Direct Search for Dark Matter with XENON100 Oral Examination Ethan Brown June 16, 2009

Overview Evidence for the existence of Dark Matter Galactic Rotation Curves Gravitational Lensing Matter Distribution Dark Matter Candidates Properties of Dark Matter The Neutralino Detection Methods Liquid Xenon Detectors XENON Experiment My PhD Project PUT A PICTURE HERE

Galactic Rotation Curves Far from galactic center Newton says: Vera Rubin et al (1970) measured Implies existence of Dark Halo

Gravitational Lensing

More Gravitational than Luminous Mass Gravitational Lensing used to measure cluster mass Compared to mass measured by X-ray observations Implies Dark Gravitational Mass

Chandra image of the Bullet Cluster shows baryonic matter displaced from gravitational matter

WMAP measurement of CMB Best Fit from WMAP : ΩBh2= 0.024 ± 0.001 ΩMh2= 0.14 ± 0.02 Remaining matter must be non baryonic Precision measurement of CMB anisotropy Measure both baryonic and non-baryonic matter densities

What is the Universe made of? 70% Dark Energy 25% Dark Matter 5% Ordinary Matter

What is Dark Matter? A good candidate: Charge and Color Neutral Has the correct abundance Does not interact strongly with normal matter Charge and Color Neutral Falls naturally out of larger theory Is detectable by experiment Many proposed solutions: WIMPS MACHOS, Sterile Neutrinos, Mirror Matter, Extra Dimensions, Daemons... Heavy Particle m~100GeV Weak scale interactions with ordinary matter Thermal equilibrium at beginning of Universe Gives correct relic abundance

Physics We Already Know Standard Model of Particle Physics Standard Model of Cosmology

SuperSymmetry (SUSY) Extend Standard Model by imposing new symmetry between bosons and fermions Doubles # of particles in SM Make sure to point out that you are aware that its the exact same figure than the slide before

SUSY Dark Matter Broken symmetry Hierarchy Problem Unification of forces R-Parity Neutral SUSY particles Particles and sparticles masses differ Breaks electroweak symmetry Difference between Higgs mass and Planck scale Modified couplings DO meet in 1 point Needs to be conserved LSP is stable 4 neutralinos mass eigenstates The lightest neutralino is stable and is an excellent dark matter candidate

Relic Density Thermal Equilibrium Neutralino is Majorana Relic Abundance Remains Neutralino is Majorana

Indirect Detection Experiments Search for signatures of WIMP annihilation Ground based telescopes VERITAS, ANTARES, IceCube Space telescopes Fermi Telescope, PAMELA

Direct Detection Experiments Cryogenic Crystals CDMS, CRESST, EDELWEISS Measure Heat and Light Liquid Noble Detectors (xenon, argon) XENON, ZEPLIN, WARP, DEEP/CLEAN Measure Charge and Light

Status of Direct Detection Search XENON10 σ < 8.8 x 10- 44 cm2 at 100GeV CDMS σ < 6.6 x 10- 44 cm2 at 60GeV

XENON Program Liquid Xenon Detector Direct Search for WIMP Nucleon Interactions Located in Gran Sasso Underground Laboratory Phased program 10kg → 100kg → 1T...

Evolution of XENON XENON10 XENON100 XENON100 Upgrade XENON 1Ton Published Results 2008 XENON100 Take Data This Fall XENON100 Upgrade Approved for Construction XENON 1Ton Proposal submitted XAX / MAX 10Ton Published concept 2008

Liquid Xenon Detectors

Electron Recoil Discrimination S2/S1 Cut Separates nuclear from electron recoils Cut at nuclear recoil mean 99.9% Rejection Xenon 10 Calibration

Self Shielding Very short interaction length Fiducial volume cut Accept events from quiet center

WIMP Signal in Liquid Xenon

XENON100 Experiment 170kg (50kg Fiducial) Sensitivity σ ~ 2x10 - 45 cm2 at 100GeV

XENON100 Detector Low Background Materials Purified Xenon by removing Kr85 242 PMTs in TPC and Active Veto mm Position Resolution

