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Gravitino Dark Matter in R-violating SUSY. M. Lola MEXT-CT-2004-014297. Work with N.E.Bomark, P.Osland and A.Raklev. Content. Dark Matter: Is observable R-violation compatible with SUSY DM? Gravitino decays in R-violating SUSY Couplings & Flavour Effects

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gravitino dark matter in r violating susy

Gravitino Dark Matter in R-violating SUSY

M. Lola


Work with N.E.Bomark, P.Osland and A.Raklev



Dark Matter: Is observable R-violation compatible with


Gravitino decays in R-violating SUSY

Couplings & Flavour Effects

Link to Lepton flavour violation: R-violation versus MSSM



Motivation for R-violating supersymmetry

In addition to couplings generating fermion masses,


- These violate lepton and baryon number

- If simultaneously present, unacceptable p decay


Ways out:

X Either kill all couplings via R-parity (SM: +1 , SUSY: -1)

LSP: stable, dark matter candidate

Colliders: Missing energy

  • Or allow subsets by baryon / lepton parities

LSP: unstable – lose (?) a dark matter candidate

Colliders: Multi-lepton/jet events


Gravitino DM in R-violating supersymmetry?

  • If LSP a gravitino, its decays very suppressed by Mp
  • The lighter the gravitino, the longer the lifetime

Questions:can gravitinos be DM even with broken R-parity?

Can we hope for BOTH DM AND R-violation in colliders?

Answer:depends on how gravitinos decay under R-violation


3-body trilinear R-violating decays

Chemtob, Moreau

Suppressed by:

  • Gravitino vertex (~1/Mp)
  • Phase space / fermion masses

(for light gravitino and heavy fermions)


2-body bi-linear R-violating decays

Takayama, Yamaguchi

Buchmuler et al.

Suppressed by:

  • Gravitino vertex (~1/Mp)
  • Neutralino-neutrino mixing

(model dependent)


Radiative 2-body trilinear R-violating decays

SL, P. Osland, A. Raklev

Suppressed by:

  • Gravitino vertex (~1/Mp)
  • Loop factors (~ fermion mass)

Radiative decays dominate for:

Smaller gravitino masses

R and L violation via operators of the 3rd generation

Small neutrino-neutralino mixing

Large gravitino lifetime (can be DM), due to:

Gravitational suppression of its couplings

Smallness of R-violating vertices

Loop, phase space, or mixing effects

Maximum stability

(neither radiative nor tree-level decays)!


Radiative versus 3-body decays

Couplings ~10^(-4) for consistency with the photon spectrum


NLSP decays

- No source of suppression other than R-violating couplings

- Decay well before BBN compatible with gravitino DM


R-violating signals: couplings & LSP decays

R-parity violating coupling

Ordinary MSSM neutralino coupling

Neutr. Decays to 3 SM particles


Link to Flavour Effects

in Fermion Masses

(i.e. Why the top mass so much larger than all others?)

Invariance under symmetry determines mass hierarchies

  • Charges such that only Top-coupling 0 flavour charge

XAll others forbidden, only appear in higher orders

Higher charge(lower generation) implies larger suppression


Flavour effects

  • SM symmetries allow 45 R-violating operators
  • Lepton & Baryon Parities forbid subsets of them

Baryon Parity:only

Bilinear R-violation allowed

  • Bilinear R-violation forbidden
  • μ term i.e. by Giudice-Masiero mech.
  • or Hall, Lykken, Weinberg mech.

Lepton Parity:only

If Z3not flavour-blind, could chose even subsets within


An example (King, Ross)

R-violating couplings of 3rd generation

(leading to large radiative decays) naturally higher


Neutrinos in R-violating SUSY

1-loop neutrino mass contributions:


R-violation: Correlated Rates depending on coupling combinations

(A. de Gouvea, S.L, K. Tobe)

To be compared with 160 and 0.92 in MSSM

(where on shell photon penguin dominates)



  • R-violating SUSY equally motivated with MSSM
  • Interesting signals but also strong bounds
  • Possible to have both gravitino DM AND

observable R-violation in colliders

  • Results sensitive to flavour effects

Probe Flavour Structure of Fundamental Theory