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Investigating Extra Dimensions at ATLAS: Insights from PASCOS 2003

The ATLAS collaboration presented critical studies on large extra dimensions at the PASCOS 2003 conference in Mumbai. Ambreesh Gupta from the University of Chicago discussed the direct and virtual production of Kaluza-Klein gravitons, the implications of Randall-Sundrum models, and potential signals such as missing energy and di-lepton resonances. Various scenarios, including the influence of extra dimensions on gauge coupling unification and radion decay modes, were explored, highlighting the LHC's capability to probe these advanced theoretical interests.

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Investigating Extra Dimensions at ATLAS: Insights from PASCOS 2003

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

  2. Spectrum of ATLAS Studies Large Extra Dimensions • KK Graviton Direct Production  Missing ET • 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

  3. 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 MD and number • of extra dimension  . L. Vacavant and I. Hinchliffe, J. Phys. G: Nucl. Part. Phys. 27 (2001) 1839

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

  5. 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)

  6. Large Extra Dim.: Graviton Virtual Exchange

  7. 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.

  8. 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

  9. 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

  10. Randall-Sundrum Model: Narrow Resonance • 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. B.C Allanach, K. Odagiri, A. Parker and B. Webber, JHEP 9 (2000) 19.

  11. Randall-Sundrum Model: Narrow Resonance mG = 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.

  12. 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.

  13. 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

  14. 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,…

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