Gravitino Dark Matter Michael Grefe Departamento de F´ısica Teorica´ Instituto de F´ısica Teorica´ UAM/CSIC Universidad Autonoma´ de Madrid Exotic Physics with Neutrino Telescopes 2013 Centre de Physique des Particules de Marseille 3 April 2013 Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 1 / 15 Motivation for Unstable Gravitino Dark Matter What Do We Know about Dark Matter? I Observed on various scales through its gravitational interaction I Contributes significantly to the energy density of the universe [M. Whittle] [ESA / Planck Collaboration] [NASA / Clowe et al.] I Dark matter properties known from observations: • No electromagnetic and strong interactions • At least gravitational and at most weak-scale interactions • Non-baryonic • Cold (maybe warm) • Extremely long-lived but can be unstable! [ESA / Planck Collaboration] Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 2 / 15 Motivation for Unstable Gravitino Dark Matter Gravitino Dark Matter: Stable or Unstable? I Stable Gravitino Dark Matter • Typical in gauge mediation with conserved R-parity −4 • No direct detection signal expected: σN ∼ MPl −4 • No annihilation signal expected: σann ∼ MPl • Collider signals from long-lived NLSP expected • Long-lived NLSP can be in conflict with BBN [The Particle Zoo] I Unstable Gravitino Dark Matter • Typical candidate in models with R-parity violation • Lifetime larger than the age of the universe −4 • No direct detection signal expected: σN ∼ MPl • Decays could lead to observable cosmic-ray signals • Collider signals from long-lived NLSP expected Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 3 / 15 Gravitino Dark Matter with Broken R Parity Models with Gravitino DM and R-Parity Violation I Bilinear R-parity violation (BRpV) [Takayama, Yamaguchi (2000), Restrepo et al. (2011)] • R-parity violation is source of neutrino masses and mixings • Predictive model: gravitino mass constrained to be below few GeV I ”µ from ν” Supersymmetric SM (µνSSM) [Lopez-Fogliani,´ Munoz˜ (2005)] • Electroweak see-saw mechanism for neutrino masses • Solves the µ-problem similar to the NMSSM • Predictive model: gravitino mass constrained to be below few GeV I Bilinear R-parity violation from B–L breaking [Buchmuller¨ et al. (2007)] • Consistent gravitino cosmology with thermal leptogenesis and BBN •O (10) GeV < m3=2 < O(500) GeV, gluino mass below a few TeV I Trilinear R-parity violation [Moreau et al. (2001), Lola et al. (2007)] • Phenemenological study, trilinear terms generically expected without R-parity I PeV neutrino events from gravitino decay? [Feldstein et al. (2013)] • Gravitino mass and lifetime: 2.4 PeV, 1028 s. Continuum neutrinos observable? Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 4 / 15 Gravitino Dark Matter with Broken R Parity Gravitino Decay Channels I Bilinear R-parity violation • Several two-body decay channels: 3=2 ! γν i ; Z νi ; W `i ; h νi • Neutrino line + continuous spectrum • Flavour of the monochromatic neutrino depends on the flavour structure of RpV [MG (2011)] f I Trilinear R-parity violation • Several three-body decay channels: G ¯ ¯ ¯ pf f˜ 3=2 ! νi `j `k ;ν i dj dk ; `i uj dk ; ui dj dk R • Depends on flavour structure of RpV • 6 (c) γ k • Continuous neutrino spectrum ℓ G ν pf • p k • Two-body decay only possible via loops: R − ℓ˜ 6 3=2 ! γν i [Lola et al. (2007)] Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 5 / 15 Gravitino Dark Matter with Broken R Parity Final State Particle Spectra I Gravitino decays produce stable cosmic rays: γ; e; p; d;ν e/µ/τ • Spectra can be simulated with PYTHIA • Soft part dominated by pion decay: νµ ∼ 2 × νe , ντ much lower • Spectral features close to high-energy cut-off from Z; W ; h decay • In addition neutrino line at E ∼ m3=2=2 1 10 y3 2 ® Z ni , ne ne Spectrum 10 y3 2 ® Z ni , nm nm Spectrum y3 2 ® Z ni , nt nt Spectrum dx dx dx dN dN x dN x 0.1 x 1 1 Spectrum 0.01 Spectrum Spectrum 0.1 0.1 Neutrino -3 Neutrino 10 100 GeV 100 GeV Neutrino 100 GeV m3 2 = 1 TeV m3 2 = 1 TeV m3 2 = 1 TeV Tau Muon Electron 10 TeV 10 TeV 10 TeV 0.01 0.01 -4 10 10-6 10-5 10-4 10-3 0.01 0.1 1 10-6 10-5 10-4 10-3 0.01 0.1 1 10-4 10-3 0.01 0.1 1 Energy x = 2 E m Energy x = 2 E m Energy x = 2 E m 3 2 3 2 [MG et al. (2013)] 3 2 Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 6 / 15 Indirect Detection of Gravitino Dark Matter Cosmic-Ray Propagation I Cosmic rays from gravitino decays propagate through the Milky Way I Experiments observe spectra of cosmic rays at Earth [NASA E/PO, SSU, Aurore Simonnet] [AMS-02 Collaboration] [IceCube Collaboration] Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 7 / 15 Directional detection can distinguish unstable gravitino from WIMPs! Indirect Detection of Gravitino Dark Matter Difference of Dark Matter Annihilations and Decays I Angular distribution of the gamma-ray/neutrino flux from the galactic halo: Dark Matter Annihilation