indirect searches for gravitino dark mattermgrefe/files/grefe_idms2011.pdf · 2014. 7. 2. ·...
TRANSCRIPT
Indirect Searches for Gravitino Dark Matter
Michael Grefe
Deutsches Elektronen-SynchrotronDESY, Hamburg, Germany
Workshop on Indirect Dark Matter SearchesHamburg – 17 June 2011
Based on work in progress in collaboration with Laura Covi and Gilles Vertongen.Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 1 / 11
Motivation for Unstable Gravitino Dark Matter
Supergravity predicts the gravitino as the spin-3/2 superpartner of the graviton Gravitinos are produced thermally after inflation:
Ω3/2h2≃ 0.27
„
TR
1010 GeV
« „
100 GeVm3/2
« „
mg
1 TeV
«2
[Bolz et al. (2001)]
Problem in models with neutralino dark matter:• Thermal leptogenesis requires high reheating temperature: TR & 109 GeV [Davidson et al. (2002)]
• Late gravitino decays are in conflict with BBN ⇒ Cosmological gravitino problem
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 2 / 11
Motivation for Unstable Gravitino Dark Matter
Supergravity predicts the gravitino as the spin-3/2 superpartner of the graviton Gravitinos are produced thermally after inflation:
Ω3/2h2≃ 0.27
„
TR
1010 GeV
« „
100 GeVm3/2
« „
mg
1 TeV
«2
[Bolz et al. (2001)]
Problem in models with neutralino dark matter:• Thermal leptogenesis requires high reheating temperature: TR & 109 GeV [Davidson et al. (2002)]
• Late gravitino decays are in conflict with BBN ⇒ Cosmological gravitino problem
Possible solution: Gravitino is the LSP and thus stable!
Correct relic density for m3/2 > O(10) GeV ⇒ Gravitino dark matter Still problematic:
• Late NLSP decays are in conflict with BBN ⇒ Cosmological gravitino problem
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 2 / 11
Motivation for Unstable Gravitino Dark Matter
Supergravity predicts the gravitino as the spin-3/2 superpartner of the graviton Gravitinos are produced thermally after inflation:
Ω3/2h2≃ 0.27
„
TR
1010 GeV
« „
100 GeVm3/2
« „
mg
1 TeV
«2
[Bolz et al. (2001)]
Problem in models with neutralino dark matter:• Thermal leptogenesis requires high reheating temperature: TR & 109 GeV [Davidson et al. (2002)]
• Late gravitino decays are in conflict with BBN ⇒ Cosmological gravitino problem
Possible solution: Gravitino is the LSP and thus stable!
Correct relic density for m3/2 > O(10) GeV ⇒ Gravitino dark matter Still problematic:
• Late NLSP decays are in conflict with BBN ⇒ Cosmological gravitino problem
Possible solution: R parity is not exactly conserved!
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 2 / 11
Gravitino Dark Matter with Bilinear R-Parity Violation
Bilinear R-Parity Violation: W/Rp= µi Hu ℓi , −L
soft/Rp
= BiHu ℓi + m2Hd ℓi
H∗
d ℓi + h.c.
Only lepton number violated ⇒ Proton remains stable!
Cosmological bounds on R-violating couplings• Lower bound: The NLSP must decay fast enough to evade BBN constraints
• Upper bound: The lepton/baryon asymmetry must not be washed out
Gravitino decay suppressed by Planck scale and small R-parity violation• The gravitino lifetime exceeds the age of the universe by many orders of magnitude
• The unstable gravitino is a viable dark matter candidate
Rich phenomenology instead of elusive gravitinos• A long-lived NLSP could be observed at the LHC → see C. Weniger’s talk
• Gravitino decays lead to possibly observable signals at indirect detection experiments
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 3 / 11
Gravitino Dark Matter with Bilinear R-Parity Violation
Bilinear R-Parity Violation: W/Rp= µi Hu ℓi , −L
soft/Rp
= BiHu ℓi + m2Hd ℓi
H∗
d ℓi + h.c.
Only lepton number violated ⇒ Proton remains stable!
Cosmological bounds on R-violating couplings• Lower bound: The NLSP must decay fast enough to evade BBN constraints
• Upper bound: The lepton/baryon asymmetry must not be washed out
Gravitino decay suppressed by Planck scale and small R-parity violation• The gravitino lifetime exceeds the age of the universe by many orders of magnitude
• The unstable gravitino is a viable dark matter candidate
Rich phenomenology instead of elusive gravitinos• A long-lived NLSP could be observed at the LHC → see C. Weniger’s talk
• Gravitino decays lead to possibly observable signals at indirect detection experiments
The gravitino is a well-motivated dark matter candidate that could be indirectlyobserved at colliders and in cosmic-ray spectra!
