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Home , Neutralino

Search for dark

WIMPs - candidates WIMPs - expected fluxes WIMP detection

Non baryonic -1 • Most of dark matter is cold – if not: problem with development of large scale structures • – can contribute to (CDM)

– To reach density of order ρc mass required to be 263−− mca ≈−10 10 eV

– No experimental evidence yet • Most popular candidate for CDM :WIMPs – Weakly Interacting Massive – Non-relativistic velocity at time of freeze-out – Weakly interacting : conventional weak couplings

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1 Non - 2

• Density of CDM as function of WIMP mass • Assume conventional weak couplings • Shaded area: Observations 0.1<Ω < 1 • Allowed masses:

MeVwimp < 47

few GeV<< Mwimp few TeV

• No signal at LEP:

Mwimp > MZ/2 = 45GeV

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Cold dark matter • Massive : – SM neutrinos have low masses – contribute to HDM – Additional convential excluded by LEP: only 3 neutrino families • Neutralino χ = Lightest SuperSymmetric Particle (LSP) in R-parity conserving SUSY theory – Lower limit from accelerators ¡ 40 GeV/c2 – Stable particle – survived from primordial era of universe • Other SUSY particles: sneutrinos, , axinos • Superheavy dark matter: Wimpzillas • Kaluza-Klein states from models with universal extra dimensions • …….

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2 -1 • Gives a unified picture of matter ( and ) and interactions (gauge and Higgs ) • Introduce symmetry between and bosons • Solves the hierarchy problem: 24− MWe10 GeV−17 M 10 GeV − 6 ≈=1910 ≈= 2 10 MPL10 GeV M t 10 GeV • Associate to all SM particles a with same mass and opposite type (-) • minimal SUSY: minimal SUSY extension to the SM – lowest nb of parameters • SUSY breaking at EW scale: 2 Higgs doublets

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SuperSymmetry - 2 • Particle table (arXiv:hep-ph/0404175v2)

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3 SuperSymmetry - 3 • Unification of gauge couplings at Planck scale 16 •MU ¡ 10 GeV

α1 = αem α2 = αweak α3 = αstrong

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neutralinos - 1 • Supersymmetric partners of gauge bosons (bino, wino, ) mix to neutralino mass eigenstates • Lightest neutralino: mixing of 4 fields

100 χχ011123131142==NB%% + NW + NH % + NH %

• Conservation of R-parity = f( number B, nb L, spin s) R ≡−()1 32B+Ls+ • SM particles: R = 1 and sparticles: R = -1 • Decay of sparticles needs min 1 SUSY particle • → LSP = lightest neutralino is stable

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4 Neutralinos - 2 • Χ0: No color, no – else condensed with baryonic matter and production of heavy isotopes

M 0 ≥ 50 GeV • Collider limits χ1

•Different measurements at LEP, and other experiments

•M0 = universal scalar mass ( + Higgs) •m/2 = universal mass (bino,wino) WMAP •WMAP: 2 regions of allowed masses Yield 0.2 < Ωχ < 0.6 Stau LSP → Mχ = O(100 GeV)

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Neutralino detection

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5 Cross sections, abundances and fluxes 1

• Neutralinos as CDM: non-relativistic at freeze-out 2 Mc kT→→ M T Boltzman gas 3 ⎛⎞−M 2 ⎜⎟ ⎛⎞MT T NT()= ⎜⎟ e⎝⎠ number density ⎝⎠2π • Freeze-out when annihilation rate < expansion rate

WNv=≤σ Ht( freeze− out ) χχ+→+ffWW,+− + , νν + , ee +− + ,...

• Cross section depends on SUSY parameters – unknown – O(weak interactions) by construction

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Cross sections, abundances and fluxes 2

2 • Weak interactions σvGM F 1 • Rewrite expansion rate *22 1.66 ()gT H = M PL

⎛⎞−M 2 • → Freeze-out condition 3 ⎜⎟ fT ()MT 2 eM⎝⎠T G22≤ ( f = csts) F M PL

• Assume constant P = Mc2/kT ¡ 25 between freeze- out and today 3 2 ()TT0 × ( T MPL ) N ()0 • Neutralino number density today σv

T0 = 2.73K

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6 Cross sections, abundances and fluxes 3

