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Significant effects of second KK particles on LKP dark matter physics

Significant effects of second KK particles on LKP dark matter physics. Mitsuru Kakizaki (ICRR, University of Tokyo). March. 23, 2005 @ Univ. of Oxford. Collaborated with Shigeki Matsumoto (ICRR) Yoshio Sato (Saitama Univ.) Masato Senami (ICRR) hep-ph/0502059.

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Significant effects of second KK particles on LKP dark matter physics

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  1. Significant effects of second KK particles on LKP dark matter physics Mitsuru Kakizaki (ICRR, University of Tokyo) March. 23, 2005 @ Univ. of Oxford • Collaborated with Shigeki Matsumoto (ICRR) Yoshio Sato (Saitama Univ.) Masato Senami (ICRR) hep-ph/0502059 • Kaluza-Klein (KK) dark matter physics is drastically affected by second KK particles in universal extra dimension (UED) models • Reevaluation of relic density of KK dark matter KK dark matter mass consistent with WMAP increases

  2. 1. Motivation • Rotation curve of galaxies: [Begeman, Broeils, Sanders (1991)] • Mass-to-light ratio of galaxy clusters: e.g. the Coma cluster: • Cosmic microwave background anisotropies: [http://map.gsfc.nasa.gov] Existence of non-baryonic cold dark matter (DM) Mitsuru Kakizaki

  3. What is the constituent of dark matter? • We need physics beyond standard model (SM) of particle physics • Weakly interacting massive particles are good candidates: • Lightest supersymmetric particle (LSP) in supersymmetric (SUSY) models: e.g. neutralino, gravitino • Lightest Kaluza-Klein particle (LKP) in universal extra dimension models • etc. Today’s topic Mitsuru Kakizaki

  4. Positron experiments • The HEAT experiment indicated an excess in the positron flux: • Unnatural dark matter substructure is required to match the HEAT data in SUSY models [Hooper, Taylor, Kribs (2004)] • KK dark matter may explain the excess [Hooper, Kribs (2004)] • Future experiments (PAMELA, AMS-02, …) will confirm or exclude the positron excess Mitsuru Kakizaki

  5. Purpose • KK dark matter physics is drastically affected by second KK particles in universal extra dimension (UED) models • Reevaluation of relic density of KK dark matter • The 1st excited mode of boson, , is a DM candidate • (Mass of 2nd KK modes) • The annihilation cross section is enhanced due to resonance of intermediate 2nd KK particles • The predicted relic abundance decreases compared with that at the tree level (Mass of 1st KK modes) [c.f. Servant, Tait (2002)] Mitsuru Kakizaki

  6. Contents Motivation Universal extra dimension (UED) Relic abundance of dark matter Resonant KK dark matter annihilation Indirect detection Collider signatures Summary New Mitsuru Kakizaki

  7. Mass spectrum 2. Universal extra dimensions Idea: All SM particles propagate compact spatial extra dimensions [Appelquist, Cheng, Dobrescu (2000)] • For simplicity, we consider one extra dimension: • Eq. of motion: in 4-dim. viewpoint • Momentum conservation in higher dim. Conservation of KK number in each vertex Mitsuru Kakizaki

  8. orbifold • To obtain chiral fermions at zero mode, we identify with • Electroweak precision measurements restrict the size: • Conservation of KK parity [+ (--) for even (odd) ] The lightest KK particle (LKP) is stable The LKP is a good candidate of dark matter c.f. The LSP stabilized by R-parity in SUSY models Mitsuru Kakizaki

  9. Mass spectra of KK states 1-loop corrected mass spectrum of the first KK level • Fourier expanded modes are degenerate in mass at each KK level: • Radiative corrections remove the degeneracy • The LKP is and nearly degenerate with SU(2)L singlet : Cutoff scale [From Cheng, Matchev, Schmaltz, PRD 036005 (2002)] Mitsuru Kakizaki

  10. 3. Relic abundance of dark matter Relic density • Thermal relic abundance Dark matter was at thermal equilibrium in the early universe Increasing After the annihilation rate dropped below the expansion rate, the number density per comoving volume is fixed Decoupling • SUSY vs UED Neutralino (LSP)Majorana fermion Small (p-wave) Large Small Dark matterSpin Annihilation cross section Relic density Allowed mass (LKP)Spin 1 boson Large (s-wave) Small Large Mitsuru Kakizaki

  11. Relic abundance of KK dark matter Including coannihilation • Preceding work: [Servant, Tait (2002)] [zero mode (SM) particle pair] e.g. t-channel exchange of 1st KK particle Without coannihilation for coannihilation However, only 1st KK modes are involved [From Servant, Tait, Nucl.Phys.B650 (2003)391] Mitsuru Kakizaki

  12. New 4. Resonant KK dark matter annihilation • Dark matter is non-relativistic at decoupling (Mass of 2nd KK modes) (The incident energy of two LKPs) • annihilation is also accompanied by s-channel 2nd Higgs bosonresonance at loop level c.f. 2nd KK modes do not couple with SM particles at tree level Mitsuru Kakizaki

  13. Thermal average of annihilation cross section Mass of • For , the incident energy matches the pole The annihilation cross section is enhanced Mitsuru Kakizaki

  14. 0 % 1 % 0.5 % 1.5 % 2 % Mass splitting in minimal UED Contour plot of mass splitting • Radiative corrections to 2nd KK Higgs boson mass: -0.5 % • Mass splitting: Resonance by Small • is realized in the minimal UED for a large parameter region Mitsuru Kakizaki

  15. Relic abundance of LKP dark matter • Resonant annihilation raises the allowed mass of LKP dark matter • The LKP Dark matter mass consistent with WMAP is around and about above the tree level result Inclusion of 2nd KK modes at loop level is important Mitsuru Kakizaki

  16. Including coannihilation • When there are particles with mass similar to the relic particle, coannihilation is important • UED modes:The LKP is nearly degenerate with the SU(2)L singlet Self-annihilation Coannihilation More relics The allowed mass is lowered compared with that w/o coannihilation c.f. SUSY models: coannihilation effects raise the allowed DM mass Mitsuru Kakizaki

  17. Contributions to coannihilation from -resonance is relatively small Dark matter abundance • Contribution to self-annihilation of from -resonance is effective • Dark matter abundance [Three flavors: ] Tree Tree WMAP WMAP Tree + Res. Tree + Res. Mitsuru Kakizaki

  18. 5. Indirect detection • Dark matter is almost at rest in the current universe • UED models predict to a good approximation Large annihilation rate due to s-channel resonance Considerable positron and gamma ray fluxes The positron excess observed by HEAT may be explainedwithout any clumpy profile of dark matter Mitsuru Kakizaki

  19. 6. Collider signatures • Large Hadron Collider (2007--) [Cheng, Matchev, Schmaltz (2002)] The discovery reach: Signals of 1st KK level are similar to those of superparticles • Future colliders is promising for distinguishing UED and SUSY Resonance by s-channel Signal of 2 lepton + large missing energy has large cross section and is almost background free [See also Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041(2005)] Mitsuru Kakizaki

  20. 7. Summary • UED models provide a viable dark matter candidate: The lightest Kaluza-Klein particle (LKP) (Mass of 1st KK particles) • (Mass of 2nd KK particles) • Kaluza-Klein dark matter physics is affected by second KK particles • The mass of relic LKP dark matter consistent with WMAP increases due to s-channel second KK resonance • Indirect detection and collider signatures are significantly affected by s-channel second KK resonance Mitsuru Kakizaki

  21. Backup slides Mitsuru Kakizaki

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