Physics at the ILC. Ariane Frey, MPI München 38. Herbstschule Maria Laach Ariane Frey, MPI München

Transcription

1 Physics at the ILC Beyond the Standard Model: Supersymmetry Extra Dimensions Heavy Z, Z, Strong EWSB Precision Physics (top, W, ) CLIC top, W LHC ILC Synergy Ariane Frey, MPI München 1

2 Higgs Profile Use precision to check whether it is the SM Higgs or signs of new physics beyong the SM 2

3 Higgs - Global Fits Interpretation of branching ratio and cross section measurements in global fits (HFITTER) %-level accuracy sensitivity beyond SM 3

4 Excellent detector resolution helps! 4

5 SUSY Higgs Bosons In MSSM two complex Higgs doublet fields needed (cancellation of triangle anomalies) Minimal possibility: two doublets (weak isospin ±1) 5 physical Higgs bosons: h,h A H ± neutral, CP-even neutral, CP-odd charged Masses at tree-level predicted as function of m A and tanβ but large rad. corrections (top, stop) m h < 135 GeV 5

6 SUSY Higgs at LHC To prove the structure of the Higgs sector, the heavier Higgs bosons have to be observed either directly or through loop-effects. Direct observation difficult in part of parameter space at LHC What s possible at a Linear Collider? 6

7 SUSY Higgs Production at ILC Production processes: ee + ee + ee + ee + ee hz β α HA 2 ~sin ( ) HZ β α ha HH ~cos ( ) Most challenging: decoupling limit sin 2 (β-α) 1, m A large h becomes SM like H/A/H ± heavy and mass degenerate γγ h,h,a γγ HH + 7

8 SUSY Higgs Bosons Very clear signal in HA bbbb MeV mass precision due to kinematic fit drawback: pair production mass reach ~ s / 2 Example for m H =250 GeV / m A =300 GeV at s = 800 GeV: s =800 GeV m A =300 GeV m H =250 GeV Reach extended into the LHC wedge region ΔM/M = % with 500 fb -1 8

9 Typical SUSY spectrum well measurable at LHC precise spectroscopy at LC 9

10 Supersymmetry - Task of LC different SUSY breaking mechanisms yield different spectra: 10

11 Supersymmetry - Task of the LC After discovery, the task is to reveal the underlying theory of SUSY breaking. The LC can do this by precision measurements of the masses and properties of the accessible part of the spectrum is it really SUSY? how is it realized? (particle content) MSSM, NMSSM, how is it broken? measure as many of the >100 parameters as possible measure them as precisely as possible -> extrapolation to high scale Note: successfully fitting the parameters of a constrained model to the observations is a necessary but not a sufficient test of the model. 11

12 This will be fun SUSY Production at ILC cross sections in the fb range o( ) events to disentangle this chaos the various LC options, in particular - tunable s - tunable beam polarisation are vital!

13 Example: Charginos Sparticle Mass precision 13

14 Example: Sleptons Pair-production Examples: γ/z %l + L/R %l L/R E - E + Simple two-body kinematics and beam-constraint allow for mass measurement of both slepton and lightest neutralino 14

15 SUSY - Dark Matter If SUSY LSP responsible for Cold Dark Matter, need accelerators to show that its properties are consistent with CMB data - Future precision on Ωh 2 ~ 2% (Planck) match this precision! - WMAP points to certain difficult regions in parameter space: Δ M= M M χ small l % 0 1 e.g. smuon pair production at 1TeV only two very soft muons! need to fight backgrounds 15

16 LSP Dark matter candidate Need to measure LSP mass, composition and couplings!! 16

17 SUSY cross checks 17

18 Selectron Couplings Symmetry of SUSY 18

19 With a little help from my friends LHC ILC SUSY cascade decay at LHC Precise measurement at ILC 19

20 SUSY Global Fit LHC ILC 20

21 SUSY Global Fit LHC ILC Gaugino mass unification S-matter unification 21

22 Extra Dimensions Completely alternative approach to solve hierarchy problem: There is no hierarchy problem Suppose the SM fields live in normal 3+1 dim. space Gravity lives in 4 + δ dimensions δ extra dimensions are curled to a small volume (radius R) 22

23 Extra Dimensions cross section for anomalous single photon production Exclusion limits (95%CL) Discovery (5 σ) 500 fb 500 GeV, 1000 fb 800 GeV 23

24 Warped Extra Dimensions gravity at normal (SM-like) strength SM brane gravity appears weak on SM brane (in our world) due to exponentially warped metric in 5 th dimension 5 th dimension φ might observe spectacular KK-excitations of the graviton + graviscalar excitations ( Radions ) which mix with the Higgs and modify its couplings + mass 24

25 Extra Dimensions Range of predictions for models with XD Effect on each particle exactly the same size! 25

26 Discovery through precision Precision measurements of SM processes are a telescope to higher scale physics Example Higgs Top quark Z and similar vector resonances Alternative EWSB etc. 26

27 Top quark 27

28 Top quark mass 28

29 Where the top mass comes into play predictions of EW parameters: Light Higgs mass prediction in SUSY: Prediction of DM density Δm H /Δm t ~ 1! 29

