Dark Matter Overview Harry Nelson UCSB INPAC Oct. 4, 2003 HNN UCSB Outline Axions Massive Particles Direct Detection Weakly Interacting No Strongly Interacting (interesting opportunities) See talks of Dave Cline (ZEPLIN),
Download ReportTranscript Dark Matter Overview Harry Nelson UCSB INPAC Oct. 4, 2003 HNN UCSB Outline Axions Massive Particles Direct Detection Weakly Interacting No Strongly Interacting (interesting opportunities) See talks of Dave Cline (ZEPLIN),
Dark Matter Overview Harry Nelson UCSB INPAC Oct. 4, 2003 HNN UCSB Outline Axions Massive Particles Direct Detection Weakly Interacting No Strongly Interacting (interesting opportunities) See talks of Dave Cline (ZEPLIN), Patrizia Meunier (CDMS-II) 10/4/03 INPAC 2 HNN UCSB Usual Simplifications of Dark Matter Local energy density, speed of DM km MeV ú0 ø 300 v 0 ø 220 (ì 0 ø 7 â 10à 4) 3 s cm (ì 20 ø 12 â 10à 6) 0? (200-2000) (170-270) … from galactic astrophysics Consists of one elementary particle (!) , 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. 10/4/03 INPAC 3 HNN UCSB Advice of Dennis the Menace 10/4/03 INPAC 4 HNN Usual Simplifications of Dark Matter UCSB 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… DM at rest: 10/4/03 vDM=0 (sun plowing through at v0 220 km/s) 2 1/2 300 km/s… useful to approximate 0 vDM INPAC 5 HNN UCSB Round up the Usual Suspects e,m,t e- 0 p n -- Our Matter 0 (SUSY, neutralino, WIMP) a axion, couples to … nonthermal, very light 10/4/03 INPAC 6 HNN UCSB Direct Detection Momentum Transfer v0 Convert a to photon – detect it axion m v0 target Massive Particle Cause target recoil – detect it 10/4/03 INPAC 7 HNN UCSB Axions (and similar) axion models (Dark matter) 1.9-3.4 meV (ADMX, LLNL-Florida-Berkeley-NRAO) 10/4/03 INPAC 8 HNN UCSB Primakoff Conversion, Microwave Detection Amplifier – power pours out of cavity when B0 applied Lower noise allows faster scanning…. Solenoid LB= 50 cm Cavity, `TM’ mode (E parallel to B0: 0- ) 10/4/03 INPAC 9 HNN UCSB Signal Level and Noise (s/n) 10-17 W from Pioneer 10 Spacecraft, 1010 km away HEMT 10-26 W (time) Substantial improvements in Ts are on the horizon (X30) from increased cooling, SQUIDS 10/4/03 INPAC 10 HNN UCSB Nuclear Recoil – Cross Section A4 10/4/03 INPAC 11 HNN UCSB WIMP Region 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.) 10/4/03 INPAC 12 HNN UCSB Event Rates... Xe Nuclear Form Factor ~ several 10-2 ev/kg/d/keV Rick Gaitskell 10/4/03 INPAC 13 HNN UCSB 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.. 10/4/03 INPAC 14 HNN UCSB DAMA:Annual Modulation in Rate • `Usual Simplification’: Halo particles are at rest, on average 2 1/2 vDM =0 km/s • Sun moves through Halo - `apparent’ wind • Earth modulates `wind’ velocity yearly vk = 15 km/s vDM1/2 300 km/s 2 Fig. from DRIFT DAMA at Gran Sasso Peak-to-peak up to 40% 10/4/03 INPAC 15 HNN UCSB DAMA Background and Signal 0.01950.031 -0.00010.019 cpd/kg/keV Energy Spectrum Bkgd 1 cpd/kg/keV 2-6 KeV 8-24 KeV Na(23) 20-70 KeV I(127) through through2000 2003… …4 6.3 Bernabei et al., astro-ph/0307403 10/4/03 INPAC 16 HNN UCSB DAMA noise... >1 pe threshold <10-4 cpd... 10/4/03 INPAC 17 HNN UCSB DAMA Allowed Regions p (cm2), =0 / through 2000 10-44 through 2003 (standard halo) 3 10-42 I 4 • 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 10/4/03 INPAC 18 HNN UCSB DAMA vs. Super-K Model dependent… but less so than I thought. Spin-dependent (Sun) Scalar (Earth) Desai, IDM 02 10/4/03 INPAC 19 HNN UCSB Discrimination of Recoils Signal Background Nucleus Recoils Electron Recoils Er v/c 710-4 Dense Energy Deposition v/c small; Bragg 0 10/4/03 INPAC Er v/c 0.3 Sparse Energy Deposition Differences the Basis of Discrimination 20 HNN UCSB Simulation (by DRIFT) 13 keV e- in 1/20 atm Ar 40 keV Ar in 1/20 atm Ar Ar pushes other Ar atoms, none go very far. Electron pushes other electrons, all go far 5 cm 10/4/03 INPAC 21 HNN UCSB Simultaneous Measurement of Phonons(Heat) + Ionization Edelweiss Temperature-20 mK E D(Temp)NTD Ge D(Temp)/D(Energy) Slow (10’s ms) Ionization - E applied Background (e- from ) … strong ionization signal… equal phonon signal Nuclear recoil… reduced (by 1/4) ionization signal, strong phonon signal 10/4/03 INPAC 22 HNN UCSB Edelweiss (depth: 4500 mwe) 0.32 kg/ Ge detector L. Chabert, EPS `03 Aachen 10/4/03 Roman Lead 3×0.32kg Germanium Detectors INPAC 23 HNN Edelweiss Data: ’s Suppressed by 1000 Bolometer 1 Bolometer 2 7.51 kg.d exposure (fiducial volume) ● Best charg. channel : 1 keV (FWHM) ● 20 keV threshold L. Chabert, ● EPS `03 Aachen 10/4/03 Bolometer 3 3.72 kg.d (fiduc.) ● Smaller exposure due to electronics problems ● 30 keV threshold INPAC ● UCSB 10.86 kg.d (fiducial) ● Good phonon channel 300 eV (FWHM) resolution during most of the runs ● Noisy charge channel ● 30 keV threshold ● 24 HNN UCSB Betas... External z GermaniumElectrode Implants Ionization electrons get trapped in this electrode E Those electrons never drift over to the other electrode… ionization signal reduced… but, all the phonons/heat still present… (ionization)/(phonons) < 1 CDMS effort: measure z 10/4/03 INPAC 25 HNN UCSB CDMS-II Projections ~1cal year, initial deployment 10/4/03 INPAC 26 HNN UCSB 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 everlower background requirements? Is Xe, with ionization, `middle way’? INPAC... 10/4/03 INPAC 27