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 3 / 11
Gravitino Decay Channels
Several contributing decay channels: ψ3/2 → γ νi , Z ∗νi , h∗νi , W ∗ℓi
• For m3/2 < mW three-body decays can play an important role [Choi et al. (2010)]
• Ratio between γ νi and other channels is model-dependent
ΓΝi
Γ*Z*Νi
Wi
W*i
ZΝi
hΝi
10 100 1000 10 000
10-5
10-4
10-3
0.01
0.1
1
Gravitino MassHGeVL
Bra
nchi
ngR
atio
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ΝΜ
Νe
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L
p
e
Γ
Ν
e
Νi
Ψ32® Z Νi , m32 = 100 GeV
0.01 0.1 1 10 100
0.001
0.01
0.1
1
10
100
Kinetic EnergyHGeVL
Spe
ctru
mdNdHlo
g 10TL
Gravitino decays produce spectra of stable cosmic rays: γ, e, p, νe/µ/τ , d• Two-body decay spectra generated with PYTHIA
• Deuteron coalescence treated on event-by-event basis
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 4 / 11
Gravitino Decay Signals in Cosmic-Ray Spectra: e+
e++e−, p, γ and ν
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Τ32 = 1027 s
m32 = 100 GeV 1 TeV 10 TeV
1 10 100 1000 10 000
10-3
0.01
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1
10
100
Kinetic EnergyHGeVL
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m32 = 100 GeV 1 TeV 10 TeV
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EnergyHGeVL
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m32 = 100 GeV 1 TeV 10 TeV
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10
100
103
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GeV
m-
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ô FréjusΝeò FréjusΝΜ
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ì AMANDA -II Unfolding ΝΜIceCube-40ΝΜ
æ IceCube-40 UnfoldingΝΜ
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 5 / 11
Gravitino Decay Signals in Cosmic-Ray Spectra: e+
e++e−, p, γ and ν
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Τ32 = 1026 s
m32 = 100 GeV 1 TeV 10 TeV
1 10 100 1000 10 000
0.01
0.03
0.1
0.3
EnergyHGeVL
Pos
itron
Fra
ctio
ne+H
e++
e-L
ª MASS-91
§ TS93
¨ CAPRICE94
ø HEAT
ì AMS-01
ç HEAT-pbaræ PAMELA
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background
Τ32 = 1027 s
m32 = 100 GeV 1 TeV 10 TeV
1 10 100 1000 10 000
10-3
0.01
0.1
1
10
100
Kinetic EnergyHGeVL
T3´
Ant
ipro
ton
Flu
xHG
eV2
m-
2s-
1sr-
1L
ª MASS-91ó IMAX¨ CAPRICE94§ CAPRICE98ì AMS-01æ PAMELA
ò BESS 95+97ø BESS 98ô BESS 99÷ BESS 00à BESS-Polar
Gravitino decay in principal could explain the rise in the positron fraction data• Explanation requires a gravitino lifetime of O(1026) s → see A. Ibarra’s talk
• Depends on flavor structure of R-parity breaking (hard e+ from W e, Wµ needed)
• Associated p from W , Z and h fragmentation in conflict with p data (not leptophilic)(Remind that p propagation introduces large uncertainties → see talk of P. Salati / A. Ibarra)
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 6 / 11
Gravitino Decay Signals in Cosmic-Ray Spectra: e+
e++e−, p, γ and ν
ª
ª
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§§
§
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background
Τ32 = 1026 s
m32 = 100 GeV 1 TeV 10 TeV
1 10 100 1000 10 000
0.01
0.03
0.1
0.3
EnergyHGeVL
Pos
itron
Fra
ctio
ne+H
e++
e-L
ª MASS-91
§ TS93
¨ CAPRICE94
ø HEAT
ì AMS-01
ç HEAT-pbaræ PAMELA
ì
ì
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ìì
ì ì ì
ìì
ìà
àààà
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à
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àà
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æ
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Τ32 = 1027 s
m32 = 100 GeV 1 TeV 10 TeV
0.1 1 10 100 1000 10 000
0.0001
0.0003
0.001
0.003
0.01
0.03
EnergyHGeVL
E2´
Gam
ma-
Ray
Flu
xHG
eVm-
2s-
1sr-
1L
ì EGRETHSreekumaret al.L
à EGRETHStronget al.L
æ Fermi LAT
Gravitino decay in principal could explain the rise in the positron fraction data• Explanation requires a gravitino lifetime of O(1026) s → see A. Ibarra’s talk
• Depends on flavor structure of R-parity breaking (hard e+ from W e, Wµ needed)
• Associated p from W , Z and h fragmentation in conflict with p data (not leptophilic)(Remind that p propagation introduces large uncertainties → see talk of P. Salati / A. Ibarra)
• Associated gamma-ray flux in conflict with Fermi LAT data for isotropic diffuse flux
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 7 / 11
Gravitino Decay Signals in Cosmic-Ray Spectra: e+
e++e−, p, γ and ν
ª
ª
ª
ª§
§§
§
¨
¨¨
¨
¨¨¨¨
¨
¨
øø
ø
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øø
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ì
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ì
ì
ì
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ç
æææææææææææ æ
ææ
æ
æ
background
Τ32 = 1026 s
m32 = 100 GeV 1 TeV 10 TeV
1 10 100 1000 10 000
0.01
0.03
0.1
0.3
EnergyHGeVL
Pos
itron
Fra
ctio
ne+H
e++
e-L
ª MASS-91
