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LHC &

LHC &. Extra Dimensions. Dr Tracey Berry Royal Holloway University of London. LHC &. Extra Dimensions. Theoretical Motivations Extra Dimensional Models Considered Signatures Covered Search Facilities: ATLAS & CMS Uncertainties

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LHC &

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  1. LHC & Extra Dimensions Dr Tracey Berry Royal Holloway University of London Getting ready for the LHC, Madrid Oct 23-27, 2006

  2. LHC & Extra Dimensions • Theoretical Motivations • Extra Dimensional Models Considered • Signatures Covered • Search Facilities: ATLAS & CMS • Uncertainties • Present Constraints and Discovery Limits for ED (ADD, RS, TeV-1, UED) • Summary of LHC Start-up Expectations • Conclusions Getting ready for the LHC, Madrid Oct 23-27, 2006

  3. Extra Dimensions: Motivations In the late 90’s Large Extra Dimensions (LED) were proposed as a solution to the hierarchy problem MEW (1 TeV) << MPlanck (1019 GeV)? Randall, Sundrum,Phys Rev Lett 83 (99) Arkani-Hamed, Dimopoulos, Dvali,Phys Lett B429 (98) RS ADD 1 highly curved ED Gravity localised in the ED Many (d) large compactified EDs In which G can propagate Planck TeV brane MPl2 ~ RdMPl(4+d)(2+d) = Mple-kRc ~ TeV  ifcompact space (Rd) is large Effective MPl ~ 1TeV if warp factorkRc ~11-12 Since then, new Extra Dimensional models have been developed and been used to solved other problems: Dark Matter, Dark Energy, SUSY Breaking, etc Some of these models can be/have been experimentally tested at high energy colliders Getting ready for the LHC, Madrid Oct 23-27, 2006

  4. G Extra Dimensional Models Arkani-Hamed, Dimopoulos, Dvali,Phys Lett B429 (98) ADD • (Many) Large flat Extra-Dimensions (LED) could be as large as a few m • In which G can propagate, SM particles restricted to 3D brane Randall, Sundrum,Phys Rev Lett 83 (99)b RS Planck TeV brane • Small highly curved extra spatial dimension • (RS1 – two branes) Gravity localised in the ED -1 Dienes, Dudas, Gherghetta,Nucl Phys B537 (99) SM chiral fermions SM Gauge Bosons W, Z, g, g TeV sized EDs • Bosons could also propagate in the bulk • Fermions are localized at the same (opposite) orbifold point: destructive (constructive) interference between SM gauge bosons and KK excitations W, Z UED G • All SM particles propagate in “Universal” ED • often embedded in large ED e, m Getting ready for the LHC, Madrid Oct 23-27, 2006

  5. Exchange ADD RS TeV-1 Experimental Signatures of ED Covered in this talk • Single jets/Single photons + missing ET • (direct graviton production in ADD) • Di-lepton, di-jet continuum modifications • (virtual graviton production in ADD) • Di-lepton, di-jet and di-photon resonances (new particles)in RS1-model (RS1-graviton) and TeV-1 ED model(ZKK) • Single leptons + missing ETin TeV-1 ED model (WKK) • Back-to-back energetic jets + missing ET (UED) • 4 jets + 4 leptons + missing ET(mUED) Emission ADD Getting ready for the LHC, Madrid Oct 23-27, 2006

  6. Present/Past ED Search Facilities Tevatron, Fermilab, USA LEP, CERN, Geneva CERN: world's largest particle physics laboratory CDF p e- p e+ D0 Tevatron: Highest energy collider operating in the world! LEP I √s = 91 GeV LEP II √s =136-208 GeV Run I √s = 1.8 TeV Run II √s = 1.96 TeV Getting ready for the LHC, Madrid Oct 23-27, 2006

  7. Future ED Search Facilities! Bigger & Better (?!) Collider & Detectors!! Higher CM of mass energy LHC: √s = 14 TeV Aim of Tev4LHC use what has been learnt at the Tevatron to fully exploit LHC’s physics potential Getting ready for the LHC, Madrid Oct 23-27, 2006

  8. ATLAS and CMS Experiments Large general-purpose particle physics detectors CMS ATLAS Total weight 7000 t Overall diameter 25 m Barrel toroid length 26 m End-cap end-wall chamber span 46 m Magnetic field 2 Tesla Total weight 12 500 t Overall diameter 15.00 m Overall length 21.6 m Magnetic field 4 Tesla Detector subsystems are designed to measure: energy and momentum of g ,e, m, jets, missing ET up to a few TeV Getting ready for the LHC, Madrid Oct 23-27, 2006

