significant effects of second kk particles on lkp dark matter physics
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Significant effects of second KK Significant effects of second KK particles on LKP dark matter particles on LKP dark matter
physicsphysics Mitsuru Kakizaki Mitsuru Kakizaki (Bonn Univ. & ICRR, Univ. of Toky(Bonn Univ. & ICRR, Univ. of Tokyo)o) 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]
12 May, 2006 Mitsuru Kakizaki 2
1. 1. MotivationMotivation
Non-baryonic cold dark matter[http://map.gsfc.nasa.gov]
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
Observations of cosmic microwave background structure of the universe etc.
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OutlineOutline 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
1. Motivation2. Universal extra dimension (UED) models3. Relic abundance of KK dark matter4. Resonance in KK dark matter annihilation5. Including various coannihilation processes6. Summary
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2. Universal extra 2. Universal extra dimension (UED) models dimension (UED) models
Idea: All SM particles propagate in flat compact spatial extra dimensions
[Appelquist, Cheng, Dobrescu, PRD64 (2001) 035002]
Dispersion relation: Momentum along the extra dimension = Mass in four-dimensional viewpoint
In case of compactification with radius , Mass spectrum for
is quantized Momentum conservation in the extra dimension
Conservation of KK number in each vertex
Macroscopic
MicroscopicMagnify
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Conservation of KK parity [+ (--) for even (odd) ]The lightest KK particle (LKP) is stableThe LKP is a good candidate for dark matter
c.f. R-parity and LSP
In order to obtain chiral fermions at zeroth KK level, the extra dimension is compactified on an orbifold
Constraints from electroweak measurements are weak:
Minimal UED modelMinimal UED model
Only two new parameters in the MUED model:: Size of extra dimension: Scale at which boundary terms vanish
[Flacke, Hooper, March-Russel, PRD73 (2006)]
[Appelquist, Cheng, Dobrescu (2001); Appelquist, Yee, PRD67 (2003)]
: Inclusion of 2-loop SM contributions and LEP2 data
More fundamentaltheory
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Mass spectra of KK statesMass spectra of KK states KK modes are degenerate in mass at each KK level:
[From Cheng, Matchev, Schmaltz, PRD 036005 (2002)]
Radiative corrections relax the degeneracy
Lightest KK Particle (LKP): Next to LKP: 1st KK singlet leptons:
1-loop corrected mass spectrum at the first KK level
Compactification 5D Lor. inv. Orbifolding Trans. Inv. in 5th dim.
1st KK Higgs bosons (for larger )
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3. Relic abundance3. Relic abundance of KK dark matter of KK dark matter
After the annihilation rate dropped below the expansion rate, the number density per comoving volume is almost fixed
Generic picture
Increasing
Decoupling
Thermal equilibrium Dark matter particles were in thermal equilibrium in the early universe
[Servant, Tait, NPB 650 (2003) 391]
Co-moving number density
Only tree level diagrams are considered
Relic abundance of the LKP
Inclu
ding
coa
nnih
ilatio
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ithou
t coa
nnih
ilatio
n
3 flavors
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4. Resonance in4. Resonance in KK dark matter annihilation KK dark matter annihilation
(Incident energy of two LKPs) Dark matter particles were non-relativistic when they decoupled
(Masses of 2nd KK modes)
LKPs annihilate through s-channel 2nd KK Higgs boson exchange at loop level
Mass splitting in MUED:
The annihilation cross section is enhanced
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Thermal average of Thermal average of annihilation cross section for annihilation cross section for LKPLKP
Smaller The averaged cross section becomes maximum at later time The maximum value is larger
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Relic abundance of the LKPRelic abundance of the LKP (without coannihilation) (without coannihilation)
2nd KK modes play an important role in calculations of the relic density of the LKP
The resonance effect raises the LKP mass consistent with the WMAP data
The --resonance in annihilation effectively reduces the number density of dark matter
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--resonance effect in : sizable
Coannihilation withCoannihilation with 1 1stst KK singlet leptons KK singlet leptons
Evolution of dark matter abundance [Three flavors: ]
--resonance effect in : relatively small
We can systematically survey 2nd KK--resonance effects
No 2nd KK--resonance in
The abundance falls below the tree level result after decoupling
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Allowed mass regionAllowed mass region Including resonance Tree level results
Charged LKP region
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5. Including various coannihilation 5. Including various coannihilation processesprocesses
[Burnell, Kribs, PRD73(2006); Kong, Matchev, JHEP0601(2006)]
1st KK mass spectrum is rather degenerate
[From Kong, Matchev, JHEP0601(2006)]]
WMAP
Disfavored byEWPT
In MUED, inclusion of full coannihilation processes lowers Resonance effects may shift the allowed mass scale
Relic abundance including coannihilation processes with all level one KK particles (ignoring resonance effects)
Inclusion of coannihilation modes with all 1st KK particleschanges the abundance
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Efficient coannihilation processesEfficient coannihilation processes through strong Higgs coupling through strong Higgs coupling
[Matsumoto, Senami, PLB633(2006)]
[From Matsumoto, Senami, PLB633(2006)]
Coannihilation effect with 1st KK Higgs bosons efficiently decrease the LKP abundance
Dependence of the LKP relic abundance on the Higgs mass (ignoring resonance effects)
WMAP
Larger Higgs mass (larger Higgs self--coupling)
Mass degeneracy between 1st KK Higgs bosons and the LKP in MUED
of 1 TeV is compatible with the observation of the abundance
Larger annihilation cross sections for the 1st KK Higgs bosons
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6. Summary6. Summary
UED models provide a viable dark matter candidate:
(Masses of 2nd KK particles)The lightest Kaluza-Klein particle (LKP)
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
(Masses of 1st KK particles)Annihilation takes place near poles
Various coannihilation processes also affect the relic abundance
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Backup slidesBackup slides
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Positron experimentsPositron experiments The HEAT experiment indicated an excess in the positron flux:
Future experiments (PAMELA, AMS-02, …) will confirm or exclude the positron excess
KK dark matter may explain the excess
Unnatural dark matter substructure is required to match the HEAT data in SUSY models[Hooper, Taylor, Silk, PRD69 (2004)]
[Hooper, Kribs, PRD70 (2004)]
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Mass splitting Mass splitting in the minimal UED model in the minimal UED model
-0.5 %
Radiative corrections to 2nd KK Higgs boson mass:
Contour plot of mass splitting
is realized in the minimal UED model for a large parameter region
Mass splitting:
--resonanceSmall
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Including coannihilationIncluding coannihilation with 1 with 1stst KK singlet leptons KK singlet leptons
The LKP is nearly degenerate with the 2nd KK singlet leptons
The allowed LKP mass region is lowered due to the coannihilation effect
c.f. SUSY models: coannihilation effect raises the allowed LSP mass
Coannihilation effect is important Annihilation cross sections
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