Searches at Accelerators

Transcription

1 Searches at Accelerators University of Liverpool

2 Outline Why search for Extra Dimensions (ED)? Motivation & different models: ADD, RS, TeV - How are ED detectable at accelerators? Signatures Where are searches being performed? Accelerator facilities What searches are being performed? Search channels What are the results? Analysis descriptions What are the future prospects? LHC MC studies

3 Extra dimensional Models Alternatives to SUSY for solving the hierarchy problem: M EW ( TeV) << M Planck (0 9 GeV)? Arkani-Hamed, Dimopoulos, Dvali, Phys Lett B49 (98) Many large compactified EDs In which G can propagate G M Pl ~ R n M Pl(4+n) (+n) Effective M Pl ~ TeV if compact space (R n )is large Randall, Sundrum, Phys Rev Lett 83 (99) highly curved ED Gravity localised in the ED Planck TeV brane Λ π = M pl e -krcπ Λ π ~ TeV if warp factor kr c ~- k/m Pl, k: curvature scale Dienes, Dudas, Gherghetta, Nucl Phys B537 (99) SM chiral fermions - TeV - sized EDs SM Gauge Bosons W, Z, γ, g See Extra Dimension lectures for more details on the theory & models! What are the experimental signatures at colliders? 3

4 Experimental Signatures for Direct Graviton emission in association with a vector-bosong Signature: ME T + jet(s), ME T + V σ depends on the number of ED g,q g,q Virtual Graviton exchange Signature: deviations in σ and asymmetries of SM processes e.g.qq l + l -, γγ g,q Or new processes e.g. gg l + l - g,q σ independent of the number of ED* Broad increase in σ due Run to Iclosely spaced summed over KK towers G jet,v f,v f,v destructive interference λ=+ New Parameters (*Hewett formalism) M s, ~ M D ~ M Pl(4+n) : string scale λ: dimensionless parameter, ± CDF Run I λ=+ M ll constructive interference λ=- 4

5 Experimental Signature for Model Virtual Graviton exchange Signature: an excess of events in dilepton/dijet/diboson channels g W u Z t H Branching Fraction γ e dσ/dm (pb/gev) 700 GeV KK Graviton at the Tevatron 0-4 New parameters: Resonance k/m0 Pl -6 =,0.7,0.5,0.3,0.,0. from 0.5 st graviton excitation mass: m positiontop to bottom LHC 0. Λ π = m M pl /kx,, m n =kx n e krcπ (J (x n )=0) GeV G KK 0.05 Ratio: k/m Pl 0-0 and subsequent tower states 0.0 Γ = ρm x (k/m pl ) width M ll (GeV) KK excitations can be excited individually on resonance RS model Dilepton channel Tevatron 700 GeV G KK M ll (GeV) Davoudiasl, Hewett, Rizzo hep-ph K/M Pl

6 Experimental Signature for and KK Gauge Bosons From 4-d point of view: Mass of SM gauge bosons (M n ) that propagate in the ED are equivalent to towers of KK states with masses : M n = (M 0 +n /R ) where (n=,, ) Potentially detectable consequences: ) Mixing among the 0 th (SM gauge boson) and the nth-modes (n=,,3..) of the W and Z bosons. (Since the entire tower of KK states have the same quantum numbers as their 0 th -state gauge boson) ) Direct production and virtual exchanges of the 0 th -state gauge bosons, AND both direct production and virtual effects of the KK states of the W, Z, γ and g bosons at high energies New Parameters R=M C - : size of the compact dimension M C : corresponding compactification scale M 0 : mass of the SM gauge boson ATLAS ee M n = M 0 hep-ph/989 6

7 ED Search Facilities Tevatron, Fermilab, USA HERA, DESY, Hamburg H p CDF p p e - ZEUS LEP, CERN, Geneva CERN: world's largest particle physics laboratory e - e + Tevatron: Highest energy collider operating in the world! D0 Run I s =.8 TeV Run II s =.96 TeV e +/- p 90 (80) GeV 7.5 GeV World s only ep collider Run I s ~ 300 GeV Run II s ~ 30 GeV LEP I s = 9 GeV LEP II s = GeV LHC ~007 s = 4 TeV 7

8 General Particle Detection Both e and γ: deposit energy in the EM calorimeter ( EM object) However, γ are uncharged, so leave no track in the tracking chamber Whereas e +/- leave a track Muons: leave a track in the tracking chamber deposit minimum energy in the calorimeters leave tracks in the muon chambers 8

