Line-of-Sight Trigger(LOST) project of LHAASO-WCDA

With a large field-of-view and almost full duty cycle, LHAASO-WCDA is appropriate to monitor the VHE emission from extra-galactic transient sources like GRBs and AGNs, or galactic variable sources like binaries, pulsars and nova. However, these sources either suffer from severe EBL absorption at high energies or have an energy spectral cutoff at sub-TeV range, making them faint or even invisible with the current sensitivity of WCDA. To fulfill WCDA’s potential, we came up with the Line-of-Sight-Trigger(LOST) to lower WCDA’s energy threshold to < 100GeV range. The main id,,ea of LOST is to have WCDA imitate a telescope, point to the source direction to enable a looser trigger and reconstruct lower energy events. We present the performance estimation of LOST and preliminary results on experiment.