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STAU SEARCHES @ CL IC

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. STAU SEARCHES @ CL IC. CLIC W ORKSHOP CERN, 16-18 October 2007. Outline. LSP and NLSP in SUSY mSUGRA points + point 

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STAU SEARCHES @ CL IC

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  1. 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 STAU SEARCHES @ CLIC CLIC WORKSHOP CERN, 16-18 October 2007

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

  3. Supersymmetry (SUSY) • 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 • ...

  4. SUGRA Model • GraMSB: gravity-mediation • SUSY breaking scale ~ 1011 GeV • sparticle masses ~ (GeV-TeV) • CMSSM& GUT unification  mSUGRA mSUGRA parameters: • GMSB: gauge-mediated • SUSY breaking scale ~ 105 GeV • LSP = Gravitino mass (~ eV-GeV) • m1/2= common gaugino mass • m0= common scalar mass • A0=trilinear coupling • tan β= ratio of VEVs • sign()= sign of Higgs mixing parameter Most interesting: gravitino LSP, stau NLSP Experimental constraint on NLSP stau: > 87.6 GeV (pair production) –Abbiendi 04

  5. mSUGRA Benchmark 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 ~ 104 – 106 s- LSP gravitino, mG ~ m0 or mG ~ 0.2 m0Points: - low m0, low m1/2, low tan  - high m0, high m1/2, high tan  - low m0, high m1/2, high tan  - high m0, high m1/2, low tan • De Roeck et al. 05 in some certain parameter space of mSUGRA, good agreement between BBN calculations and observed 6,7Li abundances O. Cakir et al. 07

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

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

  9. The benchmark points of mSUGRA This point could be probed at LHC, ILC and CLIC Point : t=2.9x106s = 33.7 day Point : t=1.7x106s = 19.4 day Point : t=6.4x104s =0.7 day Point : t=1.35x103s These points could be probed at LHC and CLIC This point could be probed only at CLIC

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

  11. unpolarized cross-sections with statistical errors

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

  13. 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 Errors on the mixing (cos~0.6) and stau mass (m)

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

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

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

  19. Significant decay modes and branching ratios of SUSY particles

  20. Detection of stau c1 = 2.087, c2 = 3.22 for steel Rossi, 52 Martyn, 06 The coresponding values of  for staus stopping in different detector parts for the benchmark points , ,  and 

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

  22. CONCLUSIONS • 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 • 6,7Li 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 Many “staus” at CLIC

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