9 Tevatron Experiments: CDF & D0 Hermitic calorimeter (central & plug)/muon coverage Excellent particle ID Precision tracking and silicon vertex detectors Central Calorimeters η < Muon System η < η <.5 η=0 η=.0 η=.0 Plug Calorimeter < η <3 η=3.0 Solenoid Time-of-Flight COT Silicon Tracker 9

10 HERA: H & ZEUS H is a finely segmented calorimeter ZEUS has a compensating calorimeter Both have good hermetic muon coverage 0

11 LEP Detectors L3

12 Summary of Searches performed Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T CDF, D0 µµ CDF, D0 ee ee+γγ γγ CDF, D0 D0 CDF e +/- X H LED LED, RS ee TeV - Emission LED Exchange LED RS TeV -

13 ED Searches Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T CDF, D0 µµ CDF, D0 ee ee+γγ γγ CDF, D0 D0 CDF e +/- X H LED LED, RS Emission LED Exchange ee TeV - LED RS TeV - 3

14 G emission: LEP γ+me T LED Search Signature: e + e - γg G escapes detection: enhanced rate of γ+me T events s-channel γ exchange t-channel γ exchange 4-particle contact interaction x γ : ratio of γ energy to beam energy θ γ : polar angle of γ relative to beam line dσ depends on M D and n dσ increases rapidly at low γ energies (Eγ) and angles dσ / dx γ dcos θ γ (pb) cos θ γ E γ / E beam 4

15 G emission: LEP γ+me T LEP: ALEPH, DELPHI, L3 s= GeV ~0.6 fb - /experiment:.9 fb - Total Search Selection cluster in the EM calorimeter with No matching charged track P tγ > 0.0 s 0.04 s No other significant detector activity Principal Background e + e - ννγ Other Background e + e - e + e - γ(γ) In low P tγ region: SM bkgd enhanced due to e + e - e + e - γ(γ),where both e have low θ and cannot be detected Events / L3 DELPHI Preliminary Data e + e νν _ γ Other Background e + e γg M D = TeV, n = E γ / E beam Good agreement with SM observed by all experiments 5

16 G emission: LEP γ+me T Lower limits on the gravity scale (M D ) derived individually by each experiment as functions of number of ED (n) σ α (/M D ) Results are combined n+.5 ALEPH DELPHI L3 Preliminary M D (TeV) LEP e + e γg 0.5 Excluded at 95% C.L. D0/CDF Number of Extra Dimensions LEP: best limits on direct G emission from collider experiments for n<6 For n>6.. 6

17 G Emission: CDF: γ+me T CDF also search for G emission: γ+me T Search Selection 87 pb - Run I - One γ with E T > 55 GeV and η < -ME T > 45 GeV - No jets with E T > 5 GeV - No tracks with p T > 5 GeV Main backgrounds Cosmic ray muons 6.3 ±.0 Z 0 γ νν+γ 3. ±.0 W eν ( γ ν) 0.9 ± 0. Prompt diphotons 0.4 ± 0. Wγ (νγ) 0.3 ± 0. Results Expected background:.0 ±.3 Observed: Data in good agreement with SM Cosmic Rays main background qq γg KK Limits n=4 M D > 0.55 TeV n=6 M D > 0.58 TeV n=8 M D > 0.60 TeV Limits not as restrictive as LEP

18 ED Searches Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T ee+γγ ee γγ CDF, D0 D0 CDF, D0 µµ CDF, D0 CDF e +/- X H LED LED, RS ee TeV - Emission LED Exchange LED RS TeV - 8

19 Real G Emission: jet(s)+me T Better limits on G emission at the Tevatron from the jets + ME T searches Search Signature: pp jet(s) + G G escapes to detection into ED G Events with large ME T g,q Recoil jet very energetic g,q jet,v Tevatron s= TeV M D =. TeV n= qq gg KK q q qg gg KK σ falls as /M D n+ for all sub-processes dominate sub-process for n> g g q g q g q q q q G KK q q q q q q q g q g g g gg gg KK g g g G KK g G KK g g g G KK G KK g G KK g g g G KK G KK g G KK n=4 p min from Pythia T (GeV) prediction from Giudice, Rattazi and Wells (hep-ph989) 9

