1. Search for Extra Dimensions at ATLAS Ambreesh Gupta University of Chicago PASCOS 2003 T.I.F.R, Mumbai, 3-8 January 2003

4. Spectrum of ATLAS Studies Large Extra Dimensions  KK Graviton Direct Production  Missing E T  KK Graviton Virtual Production  Drell-Yan TeV -1 Extra Dimensions  KK Gauge Bosons  Multi-TeV Resonance Randall-Sundrum Models  KK Graviton  TeV Resonance  Radion  Higgs Like Signature Other Scenario  (E)LED + MSSM  RGE and Di-Jet cross section  LED + singlet neutrino + 2HDM-II  H 

5. Large Extra Dim.: Graviton Direct Production  The apparent weakness of gravity could be due to diffusion of its field in extra dimension.  Gravitons will appear as tower of massive Kaluza Kline states from 4D point of view.  G (k) as external leg => Missing Energy in 4D.  ATLAS studies for sensitivity on scale M D and number of extra dimension . L. Vacavant and I. Hinchliffe, J. Phys. G: Nucl. Part. Phys. 27 (2001) 1839

6. Large Extra Dim.: Graviton Direct Production  Disentangle  and M D - Run at two different energies e.g 10 TeV and 14 TeV => need 50 fb -1.

7. Large Extra Dim.: Graviton Virtual Exchange  Signal: Deviation in DY cross section, Asymmetries.  ATLAS studies with the photon and lepton pair production. V. Kabachenko, A. Migakov, A Zenin, ATL-PHYS-2001-012  Large enhancement in di-lepton cross section. (similarly in di-photon)

8. Large Extra Dim.: Graviton Virtual Exchange

9. TeV -1 Size Extra Dimension & KK Gauge Boson  Kaluza-Kline excitation of SM Gauge possible in presence of small extra dimension R ~ 1 TeV -1  Indirect constraint from LEP R > 4 TeV -1.  ATLAS studies - Study the di-lepton resonance from  (1) /Z (1) - Implemented in PYTHIA ( M.E from T. Rizzo) G. Azuelos and G. Polesello, hep-ph/0204031.

10. TeV -1 Size Extra Dimension & KK Gauge Boson Reach: Possible to detect resonance up to 5.8 TeV In absence of peak a 95% CL of 13.5 TeV can be achieved

11. TeV Scale Gauge Coupling Unification  KK excitation of Gauge boson affect the evolution of gauge couplings.  LHC studies - Signal: Modified Di-Jet cross section C. Balzas, B. Laforge, hep-ph/0110217 Reach: 5  signal measurable for scale 5-10 TeV

12.  Geometric property of space-time is used to solve the hierarchy problem.  Kaluza-Kline excitations could be observed as well separated narrow resonance.  Atlas study on signal sensitivity and spin determination.  Signal: G (k)  e + e -,  +  -,  (WW, ZZ, tt) - Model implemented in HERWIG. - Studies done for the electron channel (also  +  -,  ) - One year of high luminosity run; 100 fb -1. Randall-Sundrum Model: Narrow Resonance B.C Allanach, K. Odagiri, A. Parker and B. Webber, JHEP 9 (2000) 19.

13. Randall-Sundrum Model: Narrow Resonance m G = 1.5 TeV 5  sensitivity up to 2.1TeV of graviton mass. Spin-1 ruled out with 90 CL up to 1.7 TeV of graviton mass.

14. Randall-Sundrum Model: Radions  In order to stabilize the size of extra dimension an additional scalar , the Radion, is proposed.  The Radion has couplings similar to SM Higgs, and mixes with it.  ATLAS studies for various Radion decay modes. Goldberger and Wise, PRL 83 (1999) 4922. G. Azuelos, D. Cavalli, H. Przysiezniak, L. Vacavant, hep-ph/0204031.

15. Randall-Sundrum Model: Radions    , ZZ  4l - SM Higgs study re- interpreted for 100 fb -1 data.    hh   bb - Study similar to MSSM. Negligible background.    hh   - High Backgrounds. Reach: 4.6, 5.7 TeV for m  = 300, 600 GeV. Reach: 1.1 TeV with m  = 600 GeV

16. Summary  LHC will be able to probe a number of Models. Studies done on - Large Extra Dimension. - Warped Extra Dimensions. - TeV -1 Size Extra Dimension.  Studies in progress for – blackholes and trans planckian scattering, universal extra dimension,…