1. STAU SEARCHES @ CLIC Ilkay Turk Cakir Turkish Atomic Energy Authority with co-authors O. Cakir, J. Ellis, Z. Kirca with the contributions from A. De Roeck, D. Schulte CLIC WORKSHOP CERN, 16-18 October 2007

2. 2 LSP and NLSP in SUSY mSUGRA points + point  production cross sections –optimization for the threshold relevant SUSY processes detection of stau conclusion Outline

3. 3 most interesting possibility offered by quantum field theory –relating to fermions to bosons unification with gravity unification of gauge couplings solution of the hierarchy problem dark matter in the Universe... Supersymmetry (SUSY)

4. 4 GraMSB: gravity-mediation –SUSY breaking scale ~ 10 11 GeV –sparticle masses ~ (GeV-TeV) –CMSSM & GUT unification  mSUGRA mSUGRA parameters: GMSB: gauge-mediated –SUSY breaking scale ~ 10 5 GeV –LSP = Gravitino mass (~ eV-GeV) Most interesting: gravitino LSP, stau NLSP Experimental constraint on NLSP stau: > 87.6 GeV (pair production) –Abbiendi 04 SUGRA Model m 1/2 = common gaugino mas s m 0 = common scalar mass A 0 = trilinear coupling tan β = ratio of VEVs sign(  ) = sign of Higgs mixing parameter

5. 5 Points: - consistent with present data from particle physics and BBN constraints -astrophysics and cosmology constrain metastable particles such as staus -comparison between calculated and observed abundance of light elements - NLSP stau has long lifetime ~ 10 4 – 10 6 s - LSP gravitino, m G ~ m 0 or m G ~ 0.2 m 0 Points:  - low m 0, low m 1/2, low tan   - high m 0, high m 1/2, high tan   - low m 0, high m 1/2, high tan   - high m 0, high m 1/2, low tan  A.De Roeck et al. 05 O. Cakir et al. 07 in some certain parameter space of mSUGRA, good agreement between BBN calculations and observed 6,7 Li abundances mSUGRA Benchmark Points

6. +  mSUGRA with gravitino LSP and stau NLSP: benchmark points , ,  and the point  Agreement between BBN calculations and the observed Li abundances Three benchmark points with astrophysical constraints

7. 7 The lighter (heavier) stau mass eigenstate is a linear combination of left and right-handed eigenstates Stau decay rate is given by In large regions of mSUGRA parameters space, the lighter stau is the NLSP ending with an LSP

8. 8 stau NLSP life-time, decay width, lenght t  6.58x10 -25 s/  (GeV) L  1.97x10 -16 m/  (GeV)

9. 9 Point  : t=2.9x10 6 s = 33.7 day Point  : t=1.7x10 6 s = 19.4 day Point  : t=6.4x10 4 s =0.7 day Point  : t=1.35x10 3 s The benchmark points of mSUGRA These points could be probed at LHC and CLIC This point could be probed only at CLIC This point could be probed at LHC, ILC and CLIC

10. 10 SUSY R-parity conservation  pair production at colliders Stau pair production S. Kraml hep-ph/9903257

11. 11 unpolarized cross-sections with statistical errors

12. 12 Red: e- (%90), e+ (%60) ;blue: e- (%90); green: unpolarized polarized cross-sections

13. 13 Errors on the mixing (cos  ~0.6) and stau mass (m  ) Polarization e- %90 e+ %60 accuracies on the measurements: (0.7, 0.005) for  (2.4, 0.01) for ,  at Ecm=1000 GeV; (8, 0.02) for  at Ecm=3000 GeV

14. 14 The total cross section in pb calculated using PYTHIA with the full ISASUGRA spectrum [Baer et al. 00], including both initial and final state radiation (ISR+FSR)

15. 15 # events Number of stau pairs produced at: E cm = 500, 1000 GeV with L=200 fb -1 E cm = 3000, 5000 GeV with L=400 fb -1 E cm (GeV)

16. 16  distribution with simulated CLIC energy spectrum  (optimize total luminosity)

17. 17 Stau pair production at benchmark points and optimal energies for slow-staus with  <0.4 optimal center of mass energies for the constraint  <0.4 : 330 GeV for  730 GeV for  700 GeV for  2500 GeV for 

18. 18 The cross sections for pair-production of supersymmetric particles in the benchmark scenarios , ,  and , as functions of  s.  (e R e R )=8.5x10 -4 pb,  (  R  R )=7.3x10 -4 pb at 3000 GeV for point  SUSY processes: cascades ending with an NLSP stau

19. 19 Significant decay modes and branching ratios of SUSY particles

20. 20 The coresponding values of  for staus stopping in different detector parts for the benchmark points , ,  and  Martyn, 06 c 1 = 2.087, c 2 = 3.22 for steel Detection of stau Rossi, 52

21. 21 The number of stau pairs with  < 0.4, stopped in GLCD

22. 22 CONCLUSIONS Many “staus” at CLIC Discussed the choice of cm energy that would maximize the  for prod. slow moving stau with  < 0.4 in a CLIC det. Presented metastable staus produced in the cascade decays of heavier sparticles, so that optimal cm energies for trapping staus higher than stau pair-prod. threshold If stau (for point , ,  ) found by the LHC, one would know optimal energy and optimal number of stopping staus 6,7 Li friendly point  features relatively heavy sparticles beyond the reach of either the LHC or the ILC, but within the kinematic reach of CLIC Even if there are some light sparticles, the heavier sparticles beyond the reach of LHC and ILC can be discovered and measured precisely at a high energy linear collider CLIC