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Dark Matter Overview

Dark Matter Overview. Harry Nelson UCSB INPAC Oct. 4, 2003. Outline. Axions Massive Particles Direct Detection Weakly Interacting No Strongly Interacting (interesting opportunities) See talks of Dave Cline (ZEPLIN), Patrizia Meunier (CDMS-II). Usual Simplifications of Dark Matter.

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Dark Matter Overview

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  1. Dark Matter Overview Harry Nelson UCSB INPAC Oct. 4, 2003

  2. Outline • Axions • Massive Particles • Direct Detection • Weakly Interacting • No Strongly Interacting (interesting opportunities) • See talks of Dave Cline (ZEPLIN), Patrizia Meunier (CDMS-II) INPAC

  3. Usual Simplifications of Dark Matter • Local energy density, speed of DM • Consists of one elementary particle (!) 0? (200-2000) (170-270) … from galactic astrophysics  , e,m,t ,e- , p , n - 7 in our few percent of Univ. 2 are composite… n ?? The DM particle that provides the clearest signal in a search might not be the most abundant – a strong argument for an eclectic mix of search techniques. INPAC

  4. Advice of Dennis the Menace INPAC

  5. vDM=0 (sun plowing through at v0  220 km/s) • DM at rest: vDM1/2  300 km/s… useful to approximate  0 2 Usual Simplifications of Dark Matter • DM not baryons (CBR, BBN; Eros/MACHO) • DM was once in thermal equibrium mass > few keV (large scale structure) mass < 340 TeV (unitarity) cross section with us  weak (10-44-10-36 cm2)… little unknown missing energy at LEP, Tevatron… mass>10’s GeV Weakly Interacting Massive Particles SUSY restored just above weak scale gives WIMPS …Attractive candidates (axions, `*zillas’, etc.) were never in thermal equilibrium… INPAC

  6. 0 (SUSY, neutralino, WIMP) a axion, couples to … non- thermal, very light Round up the Usual Suspects  e,m,t e- 0 p n -- Our Matter INPAC

  7. v0 target m Massive Particle Cause target recoil – detect it Direct Detection • Momentum Transfer Convert a to photon – detect it v0 axion INPAC

  8. axion models (Dark matter) 1.9-3.4 eV (ADMX, LLNL-Florida-Berkeley-NRAO) Axions (and similar) INPAC

  9. Primakoff Conversion, Microwave Detection Amplifier – power pours out of cavity when B0 applied Lower noise allows faster scanning…. LB= 50 cm Solenoid Cavity, `TM’ mode (E parallel to B0: 0- ) INPAC

  10. Signal Level and Noise 10-17 Wfrom Pioneer 10 Spacecraft, 1010 km away (s/n) HEMT 10-26 W (time) Substantial improvements in Ts are on the horizon (X30) from increased cooling, SQUIDS INPAC

  11. A4 Nuclear Recoil – Cross Section INPAC

  12. Large Exposure, Background: DAMA (58K kg-days, NaI) ZEPLIN (230 kg-days, Xe) IGEX (276 kg-days, Ge Ioniz) Small Exposure, Background: CDMS (28 kg-days, Ge P/I) Edelweiss (12 kg-days, Ge P/I) (DRIFT - gaseous, recoil dir.) WIMP Region INPAC

  13. Event Rates... Xe Nuclear Form Factor ~ several 10-2 ev/kg/d/keV Rick Gaitskell INPAC

  14. Compare with Common Background Rate  DRU • Shield (shield radioactive too!)… 1 ev/(kg d keV) typical • Reduce the background… HDMS , IGEX , Genius (Ge Ionization) • Exploit astron. properties (year cycle, directionality) DAMA, DRIFT • Devise detectors that can distinguish nuclear recoil from electron recoil… Edelweiss, CDMS, Xenon.. INPAC

  15. 2 vDM1/2 =0 km/s vDM1/2  300 km/s 2 DAMA at Gran Sasso Peak-to-peak up to 40% DAMA:Annual Modulation in Rate • `Usual Simplification’: Halo particles are at rest, on average • Sun moves through Halo - `apparent’ wind • Earth modulates `wind’ velocity yearly Fig. from DRIFT INPAC

  16. 0.01950.031 -0.00010.019 cpd/kg/keV Energy Spectrum Bkgd  1 cpd/kg/keV 8-24 KeV Na(23) 20-70 KeV I(127) 2-6 KeV through 2000 … 4 through 2003 … 6.3  Bernabei et al., astro-ph/0307403 DAMA Background and Signal INPAC

  17. DAMA noise... >1 pe threshold <10-4 cpd... INPAC

  18. DAMA Allowed Regions p (cm2), =0 / through 2000 (standard halo) through 2003 10-44 3 10-42 4 I • Variation mainly due to changes in halo parameters • two plots not directly comparable (different halos used) • With new result, DAMA ceases to employ `standard Maxwellian halo’ - comparisons challenging INPAC

  19. DAMA vs. Super-K Model dependent… but less so than I thought. Spin-dependent (Sun) Scalar (Earth) Desai, IDM 02 INPAC

  20. Background Electron Recoils Er v/c  0.3 Sparse Energy Deposition  Discrimination of Recoils Signal Nucleus Recoils Er v/c  710-4 Dense Energy Deposition v/c small; Bragg 0 Differences the Basis of Discrimination INPAC

  21. Ar pushes other Ar atoms, none go very far. Electron pushes other electrons, all go far Simulation (by DRIFT) 40 keV Ar in 1/20 atm Ar 13 keV e- in 1/20 atm Ar 5 cm INPAC

  22. Simultaneous Measurement of Phonons(Heat) + Ionization • Temperature-20 mK • D(Temp)/D(Energy) • D(Temp)NTD Ge • Slow (10’s ms) • Ionization - E applied Edelweiss E • Background (e- from ) … strong ionization signal… equal phonon signal • Nuclear recoil… reduced (by 1/4) ionization signal, strong phonon signal INPAC

  23. Edelweiss (depth: 4500 mwe) 0.32 kg/ Ge detector Roman Lead 3×0.32kg Germanium Detectors L. Chabert, EPS `03 Aachen INPAC

  24.   Edelweiss Data: ’s Suppressed by 1000 Bolometer 1 Bolometer 2 Bolometer 3 • 10.86 kg.d (fiducial) • Good phonon channel 300 eV (FWHM) resolution during most of the runs • Noisy charge channel • 30 keV threshold • 7.51 kg.d exposure (fiducial volume) • Best charg. channel : 1 keV (FWHM) • 20 keV threshold • 3.72 kg.d (fiduc.) • Smaller exposure due to electronics problems • 30 keV threshold L. Chabert, EPS `03 Aachen INPAC

  25. External  Ionization electrons get trapped in this electrode Electrode Implants z Those electrons never drift over to the other electrode… ionization signal reduced… but, all the phonons/heat still present… (ionization)/(phonons) < 1  E CDMS effort: measure z Betas... Germanium INPAC

  26. ~1cal year, initial deployment CDMS-II Projections INPAC

  27. Some conclusions • Axions searches about to become much more sensitive • WIMPs… • Next few years should get factor of 100 sensitivity • High Mass, Bkgd versus Low Mass, Bkgd: • How well do very high mass detectors self shield? • Can low mass, bkgd be mass produced with ever-lower background requirements? • Is Xe, with ionization, `middle way’? • INPAC... INPAC

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