30 Top Yukawa Coupling - need highest energy - heaviest quark surprises? - small cross section - complicated final state σ~g 2 tth - analysis in bb and WW decay - huge and complicated backgrounds (ttww is a 10-fermion final state) - b-tagging crucial to suppress bkg. and reduce combinatorial bkg. 30

31 Top Yukawa Coupling Result: 31

32 Top Yukawa Coupling LHC is sensitive to top Yukawa coupling of light Higgs through tth production. LC BR measurement (h bb and h WW) turns the rate measurement into an absolute coupling measurement (LC can only do it at high energy (> 800 GeV)) LHC ILC 32

33 Giga Z running 33

34 Improvement in EW parameters 34

35 If no Higgs boson(s) found. 4π 2 divergent W L W L W L W L amplitude in SM at Λ = o (1.2 TeV) GF SM becomes inconsistent unless a new strong QCD-like interaction sets on 2 2 no calculable theory until today in agreement with precision data Experimental consequences: triple gauge couplings deviations in quartic gauge couplings: LC (800 GeV): sensitivity to energy scale Λ: triple gauge couplings: ~ 8 TeV quartic gauge couplings: ~ 3 TeV complete threshold region covered 35

36 New Gauge Bosons (Z ) Heavy Z vector boson motivated by TeV scale remnants of Grand Unified Theories, string theories etc. Examples: Z in SO 10, E 6 LHC: M(Z ) up to ~ 5 TeV ILC: Unlikely to directly produce a Z (Tevatron limits approaching 1 TeV) virtual extension up to 15 TeV measuring its interference with Z,γ exchange (PETRA could measure Z properties without producing Z s) 5σ 95%CL 36

37 New Gauge Bosons (Z ) LHC ILC If Z mass is known (e.g. from LHC) ILC can measure the vector and axial-vector couplings an pin down the nature of the Z If here, related to origin of neutrino masses If here, related to origin of Higgs If here, Z comes from an extra dimension of space 37

38 Whatever LHC will find,... ILC will have a lot to say! What depends on LHC findings: 1. If there is a light Higgs (consistent with prec.ew) verify the Higgs mechanism is at work in all elements 2. If there is a heavy Higgs (inconsistent with prec.ew) verify the Higgs mechanism is at work in all elements find out why prec. EW data are inconsistent 3. 1./2. + new states (SUSY, XD, little H, Z, ) precise spectroscopy of the new states 4. No Higgs, no new states (inconsistent with prec.ew) find out why prec. EW data are inconsistent look for threshold effects of strong EWSB 38

39 C L I C THE COMPACT LINEAR COLLIDER (CLIC) STUDY Multi TeV e + e - collider up to 3 TeV J.P.Delahaye CERN SUMMER STUDENT LECTURE

40 CLIC Parameters & Backgrounds CLIC 3 TeV e+e- collider with a luminosity ~ cm -2 s -1 (1 ab -1 /year) CLIC parameters old new CLIC operates in a regime of high beamstrahlung Time between 2 bunches = 0.67ns Expect large backgrounds # of photons/beam particle e+e- pair production γγevents Muon backgrounds Neutrons Synchrotron radiation Expect distorted lumi spectrum 40

41 Higgs Production Cross section at 3 TeV: Large cross section at low masses Large CLIC luminosity Large events statistics Keep large statistics also for highest Higgs masses Low mass Higgs: Higgses/year 45K/100K for 0.5/1 TeV LC 41

42 Rare Higgs Decays: H μμ Not easy to access at a 500 GeV collider H μμ ~ 10-4 H bb as rare decay (m H > 160 GeV) Also H bb for masses up to 220 GeV g Hμμ 42

43 Higgs Potential: e+e- HHνν Precision on λ HHH for 5 ab -1 for Higgs masses in the range m H = 120 GeV m H = 140 GeV m H = 180 GeV m H = 240 GeV 3 TeV Can improve further by using spin information and polarization (factor 1.7)? precision ~ 6-8% 43

44 Heavy Higgs (MSSM) LHC: Plot for 5 σ discovery 3 TeV CLIC H, A detectable up to ~ 1.2 TeV m/m ~ 1% 44

45 Supersymmetry (Battaglia at al hep-ph/ ) # sparticles that can be detected Higher mass precision at LC vs LHC Mass measurements to O(1%) for smuons 45

46 Taking into account backgrounds, lumi spectrum, detector Precision Measurements E.g.: Contact interactions: Sensitivity to scales up to TeV 46

47 Summary A linear e+e- collider with GeV is on our wish list! Challenging machine and detector requirements, but no major obstacles. With ILC data can: establish the Higgs mechanism complete the SUSY spectrum pin down LSP dark matter see signs of new physics way beyond the ILC (and LHC) energy through precision measurements look for exotic things (extra dimensions, Z, contact interactions ) Best results when combining LHC and ILC LHC/ILC Study Group 47

48 Summary We live in exciting times: - Expect major discoveries at the TeV scale with LHC and ILC - The combination of data from LHC and ILC should give us a handle to understand the underlying physics - ILC technology at hands let s hope this dream will turn into reality - LHC startup soon highest priority: let s make this a success Many thanks to: Klaus Desch, Albert De Roeck,Ties Behnke, Karsten Buesser, Michael Hauschild, Rolf Heuer, Markus Schumacher, Stefan Tapprogge, Peter Wienemann. 48