Pre-SUSY, Bonn, Gudrid Moortgat-Pick 1 Physics at a future Linear Collider Gudrid Moortgat-Pick Hamburg University, ‘Big’ HEP questions LC technical requirements LC physics in view of LHC results Techniques at the high-energy e + e - collider Summary and some literature for further studies

Sceptical thoughts before…. Many options and ideas for experiments –Most are expensive, some ‘rather’ cheap –Should cost be a criteria? Or diversity of the physics programme? Priority lists are needed –Many lists exist (CERN strategy group, P5, UK roadmaps, German roadmaps…) But big experiments require long term planning –To which extent are physics needs in advance predictable? Particle scales? Physics Models? … Can we really weight today all options? –ILC, SLHC, LHeC, CLIC, ν-fact, DLHC, μ-collider,…. Pre-SUSY, Bonn, Gudrid Moortgat-Pick 2

(My ) Pragmatic approach Physics: what are the ‘big’ questions? –Define steps... ‘physics milestones’ –Identify which models tic which question –Common feature requirements: measure masses, couplings, spin, quantum numbers … ‘verify at quantum level’ Machine: next physics milestone achievable? –Technical requirements for a LC have been defined –Synergy with other experiments –Some degree of flexibility required: ‘the unexpected’ Pre-SUSY, Bonn, Gudrid Moortgat-Pick 3

‘Big’ questions …and possible answers Pre-SUSY, Bonn, Gudrid Moortgat-Pick 4 Shortcomings of the Standard Model Establish electroweak symmetry breaking LC Hierarchy problem? Unification of all interactions? Embedding of gravity Baryon asymmetry in Universe? Dark matter Neutrino mixing and masses Why TeV scale? Protect hierarchy between m weak and m planck Dark matter consistent with sub-TeV scale WIMPs Higgs mass with respect to large quantum corrections:

‘Big’ questions …and possible answers Pre-SUSY, Bonn, Gudrid Moortgat-Pick 5 Shortcomings of the Standard Model Establish electroweak symmetry breaking LC Hierarchy problem? LHC, LC Unification of all interactions? LC Embedding of gravity cosmo,LHC, LC Baryon asymmetry in Universe? v-, cosmo, LHC, LC Dark matter v-, cosmo, LHC, LC Neutrino mixing and masses v-, cosmo-exp. Why TeV scale? Protect hierarchy between m weak and m planck Dark matter consistent with sub-TeV scale WIMPs

‘Big’ questions …and possible answers Pre-SUSY, Bonn, Gudrid Moortgat-Pick 6 Shortcomings of the Standard Model Establish electroweak symmetry breaking LC Hierarchy problem? LHC, LC Unification of all interactions? LC Embedding of gravity cosmo,LHC, LC Baryon asymmetry in Universe? v-, cosmo, LHC, LC Dark matter v-, cosmo, LHC, LC Neutrino mixing and masses v-, cosmo-exp. Why TeV scale? Protect hierarchy between m weak and m planck Dark matter consistent with sub-TeV scale WIMPs

Why a Linear Collider? Key features of the e +e-( and γe, γ γ) collider: –Precisely defined and known cms energy of hard process (machine requirements: low beam energy spread, low beamstrahlung) –Tunable cms energy (machine requirements: flexibility, high luminosity) –Polarized initial beams (machine and detector requirements: –Clean and fully reconstructable events (hadronic, invisible) (detector requirements: jet, lepton reconstruction, full hermiticity) –Moderate backgrounds: no trigger required! rather unbiased physics…. Large potential for direct discoveries and via high precision ! Pre-SUSY, Bonn, Gudrid Moortgat-Pick 7

8 The unique advantage of e+e- Their clean signatures allow precision measurements Sensitive to the theory at quantum level (i.e. contributions of virtual particles, ‘higher orders’)! Such measurements allow predictions for effects of still undiscovered particles, but whose properties are defined by theory. t

At the precision frontier: the LC Pre-SUSY, Bonn, Gudrid Moortgat-Pick 9 ICFA Parameter Group

Synergy effects: 2/09 Questions from early LHC data ( ~10 fb -1 ) ‘Famous’ 3 cases (cf. CERN strategy documents) : –LHC not detected anything –LHC only detected SM-like Higgs –LHC detected some new physics What could the LC do –in first ILC stage of 90 up to 500 GeV? –in LC upgrades? –in multi-TeV CLIC option? Pre-SUSY, Bonn, Gudrid Moortgat-Pick 10

