Search for extra dimensions at LHC

Transcription

1 Search for extra dimensions at LHC Laurent Vacavant Lawrence Berkeley National Laboratory on behalf of the ATLAS and CMS collaborations EPS Aachen / String theory and extra dimensions / 18 July July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 1

2 Spectrum of Studies at LHC Large Extra Dimensions direct production of gravitons virtual effects of gravitons Size of ex TeV -1 -sized ED Kaluza-Klein excitations of gauge bosons tra dimensions Warped ED narrow resonance of graviton radion TransPlanckian physics: elastic scattering black holes (talk by G. Landsberg) Other implications: gauge coupling unification singlet neutrino 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 2

3 LHC Studies Objectives: establish the sensitivity to the signals start from Feynman rules derived by theorists implement the partonic X-sections in a generator use a fast simulation of detector acceptance efficiency resolution consider various physics & instrumental backgrounds try to characterize the model measurement of unique features determination of the number of dimensions parameters of underlying model? 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 3

4 Detector Performance & Simulation Detector Performance: needed for first searches: missing E T, high-p T electron, photon, detectors already optimized for that (SUSY, Higgs) example: resolution for electrons (ATLAS): E 12% 24.5% = 0.7% E EGeV ( ) ET σ m m ~ 0.8% (@ 500 GeV) Fast simulation: many aspects relevant to ED searches validated w/ full sim.: missing energy (cracks,.): OK for large E T mass resolution γγ: thorough studies for H γγ Caveat: systematic effects: linearity at TeV, instrumental bckgd, 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 4

5 Large Extra Dimensions Kaluza-Klein Gravitons ADD scenario: (cf. talk by I.Antoniadis) gravity becomes strong at TeV size of ED 1 mm SM confined in 4D, only gravity in the bulk two parameters: number of extra (compactified) dimensions: δ new fundamental mass scale M D : M D ~ TeV R C ~ mm (for δ=2) Constraints (experimental + astrophysics): talk by S.Mele Gravitons & Kaluza-Klein states: in the bulk: gravitational interaction massless G in 4D: KK states G (k), m k2 = m 02 + k 2 /R C 2 coupling: universal & weak (1/M Pl(4) ), but large # of states 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 5

6 Large Extra Dimensions Direct Production of Kaluza-Klein Gravitons Direct production at LHC: Signatures: monojet + missing energy, (photon + missing energy) ATLAS study: partonic cross-sections from G.Giudice,R.Rattazzi, J.D.Wells Nucl.Phys. B54 3 (1999) implemented in ISAJET ATLAS fast-simulation Background for jet signal: jz(νν), jw(τν), jw(eν), jw(µν) Selection: trigger: jet ( η <5) + E T miss lepton veto ( η <2.5) central jet ( η <2.5) large E T miss ATLAS: LV, I. Hinchliffe J.Phys. G: Nucl. Part. Phys (2001) 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 6

7 Large Extra Dimensions Direct Production of Kaluza-Klein Gravitons Missing energy: Sensitivity for 100 fb -1 : 100 fb -1 (1 S/ B > 5 > 100 signal events E T (jet) > 1 TeV cm -2 s -1 ) jet + G (k) signature: discovery M max D R compact M min D δ = 2 δ = TeV 7.0 TeV 8 µm 2 Å ~ 4 TeV ~ 4.5 TeV photon + G (k) signature: δ = TeV 1 pm ~ 5 TeV confirm. NB: effective theory, valid only for M min D s ˆ < M D M max D R compact M min D δ = TeV 32 µm ~3.5 TeV 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 7

8 Large Extra Dimensions Direct Production of Kaluza-Klein Gravitons Characterization of the model: Precise measurement of Xsection: difficult: case (δ=2, M D = 5 TeV) very similar to the case (δ=4, M D = 4 TeV) for instance not (yet) investigated in details measure both M D and δ Run at a different CME: σ(10 TeV) / σ(14 TeV) good discrimination if 5% accuracy on σ(10)/σ(14) > 50 fb 10 TeV new CME close to 14 TeV (otherwise small overlap of regions allowed by eff. theory) 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 8