Dark Matter Decay dJ σv dN dJ 1 dN halo DM 2 ~ ~ halo = ρ (~) ~ = h i 2 ρhalo(l) dl halo l dl dE 8π mDM dE dE 4π τDM mDM dE l.o.s.Z l.o.s.Z particle physics astrophysics particle physics astrophysics Annihilation (e.g. WIMP dark matter) NFW Anticenter • Annihilation cross section related to relic density 100 to Einasto Isothermal • Strong signal from peaked structures annihilation • Uncertainties from choice of halo profile Normalized 10 Decay (e.g. unstable gravitino dark matter) Integral decay Sight • Lifetime unrelated to production in early universe - 1 value at galactic anticenter of - • Less anisotropic signal Line -180 ° -90 ° 0 ° 90 ° 180 ° Galactic Longitude [MG (2011)] • Less sensitive to the halo model Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 8 / 15 Indirect Detection of Gravitino Dark Matter Difference of Dark Matter Annihilations and Decays I Angular distribution of the gamma-ray/neutrino flux from the galactic halo: Dark Matter Annihilation Dark Matter Decay dJ σv dN dJ 1 dN halo DM 2 ~ ~ halo = ρ (~) ~ = h i 2 ρhalo(l) dl halo l dl dE 8π mDM dE dE 4π τDM mDM dE l.o.s.Z l.o.s.Z particle physics astrophysics particle physics astrophysics Annihilation (e.g. WIMP dark matter) NFW Anticenter • Annihilation cross section related to relic density 100 to Einasto Isothermal • Strong signal from peaked structures annihilation • Uncertainties from choice of halo profile Normalized 10 Decay (e.g. unstable gravitino dark matter) Integral decay Sight • Lifetime unrelated to production in early universe - 1 value at galactic anticenter of - • Less anisotropic signal Line -180 ° -90 ° 0 ° 90 ° 180 ° Galactic Longitude [MG (2011)] • Less sensitive to the halo model Directional detection can distinguish unstable gravitino from WIMPs! Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 8 / 15 Indirect Detection of Gravitino Dark Matter Neutrino Signals from Gravitino Decays I Atmospheric neutrinos are dominant background for gravitino decay signal • Discrimination of neutrino flavours allows to reduce the background • Sensitivity best for large gravitino masses 3 ç æ - n 10 ò ò IceCube-79 ne IceCube 40 Unfolding m ò ò ó ó ó Fréjus ne IceCube-40 Forward Folding nm ó ò ò ì - n L ò AMANDA II Unfolding m 1 100 ó - ó ó AMANDA-II Forward Folding nm sr 1 ò Super-Kamiokande nm - ò s 10 2 ó ò Fréjus nm - æ n m atm. m æ ò atm. ne 1 ç æ GeV H atm. nt æ preliminary ç ì Flux æ 0.1 ò ì 26 ç æ ì t3 2 = 10 s ì æ 0.01 ì Neutrino ç æ ì ´ ì 2 æ n - ì E 10 3 æ ì 100 GeV 1 TeV 10 TeV æ 10-4 1 10 100 1000 10 000 100 000 Neutrino Energy En GeV [MG et al. (2013)] I Neutrinos from models like BRpV and µνSSMH L most likely not observable • Sensitivity to lifetimes beyond 1028 s needed at energies around 1 GeV Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 9 / 15 Indirect Detection of Gravitino Dark Matter Neutrino Detection – Upward Through-Going Muons I Muon tracks from charged current DIS of muon neutrinos off nuclei Advantages • Muon track reconstruction is well-understood at neutrino telescopes Disadvantages • Neutrino–nucleon DIS and propagation energy losses shift muon spectrum to lower energies • Bad energy resolution (∼ 0:3 in log10 E) smears out cut-off energy Upward Through-Going Muons Upward Through-Going Muons 105 10 4 atmospheric background L 10 1 - yr 2 3 - 10 1 km H 100 0.1 10 Statistical Significance Muon Flux 26 Τ32 = 10 s 1 m32 = 100 GeV 1 TeV 10 TeV 0.01 m32 = 100 GeV 1 TeV 10 TeV 26 Τ32 = 10 s 0.1 1 10 100 1000 10 000 100 000 1 10 100 1000 10 000 100 000 Energy HGeVL Energy HGeVL [MG (2011)] Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 10 / 15 Indirect Detection of Gravitino Dark Matter Neutrino Detection – Improvements With Cascades I Hadronic and electromagnetic cascades from charged current DIS of electron and tau neutrinos and neutral current interactions of all neutrino flavours Disadvantages • TeV-scale cascades are difficult to discriminate from short muon tracks Advantages • 3× larger signal and 3× lower background compared to other channels • Better energy resolution (0.18 in log10 E) helps to distinguish spectral features Shower Events 106 Shower Events 100 5 L 1 10 - yr atmospheric background 10 3 4 - 10 km H 1 103 100 0.1 Statistical Significance Shower Rate Τ = 1026 s 26 10 32 Τ32 = 10 s = 0.01 m32 100 GeV 1 TeV 10 TeV m32 = 100 GeV 1 TeV 10 TeV 1 1 10 100 1000 10 000 100 000 1 10 100 1000 10 000 100 000 Energy HGeVL Energy HGeVL [MG (2011)] Michael Grefe (IFT UAM/CSIC) Gravitino Dark Matter EPNT 2013 – 3 April 2013 11 / 15 Indirect Detection of Gravitino Dark Matter Gravitino Decay Signals in Cosmic-Ray Spectra Antiproton Flux 0.1 preliminary æ PAMELA data Astrophysical Background æ æ æ æ æ æ æ L æ æ æ 1 æ MAX 150 GeV - 0.01 æ æ sr æ æ MED 1 TeV 1 æ - MIN 5 TeV s æ 2 æ - 10-3 m æ 28 1 t = - 3 2 10 s æ GeV æ H 10-4 Flux æ 10-5 æ Antiproton 10-6 10-7 0.1 1 10 100 1000 Kinetic Energy GeV [MG et al.