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Sensitivity of the LHC Experiments to

Sensitivity of the LHC Experiments to. Extra Dimensions. Dr Tracey Berry Royal Holloway University of London On behalf of the ATLAS and CMS collaborations. Overview. LHC Experiments: ATLAS & CMS Extra Dimensional Models Searches ADD RS TeV -1

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Sensitivity of the LHC Experiments to

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  1. Sensitivity of the LHC Experiments to Extra Dimensions Dr Tracey Berry Royal Holloway University of London On behalf of the ATLAS and CMS collaborations SUSY 2007, July, Karlsruhe

  2. Overview • LHC Experiments: ATLAS & CMS • Extra Dimensional Models Searches • ADD • RS • TeV-1 • Summary of LHC Start-up Expectations • Conclusions SUSY 2007, July, Karlsruhe

  3. LHC Large Hadron Collider proton–proton collider @ center of mass energy √s = 14 TeV 25 m First collisions expected summer 2008 15 m SUSY 2007, July, Karlsruhe

  4. ATLAS and CMS Large general-purpose particle physics detectors A Large Toroidal LHC ApparatuS Compact Muon Solenoid 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 SUSY 2007, July, Karlsruhe

  5. 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 MPl2 ~ RdMPl(4+d)(2+d) G CDF Run I l=+1 Mll 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 • 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 • Signature: • Real graviton emission: in association with a vector-boson • jets + missing ET, V+missing ET • Or deviations in virtual graviton exchange e.g. Excess above di-lepton continuum SUSY 2007, July, Karlsruhe Can use LHC to search for ADD ED with d<6 d<=2 ruled out MD>1TeV from Tevatron For MPl ~ 1019 GeV and MPl(4+d) ~MEW R ~1032/d x10-17 cm deviations in s and asymmetries of SM processes

  6. J. Weng et al. CMS NOTE 2006/129 ADD Discovery Limit: Real G Emission Integrated Lum for a 5s significance discovery 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 ppg+GKK Significance: S=2(√(S+B)-√B)>5 • Signature: high-pT photon + high missing ET • Main Bkgd: irreducible Zg  nng, Also W e(m,t)n, Wg en, g+jets, QCD, di-g, Z0+jets Rates too low ppjet+GKK • Signature: high ET jet + large missing ET • Bkgd: irreducible jet+Z/W jet+ /jet+l vetos leptons: to reduce jet+W bkdg mainly Discovery limits SUSY 2007, July, Karlsruhe L.Vacavant, I.Hinchcliffe, ATLAS-PHYS 2000-016 J. Phys., G 27 (2001) 1839-50 At low pT the bkgd, particularly irreducible Zg  nng is too large require pT>400 GeV J. Phys., G 27 (2001) 1839-50 • Signature: high ET jet + large missing ET • Bkgd: irreducible jet+Z/W jet+ /jet+l jZ(nn) dominant bkgd, can be calibrated using ee and mm decays of Z. • vetos leptons: to reduce jet+W bkdg mainly Dominant subprocess MDMIN (TeV) gggG, qgqG & qqGg

  7. ADD Discovery Limit: G Exchange ppGKKmm • Two opposite sign muons & Mmm>1 TeV • Bkg: Irreducible Drell-Yan, also ZZ, WW, WW, tt (suppressed after selection cuts) Virtual graviton production 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 Fast MC V. Kabachenko et al. ATL-PHYS-2001-012 Belotelov et al., CMS NOTE 2006/076, CMS PTDR 2006 SUSY 2007, July, Karlsruhe • PYTHIA with ISR/FSR + CTEQ6L, LO + K=1.38

