Potential for Dark Matter Direct Searches in Australia Professor Elisabetta Barberio The University of Melbourne

So far only from astronomical observations DARK MATTER –Is dark matter composed of one particle species or many? –Is it a fundamental particle? –What are its properties? –How does it interact? –What is the symmetry origin of the dark matter particle? –How and when was it produced? E VIDENCE OF D ARK M ATTER

Observational constraints are no match for the creativity of theorists Many hypothesis, but not all are equally motivated N ATURE OF D ARK M ATTERPARTICLE

indirect detection direct detection - land-based - high altitude - space-based Collider searches cc p e+e+ n g _ SUPER K AMANDA CDMS DAMA EDELWEISS ZEPLIN L OOKING FOR D ARK M ATTER LHC

D IRECT DETECTION P RINCIPLE Detection of the energy deposit due to elastic scattering on nuclei of the detector Optimal sensitivity for M WIMP ~ M RECOIL Low rate < 1 evt/day/kg of detector  low background and large detector mass Deep underground sites Radio-purity of components Active/passive shielding Recoil energy ~ 20 keV  Low energy threshold 4

B ACKGROUND FOR D IRECT D ETECTION EXPERIMENTS

D IRECT DETECTION TECHNIQUES 6 WIMP Heat Ionization Light Ge Liquid Xe NaI, Xe Ge, Si CaWO 4, BGO Al 2 O 3, LiF Elastic nuclear scattering 1% energy fastest no surface effects 10% energy 100% energy slowest cryogenics WIMP Target

No dark matter direct detection experiments in the Southern Hemisphere !

DAMA team have found evidence for dark matter with DAMA/NaI (100 kg NaI target) and confirmed with more precision by DAMA/Libra (250 kg NaI target) First claim of direct detection of dark matter! More than 10 years already. D AMA L IBRA

DAMA/LIBRA Basic technique: scintillation of thallium doped NaI. 100 kg of NaI(Tl) Exposure : kg.d Coincidence between 2 PMTs Pulse shape rejection inefficient at 2 keV ee Signal extracted from background by using the annular modulation of the dark matter flux. NaI PMT

Evidence from direct detection experiments, especially DAMA/LIBRA annual modulation signal Phase and Period of modulation are predicted! t 0 = 152 (June 2), T = 1 year. D ARK M ATTER M ODULATION

The DAMA collaboration reports a modulation with a phase consistent with dark matter, and with high significance (8.9  ) DAMA/LIBRA

CDMS Currently, the most sensitive DM detection experiment. Ge, Si crystal : 7.6 cm φ, 1 cm thick 240 (100) g; 2 ionization channel 4 phonon sensors Nuclear recoil Electron recoil

CDMS II R ESULTS Mass / cross section sensitivity Better sensitivity at higher mass Same minimum cross section as XENON10 The CDMS collaboration reported the detection of two events which met the WIMP criteria.

C OGENT P-type Point-Contact (P-PC) low-capacitance, noise; long charge drift times

C O G E NT RESULTS The CoGeNT data set contains 2124 events in the keVee energy range. Background analyses suggest muons and Rn can not account for this modulation

C O G E NT AND DAMA MODULATION AMPLITUDES ARE CONSISTENT quenching factor=0.5 Independent of astrophysical uncertainties, the gray error bars are the what the DAMA signal would look like at the CoGeNT detector Red error bars are the CoGeNT modulation for maximum phase May 26 (SHM). Blue error bars are the best fit maximum phase for CoGeNT (April 18). quenching factor=0.25

S UMMARY OF D IRECT D ETECTION CDMS-II

Self-interacting Dark Matter, accumulate in the Earth (large class of DM model unexplored!) D IURNAL M ODULATION The angle between Earth's motion through the halo and normal to Earth's surface. This angle changes as the earth rotates…. Dark matter wind directly above Dark matter wind through Earth’s core

It would be extremely important to check DAMA signal in southern hemisphere. If the DAMA annual modulation signal were somehow due to background, it is reasonable to expect that it would have different phase for a detector in the southern hemisphere. There is another reason to do dark matter experiments in the Southern Hemisphere. It turns out that the southern hemisphere is much more sensitive to diurnal modulation. S OUTHERN HEMISPHERE

20 Idea: do a modulation experiment in the southern hemisphere, If the modulation is due to DM, we should see the same modulation the southern hemisphere, but where can we put an experiment? Stawell Gold Mine in Victoria The site is 5km from the town centre.

S TAWELL G OLD M INE The Stawell Gold mine is in basalt and is a decline style mine with a helical access road descending around the main ore body, with many caverns dug into the ore body along the road. The access road supports mining vehicle traffic. The mine is “dry”, has power, there are gas and fibres available

S TAWELL G OLD M INE m maximum depth, with caverns at many different depths including at1000m+ depth Many caverns have concrete sprayed surfaces More info on

S TAWELL G OLD M INE 23 INFN is proposing a new crystal experiment with two identical parts one in Gran Sasso one in Australia to check the annual modulation. There is also interest from Cogent and Liquid Xenon/Argon experts to do underground experiments in Australia First visit to the site and some preliminary background measurements at the end of January. More formal collaboration with INFN is being developed If you are interested, the contact persons Prof. G. Mould and Prof. E Barberio

Evidence for non-baryonic dark matter from many astrophysical sources The DAMA experiment may have detected galactic dark matter! Some support from CoGeNT and CRESST-II. An experiment in the southern hemisphere is needed to a) Confirm or refuse the DAMA annual modulation b) Search for Diurnal variation – completely unexplored territory... If the site availability is confirmed there is a lot of interest … C ONCLUSION