DEAP/CLEAN-ing Dark Matter: the Search for Direct Detection with - PowerPoint PPT Presentation

DEAP/CLEAN-ing Dark Matter: the Search for Direct Detection with Liquid Argon Jocelyn Monroe, Royal Holloway University of London Particle Physics Seminar Birmingham University February 8, 2012

Outline Direct Dark Matter Detection DEAP/CLEAN Experimental Technique How Will We Know When Dark Matter is Discovered? RHUL Jocelyn Monroe February 8, 2012

Standard Model of Cosmology (NASA) Dark matter is ~23% of the universe. RHUL Jocelyn Monroe February 8, 2012

What do we know about Dark Matter? optically dark density ~ 0.3 GeV/cm 3 dark matter particle mass: ~unknown interactions: very weak, ~collision-less ~150 RHUL Jocelyn Monroe February 8, 2012

Dark Matter Candidates HEPAP/AAAC DMSAG Subpanel (2007) strong e.m. weak ? interaction strengths gravity neutrino? electron t-quark masses RHUL Jocelyn Monroe February 8, 2012

#1: What is the universe made of? “The quest to elucidate the nature of dark matter and dark energy is at the heart of particle physics—the study of the basic constituents of nature...” “An answer to the question [what is dark matter] would mark a major breakthrough in understanding the universe and would open an entirely new field of research on its own.” “an area of world leading science opportunity” “significant UK leadership” “UK involvement is essential” RHUL Jocelyn Monroe February 8, 2012

Direct Detection Signal: χ N ➙ χ N χ χ Backgrounds: γ e - ➙ γ e - n N ➙ n N N ➙ N’ + α , e - ν N ➙ ν N γ γ RHUL Jocelyn Monroe February 8, 2012

E D = 1 WIMP Scattering χ 2 m D v 2 χ kinematics : v/c ~ 8E-4! Z q 2 = 2 m T E recoil 4 m D m T r = ( m D + m T ) 2 N N E recoil = E D r ( 1 − cos θ ) 2 Spin Independent: χ scatters coherently off of the entire nucleus A: σ ~A 2 D. Z. Freedman, PRD 9, 1389 (1974) Spin Dependent: only unpaired nucleons contribute to scattering amplitude: σ ~ J(J+1) RHUL Jocelyn Monroe February 8, 2012

Measurement Recoil Nucleus χ Kinetic Energy χ N ~ RHUL Jocelyn Monroe February 8, 2012

Backgrounds ? Gamma ray interactions: N rate ~ N e x (gamma flux), typically 10 million events/day/kg mis-identified electrons mimic nuclear recoil signals Neutrons: (alpha,n), U, Th fission, cosmogenic spallation eg. Study for CDMS-II Detector μ μ D.-M. Mei, A. Hime, PRD73:053004 (2006) γ N* N n nuclear recoil final state Contamination: 238 U and 232 Th decays, recoiling progeny and mis-identified alphas mimic nuclear recoils RHUL Jocelyn Monroe February 8, 2012

Irreducible Backgrounds impossible to shield a detector from coherent neutrino scattering: Φ (solar B 8 ) = 5.86 x 10 6 cm -2 s -1 ν ν JM, P. Fisher, PRD76:033007 (2007) Z N N nuclear recoil final state 1 event/ton-year =~ 10 -48 cm 2 limit in zero-background paradigm unless you measure the direction! RHUL Jocelyn Monroe February 8, 2012

The Low Background Frontier *only the two 1 event/kg/day leading limits shown 1 event/100 kg/day 1 event/100 kg/100 days so far: 3 years/ order of magnitude RHUL Jocelyn Monroe February 8, 2012

10 4 is a lot of σ 10 -24 cm 2 : σ (neutron-A elastic scattering) 10 -28 cm 2 : σ (total inelastic pp at TeVatron) 10 -35 cm 2 : σ (gg ➔ H) at LHC (Standard Model) Not to Scale 10 -39 cm 2 : σ (single top) at TeVatron 10 -40 cm 2 : σ ( ν QE) at T2K 10 -45 cm 2 : σ ( ν -e Elastic) for solar ν σ (dark matter coherent scattering)? 10 -48 cm 2 RHUL Jocelyn Monroe February 8, 2012