  8. Branching Fraction g W u Z RS model • 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 Resonance position width k = curvature, R = compactification radius 400 600 800 1000 = Mple-kRc Model RS Davoudiasl, Hewett, Rizzo hep-ph0006041 Randall, Sundrum,Phys Rev Lett 83 (99)b 5D curve space with AdS5 slice: two 3(brane)+1(extra)+time! K/MPl Mll (GeV) Signature:Narrow, high-mass resonance states in dilepton/dijet/diboson channels 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 Coupling proportional to p-1 for KK levels above the fundamental level (n>=1) for n=0 graviton couples with the gravitational strenght 1 0.5 0.1 0.05 0.01 1 extra warped dimension • Couplings of each individual KK excitation are determined by the scale, = Mple-kRc ~ TeV massesmn = kxne-krc (J1(xn)=0) LHC 1500 GeV GKK and subsequent tower states G1μ+μ- c=0.1 100 fb-1 1000 3000 5000 • Gravity localised in the ED Mll (GeV) c=0.01 100 fb-1 400 600 800 1000 I. Belotelov et al. , CMS NOTE 2006/104, CMS PTDR 2006 SUSY 2007, July, Karlsruhe Sensitive at 5s up to 2080 GeV For K/MPl=0.01

  9. RS1 Discovery Limit c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale) Best channels to search in are G(1)e+e- and G(1)gg due to the energy and angular resolutions of the detectors Allenach et al, hep-ph0211205 10fb-1 BR(Ggg) = 2* BR(Gee/mm) Reach for e and g is comparable for low coupling and MG: due to the QCD and prompt photon bkgds in the gg channel which are harder to efficiently suppress mm channel trails ee channel due to resolution < 60 fb-1 LHC completely covers the region of interest G1μ+μ- G1e+e- G1 SUSY 2007, July, Karlsruhe CMS PTDR 2006 Theoretically preferred Lp<10TeV *Reach goes up to 3.5 TeV for c=0.1 for a 20% measurement of the coupling. and for higher masses and coupling the gg is leading the reach due to the higher branching ratio

  10. Angular distributions RS1 Model Determination Spin determination of the resonance G has spin 2: ppGee has 2 components: ggGee & qqGee each with different angular distributions MG=1.5 TeV 100 fb-1 e+e- MC = 1.5 TeV LHC Spin-2 could be determined (spin-1 ruled out) with 90% C.L. up to MG = 1720 GeV with 100 fb-1 Note: acceptance at large pseudo-rapidities is essential for spin discrimination (1.5<|eta|<2.5) Allanach et al, hep-ph 0006114 SUSY 2007, July, Karlsruhe 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.

  11. TeV-1 Sized Extra Dimensions • I. Antoniadis, PLB246 377 (1990) • One extra dimension compactified on a S1/Z2 orbifold • Radius of compactification small enough  • Gauge bosons can travel in the bulk • Fermions (quarks/leptons) localized • at a fixed point (M1) or • opposite (M2) points •  destructive (M1) or constructive (M2) • interference of the KK excitations • with SM model gauge bosons ppZ1KK/1KKe+e- KK excitations of the gauge bosons (Z(k),W(k)) appear as resonances with masses : Mk = √(M02+k2/R2) where (k=1,2,…) & also interference effects! Signature: me+e- (GeV) Mn = M0 New Parameters R=MC-1 : size of compact dimension MC : compactification scale M0 : mass of the SM gauge boson • Look for l+l- decays of g and Z0 KK modes. • Also in decays (mT) of W+/- KK modes. • Or evidence of g* via dijet s or bb, tt s G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) SUSY 2007, July, Karlsruhe 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 Fermion-gauge boson couplings can be exponentially suppressed for higher KK-modes

  12. g(1)/Z(1)→e+e-/m+m- Tev-1 Sized Extra Dimensions • Search for the resonance peak Searching for deviations in the dilepton spectrum: 3 methods used L=30/80 fb-1 CMS will be able to detect a peak in the e+e- invar. Mll if MC<5.5/6 TeV. 5 discovery f ppZ1KK/1KKe+e- ATLAS: L=100 fb-1 MC (R-1)<5.8 TeV (ee+mm) 2) Search for interference in a mass window 3) Fit to kinematics of signal e+e- With 300 fb-1 can reach 13.5 TeV (ee+mm) B. Clerbaux et al. CMS NOTE 2006/083 CMS PTDR 2006b G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) ee+mm: ATLAS 5s reach is ~8 TeV for L=100 fb-1 and ~10.5 TeV for 300 fb-1 SUSY 2007, July, Karlsruhe