9 Large Extra Dimensions Virtual Exchange of Kaluza-Klein Gravitons Virtual exchange of gravitons at LHC: Signatures: deviations from SM in Drell-Yan X-sections, asymmetries (sensitivity mostly from interference terms, KK exchange M s -8 ) ATLAS study: partonic cross-sections amplitude divergent for δ > 1: naive cut-off at M ll,γγ < 0.9 M S K.Cheung hep-ph/ , J.L.Hewett hep-ph/ ATLAS: V. Kabachenko, A. Miagkov, A. Zenin, ATL-PHYS July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 9

10 Large Extra Dimensions Virtual Exchange of Kaluza-Klein Gravitons Signatures: qq,gg γγ, ll, (WW, tt, ) excess over DY events in di-lepton, di-photon mass distributions some s-channel processes not present at tree-level in SM: more central production for γγ M eff = 4 TeV M eff = 4 TeV dn dη pp γγ η 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 10

11 Large Extra Dimensions Virtual Exchange of Kaluza-Klein Gravitons Sensitivity for 100 fb -1 : P T > 800 GeV m gg > 1 TeV 5.1 TeV 6.6 TeV Mostly a discovery channel: no sensitivity on δ w/o specifying UV theory, M s cannot be related to M D 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 11

12 TeV -1 -sized Extra Dimensions Kaluza-Klein Gauge Bosons Basics: (cf. talk by I.Antoniadis) one extra dimension compactified on a S 1 /Z 2 orbifold radius of compactification small enough gauge bosons in the bulk fermions localized on: a fixed point (M1 model): invariance under y -y opposite fixed points (M2 model): under y y + 2πR Kaluza-Klein spectra for Z (k), W (k) : m k2 = m 02 + k 2 M 2 C for M C = 4 TeV: m 1 = 4 TeV, m 2 = 8 TeV look for pp γ (1) /Z (1) l + l - on top of SM Drell-Yan ATLAS study: matrix elements from T.Rizzo implemented in Pythia ATLAS fast simulation T. Rizzo, PRD (2000) ATLAS: G.Azuelos, G.Polesello, Proc. Les Houches July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 12

13 TeV -1 -sized Extra Dimensions γ (1) /Z (1) Kaluza-Klein Gauge Bosons Signatures: γ (1) /Z (1) e + e -, µ + µ - 2 TeV electron in ATLAS: E/E ~ 0.7 % (~20 % for a muon) acceptance for leptons: η < 2.5 M2 M c = 4 TeV µ + µ - M c = 4 TeV M1 SM e + e - m(e + e - ) m(l + l - ) 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 13

14 TeV -1 -sized Extra Dimensions γ (1) /Z (1) Kaluza-Klein Gauge Bosons Sensitivity from peak region: for 100 fb -1, S/ B > 5, S > 10 : M C max = 5.8 TeV Optimal reach (using interferences in tail region): likelihood fit analysis w/ MC experiments electrons e+µ 100 fb fb fb fb TeV 11 TeV 12 TeV 13.5 TeV detailed study of systematics: energy scale, calibration higher order QCD & EW corrections PDFs 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 14

15 TeV -1 -sized Extra Dimensions γ (1) /Z (1) Kaluza-Klein Gauge Bosons Characterization of the model: Z (1) or Z or RS graviton?? Forward-backward asymetries: M2 G* M1 Z 100 pb July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 15

16 TeV -1 -sized Extra Dimensions W (1) Kaluza-Klein Gauge Bosons Ditto for W (1) : Sensitivity for 100 fb -1 : from peak ~ 6 TeV optimal ~ 9 TeV Discrimination from W : more difficult under study ATLAS: G.Polesello, M. Prata, preliminary 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 16

17 Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance L E Planck brane SM brane KK graviton excitations G (k) (cf. talk by I.Antoniadis) scale Λ π coupling & width: c = k/m Pl 0.01 < k/m Pl < 0.1 mass spectrum: m n = k x n exp(-kπr c ) L E Golden channel: G (1) e + e - good acceptance good energy resolution good angular resolution also G (1) γγ Main features to check: universal couplings: G (1) µ + µ -, WW, ZZ, jj spin 2 measure r c? ATLAS: B.C. Allanach, K.Odigari, A. Parker, B. Webber JHEP 9 19 (2000), ditto + M.J.Palmer, A. Sabetfakhri hep-ph/ CMS: C.Collard, M.-C. Lemaire, P.Traczyk, G.Wrochna hep-ex/ ; I. Golutvin, P.Moissenz, V.Palichik, M.Savina, S.Shmatov 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 17