  9. Experimental Uncertainties Systematic uncertainties associated with the detector measurements • Luminosity • Energy miscalibration which affects the performance of e/g/hadron energy reconstruction • Drift time and drift velocities uncertainties • Misalignment affects track and vertex reconstruction efficiency  increase of the mass residuals by around 30% • Magnetic and gravitational field effects  can cause a scale shift in a mass resolution by 5-10% • Pile-up  mass residuals increase by around 0.1-0.2% • Trigger and reconstruction acceptance uncertainties •  Affect the background and signal • Background uncertainties: variations of the bkgd shape  a drop of about 10-15% in the significance values Getting ready for the LHC, Madrid Oct 23-27, 2006

  10. Theoretical Uncertainties • QCD and EW higher-order corrections (K-factors) • Parton Distribution Functions (PDF) • Hard process scale (Q2) • Differences between Next-to-Next-to-Leading Order (NNLO), NLO and LO calcalations  affect signal and background magnitudes, efficiency of the selection cuts, significance computation… Getting ready for the LHC, Madrid Oct 23-27, 2006

  11. SM 2XD 4XD 6XD PDF Impact on Sensitivity to ED • Extra dimensions affect the di-jet cross section through the running of as. Parameterised by number of extra dimensions d and compactification scale Mc.  So could potentially use s deviation to detect ED Ferrag, hep-ph/0407303 MC= 2 TeV MC= 2 TeV MC= 6 TeV PDF uncertainties • PDF uncertainties (mainly due to high-x gluon) give an uncertainty “zone” on the SM cross sections • This reduces sensitivity to MC from 5 TeV to 2 (3) TeV for d= 4, 6 and for d=2 sensitivity is lost (MC<2 TeV) Getting ready for the LHC, Madrid Oct 23-27, 2006

  12. MPl2 ~ RdMPl(4+d)(2+d) G Model ADD Arkani-Hamed, Dimopoulos, Dvali,Phys Lett B429 (98), Nuc.Phys.B544(1999) • (Many) Large flat Extra-Dimensions (LED), • could be as large as a few m • the maximum total number of dimensions is 3(our) + 6(extra)=9 • G can propagate in ED • SM particles restricted to 3D brane • The fundamental scale is not planckian: MD= MPl(4+d) ~ TeV • Model parameters are: • d = number of ED • MPl(4+d) = Planck mass in the 4+d dimensions For MPl ~ 1019 GeV and MPl(4+d) ~MEW R ~1032/d x10-17 cm Getting ready for the LHC, Madrid Oct 23-27, 2006

  13. MPl2 ~ RdMPl(4+d)(2+d) G Present Constraints on the Model ADD For MPl ~ 1019 GeV and MPl(4+d) ~MEW  R ~1032/d x10-17 cm • d=1  R ~1013 cm, ruled out because deviations from Newtonian gravity over solar distances have not been observed • d=2  R ~1 mm, not likely because of cosmological arguments: In particular graviton emission from Supernova 1987a* implies MD>50 TeV Closest allowed MPl(4+n) value for d=2 is ~30 TeV, out of reach at LHC Run I • Can detect at collider detectors via: • graviton emission • Or graviton exchange *Cullen, Perelstein Phys. Rev. Lett 83,268 (1999) Getting ready for the LHC, Madrid Oct 23-27, 2006 Gupta et. al. hep-ph/9904234

  14. G g,q jet,V g,q G g,q f,V g,q f,V Broad increase in s due to closely spaced summed over KK towers Run I CDF Run I l=+1 Mll ADD Collider Signatures • Real Gravitonemission in association with a vector-boson Signature: jets + missing ET, V+missing ET s depends on the number of ED Jets+ missingET, γ+ missingET • Virtual Graviton exchange Signature: deviations in s and asymmetries of SM processes e.g. qq l+l-,   & new processes e.g. gg  l+l- Excess above di-lepton continuum Getting ready for the LHC, Madrid Oct 23-27, 2006 s independent of the number of ED* in Hewett convention