  13. Distinguishing Z(1)/g(1) from Z’, RS G Distinguish • spin-1 Z(1) from spin-2 G: angular distribution of decay products • spin-1 Z(1) from spin-1 Z’ with SM-like couplings: forward-backward asymmetry due to contributions of the higher lying states, interference terms and 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 4 TeV Z(1)/g(1) or Z’ or RS Graviton? 1000 2000 3000 4000 1000 2000 3000 4000 100 pb-1 G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) 1000 2000 3000 4000 1000 2000 3000 4000 M (GeV) G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) SUSY 2007, July, Karlsruhe

  14. TeV-1 ED Discovery Limits WKK decays Search for deviations in lepton-neutrino transverse invariant mass (mTln) spectra W1  e R-1=4 TeV 1) Search for peak: L=100 fb-1 detect a peak if compactification scale (MC= R-1)<6 TeV R-1=5 TeV Sum over 2 lepton flavours R-1=6 TeV 2) Studying distribution below the peak: in mTen spectra L=100 fb-1 a limit of MC > 11.7 TeV SM SM -ve interference sizable even for MC above the ones accessible to a direct detection of the mass peak. =√2peTpnT(1-cosDf) 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 SUSY 2007, July, Karlsruhe Can’t get such a limit with Wmn since momentum spread - can’t do optimised fit which uses peak edge - due to –ve interference (M1) between SM gauge bosons and the whole tower of KK excitations

  15. TeV-1 ED g* Discovery Limits Add comment re backgrounds make this difficult and tt – used as confirmation 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). Reconstructed mass peaks M=1 TeV Detect g* by (1) deviation in dijet s (2) analysing its decays into heavy quarks Gluon excitation decays M=1 TeV± 200 GeV • 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 With 300 fb-1 Significance of 5 achieved for: ttbar channel: R-1 = 3.3 TeV bbar channel: R-1 = 2.7 TeV Although bkdg & its uncertainty makes this channel challenging SUSY 2007, July, Karlsruhe L. March, E. Ros, B. Salvachua, ATL-PHYS-PUB-2006-002

  16. LHC Start-up Expectations SUSY 2007, July, Karlsruhe

  17. Conclusions • The discovery potential of both experiments makes it possible to investigate if extra dimensions really exist within various ED scenarios at a few TeV scale: • Large Extra-Dimensions (ADD model) • Randall-Sundrum (RS1) • TeV-1 Extra dimension Model • (Universal Extra Dimensions – not shown here) • Reaches in different channels depend on the performance of detector systems: proper energy, momentum, angular reconstruction for high-energy leptons and jets, Et measurement, b-tagging and identification of prompt photons • ATLAS & CMS increasing focus on first year of data taking • Understand/optimize detector performance (calibration, alignment, …) • Understand/measure Standard Model processes (bkg sources) • Once these are achieved ATLAS & CMS could potentially have new physics results within months! SUSY 2007, July, Karlsruhe New results have been predicted with data collected in the start-up LHC weeks (integrated luminosity<1 fb-1)

  18. BACKUP SLIDES! SUSY 2007, July, Karlsruhe

  19. Lyn Evans EPS July 2007 General schedule • Engineering run originally foreseen at end 2007 now precluded by delays in installation and equipment commissioning. • 450 GeV operation now part of normal setting up procedure for beam commissioning to high-energy • General schedule has been revised, accounting for inner triplet repairs and their impact on sector commissioning • All technical systems commissioned to 7 TeV operation, and machine closed April 2008 • Beam commissioning starts May 2008 • First collisions at 14 TeV c.m. July 2008 • Luminosity evolution will be dominated by our confidence in the machine protection system and by the ability of the detectors to absorb the rates. • No provision in success-oriented schedule for major mishaps, e.g. additional warm-up/cooldown of sector SUSY 2007, July, Karlsruhe

  20. LHC General Schedule, 5 July 2007 General schedule Baseline rev. 4.0 Global pressure test &Consolidation Warm up Interconnection of the continuous cryostat Global pressure test &Consolidation Leak tests of the last sub-sectors Powering Tests Flushing Powering Tests Inner Triplets repairs & interconnections Cool-down Cool-down SUSY 2007, July, Karlsruhe

  21. 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. SUSY 2007, July, Karlsruhe

