indirect searches for gravitino dark mattermgrefe/files/grefe_idms2011.pdf · 2014. 7. 2. ·...

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



Ω3/2h2≃ 0.27

„

TR

1010 GeV

« „

100 GeVm3/2

« „

mg

1 TeV

«2




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




Ω3/2h2≃ 0.27

„

TR

1010 GeV

« „

100 GeVm3/2

« „

mg

1 TeV

«2




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!


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


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!


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

ΝΤ

ΝΜ

Νe

dH´ 103

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


Gravitino Decay Signals in Cosmic-Ray Spectra: e+

e++e−, p, γ and ν

ª

ª

ª

ª§

§§

§

¨

¨¨

¨

¨¨¨¨

¨

¨

øø

ø

ø

ø

øø

øø

ì

ì

ì

ì

ì

ì

ì

ì

ìçç

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

ª

ª

ª

ó

ó

ó

¨

¨§

§

§

§

òò

ò

òòò

ò

ò

òò

òòò

ø

ø

øø

øøø

øø

øø

øøø

ô

ô

ôô

ô

ô

ô

ô

ô

÷

÷÷

÷÷÷

÷

÷

÷

ààà

à

àà

à

à

ààà

àà

ì

ì

ì

ìì

æ

æ

æ

æ

ææ

ææ

ææææææ

ææææ æ æ

æ æ æ

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

ì

ì

ìì ì

ìì

ì ì ì

ìì

ìà

àààà

àà

à

à

àà

æ

æ

æ

æ

æ

ææ

ææ

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 LATô ô

ô

ô

ô ô

ô

ò

òò ò

òò

ò

òò

ò

ò

ì

ì

ì

ì

ì

ì

ì

ì

ì

æ

æ

æ

æ

æ

æ

æ

æ

æ

æ

æ

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




ª

ª

ª

ª§

§§

§

¨

¨¨

¨

¨¨¨¨

¨

¨

øø

ø

ø

ø

øø

øø

ì

ì

ì

ì

ì

ì

ì

ì

ìçç

ç


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


ª

ª

ª

ó

ó

ó

¨

¨§

§

§

§

òò

ò

òòò

ò

ò

òò

òòò

ø

ø

øø

øøø

øø

øø

øøø

ô

ô

ôô

ô

ô

ô

ô

ô

÷

÷÷

÷÷÷

÷

÷

÷

ààà

à

àà

à

à

ààà

àà

ì

ì

ì

ìì

æ

æ

æ

æ

ææ

ææ

ææææææ

ææææ æ æ

æ æ æ

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)




ª

ª

ª

ª§

§§

§

¨

¨¨

¨

¨¨¨¨

¨

¨

øø

ø

ø

ø

øø

øø

ì

ì

ì

ì

ì

ì

ì

ì

ìçç

ç


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


ì

ì

ìì ì

ìì

ì ì ì

ìì

ìà

àààà

àà

à

à

àà

æ

æ

æ

æ

æ

ææ

ææ

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




• Associated gamma-ray flux in conflict with Fermi LAT data for isotropic diffuse flux




ª

ª

ª

ª§

§§

§

¨

¨¨

¨

¨¨¨¨

¨

¨

øø

ø

ø

ø

øø

øø

ì

ì

ì

ì

ì

ì

ì

ì

ìçç

ç


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


ô ôô

ô

ô ô

ô

ò

òò ò

òò

ò

òò

ò

ò

ì

ì

ì

ì

ì

ì

ì

ì

ì

æ

æ

æ

æ

æ

æ

æ

æ

æ

æ

æ

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




• 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


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


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


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


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!


indirect searches for gravitino dark mattermgrefe/files/grefe_idms2011.pdf · 2014. 7. 2. ·...

Documents