  15. MPl2 ~ RdMPl(4+d)(2+d) G Present Constraints on the Model ADD For MPl ~ 1019 GeV and MPl(4+d) ~MEW  R ~1032/d x10-17 cm • d=1  R ~1013 cm, ruled out because deviations from Newtonian gravity over solar distances have not been observed • d=2  R ~1 mm, not likely because of cosmological arguments: In particular graviton emission from Supernova 1987a* implies MD>50 TeV Closest allowed MPl(4+n) value for d=2 is ~30 TeV, out of reach at LHC • LEP & Tevatron limits is MPl(4+d) ~> 1TeV • d>6 difficult to probe at LHC since cross-sections are very low Run I *Cullen, Perelstein Phys. Rev. Lett 83,268 (1999) Getting ready for the LHC, Madrid Oct 23-27, 2006

  16. q q q qqgGKK dominate sub-process for n>2 q g q g q g g q q GKK GKK GKK qggGKK q q q q q q q g q g g GKK GKK g GKK gggGKK g g g g g g g g g g g GKK g GKK GKK sfalls as 1/MDn+2 for all sub-processes g q g g _ Gkk g Gkk q Present ADD Emission Limits LEP and Tevatron results are complementary For n>4: CDF limits best jet+MET g+MET For n<4: LEP limits best Getting ready for the LHC, Madrid Oct 23-27, 2006

  17. ADD Discovery Limit: g+G Emission ppg+GKK J. Weng et al. CMS NOTE 2006/129 • G  high-pT photon + high missing ET • Main Bkgd: Zg  nng, • Signals generated with PYTHIA (compared to SHERPA) Bkgds: PYTHIA and compared to SHERPA/CompHEP/Madgraph (B) Using CTEQ6L • Full simulation & reconstruction • Theoretical uncert. Real graviton production At low pT the bkgd, particularly irreducible Zg  nng is too large require pT>400 GeV Integrated Lum for a 5s significance discovery Significance: S=2(√(S+B)-√B)>5 Also W e(m,t)n, Wg en, g+jets, QCD, di-g, Z0+jets MD= 1– 1.5 TeV for 1 fb-1 2 - 2.5 TeV for 10 fb-1 3 - 3.5 TeV for 60 fb-1 Not considered by CMS analysis: Cosmic Rays at rate of 11 HZ: main background at CDF, also beam halo muons for pT> 400 GeV rate 1 HZ Getting ready for the LHC, Madrid Oct 23-27, 2006

  18. ADD Discovery Limit: g+G Emission ATLAS L.Vacavant, I.Hinchcliffe ATLAS-PHYS 2000-016 J. Phys., G 27 (2001) 1839-50 ppg+GKK : qqgGKK Rates for MD≥ 4TeV are very low For d>2: No region where the model independent predictions can be made and where the rate is high enough to observe signal events over the background. This gets worse as d increases • Better limits from the jet+G emission which has a higher production rate This signature could be used as confirmation after the discovery in the jet channels Getting ready for the LHC, Madrid Oct 23-27, 2006

  19. ADD Discovery Limit: jet+G Emission ppjet+GKK Real graviton production gggG, qgqG & qqGg Dominant subprocess • Signature: jet + G  jet with high transverse energy (ET>500 GeV)+ high missing ET (ETmiss>500 GeV), • vetos leptons: to reduce jet+W bkdg mainly • Bkgd.: irreducible jet+Z/W jet+ /jet+l jZ(nn) dominant bkgd, can be calibrated using ee and mm decays of Z. • ISAJET with CTEQ3L • Fast simulation/reco Discovery limits L.Vacavant, I.Hinchcliffe, ATLAS-PHYS 2000-016 J. Phys., G 27 (2001) 1839-50 Getting ready for the LHC, Madrid Oct 23-27, 2006 J. Phys., G 27 (2001) 1839-50 MDMIN (TeV)

  20. ADD Parameters: jet+G Emission To characterise the model need to measure MD and d Measuring s gives ambiguous results (ppjet+GKK) Use variation of s on √s s at different √s almost independent of MD,varies with d Run at two different √s e.g. 10 TeV and 14 TeV, need 50 fb-1 Rates at 14 TeV of d=2 MD=6 TeV very similar to d=3 MD=5 TeV whereas Rates at 10 TeV of (d=2 MD=6 TeV) and (d=3 MD=5 TeV) differ by ~ factor of 2 Getting ready for the LHC, Madrid Oct 23-27, 2006 L.Vacavant, I.Hinchcliffe, ATLAS-PHYS 2000-016 J. Phys., G 27 (2001) 1839-50

