The Search for Dark MatterStatus, Zeplin II, SIGN, Future

orNature, RED in Tooth and Fang

James T. WhiteHEP Lunch

2-15-06

Dark Matter Distribution?

Dark Matter Experiments• US

– CDMS - ultra-cold Ge– ZEPLIN - two-phase LXe– XENON - two-phase LXe– CLEAN - LNe (+ LAr)– SIGN - Gaseous High Pressure Neon

• EU– DAMA - NaI– CRREST + EDELWEISS - Ge + Sapphire?– WARP - LAr– ArDM - LAr

• Others…. Genius, Drift, XMAS, EURICA … ?

ZEPLIN IIZoned Electro-luminescence and Primary

Light In Noble-gasesDB Cline, M Atac, Y Chen, Y Seo, F Sergiampietri(a), H Wang Physics and Astronomy, UCLA , (a) Pisa

GJ Alner, C Bungau, B Camanzi, JD Lewin, RM Preece, NJT Smith, PF SmithParticle Physics Department, Rutherford Appleton Laboratory, Chilton, Oxon

B Ahmed, A Bewick, D Davidge, JV Dawson, AS Howard, I Ivaniouchenkov, WG Jones, MK Joshi, V Lebedenko, I Liubarsky, R Lüscher, T J Sumner, J J QuenbyBlackett Laboratory, Imperial College of Science, Technology and Medicine, London

MJ Carson, E Daw, T Gamble, VA Kudryavtsev, TB Lawson, MJ Lehner, PK Lightfoot, JE McMillan, B Morgan, SM Pealing, M Robinson, NJC Spooner, DR ToveyDepartment of Physics and Astronomy, University of Sheffield

P PicchiICGF-CNR-Torino

JT White, J GaoDepartment of Physics, Texas A&M University

ZEPLIN II: Two-Phase XenonWIMP

5 inch VUV PMTsOperate to LN2 tempLow bkg materials

Drift Field

Electroluminescence FieldExtraction Field(~5 kV/cm for 100%)

Primary scintillation

Ionization

Secondary Scintillation

PTFE Reflector

Xenon

Signal

Primary Secondary

ZII - DAQDual OutX10 AMP

∑ out

DiscriminatorsPMTs

TriggerN out of 7

Acqiris DC265500 MHz Digitizer2 Mbyte/channel

PC

TAMU

ZII – Gas Test

Direct Detection:Expected Signal

Gammabackground

electronrecoil

Target Nuclei

nuclear recoil

WIMP orNeutron

Scintillation

Ionization

Background Discrimination

ZII - Assembly

UCLA - WANG

ZII: Internals

TAMU

ZII - InternalsTAMU

ZII - InternalsTAMU

ZII – Assembly

TAMU

ZII - Assembly

ZII - Assembly

ZII - Assembly

ZII – Gas Test

ZII ProgressSurface LXe Tests at RAL

Ba -133 Cs-137 Co-60

Cs-137 AmBe

356 keV~400 pe

356 keV~700 pe 1250 keV

~1250 pe

Two-Phase

Nuclear recoils

Zero-Field

ZIIGRID UPGRADE - TAMU

88% transparency Cold deflection test

HV UPGRADE

UCLA

TAMU

Target Integrationshowing wire mesh, field shaping rings,

the PTFE structure to confine liquid xenonand gas extraction

device

Installation of improved HV feedthrough, HV internal Cable

ZII Commissioning

S2/S1

Drift Time (ns)

S2 (p.e.)

Drift Time (us)

Alphas from Radon chain

Fit to slope gives electron lifetime

lifetime ~ 8 us and improving

Recirculating Purifier - UCLA

Commissioning

Today ! Charge Collection > 98%

Feb 14, 2006

600 ms

ZII TAMU Recoil Calibration

Zero-Field

60 keV

>300 pe

Two-Phase

S1

S2

ZII SUMMARY

All is working (Perfectly?)

Electron Lifetime > 100 ms(> 10 X drift time)

Physics Run Starting !

TAMU Calibration soon !

SIGN(Scintillation and Ionization in Gaseous Neon)

A Dark Matter/Neutrino Detector based on

Gaseous Neon

Institutions:TAMU, UCLA

FIRST !

Ans: Electron mobility !

Possibility for Primary vs Secondary Nuclear Recoil Discrimination

Why Gaseous Neon?

Nuclear recoil for neutrinos >~ 10 MeV

WIMP – Dark MatterWIMP

Ne

NuclearRecoil

F(Q2) ~ 1

Kinematics AND

Form Factor

Er

WIMP

Potential WIMP Sensitivity?

1 ton

Few 10-46 cm2 ?

