Performance of the Large-Sized Telescope prototype of the Cherenkov Telescope Array

TL;DR

This paper evaluates the performance of the LST-1 prototype of the Cherenkov Telescope Array, demonstrating its capabilities in gamma-ray detection, energy resolution, and sensitivity through observations and simulations.

Contribution

It provides the first detailed performance analysis of the LST-1 prototype, including key metrics like energy threshold, resolution, and sensitivity, based on real and simulated data.

Findings

Energy threshold estimated at 30 GeV

Angular resolution of 0.3 degrees at 100 GeV

Sensitivity of about 1.1% Crab flux above 250 GeV

Abstract

The next-generation ground-based gamma-ray Cherenkov Telescope Array Observatory (CTAO) will consist of imaging atmospheric Cherenkov telescopes (IACTs) of three different sizes distributed in two sites. The Large-Sized Telescopes will cover the low-energy end of the CTA energy range, starting at about 20 GeV. After its first years of operation at the CTA northern site, the Large-Sized Telescope prototype (LST-1) is in the final stage of its commissioning phase, having collected a significant amount of scientific data to date. In this contribution, we present the physics performance of the telescope using low-zenith Crab Nebula observations and Monte Carlo simulations fine-tuned accordingly. We show performance figures of merit such as the energy threshold, effective area, energy and angular resolution, and sensitivity based on the standard Hillas-parameters approach and following the source-independent and dependent analysis methods. The analysis threshold is estimated at 30 GeV. The energy resolution is around 30%, and the angular resolution is 0.3 degrees at 100 GeV. The best integral sensitivity of LST-1 is about 1.1% of the Crab Nebula flux above 250 GeV for 50 hours of observations. We also show the spectral energy distribution and light curve from Crab Nebula observations, which agree with results from other IACTs and link smoothly with Fermi-LAT when considering statistical and systematic uncertainties near the energy threshold.