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Stefano Scopel

Supersymmetric Dark Matter. Stefano Scopel. PPC2010, Torino, 12 July 2010. Outline. Dark Matter & susy in a nutshell examples of susy scenarios The low mass WIMP conspiracy: DAMA, CDMS2 and CoGeNT the XENON100 exclusion plot light neutralinos in the MSSM. Ω dark matter ~ 0.22.

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Stefano Scopel

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  1. Supersymmetric Dark Matter Stefano Scopel PPC2010, Torino, 12 July 2010

  2. Outline • Dark Matter & susy in a nutshell • examples of susy scenarios • The low mass WIMP conspiracy: DAMA, CDMS2 and CoGeNT • the XENON100 exclusion plot • light neutralinos in the MSSM

  3. Ωdark matter~ 0.22 Evidence for Dark Matter • Spiral galaxies • rotation curves • Clusters & Superclusters • Weak gravitational lensing • Strong gravitational lensing • Galaxy velocities • X rays • Large scale structure • Structure formation • CMB anisotropy: WMAP • Ωtot=1 • Ωdark energy~0.7 • Ωmatter~ 0.27 • Ωbaryons~0.05 • Ωvisible~0.005

  4. (Incomplete) List of DM candidates • Neutrinos • Axions • Lightest Supersymmetric particle (LSP) – neutralino, sneutrino, axino • Lighest Kaluza-Klein Particle (LKP) • Heavy photon in Little Higgs Models • Solitons (Q-balls, B-balls) • Black Hole remnants • Hidden-sector tecnipions • BEC/scalar field • … BEC/scalar field

  5. Over-constrained scenario: the concordance model

  6. x0 <σannv>int=∫<σannv>dx xf thermal cosmological density of a WIMP X ΩXh2 ~ 1/<σannv>int x0=M/T0 T0=present (CMB) temperature xf=M/Tf Tf=freeze-out temperature Xf>>1, X non relativistic at decoupling, low temp expansion for <σannv>: <σannv>~a+b/x if σann is given by weak-type interactions → ΩX~0.1-1 …+ cohannihilations with other particle(s) close in mass + resonant annihilations

  7. today’s entropy critical density freeze-out temperature # of degrees of freedom m = WIMP mass Y0 : from Boltzmann equation

  8. N.B. Very different scales conjure up to lead to the weak scale! CMB temp. Hubble par. Planck scale the WIMP “miracle”

  9. Hierarchy problem of the Standar Model: Higgs mass expected to be below a few TeV (on general grounds, perturbativity of the theory) radiative corrections to the Higgs boson: δmH2~λ2, where λ is the scale beyond which the low-energy theory no longer applies (λ=cut-off of the SM) a huge cancellation needed unless λ~TeV itself

  10. The bottom line • new physics at the electro-weak scale is cool because it kills two birds with one stone: • solves the hierarchy problem • explains the Dark Matter

  11. most popular thermal WIMP candidates from particle physics (solve hierarchy problem: MW/MPl~ 10-16) DM candidate conserved symmetry * • susy R-parity χ (neutralino) • extra dimensions K-parity B(1)(KK photon) • little Higgs T-parity BH (heavy photon) all thermal candidates, massive, with weak-type interactions (WIMPs) the most popular

  12. Why susy is so appealing: • suggested by string theory • renormalizable • solves the hierarchy problem (why mW<<mplanck) • compatible to GUT unification of gauge couplings • provides a DM candidate (if R-parity is introduced to prevent nucleon decay so that the LSP is stable)

  13. GUT unification of gauge couplings

  14. dangerous, don’t want it! WIMP signal at accelerators: missing energy+new particles produced in pairs

  15. the sneutrino [Arina, Fornengo, JHEP0711(2007)029

  16. the sneutrino allowed due to rescaling [Arina, Fornengo, JHEP0711(2007)029

  17. mixing with a right-handed component makes thing easier 2 [Arina, Fornengo, JHEP0711(2007)029

  18. mixing with a right-handed component makes thing easier relic abundance direct detection • low see-saw scale M=1 TeV needed • inelastic scattering in direct detection! Z [Arina, Fornengo, JHEP0711(2007)029

  19. The neutralino ~ ~ ~ ~ • The neutralino is defined as the lowest-mass linear superposition of bino B, wino W(3)and the two higgsino states H10, H20 : 4 3 • neutral, colourless, only weak-type interactions • stable if R-parity is conserved, thermal relic • non relativistic at decoupling  Cold Dark Matter (required by CMB data + structure formation models) • relic density can be compatible with cosmologicalobservations:0.095 ≤Ωχh2 ≤ 0.131 IDEAL CANDIDATE FOR COLD DARK MATTER

  20. stau coannihilation Higgs funnel focus point [Feng, Machev, Moroi, Wilczek] SUGRA (a.k.a. CMSSM) [Ellis, Olive, Santoso, Spanos, 1001.3651] • only few regions cosmologically allowed • variants (e.g. non-universality of soft masses at the GUT scale or lower unification scale) that increase Higgsino content of the neutralino→ lower relic abundance and higher signals neutralino density tends to be too large is the WIMP “miracle” failing?