§ TS93
¨ CAPRICE94
ø HEAT
ì AMS-01
ç HEAT-pbaræ PAMELA
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ΝΤΝe
ΝΜ
Τ32 = 1026 s
m32 = 100 GeV 1 TeV 10 TeV
1 10 100 1000 10 000 100 000
10-4
10-3
0.01
0.1
1
10
100
103
EnergyHGeVL
E2´
Neu
trin
oF
luxH
GeV
m-
2s-
1sr-
1L
ô FréjusΝeò FréjusΝΜ
Super-KamiokandeΝΜAMANDA -II ForwardΝΜ
ì AMANDA -II Unfolding ΝΜIceCube-40ΝΜ
æ IceCube-40 UnfoldingΝΜ
Gravitino decay in principal could explain the rise in the positron fraction data• Explanation requires a gravitino lifetime of O(1026) s → see A. Ibarra’s talk
• Depends on flavor structure of R-parity breaking (hard e+ from W e, Wµ needed)
• Associated p from W , Z and h fragmentation in conflict with p data (not leptophilic)(Remind that p propagation introduces large uncertainties → see talk of P. Salati / A. Ibarra)
• Associated gamma-ray flux in conflict with Fermi LAT data for isotropic diffuse flux
• For large gravitino masses constraints from neutrino flux can become important
Astrophysical sources like pulsars are required to explain the excess
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 8 / 11
Antideuteron Signals from Gravitino Decays
Antideuterons are a valuable additional indirect detection channel• In particular sensitive to low gravitino masses due to small astrophysical background
• AMS-02 and GAPS will be able to put strong constraints on light gravitino dark matter
• Complementary to gamma rays, relevance depends on branching ratio for the photon line
BESS 97-00G
AP
SHL
DBL
GA
PSHU
LDBL
AM
S-
02
AM
S-
02
background
Τ32 = 1027 s
m32 = 100 GeV 1 TeV 10 TeV
ΦF = 500 MV
0.1 1 10 100 1000
10-10
10-9
10-8
10-7
10-6
10-5
10-4
Kinetic Energy per NucleonHGeVnL
HTnL´
Ant
ideu
tero
nF
luxH
m-
2s-
1sr-
1 L
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 9 / 11
Limits on the Gravitino Dark Matter Parameter Space
excluded by diffuse flux
excluded by line searches
1 10 100 1000 10 000
1024
1025
1026
1027
1028
1029
Gravitino MassHGeVL
Gra
vitin
oLi
fetim
eHsL
Fermi LAT diffuse fluxVertongenet al. photon lineFermi LAT photon line
excluded by
antiproton flux
excluded by electron+ positron flux
excluded
by
positron
fraction
antideuteron sensitivity
100 1000 10 000
1024
1025
1026
1027
1028
Gravitino MassHGeVL
Gra
vitin
oLi
fetim
eHsL
PAMELA e+He+ + e-L
PAMELA p
Fermi LAT H.E.S.S.e+ + e-
Estimate of bounds on gravitino lifetime• Additional uncertainties from charged CR propagation
• Background subtraction could improve bounds
• Photon line bounds can be very strong for low gravitinomasses(see C. Weniger’s talk for a discussion of γ constraints)
• Antideuterons can give complementary limits at lowgravitino masses
• Neutrino bounds competitive for large gravitino masses
exclusion from
through-going muons
after 1 year at IceCube+ DeepCore
100 1000 10 000
1024
1025
1026
1027
Gravitino MassHGeVLG
ravi
tino
Life
timeHsL
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 10 / 11
Conclusion
• Gravitino dark matter with broken R parity is well motivated as it leads to acosmological scenario that is consistent with thermal leptogenesis and BBN
• The Gravitino lifetime is naturally in the range of indirect detection experimentsand can be strongly constrained using a multi-messenger approach
• Gravitino dark matter cannot explain the PAMELA excess due to strong constraintsfrom gamma rays and antiprotons
• Future antideuteron searches can provide strong constraints on light gravitinos, inparticular if the gamma-ray line signal is suppressed
• Neutrino experiments like IceCube have the capability to provide competetiveconstraints on the gravitino lifetime, in particular at large masses
New neutrino detection channels like showers and use of spectral information willallow to greatly improve the sensitivity of these experiments
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 11 / 11
Conclusion
• Gravitino dark matter with broken R parity is well motivated as it leads to acosmological scenario that is consistent with thermal leptogenesis and BBN
• The Gravitino lifetime is naturally in the range of indirect detection experimentsand can be strongly constrained using a multi-messenger approach
• Gravitino dark matter cannot explain the PAMELA excess due to strong constraintsfrom gamma rays and antiprotons
• Future antideuteron searches can provide strong constraints on light gravitinos, inparticular if the gamma-ray line signal is suppressed
• Neutrino experiments like IceCube have the capability to provide competetiveconstraints on the gravitino lifetime, in particular at large masses
New neutrino detection channels like showers and use of spectral information willallow to greatly improve the sensitivity of these experiments
Thanks for your attention!
Michael Grefe (DESY Hamburg) Indirect Searches for Gravitino Dark Matter IDMS 2011 – 17 June 2011 11 / 11