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

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

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

Jan. 23, 2005 Mitsuru Kakizaki 2

1. Motivation

Existence of non-baryonic cold dark matter (DM)Existence of non-baryonic cold dark matter (DM)

Cosmic microwave background anisotropies:

Rotation curve of galaxies:

Mass-to-light ratio of galaxy clusters:

[http://map.gsfc.nasa.gov]

e.g. the Coma cluster:

[Begeman, Broeils, Sanders (1991)]

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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

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Positron experiments

The HEAT experiment indicated an excess in the positron flux:

Future experiments (PAMELA, AMS-02, …) will confirm or exclude the positron excess

[Hooper, Kribs (2004)] KK dark matter may explain the excess

Unnatural dark matter substructure is required to match the HEAT data in SUSY models [Hooper, Taylor, Kribs (2004)]

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Purpose

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

[c.f. Servant, Tait (2002)]

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 physics is drastically affected by second KK particles in universal extra dimension (UED) models Reevaluation of relic density of KK dark matter

(Mass of 1st KK modes)

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Contents

1. Motivation2. Universal extra dimension (UED)3. Relic abundance of dark matter4. Resonant KK dark matter annihilation5. Indirect detection6. Collider signatures7. Summary

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2. Universal extra dimensions

Idea: All SM particles propagate compact spatial extra dimensionsIdea: All SM particles propagate compact spatial extra dimensions[Appelquist, Cheng, Dobrescu (2000)]

For simplicity, we consider one extra dimension:

Momentum conservation in higher dim.Conservation of KK number in each vertex

in 4-dim. viewpoint

Eq. of motion: Mass spectrum

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orbifold

Conservation of KK parity [+ (--) for even (odd) ]

The lightest KK particle (LKP) is stable

The LKP is a good candidate of dark matterThe LKP is a good candidate of dark matter

c.f. The LSP stabilized by R-parity in SUSY models

To obtain chiral fermions at zero mode, we identify with

Electroweak precision measurements restrict the size:

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Mass spectra of KK states Fourier expanded modes are degenerate in mass at each KK level:

[From Cheng, Matchev, Schmaltz, PRD 036005 (2002)]

Radiative corrections remove the degeneracy

The LKP is and nearly degenerate with SU(2)L singlet

1-loop corrected mass spectrum of the first KK level

: Cutoff scale

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3. Relic abundance of dark matter

Dark matter was at thermal equilibrium in the early universe

Neutralino (LSP)Majorana fermionSmall (p-wave)LargeSmall

(LKP)Spin 1 bosonLarge (s-wave)SmallLarge

Dark matterSpinAnnihilation cross sectionRelic densityAllowed mass

SUSY vs UED

After the annihilation rate dropped below the expansion rate, the number density per comoving volume is fixed

Thermal relic abundance

Increasing

Relic density

Decoupling

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Relic abundance of KK dark matter

Preceding work:

[From Servant, Tait, Nucl.Phys.B650 (2003)391]

However, only 1st KK modes are involvedHowever, only 1st KK modes are involved

[Servant, Tait (2002)]

[zero mode (SM) particle pair]

e.g. t-channel exchange of 1st KK particle

Including coannihilation

Without coannihilation

for coannihilation

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4. Resonant KK dark matter annihilation

(The incident energy of two LKPs)

Dark matter is non-relativistic at decoupling (Mass of 2nd KK modes)

c.f. 2nd KK modes do not couple with SM particles at tree level

annihilation is also accompanied by s-channel 2nd Higgs boson resonance at loop level

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Thermal average of annihilation cross section

The annihilation cross section is enhanced The annihilation cross section is enhanced

For , the incident energy matches the pole

Mass of

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Mass splitting in minimal UED

-0.5 %

Radiative corrections to 2nd KK Higgs boson mass:

Contour plot of mass splitting

is realized in the minimal UED for a large parameter region

Mass splitting:

Resonance bySmall100 150 200 250 300

600

800

1000

1200

1400

1 % 0 %0.5 %

2 %1.5 %

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Relic abundance of LKP dark matter

Inclusion of 2nd KK modes at loop level is important Inclusion of 2nd KK modes at loop level is important

The LKP Dark matter mass consistent with WMAP is around and about above the tree level result

Resonant annihilation raises the allowed mass of LKP dark matter

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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 　 Coannihilat

ion

The allowed mass is lowered compared with that w/o coannihilation

More relics

c.f. SUSY models: coannihilation effects raise the allowed DM mass

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Dark matter abundance

Dark matter abundance [Three flavors: ]

Contributions to coannihilation from -resonance is relatively small

Contribution to self-annihilation of from -resonance is effective

WMAP

Tree + Res.

Tree

WMAP

Tree

Tree + Res.

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5. Indirect detection

Dark matter is almost at rest in the current universe

to a good approximation

The positron excess observed by HEAT may be explainedwithout any clumpy profile of dark matter The positron excess observed by HEAT may be explainedwithout any clumpy profile of dark matter

Considerable positron and gamma ray fluxes

UED models predict

Large annihilation rate due to s-channel resonance

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6. Collider signatures Large Hadron Collider (2007--)

Future colliders is promising for distinguishing UED and SUSY

[Cheng, Matchev, Schmaltz (2002)]

[See also Battaglia, Datta, De Roeck, Kong, Matchev, hep-ph/0502041(2005)]

Signals of 1st KK level are similar to those of superparticles The discovery reach:

Resonance by s-channel

Signal of 2 lepton + large missing energy has large cross section and is almost background free

Signal of 2 lepton + large missing energy has large cross section and is almost background free

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7. Summary

UED models provide a viable dark matter candidate:

(Mass of 2nd KK particles)The lightest Kaluza-Klein particle (LKP)

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

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

(Mass of 1st KK particles)

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Backup slides