  22. 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 Q1 Z1 L1 UEDDiscovery Limit Standard UED Discovery sensitivity Signature: 4 low-pT isolated leptons (2 pairs of opposite sign, same flavour leptons) + n jets + missing ET (from 2 undetected g1) Irreducible Bckg: ttbar + n jets(n = 0,1,2), 4 b-quarks, ZZ, Zbbar Studied for low lum run ~2x1033cm-2s-1 SUSY 2007, July, Karlsruhe CMS CR 2006/057 Used a possion stat method W, Z UED G • All SM particles propagate in “Universal” ED • often embedded in large ED e, m

  23. 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 Signature: 2 back-to back jets + missing ET (>775 GeV) Irreducible Bckg: Z() jj, W(l) jj 5s discovery possible at ATLAS with 100 fb-1 if first KK excitation mass < 2.7 TeV SUSY 2007, July, Karlsruhe P. H. Beauchemin, G. Azuelos ATL-PHYS-PUB-2005-003 PYTHIA/CTEQ5L + SHERPA for bckgr. Fast simulation/reco

  24. LHC Start-up Expectations SUSY 2007, July, Karlsruhe

  25. 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 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 SUSY 2007, July, Karlsruhe

  26. 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… SUSY 2007, July, Karlsruhe

  27. 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) SUSY 2007, July, Karlsruhe

  28. 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 SUSY 2007, July, Karlsruhe

  29. 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 SUSY 2007, July, Karlsruhe

  30. 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 SUSY 2007, July, Karlsruhe J. Phys., G 27 (2001) 1839-50 MDMIN (TeV)

  31. 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 SUSY 2007, July, Karlsruhe L.Vacavant, I.Hinchcliffe, ATLAS-PHYS 2000-016 J. Phys., G 27 (2001) 1839-50

  32. 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 SUSY 2007, July, Karlsruhe Belotelov et al., CMS NOTE 2006/076, CMS PTDR 2006

  33. ADD Discovery Limits Summary Can use LHC to search for ADD ED with d<6 d<=2 ruled out MD>1TeV from Tevatron Photon+Met CMS Discovery above 3.5 TeV not possible in this channel Jet+Met ATLAS 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 CMS Exchange limits: ATLAS Exchange 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 SUSY 2007, July, Karlsruhe

  34. Branching Fraction 10-2 10-4 10–6 10-8 g W u Z RS model t 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. Allenach et al, JHEP 9 19 (2000), JHEP 0212 39 (2002) = 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 1 extra warped dimension • 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 LHC 1500 GeV GKK and subsequent tower states 1000 3000 5000 Mll (GeV) Davoudiasl, Hewett, Rizzo hep-ph0006041 SUSY 2007, July, Karlsruhe

  35. 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. SUSY 2007, July, Karlsruhe Allenach et al, hep-ph0006114 Allenach et al, hep-ph0006114 Allenach et al, hep-ph0211205 Allenach et al, hep-ph0211205 * *

  36. 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 SUSY 2007, July, Karlsruhe Likelihood estimator based on event counting suited for small event samples: S=√(2[(S+B)log(1+S/B)-S])>5

  37. 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 SUSY 2007, July, Karlsruhe

  38. 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) SUSY 2007, July, Karlsruhe BR(G→) = 2 * BR(G→ee)

  39. TeV-1 ED Discovery Limits ATLAS expectations for e and μ: 2 leptons with Pt>20GeV in |h|<2.5, mll>1TeV Reducible backgrounds from tt, WW, WZ, ZZ 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 • 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) SUSY 2007, July, Karlsruhe G. Azuelos, G. Polesello (Les Houches 2001 Workshop Proceedings), Physics at TeV Colliders, 210-228 (2001) • 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)

  40. TeV-1 ED Discovery Limits g(1)/Z(1)→e+e-/m+m- Several Methods have been used to determine the discovery limits for this signature: model independent & dependent • Model independent search for the resonance peak– lower mass limit • 2 sided search window – search for the interference • Model dependent – fit to kinematics of signal Event kinematics* can be fully defined by the 3 variables x1PA • Acceptance for leptons: |h|<2.5 x2PB G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) SUSY 2007, July, Karlsruhe • A simple number counting technique compared to the reach obtained in a detailed study of the invMss spectrum G. Azuelos, G. Polesello (Les Houches 2001 Workshop Proceedings), Physics at TeV Colliders, 210-228 (2001) Can use resonance and interference to search – model dependent and independent….