  21. g e+ e- Tevatron ADD Exchange Limits Both D0 and CDF have observed no significant excess 95% CL lower limits on fundamental Planck scale (Ms) in TeV, using different formalisms: most stringent collider limits on LED to date! D0 Run II: mm D0 Run II: ee+gg D0 Run I+II: ee+gg CDF Run II: ee 200pb-1 1.11 1.32 1.11 1.00 0.93 0.88 0.96/0.99 D0 perform a 2D search in invariant mass & angular distribution And to maximise reconstruction efficiency they perform combined ee+gg (diEM) search: reduces inefficiencies from • g ID requires no track, but g converts (ee) • e ID requires a track, but loose track due to imperfect track reconstruction/crack Getting ready for the LHC, Madrid Oct 23-27, 2006

  22. ADD Discovery Limit: G Exchange ppGKKmm Virtual graviton production • Two opposite sign muons in the final state with Mmm>1 TeV • Irreducible background from Drell-Yan, also ZZ, WW, WW, tt (suppressed after selection cuts) • PYTHIA with ISR/FSR + CTEQ6L, LO + K=1.38 • Full (GEANT-4) simulation/reco + L1 + HLT(riger) • Theoretical uncert. • m and tracker misalignment, trigger and off-line recon. inefficiency, acceptance due to PDF Confidence limits for 1 fb-1: 3.9-5.5 ТеV for n=6..3 10 fb-1: 4.8-7.2 ТеV for n=6..3 100 fb-1: 5.7-8.3 ТеV for n=6..3 300 fb-1: 5.9-8.8 ТеV for n=6..3 Getting ready for the LHC, Madrid Oct 23-27, 2006 Belotelov et al., CMS NOTE 2006/076, CMS PTDR 2006

  23. ADD Discovery Limit: G Exchange Virtual graviton production CMS Confidence limits: 1 fb-1: 3.9-5.5 ТеV for n=6..3 10 fb-1: 4.8-7.2 ТеV for n=6..3 100 fb-1: 5.7-8.3 ТеV for n=6..3 300 fb-1:5.9-8.8 ТеV for n=6..3 V. Kabachenko et al. ATL-PHYS-2001-012 Fast MC Getting ready for the LHC, Madrid Oct 23-27, 2006 Belotelov et al., CMS NOTE 2006/076, CMS PTDR 2006

  24. Branching Fraction 10-2 10-4 10–6 10-8 g W u Z RS model t = Mple-kRc Dilepton channel H Tevatron 700 GeV GKK Experimental Signature for Model RS • Model parameters: • Gravity Scale: • 1st graviton excitation mass: m1 • = m1Mpl/kx1, & mn=kxnekrc(J1(xn)=0) • Coupling constant: c= k/MPl • 1 = m1 x12 (k/Mpl)2 5D curve space with AdS5 slice: two 3(brane)+1(extra)+time! Resonance position Coupling proportional to p-1 for KK levels above the fundamental level (n>=1) for n=0 graviton couples with the gravitational strenght • Couplings of each individual KK excitation are determined by the scale, = Mple-kRc ~ TeV massesmn = kxne-krc (J1(xn)=0) width Signature:Narrow, high-mass resonance states in dilepton/dijet/diboson channels k = curvature, R = compactification radius 400 600 800 1000 K/MPl Mll (GeV) d/dM (pb/GeV) 10-2 10-4 10-6 10-8 10-10 KK excitations can be excited individually on resonance 700 GeV KK Graviton at the Tevatron k/MPl = 1,0.7,0.5,0.3,0.2,0.1 from top to bottom 1 0.5 0.1 0.05 0.01 At the LHC only the 1st excitations are likely to be seen at the LHC, since the other modes are suppressed by the falling parton distribution functions. LHC 1500 GeV GKK and subsequent tower states 1000 3000 5000 Mll (GeV) Allenach et al, JHEP 9 19 (2000), JHEP 0212 39 (2002) Davoudiasl, Hewett, Rizzo hep-ph0006041 Getting ready for the LHC, Madrid Oct 23-27, 2006

  25. Present RS Constraints D0 performed combined ee+gg (diem search) CDF performed ee & gg search, then combine Present Experimental Limits Theoretical Constraints • c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale) • Theoretically preferred Lp<10TeV assures no new hierarchy appears between mEW and Lp Getting ready for the LHC, Madrid Oct 23-27, 2006 • Theoretically preferred Lp<10TeV, otherwise the model would no longer be interesting for solving the hierarchy problem – assures no new hierarchy appears between mEW and Lp