Around the World KIMS NEWAGE, Elegants DEAP/CLEAN Picasso DRIFT COUPP Zeplin NaIAD LUX Xenon10(0) CDMS Genius DAMA DMTPC CRESST DarcSide Edelweiss IGEX, ANAIS MiMAC, ArDM RHUL Jocelyn Monroe February 8, 2012

χ χ Direct Dark Matter Signals? COGENT Z arXiv:1002.4703 DAMA/Libra N N CRESST-II arXiv:1109.0702 CDMS arXiv:0912.3592v1 dark matter? backgrounds? arXiv:1109.2589 RHUL Jocelyn Monroe February 8, 2012

Annual Modulation? June-December event rate asymmetry ~2-10% Drukier, Freese, Spergel, Phys. Rev. D33:3495 (1986) Eur. Phys. J. C56:333-355 (2008) DAMA/Libra positive result, >8 σ , inconsistent with many expts CoGeNT: 442 days, 0.5-3.0 keV ee Events/30 days CoGeNT CoGeNT modulation 42 140 (dashed result, 2.8 σ , ~consistent days 120 line) with DAMA/Libra 100 J. Collar, STSI (2011), DAMA 80 arXiv:1106.0650v1 (solid line) 60 0 100 200 300 400 500 RHUL Jocelyn Monroe February 8, 2012 Days Since Dec 3, 2009

χ χ Indirect Dark Matter Signals? ? e+ e- PAMELA arXiv:0810.4995 Fermi LAT arXiv:0905.0025 ATIC dark matter? local astrophysics? RHUL Jocelyn Monroe February 8, 2012

Outline Direct Dark Matter Detection DEAP/CLEAN Experimental Technique How Will We Know When Dark Matter is Discovered? RHUL Jocelyn Monroe February 8, 2012

Path to Discovery current experiments: 10-100 kg detector mass; zero background paradigm= any excess of events is candidate signal goal: measure dark matter properties with 100-1000 events (multi-tonne experiments); paradigm shift: search for signal above measured background, in a low background observatory DEAP/CLEAN Objectives: 1) address scalability to very large detectors, 2) measure all backgrounds in-situ, while producing a world-leading dark matter result RHUL Jocelyn Monroe February 8, 2012

Sensitivity Projections need 100-1000 events to measure dark matter mass, cross section New Techniques for Backgrounds Scalability of Detector Technology 1 event/ kg/day 1 event/ 100 kg/day 1 event/ 100 kg/ 100 days need multiple targets Complementary with High-Energy Frontier and techniques to verify signals RHUL Jocelyn Monroe February 8, 2012

cross section (cm 2 ) detector mass (ktonnes) Neutrino Lesson: key to scalability is 100 10 -45 large, open volume simple detector design 30 DEAP/CLEAN Strategy: Super-K (55 kt) draw on design successes of 10 -44 large neutrino experiments 10 Kamland DEAP/CLEAN (3 kt) 3 10 -43 1 10 -42 SNO (1 kt) MiniBooNE 10 -39 (0.8 kt) 0.1 RHUL Jocelyn Monroe February 8, 2012

DEAP/CLEAN Detector Design read out with PMTs, Liquid Argon dark matter wavelength shift digitize at 250 MHz, target (cold! 87 K) (TPB) to >400 nm maximize PE/keVee LAr scintillates at 128 nm with 4 π coverage If there is a signal, verify A 2 dependence by Ar/Ne target exchange (MiniCLEAN) RHUL Jocelyn Monroe February 8, 2012

Single Phase Detector high light yield and self-shielding of liquid noble target background discrimination from prompt scintillation timing... no electric fields = straightforward scalability 1) no pile-up from ms-scale electron drift in E 2) no recombination in E (high photons/keVee) cf. Two Phase Detector: and charge but no charge background discrimination either! (proportional scintillation) RHUL Jocelyn Monroe February 8, 2012