  41. Method 1: Lower Mass Limit • Model Independent Simple number counting technique. Naïve reach estimate for the observation of an increase in the mll distribution Choice of lower bound For each different MC value: lower bound on mll is different: chosen such to keep as much as possible of the resonance width Number of events expected in the peak for L = 100 fb-1 MC mass of lowest lying KK excitation Mlllower Signal Bkdg Arbitrary requirement for discovery: require 10 events to be detected above mll summed over the lepton flavours, and a statistical significance S= (N-NB)/√NB > 5 For 100 fb-1 using this method, the reach is MC (R-1)<5.8 TeV (ee+mm) SUSY 2007, July, Karlsruhe • A simple number counting technique compared to the reach obtained in a detailed study of the invMss spectrum Also can added effect of systematic uncertaintiesb Is there a plot of the significances? A high mll tail which might be produced by lepton mismeasurement could endanger this result. Consideration of the momentum balance of the event in the transverse plane should allow to reject events with one badly mismeasured lepton.

  42. Method 2: Mass Window 1st approach to study the off-peak region: • Evaluate NS and NB within a mass range – compare to w.r.t SM e+e- 100 fb-1 in mass window 1000< mee<2000 GeV All numbers in this table includes a contribution of 15 expected events from reducible bkgds • For ee+mm channels, the ATLAS 5s reach is ~8 TeV for L=100 fb-1 and ~10.5 TeV for 300 fb-1 Better limit than the MC (R-1)<5.8 TeV (ee+mm)for 100 fb-1 using lower bound method 1 to search for the resonance SUSY 2007, July, Karlsruhe • Parameterise the statistical significance of the s suppression as (N-NB)/√NB Method sensitive to general resonance peak search for new physics Also can added effect of systematic uncertainties

  43. x1PA x2PB Method 3: Optimal Reach and Mass Measurement • Model Dependent Use the full information in the events, not just mll g(1)/Z(1)→e+e-/m+m- Event kinematics* are fully defined by the 3 variables An optimal measurement of MC can be obtained by a likelihood fit to the reconstructed distributions for these 3 variables. With 300 fb-1 can reach 13.5 TeV (ee+mm) SUSY 2007, July, Karlsruhe • 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)

  44. 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 SUSY 2007, July, Karlsruhe 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)

  45. Distinguishing Z(1) from Z’, RS G Select events around the peak of the resonance 3750 GeV < Mee < 4250 GeV Plot cosine of the angle of the lepton, w.r.t the beam direction, the frame of the decaying resonance. (+ve direction was defined by the sign of reconstructed momentum in the dilepton system.) Angular distributions are normalized to 116 events, the number predicted with a luminosity of 100 fb-1 for the Z(1)/g(1) case SUSY 2007, July, Karlsruhe G. Azuelos, G. Polesello EPJ Direct 10.1140 (2004) 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. Schematic diagram here?

  46. TeV-1 ED Discovery Limits WKK decays • Isolated high-pT lepton >200 GeV + missing ET > 200 GeV • Invmass (l,n) (mln)> 1 TeV, veto jets • Bckg: irreducible bkdg: Wen, Also pairs: WW, WZ, ZZ, ttbar • Fast simulation/reco W1  e 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 =√2peTpnT(1-cosDf) 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 SUSY 2007, July, Karlsruhe

  47. 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 SUSY 2007, July, Karlsruhe

  48. Angular distributions Spin-1/Spin-2 Discrimination Spin-1 States:Z from extended gauge models, ZKK Spin-2 States:RS1-graviton Method: unbinned likelihood ratio statistics incorporating the angles in of the decay products the Collins-Soper farme (R.Cousins et al. JHEP11 (2005) 046). The statististical technique has been applied to fully simu/reco events. Z’ vs RS1-graviton I. Belotelov et al. CMS NOTE 2006/104 CMS PTDR 2006 Older results on spin discrimination from ATLAS can be found B.C. Allanach et al, JHEP 09 (2000) 019; ATL-PHYS-2000-029 SUSY 2007, July, Karlsruhe

  49. 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) SUSY 2007, July, Karlsruhe

  50. 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 SUSY 2007, July, Karlsruhe Used a possion stat method

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