  21. Many contributions to neutralino annihilation…

  22. …but two main classes: • fermion diagrams: mf/MWhelicity suppression due to Majorana nature of neutralino • Gauge boson diagrams: suppressed if neutralino~Bino (this is usually the case when Radiative ElectroWeak Symmetry Breaking is implemented, |μ|>>M1,M2)

  23. the WIMP paradigm is fine but the devil is in the details!

  24. The Next-to-Minimal MSSM (NMSSM) 2 Higgs (CP-even, CP-odd) MSSM+ 1 neutralino dof solves the μproblem, i.e. why μ~MEW superpotential: Higgs soft terms in the NMSSM: NMSSM particle content: The lightest neutralino: CP-even Higgs:

  25. Relic density and direct detection rate in NMSSM [Cerdeño, Hugonie, López-Fogliani, Muñoz, Teixeira] relic abundance direct detection Landau pole W χ,H lighter χ singlino H1 Z H2/2 tachyons unphysical minima M1=160 GeV, M2=320, Aλ=400 GeV, Ak=-200 GeV, μ=130 GeV, tan β=5 (sizeable direct detection) • very light neutral Higgs (mainly singlet) • light scalars imply more decay channels and resonant decays • neutralino relatively light (< decay thresholds) and mostly singlino • high direct detection cross sections (even better for lower M1)

  26. Effective MSSM: effective model at the EW scale with a few MSSM parameters which set the most relevant scales SUGRAR=0.5 • M1 U(1)gaugino soft breaking term • M2 SU(2) gaugino soft breaking term • μHiggs mixing mass parameter • tan βratio of two Higgs v.e.v.’s • mA mass of CP odd neutral Higgs boson (the extended Higgs sector of MSSM includes also the neutral scalars h, H, and the charged scalars H±) • mqsoft mass common to all squarks • mlsoft mass common to all sleptons • A common dimensionless trilinear parameter for the third family (Ab = At ≡ Amq; Aτ≡ Aml) • R ≡M1/M2 ~ ~ ~ ~ ~ ~ ~

  27. Cosmological lower bound on mχ A. Bottino, F. Donato, N. Fornengo, S. Scopel, Phys. Rev. D 68, 043506 (2003) scatter plot: full calculation upper bound on ΩCDMh2 curve: analytical approximation for minimal ΩCDMh2

  28. Color code: ● Ωχh2 < 0.095 Ωχh2 > 0.095 Neutralino – nucleon cross section The elastic cross section is bounded from below:  “funnel” at low mass A. Bottino, N. Fornengo, S. Scopel ; Phys.Rev.D67:063519,2003 ; A. Bottino, F. Donato, N. Fornengo, S. Scopel, PRD69:037302,2004

  29. The field of Dark Matter searches has been quite active recently… • CDMS2 (December 2009) • DAMA/Libra (February 2010) • CoGeNT (February 2010) • XENON100 ( May 2010)

  30. The DAMA/Libra annual modulation result • two further annual cycles collected, the first with the same setup of previous data, the second after detector upgrade in 2008 • corresponds to a further exposure of 0.34 ton year • combining DAMA/NaI and DAMA/Libra a total of 13 annual cycles collected (7 DAMA/NaI+6 DAMA/Libra) corresponding to 1.17 ton year • 8.9 σC.L. effect Bernabei at al., arXiv:1002.1028

  31. 6 years of DAMA/Libra (0.87 ton year) Bernabei at al., arXiv:1002.1028

  32. DAMA WIMP interpretation and other direct searches small viable window with MWIMP≲ 10 From Savage et al., arXiv:0901.2713

  33. The CDMS2 result 14 Ge detectors (out of a total of 30 detectors, 19 Ge and 11 Si) After the timing cut (to remove “surface events”) Efficiency of the cut~25% close to threshold Resulting exposure~194.1 kg-day When signal region is unblinded2 events survived Z. Ahmed at al., arXiv:0912.3592

  34. Background estimation due to surface “leakage” : • before unblinding: 0.6±0.1 (stat.) • after unblinding: 0.8±0.1 (stat.) ±0.2 (stat.) ~23% probability that the 2 events are just background Final comment from J. Cooly’s talk @ SLAC, 17 December 2009: Z. Ahmed at al., arXiv:0912.3592

