highly-ionizing particles in supersymmetric models
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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Highly-Ionizing Particles in Supersymmetric Models
John Ellis
King’s College London & CERN
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• 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 masses m0, gaugino masses m1/2, trilinear soft couplings Aλ, bilinear soft coupling Bμ
• Often assume universality:Single m0, single m1/2, single Aλ, Bμ: not string?
• Called constrained MSSM = CMSSM
Minimal Supersymmetric Extension of Standard Model (MSSM)
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Mass Reach as Function of Energy & Luminosity
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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 pairsHeavier sparticles lighter sparticles
• Lightest supersymmetric particle (LSP) stable
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Possible Nature of LSP
• No strong or electromagnetic interactionsOtherwise would bind to matterDetectable as anomalous heavy nucleus
• Possible weakly-interacting scandidatesSneutrino
(Excluded by LEP, direct searches)Lightest neutralino χ (partner of Z, H, γ)Gravitino
(nightmare for astrophysical detection)
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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
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Energy Loss and RangeSingly-charged particles are
highly-ionizing if moving slowlySmall range in typical
Detector materials
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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
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Parameter Plane in the CMSSM
Excluded because stau LSP
Excluded by b s gamma
Preferred (?) by latest g - 2
Assuming the lightest sparticleis a neutralino
WMAP constraint on CDM density
LHC
JE, Olive & Spanos
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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 LHCJE, Olive
LHC
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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
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Stau Lifetime in Gravitino Dark Matter Scenarios
• Gravitational-strength decay interaction
• Naturally
long
lifetime
Hamaguchi, Nojiri, De Roeck: hep-ph/0612060
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Sample Supersymmetric Parameter Plane with different NLSP Options
Lighter stau
Lighter selectron
Tau sneutrino
Electron sneutrino
In gravitino dark matter scenario
Ellis, Olive, Santoso: arXiv:0807.3736
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More Planes with different NLSPs
Lighter stau
Lighter selectron
Tau sneutrino
Electron sneutrino
In gravitino dark matter scenario
Ellis, Olive, Santoso: arXiv:0807.3736
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Gravitino Dark Matter Benchmark Models with Stau NLSP
De Roeck, JE, Gianotti, Moortgat, Olive, Pape :hep-ph/0508198
Many τ’s in final states
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Example of Stop NLSP in Gravitino Dark Matter Scenario
Requires ‘careful’ choice of parameters
Diaz-Cruz, JE, Olive, Santoso: hep-ph/0701229
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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
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Stop Lifetime in CMSSMwith Gravitino Dark Matter
2-bodydecays
3-bodydecays
Diaz-Cruz, JE, Olive, Santoso: hep-ph/0701229
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Stop the Lithium Problem
Notorious Lithium problem of Big-Bang NucleosynthesisCould be solved by metastable stop decays
Kohri, Santoso: arXiv:0811.1119
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Gluinos in Split Supersymmetry
• Long-lived because squarks heavy
• Possible gluino hadrons:Gluino-g, gluino-qqbar, gluino-qqq
• Is there a metastable charged gluino 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
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GluinoProductionat the LHC
• Large cross section @ LHC
• Significant fraction of charged particles emerge from the detector
Hewitt, Lillie, Masip, Rizzo: hep-ph/0408248
Farrar, Mackeprang, Milstead, Roberts: arXiv:1011.2964
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Production at the LHC
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Kinematical Distributions for Stops
Pseudo-rapidity distribution Velocity distribution
Johansen, Edsjo, Hellman, Milstead: arXiv:1003.4540
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Typical Velocities & Ranges
De Roeck, JE, Gianotti, Moortgat, Olive, Pape: hep-ph/0508198
Hamaguchi, Nojiri, De Roeck: hep-ph/0612060
Some fraction of slow-moving charged particles
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Searches at the LHC
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CMS Search for Metastable Particles using Tracker only
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CMS Search for Metastable Particles using Tracker and TOF
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Water Trap Concept for Stopping Metastable Charged Particles
Feng & Smith: hep-ph/0409278
Hope it does not leak! Energy distribution
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Water Trap Concept for Stopping Metastable Charged Particles
Feng & Smith: hep-ph/0409278
Angular distribution Number of trapped particles
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Possible (Meta)stable Particle Stoppers
Hamaguchi, Nojiri, De Roeck: hep-ph/0612060
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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
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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