QUPID Photo Detector Necessary for Large Scale Detectors Increased Detector Size requires Lower Background Low Activity Photo Sensor being developed 3” Photo Tube Quartz Structure Small APD at Center Necessary for Large Scale Detectors QUartz Photon Intensifying Device (QUPID)

XENON100 Upgrade Next Phase of XENON Program Already Approved and Funded QUPIDs on bottom R8520s on top Run in Existing Shield in Gran Sasso

Ton Scale and Beyond 1 Ton → 10 Ton Target 4pi QUPID Coverage XAX 10Ton Detector Xenon and Argon Targets Dark Matter, Neutrinoless DBD, pp Solar Neutrinos

My PhD Project Final Assembly of XENON100 Detector Software Development PMT Calibrations Complete Software Package Monte Carlo Simulations Signal Generation / Digitization Reconstruction / Analysis Analysis of XENON100 Data R&D / Simulations for Large Scale Detectors

Final Detector Assembly

PMT Calibration Illuminate PMTs in-situ with external LED Measure Gain by single photo electron response

Complete Software Package Simulate every physical process Particle Interactions Gamma, Neutron, WIMP Photon Propagation (Light Collection) Electron Drift including Diffusion Proportional Scintillation (S2) PMT Response FADC Digitization Run Analysis Software on MC and Data

Proportional Scintillation Simulate Electron Trajectories near Anode Generate S2 Photons by: N = 70(E/P – 1.3)P x Use Light Simulations to Generate S2 Signal

QUPID Screening Screened 4 Mechanical Samples in Gran Sasso Gator Gamma Detector < 0.91 mBq/QUPID 238U < 2.1 mBq/QUPID 232Th

QUPID Field Simulations First Working QUPID Non-uniform electron collection

Electron Trajectory Simulations 1T Detector with Conventional Wires 10T Detector with Acrylic Vessel

Light Collection Simulations

Summary Strong Observational Evidence for Dark Matter Rotation Curves Gravitational Lensing Matter Distribution SUSY and WIMPs as Dark Matter SUSY as Extension of Particle Physics Neutralino a Natural Dark Matter Candidate Detecting Dark Matter XENON100 Dark Matter Search Future Large Scale Dark Matter Detectors

BACK UP SLIDES

Precision measurements of 21cm Hydrogen line 21cm Hyperfine Transition Precisely measure redshift → velocity Follows Dark Matter Halo Model

SUSY is Broken Symmetry Broken SUSY implies particle and sparticle masses different Automatically breaks Electroweak symmetry V = (|μ|2 + mH2)|H0|2 V = (|μ|2 + mHu2)|Hu0|2 + (|μ|2 + mHd2)|Hd0|2 – (BHu0Hd0 + c.c.) + 1/8 (g2 +g'2)(|Hu0|2 - |Hd0|2) Higgs Potential : Replaced by :

Gauge Hierarchy Problem In SM, mh ~ Λ naturally But mh ~ 100 GeV and Λ ~ 1019 GeV Cancellation of 1 part in 1034

SUSY Solves This Extra term with opposite sign Since SUSY is broken, cancellation not perfect

Unification of Forces Couplings do not meet at high energy In SUSY, Couplings are modified SUSY also explains αEM < αweak < αS

Proton Decay and R Parity SUSY allows Proton Decay Forbid this with R Parity Conservation: RP = (-1)2(B-L)+2S Requires 2 super-particles in each interaction Lightest SUSY Particle (LSP) is stable Good Dark Matter Candidate

Neutral SUSY Particles

Power Spectrum Sensitive to Baryon Density Ratio of 1st to 2nd peak gives baryon density. Best fit from WMAP gives : Remaining matter must be non-baryonic .

Particle Simulations Gammas and Neutrons From Radioactive Decays in Materials From Sources for Calibration

Photon Propagation Simulate UV Photons Estimate Collection Efficiency Absorption in Xenon Reflection off of Teflon and Liquid Surface Estimate Collection Efficiency