  26. RS1 Discovery Limit 100 fb-1 MG=1.5 TeV • Best channels to search in are G(1)e+e- and G(1)gg due to the energy and angular resolutions of the LHC detectors • G(1)e+e- best chance of discovery due to relatively small bkdg, from Drell-Yan* Di-electron • HERWIG • Main Bkdg: Drell-Yan • Model-independent analysis • RS model with k/MPl=0.01 as a reference (pessimisitc scenario) • Fast Simulation Sensitive at 5s up to 2080 GeV *Reach goes up to 3.5 TeV for c=0.1 for a 20% measurement of the coupling. Allenach et al, hep-ph0006114 Allenach et al, hep-ph0211205 * Getting ready for the LHC, Madrid Oct 23-27, 2006

  27. RS1 Model Parameters A resonance could be seen in many other channels: mm, gg, jj, bbbar, ttbar, WW, ZZ, hence allowing to check universality of its couplings:  e Relative precision achievable (in %) for measurements of s.B in each channel for fixed points in the MG,Lp plane. Points with errors above 100% are not shown. Also the size (R) of the ED could also be estimated from mass and cross-section measurements. Allenach et al, hep-ph0211205 Allenach et al, JHEP 9 19 (2000), JHEP 0212 39 (2002) Getting ready for the LHC, Madrid Oct 23-27, 2006 BR(G→) = 2 * BR(G→ee)

  28. RS1 Model Determination Spin-2 could be determined (spin-1 ruled out) with 90% C.L. up to MG = 1720 GeV 100 fb-1 MG=1.5 TeV 100 fb-1 e+e- MC = 1.5 TeV LHC Note: acceptance at large pseudo-rapidities is essential for spin discrimination (1.5<|eta|<2.5) Allanach et al, hep-ph 0006114 Getting ready for the LHC, Madrid Oct 23-27, 2006 Stacked histograms Spin-2 nature of the G(1) can be measured : For masses up to 2.3 TeV (c=0.1) there is a 90 % chance that the spin-2 nature of the graviton can be determined with a 95 % C.L.

  29. RS1 Discovery Limit I. Belotelov et al. CMS NOTE 2006/104 CMS PTDR 2006 Di-lepton states G1μ+μ- c=0.01 100 fb-1 c=0.1 100 fb-1 Solid lines = 5s discovery Dashed = 1s uncert. on L • Two muons/electrons in the final state • Bckg: Drell-Yan/ZZ/WW/ZW/ttbar • PYTHIA/CTEQ6L • LO + K=1.30 both for signal and DY • Full (GEANT-4) and fast simulation/reco • Viable L1 + HLT(rigger) cuts • Theoretical uncert. • Misalignment, trigger and off-line reco • inefficiency, pile-up Misalignment during 1st period when the momentum resolution will be reduced from 1-2% to 4-5%. G1e+e- B. Clerbaux et al. CMS NOTE 2006/083 CMS PTDR 2006 Getting ready for the LHC, Madrid Oct 23-27, 2006 Likelihood estimator based on event counting suited for small event samples: S=√(2[(S+B)log(1+S/B)-S])>5

  30. RS1 Discovery Limit Di-photon states G1 • Two photons in the final state • Bckg: prompt di-photons, QCD hadronic jets • and gamma+jet events, Drell-Yan e+e- • PYTHIA/CTEQ5L • LO for signal, LO + K-factors for bckg. • Fast simulation/reco + a few points with • full GEANT-4 MC • Viable L1 + HLT(rigger) cuts • Theoretical uncert. • Preselection inefficiency M.-C. Lemaire et al. CMS NOTE 2006/051 CMS PTDR 2006 c=0.1 Di-jet states K. Gumus et al. CMS NOTE 2006/070 CMS PTDR 2006 • Bckg: QCD hadronic jets • L1 + HLT(rigger) cuts 5 Discovered Mass: 0.7-0.8 TeV/c2 Getting ready for the LHC, Madrid Oct 23-27, 2006

  31. CMS RS Discovery Limits G1μ+μ- G1 c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale) Theoretically preferred Lp<10TeV G1e+e- LHC completely covers the region of interest Getting ready for the LHC, Madrid Oct 23-27, 2006

