1 / 19

Significant effects of second KK particles on LKP dark matter physics

Significant effects of second KK particles on LKP dark matter physics. Mitsuru Kakizaki (Bonn Univ. & ICRR, Univ. of Tokyo). 12 May, 2006 @ Bielefeld Univ. Collaborated with Shigeki Matsumoto (KEK) Yoshio Sato (Saitama U.) Masato Senami (ICRR). Refs:

salene
Download Presentation

Significant effects of second KK particles on LKP dark matter physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Significant effects of second KK particles on LKP dark matter physics Mitsuru Kakizaki (Bonn Univ. & ICRR, Univ. of Tokyo) 12 May, 2006 @ Bielefeld Univ. Collaborated with • Shigeki Matsumoto (KEK) • Yoshio Sato (Saitama U.) • Masato Senami (ICRR) Refs: • PRD 71 (2005) 123522 [hep-ph/0502059] • NPB 735 (2006) 84 [hep-ph/0508283]

  2. 1. Motivation Observations of • cosmic microwave background • structure of the universe • etc. [http://map.gsfc.nasa.gov] Non-baryonic cold dark matter What is the constituent of dark matter? • Weakly interacting massive particles are good candidates: • Lightest supersymmetric particle (LSP) in supersymmetric (SUSY) models • Lightest Kaluza-Klein particle (LKP) in universal extra dimension (UED) models • etc. Today’s topic Mitsuru Kakizaki

  3. New Outline • In universal extra dimension (UED) models, Kaluza-Klein (KK) dark matter physics is drastically affected by 2nd KK particles • Reevaluation of relic density of KK dark matter including coannihilation and resonance effects Dark matter particle mass consistent with WMAP increases Motivation Universal extra dimension (UED) models Relic abundance of KK dark matter Resonance in KK dark matter annihilation Including various coannihilation processes Summary Mitsuru Kakizaki

  4. 2. Universal extra dimension (UED) models [Appelquist, Cheng, Dobrescu, PRD64 (2001) 035002] Macroscopic Idea: All SM particles propagate in flat compact spatial extra dimensions Magnify Microscopic • Dispersion relation: Momentum along the extra dimension = Mass in four-dimensional viewpoint Mass spectrum for In case of compactification with radius , is quantized • Momentum conservation in the extra dimension Conservation of KK number in each vertex Mitsuru Kakizaki

  5. Minimal UED model • In order to obtain chiral fermions at zeroth KK level, the extra dimension is compactified on an orbifold • Conservation of KK parity [+ (--) for even (odd) ] The lightest KK particle (LKP) is stable c.f. R-parity and LSP More fundamentaltheory The LKP is a good candidate for dark matter • Only two new parameters in the MUED model: : Scale at which boundary terms vanish : Size of extra dimension • Constraints from electroweak measurements are weak: [Appelquist, Cheng, Dobrescu(2001); Appelquist, Yee, PRD67 (2003)] : Inclusion of 2-loop SM contributions and LEP2 data [Flacke, Hooper, March-Russel, PRD73 (2006)] Mitsuru Kakizaki

  6. Mass spectra of KK states 1-loop corrected mass spectrum at the first KK level • KK modes are degenerate in mass at each KK level: • Compactification  5D Lor. inv. Orbifolding  Trans. Inv. in 5th dim. Radiative corrections relax the degeneracy • Lightest KK Particle (LKP):Next to LKP: 1st KKsinglet leptons: 1st KK Higgs bosons (for larger ) [From Cheng, Matchev, Schmaltz, PRD 036005 (2002)] Mitsuru Kakizaki

  7. Co-moving number density Decoupling 3. Relic abundance of KK dark matter Increasing Thermal equilibrium • Generic picture • Dark matter particles were in thermal equilibrium in the early universe • After the annihilation rate dropped below the expansion rate, the number density per comoving volume is almost fixed • Relic abundance of the LKP 3 flavors [Servant, Tait, NPB 650 (2003) 391] Without coannihilation Including coannihilation Only tree level diagrams are considered Mitsuru Kakizaki

