Gravitino Dark Matter Gravitino Dark Matter & R-Parity Violation& R-Parity Violation
M. Lola MEXT-CT-2004-014297
(work with P. Osland and A. Raklev)
Prospects for the detection of Dark Matter Spain, September 2007 (ENTAPP)
Neutralinos
Gravitinos
Sneutrinos
Axinos Severe constraints to
allowed parameter space by combined studies of
BBN and NLSP decays
LEP data
Direct Searches
SUSY (MSSM) Dark Matter CandidatesSUSY (MSSM) Dark Matter Candidates
In addition to couplings generating fermion masses, also
- These violate lepton and baryon number
- If simultaneously present, unacceptable p decay
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
R-violating supersymmetryR-violating supersymmetry
R-violating couplings & LSP decaysR-violating couplings & LSP decays
-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
Gravitino LSP in R-violating supersymmetry?Gravitino LSP in R-violating supersymmetry?
3-body trilinear R-violating decays3-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 2-body bi-linear R-violating decays
Takayama, YamaguchiBuchmuler et al.
Suppressed by:
- Gravitino vertex (~1/Mp)
-Neutralino-neutrino mixing
(model dependent)
Radiative 2-body trilinear R-violating decaysRadiative 2-body trilinear R-violating decays
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 decaysRadiative versus 3-body decays
Lifetime versus SUSY massesLifetime versus SUSY masses
Max allowed couplings Max allowed couplings (photon spectra & DM considerations)(photon spectra & DM considerations)
Photon Spectra Photon Spectra (bilinear R-violation)(bilinear R-violation)
- Non-shaded area compatible with photon spectra
- Possible solution to EGRET data for gravitinos ≥ 5 GeV
(Takayama, Yamaguchi)
NLSP decaysNLSP decays
- No source of suppression other than R-violating couplings
- Decay well before BBN compatible with gravitino DM
-SM symmetries allow 45 R-violating operators
- Lepton & Baryon Parities forbid subsets of them
Lepton Parity: only
Baryon Parity: only
Flavour effectsFlavour effects
If Z3 not flavour-blind, could chose even subsets within
(i.e. Why the top mass so much larger than all others?)
Invariance under symmetry determines mass hierarchies
Link to Flavour Effects Link to Flavour Effects in Fermion Masses in Fermion Masses
Charges such that only Top-coupling 0 flavour charge
X All others forbidden, only appear in higher orders
Higher charge (lower generation) implies larger suppression
An example (King, Ross)
R-violating couplings of 3rd generation
(leading to large radiative decays) naturally higher
Mixing effects important & can affect decays
ConclusionsConclusions
Significant parameter space where
radiative decays dominate over tree-body ones
Lifetime long enough for gravitino DM AND
observable R-violation in colliders
NLSP decays easily compatible with BBN
Photon spectrum consistent with measurements
Results sensitive to flavour effects
Probe Flavour Structure of Fundamental Theory