  32. TeV-1 Extra Dimension Model • I. Antoniadis, PLB246 377 (1990) • Multi-dimensional space with orbifolding • (5D in the simplest case, n=1) • The fundamental scale is not planckian: • MD ~ TeV • Gauge bosons can travel in the bulk •  Search for KK excitations of Z,g.. • Fermion-gauge boson couplings • can be exponentially suppressed • for higher KK-modes • Fundamental fermions (quarks/leptons) can be • localized at the same (M1) or • opposite (M2) points of orbifold •  destructive (M1) or constructive (M2) • interference of the KK excitations • with SM model gauge bosons New Parameters R=MC-1 : size of the compact dimension MC : corresponding compactification scale M0 : mass of the SM gauge boson Characteristic Signature: KK excitations of the gauge bosons appearing as resonances with masses : Mn = √(M02+n2/R2) where (n=1,2,…) & also interference effects! G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) ppZ1KK/1KKe+e- me+e- (GeV) Getting ready for the LHC, Madrid Oct 23-27, 2006 Mn = M0 In M1 case the KK gauge states couplings to SM fermions are the same as the SM ones but scaled by a factor of √2

  33. Present Constraints on TeV-1 ED D0 performed the first dedicated experimental search for TeV-1 ED at a collider Search for effects of virtual exchanges of the KK states of the Z and g • Search Signature: Signal has 2 distinct features: • enhancement at large masses (like LED) • negative interference between the 1st KK state of the Z/g and the SM Drell-Yan in between the Z mass and MC diEM search 200 pb-1 Lower limit on the compactification scale of the longitudinal ED: MC>1.12 TeV at 95% C.L. predicted background L = 200pb-1 SM Drell-Yan Better Limit: from precision electroweak data TeV-1 ED signal hc=5.0 TeV-2 MC≥4 GeV World Combined Limit MC>6.8 TeV at 95% C.L, dominated by LEP2 measurements Getting ready for the LHC, Madrid Oct 23-27, 2006

  34. TeV-1 ED Discovery Limits Di-electron states (ZKK decays) • Two high pT isolated electrons in the final state • Bckg: irreducible: Drell-Yan • Also ZZ/WW/ZW/ttabr • Signal and Bkgd: PYTHIA, CTEQ61M, PHOTOS used for inner bremsstrahlung production • LO + K=1.30 for signals, • LO + K-factors for bckg. • Full (GEANT-4) simulation/reco • with pile-up at low lum. (~1033cm-2s-1) • L1 + HLTrigger cuts • Theoretical uncert. 5 discovery limit of ppZ1KK/1KKe+e- (M1 model) With L=30/80 fb-1 CMS will be able to detect a peak in the e+e- invar. mass distribution if MC<5.5/6 TeV. B. Clerbaux et al. CMS NOTE 2006/083 CMS PTDR 2006b Getting ready for the LHC, Madrid Oct 23-27, 2006 Saturation for E>1.7TeV in the barrel and 3TeV in the end-caps EM energy corrected for energy leakage in the HAD cal. and for ECAL electronics saturation: (above)

  35. TeV-1 ED Discovery Limits ATLAS expectations for e and μ: PYTHIA + Fast simu/paramaterizedreco + Theor. uncert. In ee channel experimental resolution is smaller than the natural width of the Z(1), in mm channel exp. momentum resol. dominates the width g(1)/Z(1)→e+e-/m+m- Worse resolution for m 2 TeV e in ATLFAST: DE/E~0.7 % ~20% for m • Requiring >10 events above a given mll and S= (N-NB)/√NB > 5 With 100 fb-1 ATLAS will be able to detect resonance if MC (R-1)<5.8 TeV (ee+mm) • Acceptance for leptons: |h|<2.5 Even for lowest resonances of MC (4 TeV), no events would be observed for the n=2 resonances of Z and g at 8 TeV (Mn = √(M02+n2/R2)), which would have been the most striking signature for this kind of model. G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) Getting ready for the LHC, Madrid Oct 23-27, 2006 G. Azuelos, G. Polesello (Les Houches 2001 Workshop Proceedings), Physics at TeV Colliders, 210-228 (2001)

  36. TeV-1 ED Discovery Limits ATLAS expectations for e and μ: PYTHIA + Fast simu/paramaterizedreco + Theor. uncert. In ee channel experimental resolution is smaller than the natural width of the Z(1), in mm channel exp. momentum dominates the width ATLAS Mc=4 TeV g(1)/Z(1)→e+e-/m+m- Worse resolution for m 2 TeV e in ATLFAST: DE/E~0.7 % ~20% for m • Requiring >10 events above a given mll and and S= (N-NB)/√NB > 5 With 100 fb-1 ATLAS will be able to detect resonance if MC (R-1)<5.8 TeV (ee+mm) • Using a maximum likelihood method to fit the reconstructed distributions describing the kinematics of the event: G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) With 300 fb-1 can reach 13.5 TeV (ee+mm) Getting ready for the LHC, Madrid Oct 23-27, 2006 G. Azuelos, G. Polesello (Les Houches 2001 Workshop Proceedings), Physics at TeV Colliders, 210-228 (2001)

