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Gravitino Dark Matter in R-violating SUSY

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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

Link to Lepton flavour violation: R-violation versus MSSM

Conclusions

Motivation for R-violating supersymmetry

In addition to couplings generating fermion masses,

also

- 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)

Different picture in SUSY!

For all processes at loop level:

For:

Conclusions

- 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