18 Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Signature: G (1) e + e - discovery ATLAS, e + e - m G = 1.5 TeV, c = 0.01 CMS, e + e - m G = 1.5 TeV, c = 0.01 CMS, e + e - m G = 4 TeV, c = fb July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 18

19 Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Sensitivity: c = k/m Pl CMS, 100 fb -1 m G (GeV) LHC covers completely the interesting region 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 19

20 Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Spin determination: ATLAS, e + e -, 100 fb -1 m G = 1.5 TeV, c = 0.01 Signal: from gluon fusion 1 cos 4 θ * from quark annihilation 1 3cos 2 θ * + 4cos 4 θ * Spin-1 (Z ): 1 + cos 2 θ * Drell-Yan SM NB: acceptance at large η coverage to is essential almost no discrimination spin 1/spin 2 for η < July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 20

21 Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Spin-1 hypothesis rejection: c = k/m Pl CMS, 100 fb -1 m G (GeV) large fraction of interesting region covered by LHC. 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 21

22 Warped Extra Dimension Randall-Sundrum model: the radion The RS radion: fluctuations of distance between branes solving hierarchy problem requires kr c ~12 dynamical mechanism to do so, gives a mass to the radion, possibly lighter than G (1) W.D. Goldberger, M.B. Wise, PRL (1999) Radion phenomenology: G.Giudice, R.Rattazzi, J.D.Wells, hep-ph/ coupling similar to Higgs, mixes with Higgs (ξ parameter) enhanced coupling to gluons narrow width ATLAS: G.Azuelos, D.Cavalli, H.Przysiezniak,LV Eur.Phys.J direct C4 16 (2002) Higgs Radion ξ=0 Radion ξ=1/6 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 22

23 Warped Extra Dimension Randall-Sundrum model: the radion Reinterpretation of Higgs signals: SM Higgs 100 fb July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 23

24 Warped Extra Dimension Randall-Sundrum model: the radion Decay in two Higgses: φ hh γγ bb clean signature good kinematical constraints small background Luminosity (fb -1 ) required for 5σ discovery: ξ 0 0 1/6 1/6 Λ (TeV) m=300 GeV Reach in Λ with 30 fb -1 : m=600 GeV Λ max = 2.2 TeV (m φ =300 GeV) Complementary channel: φ hh bb ττ Λ max = 1.0 TeV (m φ =600 GeV) - 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 24

25 Higgs doublet & right-handed neutrino Model: gives ν small masses w/o see-saw singlet neutrino ψ in the bulk ψ ~ ν R, coupling reduced by R Study: charged Higss (2HDM-II) MSSM: only H τ Rν ψ in bulk: H τ Rν + τlψ asymmetry to discriminate: ATLAS: K.Assamagan, A.Deandrea, Phys. Rev D (2002) 100 fb -1 H τ ψ L MSSM Γ( H τ Lψ) Γ( H τrν ) A = Γ ( H τ ψ) +Γ ( H τ ν ) L measure polarization asymmetries use hadronic τ decays R ph jet E τ 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 25

26 Other studies (in a jumble) Studies not covered in this talk: Gauge coupling unification: di-jet cross-sections G.Balazs, B.Laforge hep-ph/ On-going studies: Black holes: MC Herwig + simulation (cf. talk by G.Landsberg) TransPlanckian elastic scattering Large Extra Dimensions: direct production of graviscalars (stringy effects) Next (see Les Houches 2003): Universal ED scenario: faking SUSY? Disentangling radion and Higgs: coupling measurements 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 26

27 Conclusion A lot of models, with very rich and various phenomenology! LHC experiments have studied/are studying many of them The LHC will be able to probe the relevant region of the parameter space for most of the models studied so far Thanks to my colleagues in ATLAS and CMS. Special thanks to: G. Azuelos, F. Gianotti, L. Pape, L. Poggioli, G. Polesello, S. Shmatov, P. Traczyk, G. Wrochna 18 July 2003 L.Vacavant - Search for extra dimensions at LHC - EPS Aachen 27