Nothing found at (early) LHC Interpretation for ILC? –‘Top’ physics – indirect searches in bb, cc, l l ( large ED, CI) –ew precision runs from Z-pole data But is then really 500 GeV as first ILC stage needed? –or better 350 GeV? High-lumi Z-factory? Pre-SUSY, Bonn, Gudrid Moortgat-Pick 11

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 12 Physics up to sqrt(s)=500 GeV: top m top = GeV

Top mass Pre-SUSY, Bonn, Gudrid Moortgat-Pick 13 We expect at the LC: From running at tt threshold: Measurement of a ‘threshold mass parameter’’ with high precision: < 20 MeV +transition to suitably defined (short-distance) top-quark mass, e.g. MS mass  δm t exp <100 MeV (dominated by theory uncertainty)

Importance of ‘top’ mass Pre-SUSY, Bonn, Gudrid Moortgat-Pick 14

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 15 EW precision measurements GigaZ option at the ILC: –high-lumi running on Z-pole/WW –10 9 Z in days of running –Needs machine changes (bypass in the current outline) High precision needs polarized beams Provides measurement of sin 2 θ W with unprecedented precision!

Electroweak precision data Pre-SUSY, Bonn, Gudrid Moortgat-Pick 16

Pre-SUSY, Bonn, Gudrid Moortgat-Pick17 Measuring the ew mixing angle Measuring the A FB, A LR can be interpreted as measuring sin 2 θ W LEP result: sin 2 θ W = ± SLC result: sin 2 θ W = ± –Discrepancy between A FB and A LR -> impact on Higgs tests !

m W vs. central value sin 2 θ eff Pre-SUSY, Bonn, Gudrid Moortgat-Pick 18 → Consistent with SM and SUSY

m W vs. SLD-value sin 2 θ eff Pre-SUSY, Bonn, Gudrid Moortgat-Pick 19 → not consistent with the SM

m W vs. LEP -value sin 2 θ eff Pre-SUSY, Bonn, Gudrid Moortgat-Pick 20 → not consistent with neither SM nor SUSY

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 21 Blondel scheme for GigaZ

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 22 Relevance in worst case scenarios Hints for new physics in worst case scenarios : – Only – No hints for SUSY Deviations at Zpole – Hints for SUSY Discrepancy

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 23 SUSY Constraints from GigaZ

What’s needed? ….polarized beams Pre-SUSY, Bonn, Gudrid Moortgat-Pick 24 e+ polarization is an absolute novelty! Expected P(e+) ~ 60%

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 25 Polarized positrons

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 26 Polarized cross sections in general Polarized cross sections can be subdivided in: σ RR, σ LL, σ RL, σ LR are contributions with fully polarized L, R beams. In case of a vector particle only (LR) and (RL) configurations contribute:

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 27 Effective polarization Effective polarization:

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 28 Relation between P eff and A LR How are P eff and A LR related? That means: With pure error propagation (and errors uncorrelated), one obtains: With

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 29 Gain in accuracy due to P(e+)

Only SM-like Higgs at early LHC Interpretation for ILC –best-suited for studying Higgs properties –precise determination of couplings: determination of Hbb is crucial! –distinction: SM- versus SUSY Higgs –t t H and trilinear Higgs coup. challenging But is then really 500 GeV as 1st step needed? –Optimize running scenarios (tunable energy, polarization) Pre-SUSY, Bonn, Gudrid Moortgat-Pick 30

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 31 Determination of Higgs properties LHC input for optimal choices of running scenarios ! → Higgs spin

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 32 Higgs physics at ILC Higgs Strahlung WW fusion

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 33 Higgs mass Use Higgsstrahlung: due to well-known initial state and well-observed Z-decays –Derive Higgs mass independently from decay ! –Only possible at a LC!