20 Real G Emission: CDF: jet(s)+me T Search Selection 84 pb - Run Ib jet E st T 80 GeV, η <. and ME T >80 GeV a second jet is allowed if E nd T > 30 GeV no isolated tracks in event (p T 0 GeV) Main background Irreducible:Z( νν)+jets, W( τν)+jets q _ q G kk g g g g G kk Predicted Data Predicted invisible Z Observed (84pb - ) Results Expected: 74 ± 6 Observed: 84 events Relative uncertainty on the signal acceptance 5 % D0 have/also search for G emission (Run I & II): Monojet +ME T presently their limits are not as restrictive as CDFs 0 E T (GeV)

21 G Emission Summary LEP and Tevatron results are complementary For n<6: LEP limits best γ+me T LEP use γ+me T, which is cleaner & has lower backgrounds than jet+me T (Tevatron), so the precision of their experiments wins out for lower values of n M D (TeV) LEP Excluded at 95% C.L. ALEPH DELPHI L3 Preliminary e + e γg D0/CDF Number of Extra Dimensions For n>6: Tevatron limits best jet+me T Tevatron better at large values of n, because of the higher energy, which is a bigger effect at larger values of n. σαtotal number of possible modes in the KK tower N KK σ α N KK α (s-hat) But this is true for each ED, so σ α ( (s-hat)) n the difference in energy is a bigger effect for n=6 than n=

22 ED Searches Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T ee+γγ ee γγ CDF, D0 D0 CDF, D0 µµ CDF, D0 CDF e +/- X H LED LED, RS Emission LED Exchange ee TeV - LED RS TeV -

23 ED Searches Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T ee+γγ ee γγ CDF, D0 D0 CDF, D0 µµ CDF, D0 CDF e +/- X H LED LED, RS Emission LED Exchange ee TeV - LED RS TeV - Many different channels in which G exchange could be detected G exchange sensitive to several ED models - similarities/distinct features of their search strategies. 3

24 Search for G Exchange? Similarities Search Signature Deviations in (ee, µµ, γγ) cross sections (σ) and angular distributions from SM processes caused by G exchange Dilepton Channel Z/γ l + l - l - Standard Model Diphoton Channel l + l - l + l - Extra Dimensions Clean experimental signature (ee,µµ) even in a hadron collider Low backgrounds & Z 0 peak used as a calibration point (ee,µµ) Distinguish New Physics Models Resonance in RS model and broad change in σ in ADD model Spin graviton used to distinguish between other new physics 4

25 Tevatron Exchange Search Strategies CDF Search Strategy: ee, µµ, γγ Perform signature based searches Compare data to expectation D fits in invariant mass performed (and angular distribution studied) Determine spin dependent acceptance and then σ.br Interpret data & set limits on many new models! E.g. (ee & µµ): Spin-0 : RPV sneutrinos Spin- : Z, Technicolor ρ, ω Spin- : RS G, LED, etc.. l + l + X? X? l - l - D0 Search Strategy: ee, µµ, γγ Perform more ED specific searches Optimise for specific search: ADD case: combine ee+γγ to gain in efficiency 3D fits in angular distribution and invariant mass performed 5

26 ED Searches Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T ee+γγ ee γγ CDF, D0 D0 CDF, D0 µµ CDF, D0 CDF e +/- X H LED LED, RS Emission LED Exchange ee TeV - LED RS TeV - 6

27 G Exchange: D0 ee+γγ ADD LED ADD: many Large ED in which gravitons can propagate Search for spin- broad σ change study invariant mass & angular distribution Since D0 doing a ADD specific search, not searching for any new physics & G couples to both γγ and ee D0 combine ee+γγ diem search diem Mass Spectrum Events/0 GeV Data DØ Run II Preliminary QCD 00 pb - Signal prediction SM diem Mass, GeV This maximises reconstruction efficiency. 7

28 Similarities e/γ Id/Misid-entification in Detectors Both e and γ deposit energy in the EM calorimeter ( EM object) Differences However, γ are uncharged, so leave no track in the tracking chamber Whereas e +/- leave a track Inefficiencies arise if: γ ID requires no track, but γ converts ( ee) γ e + e - e ID requires a track, but loose track due to imperfect track reconstruction/crack To maximise reconstruction efficiency: D0 combine ee+γγ diem search 8

