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

2. 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

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

4. Gravitational Lensing

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

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

7. WMAP measurement of CMB
Best Fit from WMAP :
ΩBh2= ± 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

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

9. 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

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

11. 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

12. 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

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

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

15. 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

16. Status of Direct Detection Search
XENON10
σ < 8.8 x cm2 at 100GeV
CDMS
σ < 6.6 x cm2 at 60GeV

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

18. 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

19. Liquid Xenon Detectors

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

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

22. WIMP Signal in Liquid Xenon

23. XENON100 Experiment 170kg (50kg Fiducial)
Sensitivity σ ~ 2x cm2 at 100GeV

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

25. 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)

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

27. 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

28. 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

29. Final Detector Assembly

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

31. 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

32. 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

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

34. QUPID Field Simulations
First Working
QUPID
Non-uniform electron collection

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

36. Light Collection Simulations

37. 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

38. BACK UP SLIDES

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

40. 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 :

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

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

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

44. 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

45. Neutral SUSY Particles

46. 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 .

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

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