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
Highly-Ionizing Particles in Supersymmetric Models
John Ellis
King’s College London & CERN
• 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)
Mass Reach as Function of Energy & Luminosity
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
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)
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
Energy Loss and RangeSingly-charged particles are
highly-ionizing if moving slowlySmall range in typical
Detector materials
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
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
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
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
Stau Lifetime in Gravitino Dark Matter Scenarios
• Gravitational-strength decay interaction
• Naturally
long
lifetime
Hamaguchi, Nojiri, De Roeck: hep-ph/0612060
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
More Planes with different NLSPs
Lighter stau
Lighter selectron
Tau sneutrino
Electron sneutrino
In gravitino dark matter scenario
Ellis, Olive, Santoso: arXiv:0807.3736
Gravitino Dark Matter Benchmark Models with Stau NLSP
De Roeck, JE, Gianotti, Moortgat, Olive, Pape :hep-ph/0508198
Many τ’s in final states
Example of Stop NLSP in Gravitino Dark Matter Scenario
Requires ‘careful’ choice of parameters
Diaz-Cruz, JE, Olive, Santoso: hep-ph/0701229
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
Stop Lifetime in CMSSMwith Gravitino Dark Matter
2-bodydecays
3-bodydecays
Diaz-Cruz, JE, Olive, Santoso: hep-ph/0701229
Stop the Lithium Problem
Notorious Lithium problem of Big-Bang NucleosynthesisCould be solved by metastable stop decays
Kohri, Santoso: arXiv:0811.1119
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
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
Production at the LHC
Kinematical Distributions for Stops
Pseudo-rapidity distribution Velocity distribution
Johansen, Edsjo, Hellman, Milstead: arXiv:1003.4540
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
Searches at the LHC
CMS Search for Metastable Particles using Tracker only
CMS Search for Metastable Particles using Tracker and TOF
Water Trap Concept for Stopping Metastable Charged Particles
Feng & Smith: hep-ph/0409278
Hope it does not leak! Energy distribution
Water Trap Concept for Stopping Metastable Charged Particles
Feng & Smith: hep-ph/0409278
Angular distribution Number of trapped particles
Possible (Meta)stable Particle Stoppers
Hamaguchi, Nojiri, De Roeck: hep-ph/0612060
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
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