29 G Exchange: D0 ee+γγ ADD LED Search selection 00 pb - two isolated EM objects, E T >5GeV central (CC) or plug and central (EC) diem Mass Spectrum - Central End Plug 0 SM Events/0 GeV Data DØ Run II Preliminary QCD 00 pb - Signal prediction diem Mass, GeV diem cosθ* Spectrum 500 DØ Run II Preliminary MC studies show adding EE degrades the sensitivity slightly, due to the large background in this channel Events/ cosθ* 9

30 D0 ee+γγ ADD LED D0 perform a combined fit of the invariant mass and angular information Fit combined M ee, γγ and cosθ* spectrum to extract limits Events Events SM Prediction DØ Run II Preliminary SM events expected to be distributed 3 3 uniformly 0 0 in cosθ* diem Mass, GeV diem Mass, GeV cosθ* cosθ* Events Events diem Mass, GeV diem Mass, GeV Data ED Signal QCD Background Signal events are accumulated at low cosθ* & low mass, 3 3 high mass 0 high cosθ* cosθ* cosθ* Parameterise σ in terms of η = λ/ M 4 s σ = σ SM + ησ INT + η σ KK + σ BG SM Interference ED term Background 3D templates used to set limits Bayesian likelihood fitting used to set 95%CL on η G η G translated into a 95% CL mass limit on fundamental Planck Scale (M s ) 30

31 D0 s highest mass events 8 events with M>350 GeV 6 form a bump around 400 GeV Z ee resonance? No: have or 0 tracks AND Bump twice as narrow as expected from a narrow resonance smeared with typical D0 EM calorimeter resolution highest mass events: have very low cosθ* (0.0, 0.03) One is a e + e - pair and the other γγ excellent candidates for new physics beyond the SM! diem Mass Spectrum Events/0 GeV DØ Run II Preliminary diem Mass, GeV i.e. possess kinematics typical of signal from large ED. (Very high scattering angle: close to π/.) Intriguing events but consistent with the SM 3

32 D0 s highest mass event D0 s highest-mass DY candidate ever observed! Event Callas Run 7785 Event Thu Dec 4 8:34:8 003 E scale: 4 GeV diem Mass Spectrum 4 0 DØ Run II Preliminary +z Events/0 GeV Mass = 475 GeV 80 Run 7785 Event Thu Dec 4 8:34:9 003 ET scale: 0 8 GeV diem Mass, GeV Looking forward to results with more data from Run II (higher statistics)!

33 G Exchange: CDF ee ADD LED CDF perform a similar search Differences: ee channel only fit invariant mass only Search selection 00 pb - two isolated e, E T > 5 GeV central e (CC) or central and forward e (CP) N exp =. N obs =4 for M ee >300 GeV/c N exp = 4.6 N obs = 9 for M ee >350 GeV/c σ = σ SM + η σ INT + η σ KK Events / 5 (GeV/c Events / 5 (GeV/c - CDF Run II Preliminary (00 pb ) 0 4 Data Drell - Yan 0 3 QCD Background ττ, WW, WZ, tt ) ) CDF Run II Preliminary (00 pb Data SM Background Main Backgrounds Dielectron Mass (GeV/c Direct KK Interference Central - Central M s ) - ) = 850 GeV ) Dielectron 400 Mass (GeV/c

34 D0 µµ ADD LED Events / 4 GeV D0 µµ search performed in a similar way to the D0 ee+γγ search 50 pb - Search Selection p T µ,µ >5 GeV Isolated tracks M µµ >50 GeV Cosmics removed Data SM Monte Carlo Events / DØ Run II Preliminary 50 pb - Events D fits to extract limits Standard Model Monte Carlo µ µ Mass (GeV) -4 SM + ED terms ( η G =3.0 TeV ) Cos(θ*) Events Data µ µ Mass (GeV) DØ Run II Preliminary Cos(θ*) Dimuon Invariant Mass (GeV) * Cos(θ ) N exp =6.4 N obs =5 for M ee >300 GeV/c N exp =.3 N obs = for M ee >450 GeV/c Events µ µ Mass (GeV) Cos(θ*) No deviation in data from SM 34

35 Tevatron ADD LED limits Both D0 and CDF have observed no significant excess 95% CL lower limits on fundamental Planck scale (M s ) in TeV, using different formalisms: GRW HLZ for n= Hewett D0 Run II: µµ D0 Run II: ee+γγ D0 Run I+II: ee+γγ CDF Run II: ee GRW 3 4HLZ for n= λ=+/- Hewett /0.95 λ=+/ / /na /0.99 D0 Run II µµ result: tightest limits on LED from a single measurement in this channel! D0 combined ee+γγ Run I & Run II result is the most stringent limit on LED to date! 35