ASSUMING:1)Threshold ~ 1 keVee2)Good Discrimination

Neutrino Applications? -Supernova

E ~ 3 x 1053 ergs

νe ~ 3.0 x 1057

νebar ~ 2.1 x 1057

νx ~ 5.2 x 1057

~ 10 kpc Earth

# neutrinos:sum

Horowitz, Coakley, McKinsey,PRD 68 023005 (2003)

Neon Elastic Scattering

Z0

neutrino

neon nucleus

A = 20Z=10N=10

σ ~ 0.42 x 10-44 N2 (E/1 MeV)2 cm2

Neon Response

Observed Spectrum

Events per ton

10 ton detector ~25 NR evts @ 10 kpc

Solar Neutrinos

Er_MAX = (2/A) (Eν2/1 MeV)2 keV ~ 10 keV for Ev = 10 MeV

8Be: Flux ~106/cm2/s E > 10 MeV

Coherent Nuclear Scattering:

~ 15 evts/year/ton Er: 3 10 KeV

σ ~ 0.42 x 10-44 N2 (E/1 MeV)2 cm2

<Er> = Er_MAX/3 keV

Drukier, Stodolsky, PRD 30 (11) (1984)2295-2309

Cabrera, Krauss, Wilczek, PRL 55(1)(1985)25-28

SIGNAL? Threshold?100 Bar Test Cell

Test Cell

PMT

Radioactivesource

+HV- HV

Sapphire

100 atm NeXe ElectrofluorescenceMostly 175 nmPMT

Cell

Argon Flow Charge Amp

55Fe Signal

Primary

Secondary

Photoelectric from SSQE ~ .02% @175 nm

charge preamp signal- note kink

Light

Charge

~2 us

55Fe SpectraLight

Charge

1 KeV Threshold Feasible !

Nuclear Recoil Discrimination?4-PMT 100 bar Test Cell

4-PMT Test Cell

PTFE reflector

Field tube

4-PMT Test Cell SignalsNeutron EventGamma Event

Areas Samei.e. ionization same

Secondary(S2)

Primary(S1)

Nuclear Recoil Discrimination: S2 vs S1

AmBe Neutron Source

100 bars Ne/Xe(0.5%)

Zoomed View

Red-Cs-137 + Co-60 run

Gammas

Neutrons

S2/S1 vs S1

Primary Shape?

S2/S1 AND Primary ShapeDiscrimination!

Primary Pulse Shape Discrimination

Gammas

Neutrons

Rejection Power? – not yet estimated

SIGN concept

• Neon Gas – P >= 100 atm– + Xenon 0.1-0.5 % ?

• CsI Photocathode• Sense & Field wires• WLS fibers

e.g.Diameter ~ 50 cmLength ~ 5 mMass >~ 100kg @ 100 atm

WIMP

Primary IonizationPrompt Scintillation

Photoelectrons

Cylinder

Pressure Vessels?•Composite cylinders•Carbon, Kevlar wound•Some rated > 10000 psi !•Used on mass transit (Methane))•Used for Hydrogen fuel cells•On jets, spacecraft•DOT certified !•Perhaps cast in acrylic blocks

SIGN Conceptual Design

PMTBoth Ends

Charge Readout-Both Ends-Can sum wires

MgF2- coatedLEXAN light guide

WLS FibersCoated With TPB

Structure of Inner Cylinder

Blue-Green WLS Fiber

TPBVUV toblue

Sense wire

Stainless Steel Inner CylinderHollow, Stiff

Field/Gating Wires

Infrastructure Requirements100 bar with 2m Water Shield

1 ton @ 100 bars

10 tons

~ 9 x 9 x 9 m

Gas Storage ~ 5X4X4 mElectronics ~ 3X3X3 m

Need to discuss with engineers

SIGN Summary• Room-Temperature, High-Pressure, Gaseous

Neon appears to have excellent potential as a dark matter (and neutrino) Target

• It is radio-quiet!• Shows excellent (potential) NR Discrimination in

BOTH S2/S1 and Primary Pulse Shape !• ~ $80k/ton• Will be important in the future to help pin down

mass?

Possible 100 kg Detector

SIGN – Radio Assay?

Drift time

Charge

Alphas

Auger electrons35-55 keV

Nuclear recoils?Neptunium 237?

Am-241 source in situ

ZEPLIN II/III

FUTURE ?

Active Xe

Xe Self shield

Vacuum

HV

CsI Coated

CsI internal photo-cathode –4-pi light collection (except shadow)6 photo-electron/keV1.6 ton fiducial, 5.8 ton total28 cm xenon self shieldStructurally soundMinimized field shaping structure (Less materials)Extremely low backgroundMeasure both scintillation and ionization (3-D events mapping)background rejectionCompact design

CablingUCLA - TAMU

Reverse operation of a cold-emissionDevice to achieve charge gain in

liquid near the tip

Future – PMT-Less LXe

UNCD-coated

M. Hajra, JOURNAL OF APPLIED PHYSICSVOLUME 94, NUMBER 6

Si Uncoated

Extremely sharpand uniformly distributed micro-

tips can be manufactured in

large scale

SUMMARY

• ZEPLIN II – run begins now – reach? 10-8 pb/nucleon?

• SIGN – TAMU Innovation – will certainly exist in the future if only to measure WIMP mass and Halo velocity distribution

• TAMU-UCLA – PMT-Less Detectors –preparing proposals now

• The future of DM Research is Bright!