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