  8. New 4. Resonance in KK dark matter annihilation • Dark matter particles were non-relativistic when they decoupled (Incident energy of two LKPs) (Masses of 2nd KK modes) • Mass splitting in MUED: • LKPs annihilate through s-channel 2nd KK Higgs boson exchange at loop level The annihilation cross sectionis enhanced Mitsuru Kakizaki

  9. Thermal average of annihilation cross section for LKP Smaller The averaged cross section becomes maximum at later time The maximum value is larger Mitsuru Kakizaki

  10. Relic abundance of the LKP (without coannihilation) • The --resonance in annihilation effectively reduces the number density of dark matter • The resonance effect raises the LKP mass consistent with the WMAP data 2nd KK modes play an important role in calculations of the relic density of the LKP Mitsuru Kakizaki

  11. Coannihilation with 1st KK singlet leptons • We can systematically survey 2nd KK--resonance effects • --resonance effect in : sizable • --resonance effect in : relatively small • No 2nd KK--resonance in • Evolution of dark matter abundance [Three flavors: ] The abundance falls below the tree level result after decoupling Mitsuru Kakizaki

  12. Allowed mass region Tree level results Including resonance Charged LKP region Mitsuru Kakizaki

  13. 5. Including various coannihilation processes [Burnell, Kribs, PRD73(2006); Kong, Matchev, JHEP0601(2006)] Relic abundance including coannihilation processes with all level one KK particles (ignoring resonance effects) • 1st KK mass spectrum is rather degenerate Disfavored byEWPT Inclusion of coannihilation modes with all 1st KK particleschanges the abundance WMAP • In MUED, inclusion of full coannihilation processes lowers • Resonance effects may shift the allowed mass scale [From Kong, Matchev, JHEP0601(2006)]] Mitsuru Kakizaki

  14. Efficient coannihilation processes through strong Higgs coupling [Matsumoto, Senami, PLB633(2006)] Dependence of the LKP relic abundance on the Higgs mass (ignoring resonance effects) • Larger Higgs mass (larger Higgs self--coupling) • Mass degeneracy between 1st KK Higgs bosons and the LKP in MUED WMAP • Larger annihilation cross sections for the 1st KK Higgs bosons Coannihilation effect with 1st KK Higgs bosons efficiently decrease the LKP abundance [From Matsumoto, Senami, PLB633(2006)] • of 1 TeV is compatible with the observation of the abundance Mitsuru Kakizaki

  15. 6. Summary • UED models provide a viable dark matter candidate: The lightest Kaluza-Klein particle (LKP) • (Masses of 2nd KK particles) (Masses of 1st KK particles) Annihilation takes place near poles • We evaluate the relic abundance of the LKP including resonance and coannihilation with the 1st KK singlet leptons, and find the allowed compactification scale shifts upward due to the resonance effect • Various coannihilation processes also affect the relic abundance Mitsuru Kakizaki

  16. Backup slides Mitsuru Kakizaki

  17. 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, Silk, PRD69 (2004)] • KK dark matter may explain the excess [Hooper, Kribs, PRD70 (2004)] • Future experiments (PAMELA, AMS-02, …) will confirm or exclude the positron excess Mitsuru Kakizaki

  18. Mass splitting in the minimal UED model Contour plot of mass splitting • Radiative corrections to 2nd KK Higgs boson mass: -0.5 % • Mass splitting: Small --resonance • is realized in the minimal UED model for a large parameter region Mitsuru Kakizaki

  19. Including coannihilation with 1st KK singlet leptons • The LKP is nearly degenerate with the 2nd KK singlet leptons Coannihilation effect is important • Annihilation cross sections The allowed LKP mass region is lowered due to the coannihilation effect c.f. SUSY models: coannihilation effect raises the allowed LSP mass Mitsuru Kakizaki

More Related