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Cryogenic Dark Matter Search Harry Nelson UCSB Journal Club March 12, 2004

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CDMS Collaboration

Brown University

Stanford University

M. Attisha, R.J. Gaitskell, J-P. Thompson

Case Western Reserve University D.S. Akerib, M.R. Dragowsky, D.Driscoll, S. Kamat, T.A. Perera, R.W. Schnee, G.Wang

Fermi National Accelerator Laboratory D.A. Bauer, M.B. Crisler, R. Dixon, D. Holmgren, E. Ramberg

Lawrence Berkeley National Laboratory J.H Emes, R.R. Ross, A. Smith

Princeton University T. Shutt

Santa Clara University B.A. Young

3/12/04

UCSB

Cryogenic Dark Matter Search

L. Baudis, P.L. Brink, B. Cabrera, C. Chang, W. Ogburn, T. Saab

University of California, Berkeley M.S. Armel, A. Lu, V. Mandic, P.Meunier, N. Mirabolfathi, W. Rau, B. Sadoulet, D. Seitz, A. Spadafora, K. Sundqvist

University of California, Santa Barbara R. Bunker, D.O. Caldwell, R. Ferril, R. Mahapatra, H. Nelson, J. Sander, C. Savage, S. Yellin

University of Colorado at Denver M. E. Huber

University of Minnesota P. Cushman, L. Duong, A. Reisetter

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UCSB

Plan z

Massive Dark Matter

z

Direct Detection

z

The ZIP Detector

z

Data

z

Future

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Primack Pyramid

UCSB

We are 1 in 10,000 of the energy in Universe… Our form of matter less than dark matter by factor of 5 or so in energy... Who ordered that?

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Leading Thinkers

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z

Origin of Dark Matter

During inflation 〉 〉

Axion, superpartner Axino *Zillas →Could

〉

z

UCSB

have only gravitational interactions!

Few constraints…

During thermal equilibration phase of Big Bang… 〉 〉

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m > few keV (currently observed large scale structure) m > 10 or so GeV (nothing new at accelerators)

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Candidates

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Coincidence or Clue… `WIMP’ ’

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WIMP/nucleon σ≈10-42 cm

UCSB

Exper. CDMS DAMA Theory SUSY: various constraints including Big Bang

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Galactic Dark Matter

UCSB

R is the distance from center v

v is the speed (tangential)

R

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UCSB

The Dark Ball Bulge

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Disk

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Dark Matter `Halo’ (aka Aura)

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UCSB

What about our home galaxy (Milky Way)? χ

χ

χ χ

χ

χ χ

χ

χ

χχ

χ

χ

χ

χχ

χ

χ

χ

χ

χ

χ

χ

χ χ

χ

Honma and Sofue, 1996

v 220 km/s Without the Dark Halo (Binney & Tremaine)

∆:v0=180 km/s ⊕

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From Galactic Astrophysics… z

Local energy density, speed of DM MeV ú 0 ø 300 3 cm

0? (200-2000)

z

UCSB

DM at rest:

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km v 0 ø 220 (ì 0 ø 7 â 10 à4) s (ì 20 ø 12 â 10 à6) (170-270)

〈vDM〉=0 (sun plowing through at v0 ≈ 220 km/s) 2 〉1/2 ≈ 300 km/s… useful to approximate ≈ 0 〈vDM

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Direct Detection: Signal and Main Background

Signal

Nucleus Recoils

Background Electron Recoils

Er

v/c ≈ 7×10-4 dense energy deposition ionization efficiency low distinct ionization energy scale

0 χ (calibrate: neutron) 3/12/04

UCSB

γ

Er v/c ≈ 0.3

Sparse Energy Deposition

Differences the Basis of Particle ID

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Rate of Main Background

UCSB

≡ DRU • Shield (shield radioactive too!)… 1 ev/(kg d keV) typical • Reduce the background… HDMS , IGEX , Genius • Exploit astron. properties (year cycle, directionality) DAMA, DRIFT • Devise detectors that can distinguish nuclear recoil from electron recoil… Edelweiss, CDMS, Xenon.. 3/12/04

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Nuclear Recoil – Cross Section

∝A4

`scalar’ or SI (Spin Independent) 3/12/04

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Nuclear Recoil – Diffraction

UCSB

Iodine (A=127) DAMA 0 110 220 330 keV ER 3/12/04

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Nuclear Recoils from Massive Dark Matter z

Deposit 10’s of keV; high target A favored

z

Target A