Towards Direct Detection of WIMPs with the Cryogenic Dark Matter Search Enectali Figueroa-Feliciano Massachusetts Institute of Technology For the CDMS Collaboration
Towards Direct Detection of WIMPs with the Cryogenic Dark Matter Search Enectali Figueroa-Feliciano Massachusetts Institute of Technology For the CDMS Collaboration
The CDMS Collaboration • Caltech • Syracuse University • Case Western Reserve • UC Berkeley • FNAL • UC Santa Barbara • MIT • University of Colorado at Denver • NIST • University of Florida • Queen’s University • University of Minnesota • Santa Clara University • University of Texas A&M • Stanford University • University of Zurich Enectali Figueroa-Feliciano - SUSY09
The Concordance Model of Cosmology 0.03% All rocky planets and their inhabitants are found here Free H & He 3% Dark Matter 23% Dark Energy 73% Dark Energy Dark Matter Free H & He Stars and Gas Neutrinos Heavy Elements (Us) Enectali Figueroa-Feliciano - SUSY09
The Concordance Model of Cosmology 0.03% All rocky planets and their inhabitants are found here Free H & He 3% Dark Matter 23% Dark Energy 73% We don’t know what 96% of the Dark Energy Dark Matter Universe Free H & He Stars and Gas is made of!!! Neutrinos Heavy Elements (Us) Enectali Figueroa-Feliciano - SUSY09
The Concordance Model of Cosmology 0.03% All rocky planets and their inhabitants are found here Free H & He 3% Dark Matter 23% Dark Energy 73% We don’t know what 96% of the Dark Energy Dark Matter Universe Free H & He Stars and Gas is made of!!! Neutrinos Heavy Elements (Us) Enectali Figueroa-Feliciano - SUSY09
The Nature of Dark Matter • The Missing Mass Problem: • Dynamics of stars, galaxies, and clusters • Rotation curves, gas density, gravitational lensing • Large Scale Structure formation • Wealth of evidence for a particle solution • No good MOND, Bullet Cluster, • Microlensing (MACHOs) limit < 1 AU • Non-baryonic • Height of acoustic peaks in the CMB ( Ω b) • Power spectrum of density fluctuations ( Ω m) • Primordial Nucleosynthesis • And STILL HERE! • Stable, neutral, non-relativistic • Interacts via gravity and/or weak force Enectali Figueroa-Feliciano - SUSY09
Zeroing on WIMPs • We “know” that Dark Matter • Has mass • Is non-baryonic • Was non-relativistic early on in cosmological time • Has a certain annihilation cross section • One theoretical candidate for such a particle is called the Weakly Interacting Massive Particle: WIMP (Roszkowski 2004) • This talk will focus on one particular WIMP candidate, the lightest supersymmetric particle commonly referred to as the neutralino Enectali Figueroa-Feliciano - SUSY09
Zeroing on WIMPs • We “know” that Dark Matter • Has mass • Is non-baryonic • Was non-relativistic early on in cosmological time • Has a certain annihilation cross section (Roszkowski 2004) χ • One theoretical candidate for such a particle is called the Weakly Interacting Massive Particle: WIMP • This talk will focus on one particular WIMP candidate, the lightest supersymmetric particle commonly referred to as the neutralino Enectali Figueroa-Feliciano - SUSY09
Direct Detection Astrophysics of WIMPs moo • Energy spectrum & rate depend on WIMP distribution in Dark Matter Halo • “Spherical-cow” assumptions: isothermal and spherical, Maxwell-Boltzmann velocity distribution • v o = 220 km/s, <v> = 270 km/s, v esc = 650 km/s • ρ = 0.3 GeV / cm 3 • Assume mass = 60 GeV/c 2 • Density = 5000 part/m 3 10 WIMPs on average, inside a 2 liter bottle (if mass=60 x proton) Enectali Figueroa-Feliciano - SUSY09
The Dark Matter Wind apparently “blows” from Cygnus Our speed relative to the halo is ~220 km/s Enectali Figueroa-Feliciano - SUSY09
Flux • Density: 0.3 GeV/cm 3 • Mass: assume 60 GeV/c 2 • ~220 km/s • ~100,000 particles/cm 2 /sec • About 20 million/hand/sec Enectali Figueroa-Feliciano - SUSY09