  37. Distinguishing Z(1) from Z’, RS G • Spin 1 Z(1) signal can be distinguished from a spin-2 narrow graviton resonance using the angular distribution of its decay products. • Z(1) can also be distinguished from a Z’ with SM-like couplings using the distribution of the forward-backward asymmetry: due to contributions of the higher lying states, the interference terms and the additional √2 factor in its coupling to SM fermions. The Z(1) can be discriminated for masses up to about 5 TeV with L=300fb-1. 4 TeV resonances Z(1) or Z’ or RS Graviton? ATLAS G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) Getting ready for the LHC, Madrid Oct 23-27, 2006 G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004)

  38. TeV-1 ED Discovery Limits WKK decays W1  e • Isolated high-pT lepton + missing ET • Invmass (l,n) > 1 TeV, veto jets • Bckg: irreducible bkdg: Wen, Also pairs: WW, WZ, ZZ, ttbar • Fast simulation/reco R-1=4 TeV R-1=5 TeV R-1=6 TeV Sum over 2 lepton flavours For L=100 fb-1 a peak in the lepton-neutrino transverse invariant mass (mTln) will be detected if the compactification scale (MC= R-1) is < 6 TeV SM SM mTen (GeV) If a peak is detected, a measurement of the couplings of the boson to the leptons and quarks can be performed for MC up to ~ 5 TeV. G. Polesello, M. Patra EPJ Direct, ATLAS 2003-023 G. Polesello, M. Patra EPJ Direct C 32 Sup.2 (2004) pp.55-67 Getting ready for the LHC, Madrid Oct 23-27, 2006

  39. TeV-1 ED Discovery Limits WKK decays W1  e If no signal is observed with100 fb-1 a limit of MC > 11.7 TeV can be obtained from studying the mTendistribution below the peak: R-1=4 TeV R-1=5 TeV Here: suppression in s R-1=6 TeV - due to –ve interference (M1) between SM gauge bosons and the whole tower of KK excitations SM - sizable even for MC above the ones accessible to a direct detection of the mass peak. SM mTen (GeV) - Can’t get such a limit with Wmn since momentum spread - can’t do optimised fit which uses peak edge G. Polesello, M. Patra EPJ Direct, ATLAS 2003-023 G. Polesello, M. Patra EPJ Direct C 32 Sup.2 (2004) pp.55-67 Getting ready for the LHC, Madrid Oct 23-27, 2006

  40. TeV-1 ED g* Discovery Limits This is more challenging than Z/W which have leptonic decay modes Detect KK gluon excitations (g*) by reconstructing their hadronic decays (no leptonic decays). Detect g* by (1) deviation in dijet s (2) analysing its decays into heavy quarks SM SM Coupling of g* to quarks = √2 * SM couplings  g*  wide resonances decaying into pairs of quarks Getting ready for the LHC, Madrid Oct 23-27, 2006

  41. TeV-1 ED g* Discovery Limits Reconstructed mass peaks Gluon excitation decays M=1 TeV • bbar or ttbar jets • For ttbar one t is forced to decay leptonically • Bckg: SM continuum bbar, ttbar, 2 jets, W +jets • PYTHIA • Fast simulation/reco M=1 TeV± 200 GeV Width expected to be G(g*) = 2 asM where M=g* mass  G(g*) ~ 200 GeV for M=1 TeV SM M=1 TeV For M=1 TeV natural width ~= experimental effects (fragmentation and detector resolution) Getting ready for the LHC, Madrid Oct 23-27, 2006 L. March, E. Ros, B. Salvachua, ATL-PHYS-PUB-2006-002

  42. TeV-1 ED g* Discovery Limits Reconstructed mass peaks M=1 TeV Mass windows used to evaluate the significance M=2 TeV M=1 TeV± 200 GeV M=3 TeV± 600 GeV 3 years at HL running With 300 fb-1 Significance of 5 achieved for: ttbar channel: R-1 = 3.3 TeV bbar channel: R-1 = 2.7 TeV Getting ready for the LHC, Madrid Oct 23-27, 2006 L. March, E. Ros, B. Salvachua, ATL-PHYS-PUB-2006-002