36 ED Searches Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T ee+γγ ee γγ CDF, D0 D0 CDF, D0 µµ CDF, D0 CDF e +/- X H LED LED, RS Emission LED Exchange ee TeV - LED RS TeV - 36

37 G Exchange: D0 RS ee+γγ RS: extra compactified/warped ED in which G can propagate Search for spin- resonance in invariant mass spectrum Search Selection 75pb - isolated EM objects with E T >5 GeV central e (CC) or forward and central e (EC) Events / 0 GeV DØ Run II, 75 pb a) Data Total Background SM Background QCD Background 300 GeV RS Graviton k/m Pl =0.05 N obs = DiEM Mass (GeV) 37

38 G exchange: D0 RS µµ Search Selection 46pb - high Pt (>5 GeV) µ Minimum ionising particles Match a track in central tracking chamber Signal in the µ drift chambers (if fiducial) Events / 4 GeV DØ Run II, 46 pb b) Data SM Background 300 GeV RS Graviton k/m Pl =0.05 No opposite charge requirement, as determination of efficiency degrades fast at high p T Cosmic Rays reduced by requiring µ arrival times at the µ detector consistent with those from beam collisions N obs = Dimuon Mass (GeV) Good agreement between data and expected background 38

39 G exchange: D0 RS D fits used to extract limits Different search windows are used for the ee+γγ : µµ channels because of the different detector resolutions Events / 0 GeV DØ Run II, 75 pb a) Data Total Background SM Background QCD Background 300 GeV RS Graviton k/m Pl =0.05 Events / 4 GeV DØ Run II, 46 pb b) Data SM Background 300 GeV RS Graviton k/m Pl = DiEM Mass (GeV) ee+γγ: EM energy determined using calorimeters Dimuon Mass (GeV) µµ: p T measured in tracker 39

40 G exchange: D0 RS D fits used to extract limits Different search windows are used for the ee+γγ : µµ channels because of the different detector component resolutions Events / 0 GeV DØ Run II, 75 pb a) 6σ Data Total Background SM Background QCD Background 300 GeV RS Graviton k/m Pl =0.05 Events / 4 GeV DØ Run II, 46 pb b) Data SM Background 300 GeV RS Graviton k/m Pl = DiEM Mass (GeV) ee+γγ: EM energy determined using calorimeters Symmetric windows width 6 x detector resolution Dimuon Mass (GeV) µµ: p T measured in tracker Asymmetric windows only lower mass bound used (due to long high-mass tail) 40

41 Events / 0 GeV DØ Run II, 75 pb a) Data Total Background SM Background QCD Background 300 GeV RS Graviton DiEM Mass (GeV) G exchange: D0 RS ee+γγ k/m Pl =0.05 significance of upward fluctuation at 400 GeV < σ Events / 4 GeV DØ Run II, 46 pb b) Data SM Background 300 GeV RS Graviton Dimuon Mass (GeV) Small excess in µ channel Combined limits slightly less restrictive due to the overall small excess of observed events in the µµ channel 4

42 ) (pb) - l + l () σ BR(G % CL µµ Limits µµ Sensitivity 95% CL ee+γγ Limits ee+γγ Sensitivity k / M Pl = 0.0 k / M Pl = 0.0 k / M Pl = 0.05 k / M Pl = 0. G exchange: D0 RS DØ Run II pb k / M Pl DØ Run II pb RS Model 95% C.L. Excluded Domain µ µ ee+γγ & combined Graviton Mass (GeV) Excluded mass limits: 785 GeV for k/m Pl =0. 50 GeV for k/m Pl = Graviton Mass (GeV) Below excluded from precision electroweak data Λ π >0 TeV which requires a significant amount of fine-tuning Most restrictive limits on the RS model parameters to date! 4

43 G exchange: CDF RS ee (PP) CDF also performed a Run II RS search in the ee (& γγ separately) channel include CC + CP (same as ADD ee data) add PP ee events Search Selection forward EM clusters (PP) isolated with E T > 5 GeV New for Run II: increase acceptance! New tracking algorithm developed for P photons require a silicon track ee (PP) QCD dijets (misidentified jet) background larger in the plug region than in central N exp =.7 ± 0.7 N obs =8 for M ee >300 GeV/c N exp =.4 ± 0.3 N obs =3 for M ee >350 GeV/c 43