331− • Energy density PT0 610× −1 ρχ = MN ()0 GeV s MvPL σσ v −25 ρχ 10 31− Ω=χ cm s ρσc v • Velocity of relic neutralinos at freeze-out from kinetic energy 1 13kT v 2 Mvvc2 =→3 0.3 →≈ 0.3 22c ( P) • For Ω=1 → σχ( +→ χ X ) ≈10−35cm 2 ≈ O( pb) • O(weak interactions)

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neutralino density vs mass

• Allowed variation of neutralino density as function of mass

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7 Direct detection 1 • WIMP velocity today O(galactic objects) −31− vckmswimp 10= 270 • Energy density in galactic halo much larger than on average in universe (gravitational effects in galaxy)

• density: 3 ρwimp 0.3GeV cm • Measure recoil spectrum (N’ or X) in detector • E(N’ or X) = O(keV) χ +→+NNχ ′ elastic scattering χχ+→+NXinelastic scattering

• Spin-dependent and spin-independent couplings

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Direct detection 2 • Annual modulations due to movement of solar system in galactic WIMP halo, WIMP wind • Observed by DAMA – not confirmed by other experiments

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8 results: spin independent couplings • experimental upper limits (lines) on neutralino- spin-independent cross section as function of neutralino mass • Sensitivity O(10-10pb) • Theory (areas) predictions: constrained MSSM – projection from multi- parameter space

σ (weak) ≈=10−36 cm 2 pb

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Results: spin dependent couplings

• Processes do not add up coherently • No cancellations • Larger cross sections • Cross section O(10-3pb)

Allowed region

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9 Direct detection techniques

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Indirect detection 1

ρχ velocity χ distribution Earth Sun σ scatt νμ ν int.

*capture μ qq Detector

*annihilation χχν→→→ll L μ WZH±,, 18.03.09 Astro-particle physics 20

10 Indirect detection 2 • Detect annihilation products: neutrinos, gamma rays, , .. • WIMPs accumulate in heavy celestial bodies: Earth, Sun, Galactic Centre • flux from • neutralino annihilation in Sun

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Dark energy

Hubble plot at large redshifts Vacuum energy Cosmological constant

11 Hubble plot at large redshift • At given time in history vacuum energy must dominate 1 over matter and radiation ρ Tt42− r R 4 1 ρ Tt32− m R 3

ρ v cst • Universe accelerates (deceleration parameter q<0) when vacuum energy dominates: ρvrm>+ρρ2

• Evidence for present day acceleration from SNIa redshift measurements

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Supernovae Ia • Absence of hydrogen lines in spectrum • Light output from different SNIa differ by only 6% - can be used as ‘standard candles’ • Measure redshift and luminosity distance (or apparent magnitude) • Supernova Cosmology project: 414 SN data from 3 independent datasets • Some SN observed at high redshift, up to z=1.7 • Relation between luminosity distance and redshift depends on energy content of universe

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Hubble plot with high z SNIa

Empty universe: Vacuum dominated Ωm= Ωr=0 & flat Ωk=1 No acceleration, no deceleration

At high z (early universe)

DL increases faster than Matter dominated for empty universe: & flat accelerated expansion

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13 Hubble plot at high z

• best fit

• Empty universe

Difference between

measured DL and expected relation for empty universe

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SN cosmology project 2008

effective magnitude m vs z

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14 Constraints from all observations

• SN observations • CMB: WMAP mapping of cosmic microwave background • BAO: baryon acoustic oscillations – anisotropies in cluster surveys originating in early univserse

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Link with cosmological constant - 1 • Introduced by Einstein to obtain static universe • supposed to be related to Λ

Λ = 8πGρvac • But should also be related to natural scale of gravity:

Planck scale 1 5 2 219⎛⎞hc • Planck mass energy M PLcGeV==×⎜⎟1.2 10 ⎝⎠G

h • In cube of side = Planck length LPL = M PLc

4 Mc2 • → expected energy density !!! ( PL ) 123− 3 3 10 GeV m ()hc

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15 Link with cosmological constant - 2 • Large variation of vacuum to matter density with time

ρv 2 3 ρm ()1+ z • For z=1000 (matter-radiation decoupling) expect -9 ρv/ρm ¡ 10

• But today ratio ρv/ρm ¡ 2 and of order of critical density! • Change of ratio with time: 5th type of interaction, quintessence? • Antropic principle: life exists only when laws of physics allow it

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