  43. TeV-1 ED g* Discovery Limits M=1 TeV M=2 TeV Although with 300 fb-1 Significance of 5 achieved for: bbar channel: R-1 = 2.7 TeV However, it is not in general possible to obtain a mass peak well separated from the bkdg.  it is unlikely that an excess of events in the g*bbar channel could be used as evidence of the g* resonance, since there are large uncertainties in the calculations of the bkdgs. For M=1TeV the peak displacements could be used as evidence for new physics if the b-jet energy scale can be accurately computed. Getting ready for the LHC, Madrid Oct 23-27, 2006 L. March, E. Ros, B. Salvachua, ATL-PHYS-PUB-2006-002

  44. TeV-1 ED g* Discovery Limits But in g*ttbar, the bkdg is mainly irreducible and not so large. g* resonance can be detected in this decay channel if the tt-bar s can be computed in a reliable way. M=1 TeV± 200 GeV M=3 TeV± 600 GeV Conclusion: g* decays into b-quarks are difficult to detect, decays into t-quarks might yield a significant signal for g* mass below 3.3 TeV. This could be used to confirm the presence of g* in the case that an excess in the dijet s is observed. Getting ready for the LHC, Madrid Oct 23-27, 2006 L. March, E. Ros, B. Salvachua, ATL-PHYS-PUB-2006-002

  45. 600 570 g1 1 Q1 Z1 L1 Universal Extra Dimensions Standard/Minimal UED • All particles can travel into the bulk, so each SM particle has an infinite tower of KK partners • Spin of the KK particles is the same as their SM partners • In minimal UED: 1 ED compactified in an orbifold (S1/Z2) of size R • KK parity conservation  the lightest massive KK particle (LKP) is stable (dark matter candidate). • Level one KK states must be pair produced • Mass degeneration except if radiative corrections included The model parameters: compactificaton radius R, cut-off scale , mh Thick/Fat brane • SM brane is endowed with a finite thickness in the ED • Gravity-matter interactions break KK number conservation: • ● 1st level KK states decay to G+SM. • ● If radiative corrections  mass degeneracy is broken and  and leptons are produced. Getting ready for the LHC, Madrid Oct 23-27, 2006

  46. Present Constraints on UED Bounds to the compactification scale: • Precision EWK data measurements set a lower bound of R-1 > 300 GeV • Dark matter constraints imply that 600 < R-1 <1050 GeV Phys. Rev. D64, 035002 (2001) Appelquist, Cheung, Dobrescu Servant , Tait, Nucl. Phys. B650,391 (2003) Getting ready for the LHC, Madrid Oct 23-27, 2006

  47. l l 1 Z1 p p q L1 q Q1 Geo accep L1,HLT 2 OSSF 4 ISO b-tag veto pTl< ETmiss Z veto 600 g1 g1 q Q1 570 q L1 1 Z1 l l g1 1 Z1 Q1 L1 UEDDiscovery Limit Standard UED Final State: 4 low-pT isolated leptons (2 pairs of opposite sign, same flavour leptons) + n jets + missing ET (from 2 undetected g1) Getting ready for the LHC, Madrid Oct 23-27, 2006 Used a possion stat method

  48. UEDDiscovery Limit Standard UED • 4 leptons in the final state + missing pT • Irreducible Bckg: ttbar + n jets (n = 0,1,2), 4 b-quarks, ZZ, Zbbar • To improve bkdg rejection over signal: apply b-tagging and Z-tagging vetoes • CompHEP for signal and CompHEP, PYTHIA, Alpgen for bckg. with CTEQ5L • Full simulation/reco + L1 + HLT(rigger) cuts • Theoretical and experimental uncert. Discovery sensitivity Studied for low lum run ~2x1033cm-2s-1 Getting ready for the LHC, Madrid Oct 23-27, 2006 Used a possion stat method

  49. G jet p p q1,g1 jet q1,g1 G 5 UEDDiscovery Limit Thick brane in UED with TeV-1 size Significance vs Mass of 1st KK excitation S 100 fb-1 ~2.7 TeV • 2 back-to back jets + missing ET (>775 GeV) • Irreducible Bckg: Z() jj, W(l) jj • PYTHIA/CTEQ5L + SHERPA for bckgr. • Fast simulation/reco 5s discovery possible at ATLAS with 100 fb-1 if first KK excitation mass < 2.7 TeV Getting ready for the LHC, Madrid Oct 23-27, 2006 P. H. Beauchemin, G. Azuelos ATL-PHYS-PUB-2005-003

  50. LHC Start-up Expectations Getting ready for the LHC, Madrid Oct 23-27, 2006

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