10 2011 Exp. 2011-2012 Exp. -6 2011 Obs. 2011-2012 Obs. Figure 16: The observed local p-value forSignal strength ( -0.5 decay modes with high mass-resolution channels, 10gg -7 • Now have to establish the natureObserved of the 10 -1 5 σ 2012 Exp. s = 7 TeV: Ldt = 4.7 fb -1 -2 ln ( )<1 -8 ∫ and ZZ, as a function of the SM Higgs boson(c) mass. The dashed lineλ µ shows the expected local10 -1 2012 Obs. s = 8 TeV: ∫Ldt = 5.8 fb observed boson! 10-9 p-values for a SM Higgs boson with a mass110mH 150. 200 300 400 500 110 115 120 125 130 135 140 145 m [GeV] mH [GeV] H Figure 7: Combined search results: (a) The observed (solid) 95% CL Figure 8: The observed local p0 as a function of the hypothesized ( ) limits on the signal strength as a function of mH and the expec- Higgs boson mass for the (a) H ZZ ∗ 4",(b)H γγ and (c) suggested in Ref. [111], and corresponds to 4.6 s (4.5 s). These results confirm the very( low) → → → tation (dashed) under the background-only hypothesis. The dark H WW ∗ "ν"ν channels. The dashed curves show the expected probability for an excess as largeand or light larger shaded than bands that show observedthe 1σ and to2σ ariseuncertainties from on a the statisticallocal→ fluctu-p under→ the hypothesis of a SM Higgs boson signal at that mass. ± ± 0 ation of the background. The excessbackground-only constitutes expectation. the observation (b) The observed of (solid) a new local particlep0 as a withResults a mass are shown separately for the √s = 7TeVdata(dark,blue),the function of mH and the expectation (dashed) for a SM Higgs boson √s = 8TeVdata(light,red),andtheircombination(black). near 125 GeV, manifesting itselfsignal in decays hypothesis to (µ two= 1) photons at the given or mass. ZZ. (c) TheseThe best-fit two signal decay modes in- dicate that the new particle is astrength boson;µ ˆ as the a function two-photon of mH.Thebandindicatestheapproximate decay implies that its spin is different from one [129, 130]. 68% CL interval around the fitted value. H WW( ) eνµν channels combined is 4.9 σ,andoc- 7.2 Mass of the observed boson → ∗ → curs at mH = 126.5GeV(3.8σ expected). provide fully reconstructed candidates with high reso- The mass mX of the observed boson is determined using the gg and ZZ decay modes, with The significance of the excess is mildly sensitive to the former dominating the precisionlution of in invariantthe measurement. mass, as shown The in calibration Figures 8(a) of and the energy scale 8(b). These excesses are confirmed by the highly sen- uncertainties in the energy resolutions and energy scale in the gg decay mode is achieved with reference to the known Z boson mass, as described sitive but low-resolution H WW( ) "ν"ν channel, as systematic uncertainties for photons and electrons; the → ∗ → in Section 5.1. There are two mainshown sources in Fig. of 8(c). systematic uncertainty: (i) imperfect simulationeffect of the muon energy scale systematic uncertain- of the differences between electrons and photons and (ii) the need to extrapolate fromties ism negligible.Z to The presence of these uncertainties, The observed local p0 values from the combination mH 125 GeV. The systematic uncertainties are evaluated by making comparisonsevaluated between as described in Ref. [138], reduces the local ⇡ of channels, using the asymptotic approximation, are data and simulated samples of Z ee and H gg (mH = 90 GeV). The two uncertainties,significance to 5.9 σ. shown! as a function! of mH in Fig. 7(b) for the full mass which together amount to 0.5%,range are assumed and in Fig. to 9 for be the fully low correlated mass range. between all the ggTheevent global significance of a local 5.9 σ excess any- categories in the 7 and 8 TeV data. For the ZZ 4` decay mode the energy scale (for electrons) The largest local! significance for the combination of where in the mass range 110–600GeV is estimated to and momentum scale (for muons)the are 7 and calibrated 8 TeV data using is found the leptonic for a SM decays Higgs boson of the Z boson,be approximately with 5.1 σ,increasingto5.3σ in the range an assigned uncertainty of 0.4%.mass hypothesis of mH=126.5 GeV, where it reaches 110–150GeV, which is approximately the mass range 6.0 σ,withanexpectedvalueinthepresenceofaSM not excluded at the 99% CL by the LHC combined SM Figure 17 shows the two-dimensional 68% CL regions for the signal strength s/s versus m Higgs boson signal at that mass of 4.9 σ (see also Ta- SM Higgs bosonX search [139] and the indirect constraints for the three channels (untagged gg, dijet-tagged gg, and ZZ 4`). The combined 68% CL ble 7). For the 2012 data alone,! the maximum lo- from the global fit to precision electroweak measure- contour shown in Fig. 17 assumes that the relative event yields( ) among the three channels are cal significance for the H ZZ ∗ 4", H γγ and ments [12]. those expected from the standard model, while the overall→ signal→ strength→ is a free parameter. 18 To extract the value of mX in a model-independent way, the signal yields of the three channels Hadron and Lepton Colliders p p e+ e- • Proton (anti-) proton colliders: • Electron positron colliders: • Energy range high (limited by • Energy range limited (by RF bending magnets power) power) • Composite particles, different • Pointlike particles, well defined initial state constituents and initial state quantum numbers energies in each collision and energies • Difficult hadronic final states • Easier final states • Discovery machines • Precision machines • Precision measurement potential • Discovery potential Hadron or Lepton Colliders pp ! H + X e+e- ! HZ Collider History SUPERSYMMETRY backgrounds from the SM and, more importantly, from SUSY itself. At the LHC, sparticle mass differences can be determined by measuring the endpointsoredgesofinvariantmass spectra (with some assumptions on particle identification within the chains) and this results in a strong correlation between the extracted masses; in particular, the LSP mass can be constrained onlyFuture weakly Lepton [15]. Therefore, Collider only in Requirements specific constrained scenarios with a handful of input parameters, that some elements of SUSY can be reconstructed in the complicated environment of the LHC. • The e+e- cross section drops 700 ~1/s; some t-channel processes + - SPS1a! mass spectrum 100000 ff σ(e e ) [fb] m[GeV] rise logarithmically g˜ 600 t˜ q˜ 2 L ˜b 10000 q˜R 2 WW ˜ 500 b1 • The key parameters are: ZZ ± 1000 0 0 H χ˜0 ± H ,A 4 χ˜ 400 • the right energyχ˜0 window2 tt 3 ˜ t1 HZ • luminosity 100 300 10 + + - 200 ˜ ± - lL τ˜2 χ0 χ µµ χ11 χ ν˜ ˜2 ˜1 1 1 ν˜l τ t1t1 ˜ h0 lR 0 0 100 τ˜1 χ˜0 1 1 χ1 χ 2 s[GeV] 0 0.1 200 350 500 1000 FIGURE 5.1. The spectrum of SUSY and Higgs particles in the benchmark SPS1a! cMSSM point [179] (left) and the production cross sections for various SM and SUSY processes in e+e− collisions as a function of the c.m. energy in this scenario (right). On the other hand, the non–colored SUSY particles (and certainly the lightest Higgs boson) would be accessible at the ILC with a c.m.