the electron plus positron spectrum from annihilation of ......2015/10/29 · i. v. moskalenko...
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The electron plus positron spectrum from annihilation of Kaluza-Klein dark matter
and comparison with recent measurements
Dept. Physical Sciences, Ritsumeikan UnivSatoshi Tsuchida, Masaki Mori
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Contents
• Kaluza-Klein Dark Matter
• LKP annihilation modes
• The effects of propagation
• Total positron fraction
• Comparison with recent measurements
• Summary
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We assume the first excited state (LKP) :
Kaluza-Klein Dark Matter
• UED (Universal Extra Dimensions)
Only 1 extra dimension
• Kaluza-Klein dark matter mass
Mass range = 300GeV - 1000GeV
L. Bergstrom et al, Phys. Rev. Lett 94(2005) 131301
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The edge structure is
predicted at the LKP mass
Cheng et al., Phys. Rev. Lett. 89 (2002) 211301
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The predicted edge structure
has not been observed
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Positron fractionBy AMS-02 observation…
The positron excess above 10 GeV is reported
M. Aguilar et al., PRL 110. 141102 (2013)
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Annihilation modes• Kaluza-Klein dark matter
There are many modes containing the electron as the final products
Line
Electron – Positron Pair (𝑒+𝑒−)
Continuum
Components Branching Ratio
Muon Pair (𝜇+𝜇−) 20 %
Tauon Pair (𝜏+𝜏−) 20 %
Quark Pairs 12 %
Gauge Bosons 1.5 %
Total
L. Bergstrom, Phys. Rev. Lett. 131301 (2005)
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CreationThe energy distribution for Line and Continuum components
when LKP annihilates in the Galactic halo
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Flux
• The Electron-Positron Flux
• The Green function for Propagation
By determining the parameters a, b, and c,
the form of propagation is determined
I. V. Moskalenko & A. W. Strong, PRD 60 (1999) 063003
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Isothermal model𝜌 = 0.43 GeV/cm3 :
Local DM density
𝑟𝑐 = 2.8 kpc : Core radius
Evans model𝜌 = 0.51 GeV/cm3
𝑟𝑐 = 7.0 kpc
Alternative model𝜌 = 0.38 GeV/cm3
𝑟𝑐 = 0.9 kpc
Upper case 10 kpc
Lower case 4 kpc
Our case 8.5 kpcI. V. Moskalenko & A. W. Strong, PRD 60 (1999) 063003
I. V. Moskalenko & A. W. Strong, ApJ 493 (1998) 694
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Boost factor• Boost factor
The factor which may enhance the signal from LKP
annihilation in the Galactic halo
• Cross Section
The value of boost factor is determined based on this cross section
Cheng et al., Phys. Rev. Lett. 89 (2002) 211301
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Line and Continuum Flux
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Positron Fraction
Total positron fraction
𝐹𝐿𝐾𝑃 : Flux from LKP annihilation𝐹𝐶𝑜𝑛𝑣 : The “Conventional” Flux𝑓𝐿𝐾𝑃 : Positron fraction for the LKP (=0.5)𝑓𝐶𝑜𝑛𝑣 : Positron fraction for 𝐹𝑐𝑜𝑛𝑣𝐵𝑓 : The Boost Factor
Q. Yuan and X. J. Bi, Phys. Lett. B727, 1 (2013)
I. V. Moskalenko and A. W. Strong, Astrophys. J 493, 694 (1998).
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Comparison with recent measurements
𝐵𝑓=2.7 × 102
𝐵𝑓=2.2 × 103
𝐵𝑓=1.5 × 104
𝐵𝑓=3.7 × 104
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Boost factor
Boost factor becomes larger
For heavier LKP mass
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By AMS-02 data, 300 GeV LKP mass is not relevant
More strict observation is expected for high energy region
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Summary
• The flux from LKP can fit to AMS-02 data for positron excess
• The value of boost factor depends on LKP mass, and it is larger for heavier LKP mass than for lighter
• Light LKP mass, such as 300 GeV, may be excluded, because the edge structure has not been observed by some experimental data
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Thank you for listening
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Electron plus positron spectrum
M. Di Mauro et al., JCAP 04 (2014) 006
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Positron Fraction
M. Di Mauro et al., JCAP 04 (2014) 006