44 Search Selection isolated γ E T >5 GeV central γ (CC) G exchange: CDF RS γγ Backgrounds Standard Model diphoton production (dominant at very high masses) Fakes: γ-jet and jet-jet, where jet fragments into a hard π 0 γγ N exp =4.±.0 N obs = for M ee >300 GeV/c N exp =.5±0.5 N obs = for M ee >350 GeV/c 44

45 Search Selection isolated µ P T >0 GeV η µ <, η µ <.5* Veto cosmic rays using track-timing cuts G Exchange: CDF RS µµ Muon System η < η <.5 Solenoid Time-of-Flight COT Silicon Tracker N exp =5. ± 0.3 N obs =6 for M ee >300 GeV/c N exp =3. ± 0. N obs = for M ee >350 GeV/c µ may include tracks w/o µ chamber information 45

46 CDF RS Graviton Limits Setting 95 % C.L. upper limits on σ.br(σ γγ/ll): γγ: Like D0 ee+γγ, CDF use ±3σ windows around M G, but in D only ee+µµ: CDF use a binned likelihood method to fit D M ll spectra Channel Luminosity (pb - ) M G (GeV/c ) K/M Pl =0.0 M G (GeV/c ) K/M Pl =0. ee µµ ee+µµ γγ ee has largest acceptance at low mass γγ has largest acceptance at high mass BR(G γγ) = * BR(G ee) CDF limits not as exclusive as D0 s γ e 46

47 G exchange: CDF RS Searches CDF perform -D fits, but also study (ee, µµ, γγ) angular distributions µµ ee γγ Good agreement with SM prediction 47

48 ED Searches Signature Experiment Model Graviton Emission Graviton Exchange Boson Exchange γ+me T LEP, CDF LED jets+me T ee+γγ ee γγ CDF, D0 D0 CDF, D0 µµ CDF, D0 CDF e +/- X H LED LED, RS Emission LED Exchange ee TeV - LED RS TeV - 48

49 H LED Searches H Search Strategy Perform signature based searches Measure inclusive σ s e +/- p e +/- X over a huge range in 4-momentum transfer (Q ) Compare data to expectation GeV/c Interpret data & set limits on many new models! E.g. Contact interactions Leptoquarks R-parity violating squarks Search for e or q substructure (Form Factor Analysis) Fix the SM and its parameters, in particular the parton distributions, using experimental data at low Q, where the theory is well established. Then extrapolate the prediction towards Q, (where distance scales down to /000 of the proton radius are probed), where deviations due to new physics are expected to be most prominent & could indicate the presence of quark substructure or new particles 49

50 G exchange: H LED Search In DIS, G-exchange may contribute to the e-q subprocess, but the new interaction also induces e-g scattering which is not present in the SM. To Set Limits Parameterise σ in terms of η = λ/ M 4 s SM + ED + Interference Fit the differential σ to the formula above treating λ/m s 4 as a free parameter Extract limits on M s dσ/dq / dσ SM /dq 3 0 H M s GeV s =580 GeV λ=+ M s =60 s GeV λ= combined limits: M s =80 s GeV λ=+ M s =780 s GeV GeV λ= Large Extra Dimensions e p NC data s=39 GeV e + p NC data s=39 GeV λ=±: constructive or destructive interference Q (GeV ) H M s GeV s =770 GeV λ=+ M s =730 GeV GeV λ= combined limits: M s s =80 GeV GeVλ=+ λ=+ M s s =780 GeV GeVλ= λ= Q (GeV ) 50

51 ED Searches Signature Experiment Model Graviton Emission γ+me T LEP, CDF LED jets+me T CDF, D0 Emission Graviton Exchange ee+γγ ee D0 CDF, D0 LED, RS LED µµ CDF, D0 Exchange γγ CDF e +/- X H LED Boson Exchange ee D0 TeV - LED RS TeV - 5

