Cracow Epiphany Conference 2010 The Argon Dark Matter

Cracow Epiphany Conference 2010 The Argon Dark Matter Experiment Małgorzata Harańczyk IFJ PAN Kraków Sławomir Mania University of Silesia

Collaboration Switzerland ETH Zurich University Spain University of Granada CIEMAT Poland Soltan Institute for Nuclear Studies, Warszawa H. Niewodniczański Institute of Nuclear Physics , Kraków University of Silesia England University of Sheffield Małgorzata Harańczyk IFJ PAN Kraków 2

Outline • Conceptual design of the Ar. DM detector • Small R&D test setup with LEM readout • Status of the experiment Małgorzata Harańczyk IFJ PAN Kraków 3

Ar. DM • New generation WIMP detector (simultaneous measurement of light and charge) • 850 kg liquid Argon detector • Measurement of WIMP recoil energy spectrum Energy threshold ~30 ke. V, 3 -D imaging, Trigger rate below 1 k. Hz Małgorzata Harańczyk IFJ PAN Kraków 4

Conceptual design A WIMP collides with Argon inside the detector… …transmitting its kinetic energy to the nucleus… …the Argon nucleus recoils…. Scintillation light and ionization electrons are produced from interactions with neighbouring Argon atoms Małgorzata Harańczyk IFJ PAN Kraków light + charge signals 5

Conceptual design • Large volume high electric field, Extraction of the ionization electrons from the liquid into the gas phase • Large area position sensitive charge readout with LEM’s (3 rd-dimension from drift time) • Large area VUV sensitive light readout with good time resolution (also used for trigger) Efficient liquid argon purification system Careful choice of detector materials (to keep low the background due to natural radioactivity) Małgorzata Harańczyk IFJ PAN Kraków 6

Conceptual design 80 cm 120 cm Małgorzata Harańczyk IFJ PAN Kraków 7

First test – May 2009 • 22 Na and 137 Cs sources • Only half (7) of the PMTs were installed • No drift electric field -Light yield is consistent with expectations (0. 5 p. e. /ke. V with 7 PMTs); -First successful detection of 50 ke. V signal in 1 t detector; Małgorzata Harańczyk IFJ PAN Kraków 8

Small setup for charge readout R&D Small double-phase argon TPC Max drift length 20 cm (0. 5 k. V/cm) One LEM 1 mm x 10 cm Large Electron Multiplier Małgorzata Harańczyk IFJ PAN Kraków 9

Small R&D setup Before … and after measurements. A few days long run of stable work with 34 k. V/cm in LEM holes Małgorzata Harańczyk IFJ PAN Kraków 10

3 D event imaging Typical cosmic muon event the charge readout with striped LEM and anode plates (2 D) + the light signal to define t 0 drift time = a precise 3 D reconstruction of the event Data were taken by MH and SM during tests at CERN in summer 2009 Małgorzata Harańczyk IFJ PAN Kraków 11

3 D event imaging Małgorzata Harańczyk IFJ PAN Kraków 12

The near future • Next test of the Ar. DM detector foreseen in February 2010 14 PMT, drift electric field to measure ionization • Tests of new types of LEMs are going on with a small test setup (the full size prototype is still in a design phase) • Detector ready for underground operation by the end of 2010 Małgorzata Harańczyk IFJ PAN Kraków 13

SUN LAB The Sieroszowice Underground LABoratory -one of three possible locations for the underground Ar. DM operation KGHM copper mine in the west-southern Poland Salt cavern 1 km below the surface 2200 m. w. e very low level of natural radioactivity background ! Małgorzata Harańczyk IFJ PAN Kraków 14

Acknowledgements We want to express our gratitude to Andre Rubbia, and Alberto Marchionni for making it possible to work with Ar. DM team in CERN. We would like to thank Filippo Resnati, and Devis Lussi for the kind hospitality extended to us. Małgorzata Harańczyk IFJ PAN Kraków 15

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Background rejection Neutrons: from radioactive elements in materials and from cosmic muons Electrons/Gammas: from radioactive elements ⇒ Neutron events look like WIMP-events ⇒ in Liquid argon e/g events look different from WIMP-events – Different shape of the scintillation light (ratio fast/slow components) – Different light/charge ratios Małgorzata Harańczyk IFJ PAN Kraków 17

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