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 34 Higgs properties

Something ‘new’ detected at early LHC SUSY-like signals (many tics at big questions!) –At least partial spectrum accessible at ILC –‘light’ SUSY consis- tent with precision fits Extra gauge bosons and/or large extra dimensions (some tics at big questions!) –High precision in indirect searches allow model distinction and couplings determination Pre-SUSY, Bonn, Gudrid Moortgat-Pick 35

Goals and features at a LC Direct production up to kinematical limit –tunable energy: threshold scans ! Extremely clean signatures –polarized beams available –impressive potential also for indirect searches via precision Unraveling the structure of NP –precise determination of underlying parameters –model distinction through model independent searches High precision measurements –test of the Standard Model (SM) with unprecedented precision –even smallest hints of NP could be observed Discovery of new phenomena via high energy and high precision! Pre-SUSY, Bonn, Gudrid Moortgat-Pick 36

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 37 Discovery of SUSY

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 38 SUSY mass measurement im continuum

Pre-SUSY, Bonn, Gudrid Moortgat-Pick39 Masses and spin via threshold scans Assume LHC provides mass of a SUSY particle:

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 40 Mass measurement of the LSP mass

Properties of WIMP’s: mass+spin Reconstruct the `invisible’: –via recoil mass distribution Pre-SUSY, Bonn, Gudrid Moortgat-Pick 41

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 42 Verify SUSY properties at ILC

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 43 Slepton `chiral’ quantum numbers

Sensitivity to heavy SUSY particles Challenging scenarios: –multi-TeV sfermions, only few light gauginos (‘focuspoint-like’) also very difficult for LHC … –sensitivity to heavy sneutrinos in t-channel Pre-SUSY, Bonn, Gudrid Moortgat-Pick 44 Suitable observable: Precise measurement of asymmetry copes with multi-TeV particles !

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 45 Free parameters in the MSSM

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 46 SUSY parameter determination Exploit just light SUSY particle spectrum at ILC and determine the parameters (see below) Combine it with LHC results via prediction of heavier states

SUSY multi-parameter fits: LHC Pre-SUSY, Bonn, Gudrid Moortgat-Pick 47

SUSY multi parameter fits: LHC+ILC Pre-SUSY, Bonn, Gudrid Moortgat-Pick 48

Aside: Disney World of SUSY scenarios Pre-SUSY, Bonn, Gudrid Moortgat-Pick 49 Often (ab)used plots: 13 SUSY ‘benchmarks’ scenarios out of millions … really a true representative choice ? Consistent with current bounds? heavy masses often mass degenerated: no resolution (beamstrahlung!) has been taken into account… really a reliable ‘counting’ ? experimental verification of properties not studied … really a useful basis for future decisions? Pure particle counting as justification of the energy scale -but what’s about the achievable precision? -but what can be learned via precisions observables at lower energies? (GigaZ, A FB,…) General feature: in order to be consistent with existing experimental bounds, e.g. with g μ -2:  a few gauginos have to be rather light ! ….s ufficient as 1.step

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 50 Indirect searches: extra dimensions

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 51 Extra dimensions

Pre-SUSY, Bonn, Gudrid Moortgat-Pick52 Physics up to 1 TeV Direct search for extra dimensions

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 53 Direct search for extra dimensions

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 54 Multi-TeV option at CLIC - Higgs

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 55 Summary e+e- physics (LEP, SLC, B-factories) has been the core of high precision physics over the last decade We expect a fascinating future in the next years: LHC will shed first light on the mysteries of EW symmetry breaking Rich program and high physics potential of a LC: The LC will unravel the new physics and enter a new precision frontier ! –Thresholds scans and polarized beams mandatory Staged approach of a LC seems reasonable… Stay tuned for the LHC and the (I)LC!

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 56 Some literature ILC physics: TESLA TDR, physics part hep-ph/ ILC RDR, arXiv: LHC/ILC interplay: G. Weiglein, Phys. Rept. 426, 47 (2006), hep-ph/ Polarization+Spin: GMP, POWER report, Phys. Rept. 460,131 (2008), hep-ph/ webpage:

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 57 Beam polarization at colliders

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 58 Electron polarization

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 59 How to describe the spin?

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 60 Remarks about couplings structure Definition: Helicity λ=s * p/|p| ‘projection of spin’ Chirality = handedness is equal to helicity only of m=0!

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 61 General remarks, cont.

Pre-SUSY, Bonn, Gudrid Moortgat-Pick 62 Background suppression

Dark matter analysis at LC High precision in parameter determination required for reliable DM prediction –Parameter ranges where abrupt changes of neutralino character happen –Precise determination of M 1,M 2 ….required Pre-SUSY, Bonn, Gudrid Moortgat-Pick 63 V. Morton-Thurtle