52 TeV - ee Search First dedicated experimental search for TeV - ED at a collider Search for effects of virtual exchanges of the KK states of the Z and γ Search Signature: Signal has distinct features: enhancement at large masses (like LED) negative interference between the st KK state of the Z/γ and the SM Drell-Yan in between the Z mass and M C Search Selection 00pb - Same as LED diem search except: at least EM cluster has to have a matching track & no track isolation requirement Data are in excellent agreement with Drell-Yan production, so proceed to set limits diem Mass Spectrum Events/0 GeV DØ Run II Preliminary CC-CC predicted background L = 00pb - SM Drell-Yan TeV - ED signal η c =5.0 TeV diem Mass, GeV 5

53 TeV - ee D0 Events Events SM Prediction DØ Run diem Mass, GeV ED Signal diem Mass, GeV cosθ* cosθ* II Preliminary Events Events diem Mass, GeV diem Mass, GeV Data cosθ* QCD Background cosθ* Extract limits on M C by fitting D distributions to the sum of the SM, interference, and the direct gravity templates Lower limit on the compactification scale of the longitudinal ED: M C >. TeV at 95% C.L. World Combined Limit M C >6.8 TeV at 95%C.L. Better limits come from precision measurements 53

54 Summary of Present Limits But what of the Future? Present limits are up to ~ TeV Future: More data to be analysed and to come: Delivered HERA: ~0pb - Tevatron: > fb - Analysed Goal ~80pb - >700pb - (007) ~400 pb fb - (009) Promising observation potential, hope to discover ED if they exist! Or extend limits: Tevatron Run IIa ( fb - ) extend limits: ADD: up to about M S = TeV RS: m from 0.5 to TeV for k/m Pl 0.0 to 0. And after that..? 54

55 What limits can we reach in the future? Next generation of detectors being built LHC (007): s = 4 TeV What limits can we expect to reach? ATLAS pit MC studies already on their way! 55

56 γ+ ME T M D MAX (TeV) δ= HL 00fb - 4 LED ADD: G Direct Emission ATLAS jet+ ME T M MAX (TeV) D δ= δ=3 δ=4 LL 30fb HL 00fb To characterise the model need to measure M D and δ Disentangle δ and M D : Measuring σ gives ambiguous results Run at two different s (δ=, M D =5TeV very similar to δ=4, M D =4TeV) e.g. 0 TeV and 4 TeV => need 50 fb -. 56

57 LED ADD: Virtual G Exchange ATLAS extends reach up to ~ 6/7 TeV with 0 fb - /00 fb - (n dependent) 57

58 RS constraints Tevatron 0 pb - fb - Dijet and dilepton data 0.0 K/M Pl Curvature of 5 th dimension R 5 < M Allowed 0.07 Region Λ 0.05 π < 0 TeV Solve hierarchy Oblique Parameters 0 fb - 00 fb - LHC Dilepton data m (GeV) BR(G γγ) = *BR(G ee) LHC completely covers the region of interest (hep-ph ) 58

59 RS constraints Distinguish RS model from other new physics Distinguish Z (spin ) /G (spin ) from e + e - st resonance by studying angular distribution If many resonances observed: study separation: is it characteristic Bessel spacing? dσ/dm (pb/gev) 0 - M ll (GeV) Dilepton 700 GeV KK Graviton at the K/MPl Tevatron 0-4 k/m 0-6 Pl =,0.7,0.5,0.3,0.,0. from 0.5 top to bottom LHC GeV G KK and subsequent tower states M ll (GeV) (hep-ph ) 59

60 TeV - Sized ED & KK Gauge Boson Fermions are open strings excitations with ends stuck to our brane but gauge Bosons could also propagate in the bulk. Search for KK excitations of Z, γ, Worse resolution for µ ATLAS M c =4 TeV γ () /Z () e + e - /µ + µ - TeV e in ATLAS: E/E~0.7 ~0% for µ Acceptance for leptons: η <.5 Reach: Possible to detect resonance up to 5.8 TeV In absence of peak a 95% CL of 3.5 TeV can be achieved G. Azuelos, G. Polesello (Les Houches 00 Workshop Proceedings) 60

61 TeV - Sized ED & KK Gauge Boson Distinguish RS model from other new physics Z () or Z or RS Graviton? ATLAS 6

62 Concluding Remarks No significant sign of new physics! Increasing number of channels being used to search for EDs Many searches underway: e.g. pp ττ, pp jet jet, pp G ZZ Existing analyses being refined & improved Updates imminent e.g. pp ee, pp jet+me T, Present limits are up to ~ TeV LHC will enable searches probe up to ~ 5-6 TeV Will HERA/Tevatron discover new physics before LHC? 6