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]

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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

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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