1. Paris 22/4 UED Albert De Roeck (CERN) 1 Identifying Universal Extra Dimensions at CLIC  Minimal UED model  CLIC experimentation  UED signals & Measurements M. Battaglia, A Datta, A. De Roeck, K. Kong, K. Matchev

2. Paris 22/4 UED Albert De Roeck (CERN) 2 Cheng, Schmaltz and Matchev hep/ph0205314 R size of extra dim. KK partners for all particles

3. Paris 22/4 UED Albert De Roeck (CERN) 3 MUED Phenomenology Hadron collider searches may be problematic  soft decay products  All particles get partners with SAME spin  Particles are pair produced (KK number conservation) Radiatively corrected mass spectrum

4. Paris 22/4 UED Albert De Roeck (CERN) 4 Detecting MUEDs at pp colliders Discovery reach for MUEDs using the 4lepton+ missing E T channel  R -1 = 20 Good discovery potential at the LHC hep/ph0205314

5. Paris 22/4 UED Albert De Roeck (CERN) 5 MUED signals Experimental Signatures almost identical to Supersymmetry Partners for all particles with identical interactions Lightest KK state (  1 ) is stable like LSP –Also a dark matter candidate Differences Cross sections Spin of the partner (Same for KK, differ by ½ for SUSY) –Different  dependence of the threshold behaviour of KK pair or SUSY pair production No a priori extended Higgs sector –No A,H,H ±, less gauginos The KK spectrum repeats n times (higher levels)  Not obvious if these can be used at LHC (under study) LC for proper interpretation of the signal.  CLIC as a case study

6. Paris 22/4 UED Albert De Roeck (CERN) 6 Study (s)muon production Study the processes MUED n=1 KK modes and n=2  2 and Z 2 included in CompHEP (41.10) Fix R -1 = 500 GeV,  R=20 Match SUSY parameters to get same spectrum

7. Paris 22/4 UED Albert De Roeck (CERN) 7 CLIC Simulation SIMDET for detector response Reconstruct muons Realistic luminosity Spectrum  s = 3 TeV ~ 4  evts/bx

8. Paris 22/4 UED Albert De Roeck (CERN) 8 Analysis Signal (14 fb) background (20 fb) Event selection  Reconstruct 2 muons  Missing energy > 2.5 TeV  Transverse energy below 150 GeV  Sphericity larger than 0.05  M Z filter  Reduces background with a factor ~5-10

9. Paris 22/4 UED Albert De Roeck (CERN) 9 Comparison: angular distributions of muons Production polar angle  of the decay muons If mass difference M  1 -M  1 small  correlation between muons & parents Theoretical prediction After detector simulation  2 fit: can distinguish UED from SUSY at 5  with 350 fb -1 at  s= 3 TeV signal total

10. Paris 22/4 UED Albert De Roeck (CERN) 10 Different Cross Section  Different rate  Different onset Difference due to -Both left & right handed Doublets in MUED -Fermions  Bosons T. Tait LHCLC document     3 3

11. Paris 22/4 UED Albert De Roeck (CERN) 11 Threshold scan Sensitivity to the mass 1S1S 1D1D with beamstrahlung Standard curve Move  1 S by -2.5 GeV Move  1 D by -2.5 GeV  M = ±0.11 GeV for  1 S and ±0.23 GeV for  1 D

12. Paris 22/4 UED Albert De Roeck (CERN) 12 Muon Energy Spectrum Inclusive muon energy spectrum  determined by two body kinematics Measure endpoints  1 D and  1 S masses from threshold scan  M  1 ~ 0.25 GeV for 1 ab -1 after detector simulation

13. Paris 22/4 UED Albert De Roeck (CERN) 13 Radiative return Radiative return to the Z 2 Peak in the photon spectrum Not present for SUSY

14. Paris 22/4 UED Albert De Roeck (CERN) 14 Conclusions MUED and SUSY signals at the LHC may look very similar at LHC Not yet clear if LHC can distinguish between both cases –E.g if H,A expected to be at high mass or level 2 KK out of reach A linear collider can provide decisive information Here a case study with ~ 500 GeV KK muons (smuons) at CLIC including detector & beam smearing effects and backgrounds –Cross sections –Spin analysis of the new particles –Threshold measurements –Radiative returns This scenario: 350 fb -1 sufficient for separation Mass determination of the KK-muons and LKP, including all effects, amounts to  M/M of better than 0.1% with 1 ab -1 (= 1 CLIC year) each for threshold scans and inclusive muon spectra