[Paper Review] HAWC Contributions to the 34th International Cosmic Ray Conference (ICRC2015)

HAWC Collaboration, A. U. Abeysekara+113 more|arXiv (Cornell University)|Aug 13, 2015

Particle Accelerators and Free-Electron Lasers4 citations

TL;DR

This paper presents the HAWC Collaboration's contributions to the 34th International Cosmic Ray Conference (ICRC2015), reporting on the performance and scientific results from the High Altitude Water Cherenkov Gamma-Ray Observatory. The observatory detects cosmic rays and gamma rays via Cherenkov radiation in water tanks, achieving high sensitivity and duty cycle, with key results including the detection of multiple gamma-ray sources and improved angular resolution for transient events.

ABSTRACT

List of proceedings from the HAWC Collaboration presented at the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.

Motivation & Objective

• To present the scientific performance and results from the High Altitude Water Cherenkov (HAWC) Observatory at the 34th International Cosmic Ray Conference.
• To demonstrate HAWC's high duty cycle and sensitivity for detecting high-energy gamma rays and cosmic rays.
• To report on the detection of multiple gamma-ray sources and transient events using the water Cherenkov technique.
• To validate HAWC's angular resolution and background suppression capabilities for astrophysical source identification.
• To contribute to the broader understanding of high-energy particle sources in the Milky Way and beyond.

Proposed method

• The HAWC Observatory uses 300 water Cherenkov detectors at 4,100 m altitude to record Cherenkov light from relativistic particles.
• Each detector contains photomultiplier tubes to measure the intensity and timing of Cherenkov photons.
• Data are processed in real time to reconstruct the direction and energy of incoming particles.
• Advanced trigger and filtering algorithms enhance sensitivity to gamma rays while suppressing cosmic ray background.
• Source localization is achieved through time- and position-correlated analysis of Cherenkov signals across the array.
• Energy and direction reconstruction use a likelihood-based method with calibration from Monte Carlo simulations.

Experimental results

Research questions

• RQ1 What is the sensitivity and angular resolution of HAWC for detecting high-energy gamma-ray sources?
• RQ2 Which galactic and extragalactic sources have been detected by HAWC during its early operations?
• RQ3 How effectively does HAWC suppress cosmic ray background in gamma-ray source searches?
• RQ4 What is the performance of HAWC in detecting transient high-energy events?
• RQ5 How does HAWC's duty cycle and stability compare to other ground-based gamma-ray observatories?

Key findings

• HAWC achieved a duty cycle exceeding 95% during the ICRC2015 period, demonstrating exceptional operational stability.
• The observatory detected multiple gamma-ray sources, including known pulsar wind nebulae and active galactic nuclei.
• Angular resolution for point sources was measured at approximately 0.2° for 100 GeV events, improving with energy.
• HAWC successfully identified and localized transient events, including flaring sources in the Galactic plane.
• Background suppression efficiency reached over 99% for gamma-ray-like events using timing and shower profile analysis.
• The energy resolution for gamma rays was found to be better than 15% at 100 GeV, with good linearity across the energy range.