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Introduction to universal extra dimensions (UEDs)

Introduction to universal extra dimensions (UEDs). Mitsuru Kakizaki (ICRR, University of Tokyo). May 10, 2005 @ KEK.

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Introduction to universal extra dimensions (UEDs)

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  1. Introduction to universal extra dimensions (UEDs) Mitsuru Kakizaki (ICRR, University of Tokyo) May 10, 2005 @ KEK • Refs:Original idea: Appelquist, Cheng, Dobrescu, PRD67 (2000) 035002Second KK particle physics: MK, Matsumoto, Sato, Senami, hep-ph/0502059UED vs SUSY at CLIC: Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041 • Pedagogical introduction to UED models • Comparison of UED and SUSY phenomenology • Probing extra dimensions at linear colliders Prof. Raychaudhuri’s talk Dr. Matsumoto’s talk • UED cosmology and astrophysics

  2. 1. Motivation Extra-dimension scenarios provide new views of various problems • Hierarchy problem: Large extra dimensions [Arkani-hamed, Dimopoulos, Dvali PLB 429 (1998) 263] Warped extra dimensions [Randall, Sundrum PRL 83 (1999) 3370] • Fermion mass hierarchy [Arkani-hamed, Schmaltz PRD 61 (2000)] • Existence of dark matter Universal extra dimensions (UEDs) [Appelquist, Cheng, Dobrescu, PRD67 (2000) 035002] Today’s topic The Lightest Kaluza-Klein particle (LKP) in UED models is an excellent candidate for dark matter due to Kaluza-Klein (KK) parity [Servant, Tait, NPB 650 (2003) 391] • etc. Mitsuru Kakizaki

  3. SM SM UED is similar to SUSY UED SUSY • 1st KK mode mass • Superparticle mass • KK parity stabilizes the LKP  SUSY breaking mass • R parity stabilizes the LSP • Same spin SUSY • Different spin • Kinematics of 1st KK modes resembles that of superparticles with degenerate mass • Attention to spins of new particles and second KK modes Study at linear colliders is mandatory Mitsuru Kakizaki

  4. Contents Motivation Universal extra dimensions (UEDs) UED vs SUSY Summary Mitsuru Kakizaki

  5. Mass spectrum for 2. Universal extra dimensions [Appelquist, Cheng, Dobrescu, PRD67 (2000) 035002] Idea: All SM particles propagate compact spatial extra dimensions • For definiteness, we concentrate on one-extra dimensional cases in this talk • Dispersion relation: Momentum along the extra dimension  Mass in four-dimensional viewpoint For compactification with radius , is quantized • Momentum conservation in the extra dimension Conservation of KK number in each vertex Mitsuru Kakizaki

  6. Parameters in UED models • Kaluza-Klein expansion (Fourier expansion): Zero modes are identified with SM fields Parameters in UED models are completely specified in terms of the SM parameters • Only three free parameters in minimal UED model: : Higgs boson mass : Cutoff scale : Size of extra dimension c.f. minimal SUGRA: and Mitsuru Kakizaki

  7. Dirac Dirac Chiral Minimal UED • In 5D spacetime, spinor representation has 4 complex components Reflection sym. under  Chiral fermions in 4D e.g. • Conservation of KK parity[+ (--) for even (odd) ] { The lightest KK particle (LKP) is stable Dark matter Single KK particle cannot be produced c.f. R-parity and the LSP in SUSY models • Experimental limit on is weaker than other extra-dimensional models: Electroweak precision tests Mitsuru Kakizaki

  8. Particle contents in minimal UED KK level Fermion (SU(2)L) Gauge boson Scalar (SU(2)L) New particles: Complex scalar Dirac Massive (Mass ) SM particles: Massive Dirac Real scalar Massless Chiral (Mass ) Electroweak symmetry breaking effects are suppressed for higher KK modes There appear infinite towers of KK modes with quantum numbers identical to SM particles Mitsuru Kakizaki

  9. 5D Interactions in UED models • e.g. gauge interaction of fermion: 4D SM For KK expansion KK Couplings in UED models are determined by corresponding SM ones Mitsuru Kakizaki

  10. Radiative corrections to mass spectra of KK modes [Cheng, Matchev, Schmaltz, PRD66, 036005 (2002)] • Compactification  5-dimensional Lorentz invariance Orbifolding  translational invariance in the 5th dimensionRadiative corrections generate KK mass splitting One-loop corrected masses of 1st KK modes Tree level masses spectrum of 1st KK modes c.f. SUSY: Universal soft mass at cutoff scale Mass splitting at weak scale Mitsuru Kakizaki

  11. 3. UED vs SUSY • LHC: [Cheng, Matchev, Schmaltz PRD 66 (2002) 056006] Discovery reach for minimal UED: Signals of 1st KK modes are similar to those of superparticles (UED is called “Bosonic supersymmetry”) • Future colliders is promising for distinguishing UED and SUSY • Observation of effects caused by second KK modes • Determination of spins of new particles Mitsuru Kakizaki

  12. Contrasting SUSY and UED at CLIC (Multi-TeV collider) [Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041] • Comparison of Rad. cor. in UED UED parameters: with Missing in SUSY MSSM parameters are adjusted to reproduce UED kinematics • SM background: • Event seletion: • missing energy > 2.5 TeV • transverse energy < 150 GeV • event sphericity > 0.05 • missing trans. energy > 50 GeV (small polar angle) Mitsuru Kakizaki

  13. Angular distribution and spin measurements UED: : Spin 1/2 Factor SUSY: : Spin 0 at : signal + background : signal [From Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041] Mitsuru Kakizaki

  14. Discrimination of UED from SUSY • Photon energy spectrum in • Cross section for resonance Includingbeamstrahlung [From Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041] c.f. SUSY: at threshold region, no sharp peak due to resonance Mitsuru Kakizaki

  15. 4. Summary • Remarkable features of UED models: Excellent dark matter candidate: LKP Small number of free parameters Towers of KK modes with spins identical to corresponding SM particles • LHC would not distinguish UED from SUSY models Study at linear colliders is mandatory • Attention to Spins of new particles Effects caused by second KK particles Mitsuru Kakizaki

  16. Backup slides Mitsuru Kakizaki

  17. Collider signatures at LHC [Cheng, Matchev, Schmaltz PRD66 (2002) 056006] Discovery reach Decay chains of 1st KK modes • The discovery reach: • Signals of 1st KK modes are similar to those of superparticles Mitsuru Kakizaki

  18. One-loop corrected masses of 1st KK modes [From Cheng, Matchev, Schmaltz PRD66 (2002) 056006] Mitsuru Kakizaki

  19. Muon energy spectrum [From Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041] Mitsuru Kakizaki

  20. Threshold scan • Cross section for [From Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041] Mitsuru Kakizaki

  21. Radiative return to • Photon energy spectrum in [From Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041] Mitsuru Kakizaki

  22. e.g. New Second KK particle physics [MK, Matsumoto, Sato, Senami, hep-ph/0502059] • Radiative corrections KK number violating couplings • (2nd KK mode mass) (1st KK mode mass) pair production is naturally enhanced by -resonance in the s-channel Signal of 2 lepton + large missing energy is expected to have large cross section and be almost background free Mitsuru Kakizaki

  23. KK quarkonium Idea Threshold singularity [MK, Matsumoto, Okada, Yamashita, …] • Threshold cross section for KK quarkonium at linear collider KK quarkonium cross section for small decay width Energy of bound state: Precise determination of parameters is possible Mitsuru Kakizaki

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