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Highly-Ionizing Particles in Supersymmetric Models

Highly-Ionizing Particles in Supersymmetric Models. John Ellis King ’ s College London & CERN. Minimal Supersymmetric Extension of Standard Model (MSSM). Particles + spartners No highly-charged particles expected, BUT …. 2 Higgs doublets, coupling μ , ratio of v.e.v. ’ s = tan β

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Highly-Ionizing Particles in Supersymmetric Models

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  1. Highly-Ionizing Particles in Supersymmetric Models John Ellis King’s College London & CERN

  2. Minimal Supersymmetric Extension of Standard Model (MSSM) • Particles + spartners • No highly-charged particles expected, BUT …. • 2 Higgs doublets, coupling μ, ratio of v.e.v.’s = tan β • Unknown supersymmetry-breaking parameters: Scalar massesm0, gaugino massesm1/2, trilinear soft couplingsAλ, bilinear soft couplingBμ • Often assume universality: Singlem0, singlem1/2, singleAλ,Bμ: not string? • Called constrained MSSM = CMSSM

  3. Mass Reach as Function of Energy & Luminosity

  4. Lightest Supersymmetric Particle • Stable in many models because of conservation of R parity: R = (-1) 2S –L + 3B where S = spin, L = lepton #, B = baryon # • Particles have R = +1, sparticles R = -1: Sparticles produced in pairs Heavier sparticles  lighter sparticles • Lightest supersymmetric particle (LSP) stable

  5. Possible Nature of LSP • No strong or electromagnetic interactions Otherwise would bind to matter Detectable as anomalous heavy nucleus • Possible weakly-interacting scandidates Sneutrino (Excluded by LEP, direct searches) Lightest neutralino χ(partner of Z, H, γ) Gravitino (nightmare for astrophysical detection)

  6. Scenarios for Metastable Sparticles • Maybe R-parity not exact? • No stable sparticle • Next-to-lightest sparticle (NLSP) may be long-lived • Could be charged or neutral • Scenarios for long-lived NLSP: • Small mass difference from neutralino LSP • Gravitino LSP • Gluinos in split supersymmetry

  7. Energy Loss and Range Singly-charged particles are highly-ionizing if moving slowly Small range in typical Detector materials

  8. Next-to-Lightest Supersymmetric Particle (NLSP) ? • In neutralino dark matter scenarios: • Lighter stau? • Could be long-lived if mstau–mLSP small • In gravitino dark matter scenarios: • Lighter stau, selectron or sneutrino? • Lighter stop squark? • gluino, …? • Naturally long-lived • Decay interaction of gravitational strength

  9. Parameter Plane in the CMSSM Assuming the lightest sparticle is a neutralino LHC Excluded because stau LSP Excluded by b  s gamma WMAP constraint on CDM density Preferred (?) by latest g - 2 JE, Olive & Spanos

  10. Stau NLSP with Neutralino LSP • Along coannihilation strip of CMSSM parameter space favoured by dark matter density • Generally small stau-neutralino mass difference • May well be < 2 GeV • Favoured by LHC LHC JE, Olive

  11. Stau NLSP with Neutralino LSP • 2-, 3- or 4-body decays may dominate, depending on mstau–mLSP • Lifetime > 100 ns for mass difference < mτ Jittoh, Sato, Shimomura, Yamanaka: hep-ph/0512197

  12. Stau Lifetime in Gravitino Dark Matter Scenarios • Gravitational-strength decay interaction • Naturally long lifetime Hamaguchi, Nojiri, De Roeck: hep-ph/0612060

  13. Sample Supersymmetric Parameter Plane with different NLSP Options In gravitino dark matter scenario Lighter stau Lighter selectron Tau sneutrino Electron sneutrino Ellis, Olive, Santoso: arXiv:0807.3736

  14. More Planes with different NLSPs In gravitino dark matter scenario Lighter stau Lighter selectron Tau sneutrino Electron sneutrino Ellis, Olive, Santoso: arXiv:0807.3736

  15. Gravitino Dark Matter Benchmark Models with Stau NLSP Many τ’s in final states De Roeck, JE, Gianotti, Moortgat, Olive, Pape :hep-ph/0508198

  16. Example of Stop NLSP in Gravitino Dark Matter Scenario Requires ‘careful’ choice of parameters Diaz-Cruz, JE, Olive, Santoso: hep-ph/0701229

  17. More Examples of Gravitino Dark Matter Scenarios with Stop NLSP Requires ‘careful’ choice of parameters – but quite generic Diaz-Cruz, JE, Olive, Santoso: hep-ph/0701229

  18. Stop Lifetime in CMSSMwith Gravitino Dark Matter 2-body decays 3-body decays Diaz-Cruz, JE, Olive, Santoso: hep-ph/0701229

  19. Stop the Lithium Problem Notorious Lithium problem of Big-Bang Nucleosynthesis Could be solved by metastable stop decays Kohri, Santoso: arXiv:0811.1119

  20. Gluinos in Split Supersymmetry • Long-lived because squarks heavy • Possible gluino hadrons: Gluino-g, gluino-qqbar, gluino-qqq • Is there a metastable chargedgluino hadron? • Gluino hadrons may flip charge as they pass through matter • Gluino mesons may change into baryons: • e.g., gluino-uubar + uudgluino-uud + uubar Hewitt, Lillie, Masip, Rizzo: hep-ph/0408248

  21. GluinoProductionat the LHC Hewitt, Lillie, Masip, Rizzo: hep-ph/0408248 • Large cross section @ LHC • Significant fraction of charged particles emerge from the detector Farrar, Mackeprang, Milstead, Roberts: arXiv:1011.2964

  22. Production at the LHC

  23. Kinematical Distributions for Stops Velocity distribution Pseudo-rapidity distribution Johansen, Edsjo, Hellman, Milstead: arXiv:1003.4540

  24. Typical Velocities & Ranges Some fraction of slow-moving charged particles De Roeck, JE, Gianotti, Moortgat, Olive, Pape: hep-ph/0508198 Hamaguchi, Nojiri, De Roeck: hep-ph/0612060

  25. Searches at the LHC

  26. CMS Search for Metastable Particles using Tracker only

  27. CMS Search for Metastable Particles using Tracker and TOF

  28. Water Trap Concept for Stopping Metastable Charged Particles Energy distribution Hope it does not leak! Feng & Smith: hep-ph/0409278

  29. Water Trap Concept for Stopping Metastable Charged Particles Number of trapped particles Angular distribution Feng & Smith: hep-ph/0409278

  30. Possible (Meta)stable Particle Stoppers Hamaguchi, Nojiri, De Roeck: hep-ph/0612060

  31. Extract Cores from Surrounding Rock? • Use muon system to locate impact point on cavern wall with uncertainty < 1cm • Fix impact angle with accuracy 10-3 • Bore into cavern wall and remove core of size ~ 1cm × 1cm × 10m = 10-3m3 • Can this be done before staus decay? • Caveat radioactivity induced by collisions • Several technical stops each year • Not possible if lifetime ~104s, possible if ~106s? De Roeck, JE, Gianotti, Moortgat, Olive, Pape :hep-ph/0508198

  32. Summary • Few prospects for multiply-charged sparticles • Many prospects for long-lived singly-charged sparticles • Staus, stops, selectrons, … • Some would be produced with low velocities, hence highly-ionizing • Production rates within MoEDAL reach

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