First limit on WIMP cross section with low background CsI(Tℓ) crystal detector

The Korea Invisible Mass Search (KIMS) Collaboration has been carrying out WIMP search experiment with CsI(Tℓ) crystal detectors at the YangYang Underground Laboratory. A successful reduction of the internal background of the crystal was done and a good pulse shape discrimination was achieved. We report the first result on WIMP search obtained with 237 kg days data using one full-size CsI(Tℓ) crystal of 6.6 kg mass.