intro to neutralino dark matter Pearl Sandick University of Minnesota

Why study Supersymmetry? MSSM Neutralino Dark Matter Constrained MSSM 5/17/20152Pearl Sandick

 Aesthetically “neat” extension  Stabilizes the Higgs vev (Hierarchy Problem)  Gauge coupling unification  Predicts a light Higgs boson 5/17/20153Pearl Sandick

 Aesthetically “neat” extension R. Haag, J. T. Lopuszanski and M. Sohnius Nucl. Phys. B 88 (1975) 257 Coleman-Mandula Theorem: “ impossibility of combining space-time and internal symmetries in any but a trivial way” Phys. Rev. 159: 1251–1256 By including both commuting and anticommuting generators, get consistent theory with interplay of Poincaré and internal symmetries, i.e. boson fermion. Supersymmetry is the only nontrivial extension of the Pioncaré algebra in a consistent 4-d QFT. 5/17/20154Pearl Sandick

 Aesthetically “neat” extension  Stabilizes the Higgs vev (Hierarchy Problem) Classical Higgs Potential: V = m H 2 |  | 2 + |  | 4 SM requires  0, so = (-m H 2 / 2 ) 1/2  174 GeV  -m H 2  (100 GeV) 2 But m H 2 gets quantum corrections from particles that interact with the Higgs field! 5/17/20155Pearl Sandick

 Aesthetically “neat” extension  Stabilizes the Higgs vev (Hierarchy Problem) SM: SUSY: SUSY maintains hierarchy of mass scales. 5/17/ Pearl Sandick

 Aesthetically “neat” extension  Stabilizes the Higgs vev (Hierarchy Problem)  Gauge coupling unification Near miss! Just right! 5/17/20157Pearl Sandick

 Aesthetically “neat” extension  Stabilizes the Higgs vev (Hierarchy Problem)  Gauge coupling unification  Predicts a light Higgs boson MSSM: 105 GeV < m h < 135 GeV LEP: GeV < m h < 182 GeV ~ ~ LEP Collaborations and Electroweak Working Group, arXiv: /17/20158Pearl Sandick

MSSM: Minimal Supersymmetric Standard Model Has the minimal particle content possible in a SUSY theory. 5/17/20159Pearl Sandick

quarks and squarks leptons and sleptons W boson and wino gluon and gluino B boson and bino Higgs bosons and higgsinos Fermions and sfermions gauge bosons and gauginos 5/17/201510Pearl Sandick

Neutralinos are an excellent dark matter candidate! The lightest one may be a stable WIMP with   h 2   DM h 2 Caveat: The lightest SUSY particle (LSP) is stable if R-parity is conserved. R = (-1) 3B+L+2S = +1 for SM particles -1 for sparticles Why conserve R-parity? Stability of proton Neutron-antineutron oscillations Neutrino mass Ad hoc? SO(10) GUTs B and L numbers become accidental symmetries of SUSY 5/17/201511Pearl Sandick

Neutralinos are an excellent dark matter candidate! The lightest one may be a stable WIMP with   h 2   DM h 2 Properties of neutralino LSP will depend on its composition. 5/17/201512Pearl Sandick

Explicitly add [soft] SUSY-breaking terms to the theory: Masses for all gauginos and scalars Couplings for scalar-scalar and scalar-scalar-scalar interactions CMSSM (similar to mSUGRA) Assume universality of soft SUSY-breaking parameters at M GUT Free Parameters: m 0, m 1/2, A 0, tan(  ), sign(  ) Don’t observe boson-fermion degeneracy, so SUSY must be broken (How?) Most general case (MSSM) has > 100 new parameters! OR make some assumptions about SUSY breaking at a high scale, and evolve mass parameters down to low scale for observables 5/17/201513Pearl Sandick

1. Assume neutralinos were once in thermal equilibrium 2. Solve the Boltzmann rate equation to find abundance now 5/17/201514Pearl Sandick

Situations when care must be taken to properly calculate (approximate) the relic density: 1. s - channel poles 2 m   m A 2. Coannihilations m   m other sparticle 3. Thresholds 2 m   final state mass Griest and Seckel (1991) 5/17/201515Pearl Sandick

m h > 114 GeV m  ± > 104 GeV BR(b  s  ) HFAG BR(B s   +  -- ) CDF (g  -- 2)/2 g-2 collab. LEP 0.09    h 2  0.12 Apply constraints from colliders and cosmology: 5/17/201516Pearl Sandick

 2 < 0 (no EWSB) stau LSP LEP Higgs mass Relaxed LEP Higgs LEP chargino mass g  --2 suggested region Focus Point Coannihilation Strip 5/17/201517Pearl Sandick

bsbs B  +  -- Rapid annihilation funnel 2m   m A 5/17/201518Pearl Sandick

1.Direct detection Solid state: CDMS, SuperCDMS, EDELWEISS… Liquid nobles: XENON10, XENON100/LUX, ArDM, DEEP, CLEAN, WARP, ZEPLIN… 2.Indirect detection Detect neutralino annihilation/decay products terrestrially (ICEcube, ANITA) or in space (PAMELA, GLAST) 3.Colliders 5/17/201519Pearl Sandick

Effective 4-fermion lagrangian for neutralino-nucleon scattering (velocity-independent pieces): If neutralinos are DM, they are present locally, so will occasionally bump into a nucleus. spin dependent spin independent (scalar) Fraction of nucleus participates Important for capture & annihilation rates in the sun Whole nucleus participates Best prospects for direct detection 5/17/201520Pearl Sandick

tan  = 10, M in = M GUT CDMS II (2006) XENON 10 XENON 100 SuperCDMS Pass all constraints (blue) Only fail relaxed Higgs mass constraint (green) 5/17/201521Pearl Sandick

tan  = 10, M in = M GUT CDMS II (2006) XENON 10 XENON 100 SuperCDMS 5/17/201522Pearl Sandick

tan  = 50, M in = M GUT 5/17/201523Pearl Sandick

Even if the universe is supersymmetric, many questions remain: Is R-parity conserved? Is the LSP the lightest neutralino? Is SUSY minimal (MSSM)? Is SUSY breaking universal? Ect. 5/17/201524Pearl Sandick