1. Collider signatures of gravitino dark matter with a sneutrino NLSP
Euro-GDR SUSY, Nov 2007, Brussels, Belgium
Collider signatures of gravitino dark matter with a sneutrino NLSP
Sabine Kraml
LPSC Grenoble
based on:
L. Covi, SK, JHEP08(2007)015
D.T. Nhung, SK, in preparation

2. Gravitino DM with sneutrino NLSP
Contents
Introduction
no-scale SUSY with NUHM
RGE analysis of mass hierarchies
Sneutrino NLSP region (with gravitino LSP)
Mass patterns
3-body decays of sleptons
Impact on LHC cascade decays
Gravitino relic density and BBN
Conclusions
S. Kraml
Gravitino DM with sneutrino NLSP

3. Higgs-exempt no-scale supersymmetry
Evans, Morrissey, Wells ‘06
Higgs-exempt no-scale supersymmetry
Vanishing scalar soft terms at M(GUT)
Free parameters
Possible in GUTs with sequestered scalar sector, gaugino mediation, conformal dynamics,….
Buchmüller, Kersten, Schmidt-Hoberg ‘05
Buchmüller, Covi, Kersten, Schmidt-Hoberg ‘06
S. Kraml
Gravitino DM with sneutrino NLSP

4. Gaugino-mediated SUSY breaking
Kaplan, Kribs, Schmaltz ‘99
Chacko, Luty, Nelson, Ponton ‘99
Gaugino-mediated SUSY breaking
SUSY breaking occurs through a superfield S localized on a 4-dim brane in a higher-dim theory.
Gauge and Higgs superfields live in the bulk and couple directly to S
 gaugino and Higgs fields acquire soft masses at tree level
Squarks and sleptons are confined to a brane w/o direct coupling to S
 no-scale boundary conditions
hidden
visible
SUSY
MSSM
gauge & Higgs
superfields
Buchmüller, et al.
S. Kraml
Gravitino DM with sneutrino NLSP

5. Gravitino DM with sneutrino NLSP
RGE analysis
1-loop running of scalar mass parameters
Compare with gaugino mass parameters
SGUT  0:
mE  M1  mL
SGUT  0:
mL  M1  mE
S. Kraml
Gravitino DM with sneutrino NLSP

6. Gravitino DM with sneutrino NLSP
Gaugino mediation
= SGUT
Masses computed with SOFTSUSY
S. Kraml
Gravitino DM with sneutrino NLSP

7. Gravitino DM with sneutrino NLSP
Evans, Morrissey, Wells ‘06
Gravitino LSP
S. Kraml
Gravitino DM with sneutrino NLSP

8. -Sneutrino NLSP region (assuming a gravitino LSP)

9.  NLSP region: peculiar mass spectra
L. Covi, SK ‘07
 NLSP region: peculiar mass spectra ~ A: B: C:
B,C
Visible 1 decays,
3-body decays of sleptons
dashed blue lines: sneutrino-stau mass difference (small!)
S. Kraml
Gravitino DM with sneutrino NLSP

10. Gravitino DM with sneutrino NLSP
dominant
S. Kraml
Gravitino DM with sneutrino NLSP

11. LHC cascade decays m of few GeV  soft decay products
99%
33%
32%
19%
m of few GeV  soft decay products
need to be able to measure low-pT e and 
S. Kraml
Gravitino DM with sneutrino NLSP

12. LHC cascade decays -cont-
~70%
Last step invisible,
looks like 1 LSP
32% %
2 SFOS leptons + 1 
32% %
may fake LFV?
60% % 
NB: in mSUGRA this would be a right slepton
S. Kraml
Gravitino DM with sneutrino NLSP

13. Gravitino DM with sneutrino NLSP
LHC cascade decays -cont2-
S. Kraml
Gravitino DM with sneutrino NLSP

14. Gravitino DM with sneutrino NLSP
D.T. Nhung, SK, in prep.
Slepton 3-body decays
 
Computed all slepton 3-body decays into other sleptons and implemented them
in SDECAY. (NB: discussed within GMSB by Ambrosanio et al ‘97)
S. Kraml
Gravitino DM with sneutrino NLSP

15. Gravitino relic density and BBN constraints
NB: gaugino mediation favours gravitino mass of O(GeV)

16. Gravitino relic density
Non-thermal production (superWIMP effect)
 negligible for sneutrino NLSP:
Thermal production
S. Kraml
Gravitino DM with sneutrino NLSP

17. Gravitino DM with sneutrino NLSP
Kanzaki, Kawasaki, Kohri, Moroi ‘06
BBN constraints
Stem from (hadronic) 3- and 4-body
sneutrino decays into the gravitino *
* With this approx., no constraint for m < 300 GeV ~
S. Kraml
Gravitino DM with sneutrino NLSP

18. BBN constraints -cont-
L. Covi, SK ‘07
BBN constraints -cont-
Complete calculation of Y with microMEGAs gives a bit stronger bounds
than estimate by Kanzaki et al. But still much less constrained than stau NLSP.
S. Kraml
Gravitino DM with sneutrino NLSP

19. Gravitino DM with sneutrino NLSP
Conclusions
In models with non-universal Higgs masses and large S<0, left-chiral sleptons can be lighter than the 10
The gravitino is a natural dark matter candidate in such a case. Sneutrino NLSP much less constrained by BBN than stau.
LHC cascades characterized by 3-body slepton decays at the end of the chain  mixed flavors, soft leptons  challenging
ILC analysis also complicated by 3-body decays (e.g., selectron-pair production leading to e  Emiss signature)
Dedicated experimental analysis to establish LHC/ILC potential for such a scenario would be very interesting.
S. Kraml
Gravitino DM with sneutrino NLSP