Measurement of threshold of superheated liquid detector for dark matter search

The existence of dark matter (DM) offers a good explanation for various astrophysical and cosmological phenomena, ranging from rotation of the galaxies to the large scale inhomogeneities in the cosmic microwave background radiation. Weakly Interacting Massive Particles (WIMPs) are the most promising DM candidates. WIMPs are expected to interact with the detector nuclei via elastic scattering similar to neutrons, resulting in nuclear recoils. Direct detection of DM experiments are looking for the signature of nuclear recoils produced by WIMPs. The superheated liquid detector technology provides a promising approach to direct detection of DM search experiment. PICO is one of such dark matter search experiment running at SNOlab, Sudbury with bubble chamber containing superheated liquid as the target. In addition to the high mass region, the future DM experiments are aiming to search for the signal in the low WIMP mass region also. For the investigation of low WIMP mass region (below 10 GeV/c 2 ), the target containing hydrogen nuclei is effective. In the lower WIMP mass region, the detector needs to be operated at lower threshold energy. The Superheated liquid detector is sensitive to gamma rays at lower threshold. Therefore, for the low mass WIMP run at lower threshold, the gamma sensitive temperature of the detector needs to be investigated. In the present work R-134A (C2H2F4, b.p.-26.3 0 C) liquid has been chosen as active liquid in Superheated Droplet Detector. Experimental study has been performed to determine the gamma threshold temperature. The threshold energy for bubble nucleation at various temperatures has been calculated. The energy deposition inside the liquid has been calculated using SRIM code and the required ion energy for bubble nucleation at the various temperatures including the threshold has been estimated.