Physics Department Seminar
Dr. Pierre Gorel
Research Scientist
Tuesday, September 18, 2018

NEWS-G @ SNOLAB: Looking for Weakly Interacting (not so) Massive Particles with a Spherical Proportional Counter

One of the oldest tool for detecting ionizing particles, gas detectors still have a wide range of applications. Gas ionization requires little energy, typically few tens of electron-volt. Thus it is an attractive technology to look for the elusive dark matter, which is thought to be 5 times more abundant than baryonic matter in the Universe.

The Weakly Interacting Massive Particles (WIMP) with a mass higher than 10’s GeV/c2 has been a favoured candidate for dark matter. It is in part because they are predicted by popular extensions of the Standard Model, the Super Symmetry (SUSY) models. But decades of search for WIMPs and SUSY particles have yet to give positive results. So the hunt has been extended to lower masses with a new generation of detectors aiming at sub-GeV WIMPs.

In this field, NEWS-G proposes to use a Spherical Proportional Counter (SPC) of large diameter. Thank to its geometry, such detector has a very low intrinsic electronic noise and high gain capability due to the avalanche mechanism. It maximizes the low threshold potential of the gas detector. The SEDINE detector (60 cm diameter) has been running at the Laboratoire Souterrain de Modane for the past few years, providing worldwide leading sensitivity at sub-GeV dark matter mass. Using the gathered experience, a 1.4 m diameter detector is now under construction. To maximize the sensitivity to a light WIMP interaction, the sphere will be filled with light gases mixtures (Ne, He or H-based). It will be deployed at SNOLAB (Sudbury, ON), where the 2 km of rock overburden will provide adequate shielding against cosmic rays.

In this talk, I will introduce the principle of the SPC and give an overview of the dark matter question. I will then describe the results provided by the SEDINE detector. I will end with a full description of NEWS-G at SNOLAB and its physics program.