Principles of Direct Detection Our choice of Target Nucleus Knowledge of Nuclear Structure � 2 � 3 j 1 ( qR 1 ) m χ m N m χ m p � − ( qs ) 2 � F 2 ( Q ) = m r = m r − p = exp qR 1 m χ + m N m χ + m p dR σ 0 ρ 0 F 2 ( Q ) T ( Q ) = √ πv 0 m χ m 2 dE R r Input from Particle Physics Input from Astrophysics � m r − v 2 min /v 2 � � T ( Q ) = exp � 2 0 A 2 σ χ − p σ 0 = � E R m N m r − p v 0 ≈ 220 km/s v min = 2 m 2 r Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate M χ = 100 GeV/c 2 Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 Xe Si 3 10 Ge 2 10 1 10 0 50 100 Recoil [keV] Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting • Elastic scattering of a WIMP from a WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate nucleus deposits a small, but detectable M χ = 100 GeV/c 2 amount of energy ~ few x 10 keV Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 Xe Si 3 10 Ge 2 10 1 10 0 50 100 Recoil [keV] Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting • Elastic scattering of a WIMP from a WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate nucleus deposits a small, but detectable M χ = 100 GeV/c 2 amount of energy ~ few x 10 keV Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 • Featureless exponential energy Xe spectrum with 〈 E 〉 ~ 50 keV Si 3 10 Ge 2 10 1 10 0 50 100 Recoil [keV] Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting • Elastic scattering of a WIMP from a WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate nucleus deposits a small, but detectable M χ = 100 GeV/c 2 amount of energy ~ few x 10 keV Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 • Featureless exponential energy Xe spectrum with 〈 E 〉 ~ 50 keV Si 3 10 • no obvious peak, knee, break, Ge ... that determines M χ or v 0 2 10 1 10 0 50 100 Recoil [keV] Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting • Elastic scattering of a WIMP from a WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate nucleus deposits a small, but detectable M χ = 100 GeV/c 2 amount of energy ~ few x 10 keV Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 • Featureless exponential energy Xe spectrum with 〈 E 〉 ~ 50 keV Si 3 10 • no obvious peak, knee, break, Ge ... that determines M χ or v 0 2 10 • Expected rate < 0.01/kg-day (based on σ n χ and ρ ) 1 10 0 50 100 Recoil [keV] Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting • Elastic scattering of a WIMP from a WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate nucleus deposits a small, but detectable M χ = 100 GeV/c 2 amount of energy ~ few x 10 keV Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 • Featureless exponential energy Xe spectrum with 〈 E 〉 ~ 50 keV Si 3 10 • no obvious peak, knee, break, Ge ... that determines M χ or v 0 2 10 • Expected rate < 0.01/kg-day (based on σ n χ and ρ ) 1 10 0 50 100 • Radioactive background million times Recoil [keV] higher Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting • Elastic scattering of a WIMP from a WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate nucleus deposits a small, but detectable M χ = 100 GeV/c 2 amount of energy ~ few x 10 keV Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 • Featureless exponential energy Xe spectrum with 〈 E 〉 ~ 50 keV Si 3 10 • no obvious peak, knee, break, Ge ... that determines M χ or v 0 2 10 • Expected rate < 0.01/kg-day (based on σ n χ and ρ ) 1 10 0 50 100 • Radioactive background million times Recoil [keV] higher • Background Reduction/Rejection is key Enectali Figueroa-Feliciano - SUSY09
WIMP Hunting • Elastic scattering of a WIMP from a WIMP Differential Event Rate WIMP Elastic Scattering Differential Rate nucleus deposits a small, but detectable M χ = 100 GeV/c 2 amount of energy ~ few x 10 keV Counts [#10 − 6 /kg/keV/day] σ χ - N = 10 -45 cm 2 4 10 • Featureless exponential energy Xe spectrum with 〈 E 〉 ~ 50 keV Si 3 10 • no obvious peak, knee, break, Ge ... that determines M χ or v 0 2 10 • Expected rate < 0.01/kg-day (based on σ n χ and ρ ) 1 10 0 50 100 • Radioactive background million times Recoil [keV] higher • Background Reduction/Rejection is key Low Background (< 1) Almost a Prerequisite for Discovery Enectali Figueroa-Feliciano - SUSY09
The Signal and Backgrounds Background (gammas) Signal (WIMPs) E r Nucleus Electron Recoils Recoils E r v/c ≈ 7 × 10 -4 = 210 km/s v/c ≈ 0.3 E r ≈ 10’s KeV ionization phonons γ χ 0 Enectali Figueroa-Feliciano - SUSY09
The Signal and Backgrounds Background (gammas) Signal (WIMPs) E r Nucleus Electron Recoils Recoils E r v/c ≈ 7 × 10 -4 = 210 km/s v/c ≈ 0.3 E r ≈ 10’s KeV ionization phonons Neutrons also interact with nuclei, but mean free path a few cm γ χ 0 Enectali Figueroa-Feliciano - SUSY09
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