intro to intro to neutralino dark matterneutralino dark matter

Pearl SandickUniversity of Minnesota

• Why study Supersymmetry?

• MSSM Neutralino Dark Matter

• Constrained MSSM

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Aesthetically “neat” extension Stabilizes the Higgs vev (Hierarchy

Problem) Gauge coupling unification

Predicts a light Higgs boson

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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.

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Aesthetically “neat” extension Stabilizes the Higgs vev (Hierarchy

Problem)

Classical Higgs Potential: V = mH2 ||2 + ||4

SM requires <> 0, so

<> = (-mH2 / 2 )1/2 174 GeV

-mH2 (100 GeV)2

But mH2 gets quantum corrections from particles that interact with the Higgs

field!

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Aesthetically “neat” extension Stabilizes the Higgs vev (Hierarchy

Problem)

...8

22

2

2 UV

f

Hm

SM:

22 )log( HUVH mm SUSY:

SUSY maintains hierarchy of mass scales.

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Aesthetically “neat” extension Stabilizes the Higgs vev (Hierarchy

Problem) Gauge coupling unificationNear miss! Just right!

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Aesthetically “neat” extension Stabilizes the Higgs vev (Hierarchy

Problem) Gauge coupling unification

Predicts a light Higgs boson

MSSM: 105 GeV < mh < 135 GeV

LEP: 114.4 GeV < mh < 182 GeV~ ~

LEP Collaborations and Electroweak Working Group, arXiv:0712.0929

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MSSM:

Minimal Supersymmetric Standard Model

Has the minimal particle content possiblein a SUSY theory.

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quarks and squarks

leptons and sleptons

W boson and winogluon and gluino

B boson and bino

Higgs bosons and higgsinos

Fermions and

sfermions

gauge bosonsand gauginos

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• Neutralinos are an excellent dark matter candidate!

• The lightest one may be a stable WIMP with h2 DMh2

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

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• Neutralinos are an excellent dark matter candidate!

• The lightest one may be a stable WIMP with h2 DMh2

Properties of neutralino LSP will depend on its composition.

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Explicitly add [soft] SUSY-breaking terms to the theory:Masses for all gauginos and scalarsCouplings for scalar-scalar and scalar-scalar-scalar interactions

CMSSM (similar to mSUGRA)Assume universality of soft SUSY-breaking parameters at MGUT

Free Parameters: m0, m1/2, A0, 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

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1. Assume neutralinos were once in thermal equilibrium

2. Solve the Boltzmann rate equation to find abundance now

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Situations when care must be taken to properly calculate (approximate) the relic density:

1. s - channel poles• 2 m mA

2. Coannihilations• m mother sparticle

3. Thresholds• 2 m final state mass

Griest and Seckel (1991)

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mh > 114 GeVm± > 104 GeVBR(b s ) HFAGBR(Bs +--) CDF(g -- 2)/2 g-2 collab.

LEP

0.09 h2 0.12

Apply constraints from colliders and cosmology:

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2 < 0(no EWSB)

stau LSP

LEP Higgs mass

Relaxed LEP HiggsLEP chargino mass

g--2 suggested region

FocusPoint

Coannihilation Strip

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bs

B+--

Rapid annihilation funnel 2m mA

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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

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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 dependentspin independent

(scalar)• Fraction of nucleus participates

• Important for capture & annihilation rates in the sun

• Whole nucleus participates• Best prospects for direct detection

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tan = 10, Min = MGUT

CDMS II (2006)

XENON 10

XENON 100SuperCDMS

•Pass all constraints (blue)

•Only fail relaxed Higgs mass constraint (green)

WMAPDM

WMAPDM

0

then If

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tan = 10, Min = MGUT

CDMS II (2006)

XENON 10

XENON 100SuperCDMS

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tan = 50, Min = MGUT

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