Pass 8: Toward the Full Realization of the Fermi-LAT Scientific Potential

TL;DR

This paper discusses the development of Pass 8, a comprehensive overhaul of the Fermi-LAT data analysis pipeline, aiming to enhance sensitivity, reduce background, and extend energy coverage for gamma-ray observations.

Contribution

It introduces Pass 8, a major revision of the Fermi-LAT event analysis, improving data quality and expanding energy range based on extensive detector and environment understanding.

Findings

Reduced background contamination and increased effective area.

Improved point-spread function and systematic uncertainty understanding.

Extended energy reach below 100 MeV and above a few hundred GeV.

Abstract

The event selection developed for the Fermi Large Area Telescope before launch has been periodically updated to reflect the constantly improving knowledge of the detector and the environment in which it operates. Pass 7, released to the public in August 2011, represents the most recent major iteration of this incremental process. In parallel, the LAT team has undertaken a coherent long-term effort aimed at a radical revision of the entire event-level analysis, based on the experience gained in the prime phase of the mission. This includes virtually every aspect of the data reduction process, from the simulation of the detector to the event reconstruction and the background rejection. The potential improvements include (but are not limited to) a significant reduction in background contamination coupled with an increased effective area, a better point-spread function, a better understanding of the systematic uncertainties and an extension of the energy reach for the photon analysis below 100 MeV and above a few hundred GeV. We present an overview of the work that has been done or is ongoing and the prospects for the near future.