  35. The 2 CDMS events and light relic neutralinos effMSSM including uncertainty on hadronic matrix elements DAMA no channeling DAMA channeling Scatter plot: reference value for hadronic matrix elements 90% C.L. interval for 2 observed events: 0.53→5.3 x 0.098<Ωχh2<0.122 •Ωχh2<0.098 Bottino, Donato, Fornengo, Scopel, PRD81 107302(2010), arXiv:0912.4025

  36. The 2 CDMS events and light relic neutralinos effMSSM including uncertainty on hadronic matrix elements DAMA no channeling DAMA channeling Scatter plot: reference value for hadronic matrix elements 95% C.L. interval using spectral info (maximum likelihood method, no background) x 0.098<Ωχh2<0.122 •Ωχh2<0.098 Bottino, Donato, Fornengo, Scopel, PRD81 107302(2010), arXiv:0912.4025

  37. The 2 CDMS events and light relic neutralinos effMSSM including uncertainty on hadronic matrix elements DAMA no channeling DAMA channeling Scatter plot: reference value for hadronic matrix elements 85% C.L. interval using spectral info (maximum likelihood method, background included) x 0.098<Ωχh2<0.122 •Ωχh2<0.098 Bottino, Donato, Fornengo, Scopel, PRD81 107302(2010), arXiv:0912.4025

  38. The CoGeNT experiment Germanium ionization detector with new geometry (P-type point contact, PPC) standard coaxial geometry P-type Point Contact (PPC) Reduction of electronic noise Surface event rejection using rise-time cuts → very low threshold<400 eV

  39. The new CoGeNT result (C.E. Aalseth et al., 1002.4703) fit of the observed count rate using 28 bins and 3 components: • L/K shell electron-capture peaks from 71Ge (1 parameter) • Exponentially decaying background (2 parameters, amplitude and exponent) • Free constant background (1 parameter) • DM component (2 parameters) • For 7 GeV < mWIMP<11 GeV the chi square probability drops < 10% if the DM component is zero • → need additional exponential, WIMP signal indication?

  40. The new CoGeNT result (C.E. Aalseth et al., 1002.4703)

  41. The XENON10 limit • nowadays widely considered the most competitive Dark Matter Search experiment • dual-phase Xenon allows to measure ionization and scintillation at the same time Anticorrelation between the prompt scintillation in the liquid and the proportional scintillation in the gas (the latter produced by the charges produced in ionization and taken out by electric field). The sum of ionization and scintillation is proportional to the total deposited energy

  42. Discrimination between background (β and γ) and recoils+neutrons ←for a gamma source S2/S1 is larger ←for a neutron source S2/S1 is smaller J. Angle et al., Phys. Rev. Lett. 100 (2008) 021303, arXiv: 0706.0039.

  43. MAY 2010: the first XENON100 result (1005.0380): N.B.: the XENON100 limit is slightly less constraining than the XENON10 one

  44. A small threshold is crucial to be sensitive to WIMP induced nuclear recoils

  45. Two major limitations: The response in the detector is not homogeneous (ionization strongly depends on the position due to different reflection at the liquid-gas surface, impurities, charge recombination, local electric field). However position information is available event by event (89 photomultipliers + vertical drift timing info), so the response can be mapped using internal neutron-activated 131Xe (emitting 164 keV gammas) and 129Xe (emitting 236 keV gammas) This map, along with a Monte Carlo, is used to renormalize the events. However no direct map is available at energies below 164 keV. What happens @ 4 keV? Aprile et al., arXiv:1001.2834

  46. Energy calibration only available at 122 keV and 662 kev (the characteristic X-ray peak @ 30 keV from 57Co is barely visible at the edge of the sensitive volume) The energy scale at lower energy is extrapolated from 122 kev to 4 kev assuming a linear response. However between 122 keV and 662 keV the response is already non linear (the light yield is 2.2 p.e./kev @662 keV and 3.1 p.e./keV @122 keV).

  47. Comparison with other experiments CDMS and Edelweiss calibration: Neutrons from 252Cf source activate 71Ge that decays to 71Ga (T1/2~16 days) producing a peak at 10.4 keV Additional calibration points: 133Ba (γ lines at 303, 356 and 384 keV) DAMA calibration: the 3.2 keV peak from 40K provides the lowest-energy calibration point

  48. Am241 calibration in KIMS Am calibration -> ~5 p.e /keV 13.9keV Np L X-ray 17.8keV Np L X-ray 20.8keV Np L X-ray 26.35keV gamma Cs, I X –ray escape 59.54 gamma Relative intensity..... E(keV) S. C. Kim’s talk, KIMS Coll. , Yongpyong, February 2010

  49. People in XENON are aware of the problem and plan to use a lower calibration point from E. Aprile’s talk, SJTU workshop, june 2009 In short: for the time being, the 4 keV threshold and the linear response of XENON10(0) rely on an extrapolation at the energies where the WIMP signal is expected

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