1,138 research outputs found
Gamma/Hadron Separation with the HAWC Observatory
The High Altitude Water Cherenkov (HAWC) gamma-ray observatory observesatmospheric showers produced by incident gamma rays and cosmic rays with energyfrom 300 GeV to more than 100 TeV. A crucial phase in analyzing gamma-raysources using ground-based gamma-ray detectors like HAWC is to identify theshowers produced by gamma rays or hadrons. The HAWC observatory records roughly25,000 events per second, with hadrons representing the vast majority() of these events. The standard gamma/hadron separation technique inHAWC uses a simple rectangular cut involving only two parameters. This workdescribes the implementation of more sophisticated gamma/hadron separationtechniques, via machine learning methods (boosted decision trees and neuralnetworks), and summarizes the resulting improvements in gamma/hadron separationobtained in HAWC.<br
Searching for TeV Dark Matter in Irregular dwarf galaxies with HAWC Observatory
We present the results of dark matter (DM) searches in a sample of 31 dwarf
irregular (dIrr) galaxies within the field of view of the HAWC Observatory.
dIrr galaxies are DM dominated objects, which astrophysical gamma-ray emission
is estimated to be negligible with respect to the secondary gamma-ray flux
expected by annihilation or decay of Weakly Interacting Massive Particles
(WIMPs). While we do not see any statistically significant DM signal in dIrr
galaxies, we present the exclusion limits () for annihilation
cross-section and decay lifetime for WIMP candidates with masses between
and . Exclusion limits from dIrr galaxies are relevant and
complementary to benchmark dwarf Spheroidal (dSph) galaxies. In fact, dIrr
galaxies are targets kinematically different from benchmark dSph, preserving
the footprints of different evolution histories. We compare the limits from
dIrr galaxies to those from ultrafaint and classical dSph galaxies previously
observed with HAWC. We find that the contraints are comparable to the limits
from classical dSph galaxies and orders of magnitude weaker than
the ultrafaint dSph limits.Comment: 22 pages, 11 figures, 3 table
The TeV Sun Rises: Discovery of Gamma rays from the Quiescent Sun with HAWC
We report the first detection of a TeV gamma-ray flux from the solar disk
(6.3), based on 6.1 years of data from the High Altitude Water
Cherenkov (HAWC) observatory. The 0.5--2.6 TeV spectrum is well fit by a power
law, dN/dE = , with TeV cm s and . The flux
shows a strong indication of anticorrelation with solar activity. These results
extend the bright, hard GeV emission from the disk observed with Fermi-LAT,
seemingly due to hadronic Galactic cosmic rays showering on nuclei in the solar
atmosphere. However, current theoretical models are unable to explain the
details of how solar magnetic fields shape these interactions. HAWC's TeV
detection thus deepens the mysteries of the solar-disk emission.Comment: 15 pages, 8 figures including supplementary material. Accepted for
publication in Physical Review Letter
Limits on the Diffuse Gamma-Ray Background above 10 TeV with HAWC
The high-energy Diffuse Gamma-Ray Background (DGRB) is expected to be
produced by unresolved isotropically distributed astrophysical objects,
potentially including dark matter annihilation or decay emissions in galactic
or extragalactic structures. The DGRB has only been observed below 1 TeV; above
this energy, upper limits have been reported. Observations or stringent limits
on the DGRB above this energy could have significant multi-messenger
implications, such as constraining the origin of TeV-PeV astrophysical
neutrinos detected by IceCube. The High Altitude Water Cherenkov (HAWC)
Observatory, located in central Mexico at 4100 m above sea level, is sensitive
to gamma rays from a few hundred GeV to several hundred TeV and continuously
observes a wide field-of-view (2 sr). With its high-energy reach and large area
coverage, HAWC is well-suited to notably improve searches for the DGRB at TeV
energies. In this work, strict cuts have been applied to the HAWC dataset to
better isolate gamma-ray air showers from background hadronic showers. The
sensitivity to the DGRB was then verified using 535 days of Crab data and Monte
Carlo simulations, leading to new limits above 10 TeV on the DGRB as well as
prospective implications for multi-messenger studies.Comment: 8 pages, 3 figure
Gamma-ray Emission from Classical Nova V392 Per: Measurements from Fermi and HAWC
This paper reports on the -ray properties of the 2018 Galactic novaV392 Per, spanning photon energies 0.1 GeV to 100 TeV by combiningobservations from the Fermi Gamma-ray Space Telescope and the HAWC Observatory.In one of the most rapidly evolving -ray signals yet observed for anova, GeV rays with a power law spectrum with index were detected over eight days following V392 Per's optical maximum. HAWCobservations constrain the TeV -ray signal during this time and alsobefore and after. We observe no statistically significant evidence of TeV-ray emission from V392 Per, but present flux limits. Tests of theextension of the Fermi/LAT spectrum to energies above 5 TeV are disfavored by 2standard deviations (95\%) or more. We fit V392 Per's GeV rays withhadronic acceleration models, incorporating optical observations, and comparethe calculations with HAWC limits.<br
Search for Gamma-Ray and Neutrino Coincidences Using HAWC and ANTARES Data
In the quest for high-energy neutrino sources, the Astrophysical
Multimessenger Observatory Network (AMON) has implemented a new search by
combining data from the High Altitude Water Cherenkov (HAWC) observatory and
the Astronomy with a Neutrino Telescope and Abyss environmental RESearch
(ANTARES) neutrino telescope. Using the same analysis strategy as in a previous
detector combination of HAWC and IceCube data, we perform a search for
coincidences in HAWC and ANTARES events that are below the threshold for
sending public alerts in each individual detector. Data were collected between
July 2015 and February 2020 with a livetime of 4.39 years. Over this time
period, 3 coincident events with an estimated false-alarm rate of
coincidence per year were found. This number is consistent with background
expectations.Comment: 12 pages, 5 figures, 3 table
Horizontal muon track identification with neural networks in HAWC
Nowadays the implementation of artificial neural networks in high-energyphysics has obtained excellent results on improving signal detection. In thiswork we propose to use neural networks (NNs) for event discrimination in HAWC.This observatory is a water Cherenkov gamma-ray detector that in recent yearshas implemented algorithms to identify horizontal muon tracks. However, thesealgorithms are not very efficient. In this work we describe the implementationof three NNs: two based on image classification and one based on objectdetection. Using these algorithms we obtain an increase in the number ofidentified tracks. The results of this study could be used in the future toimprove the performance of the Earth-skimming technique for the indirectmeasurement of neutrinos with HAWC.<br
A Contribution of the HAWC Observatory to the TeV era in the High Energy Gamma-Ray Astrophysics: The case of the TeV-Halos
We present a short overview of the TeV-Halos objects as a discovery and a
relevant contribution of the High Altitude Water \v{C}erenkov (HAWC)
observatory to TeV astrophysics. We discuss history, discovery, knowledge, and
the next step through a new and more detailed analysis than the original study
in 2017. TeV-Halos will contribute to resolving the problem of the local
positron excess observed on the Earth. To clarify the latter, understanding the
diffusion process is mandatory.Comment: Work presented in the 21st International Symposium on Very High
Energy Cosmic Ray Interactions(ISVHECRI 2022) as part of the Ph. D. Thesis of
Ramiro Torres-Escobedo (SJTU, Shanghai, China). Accepted for publication in
SciPost Physics Proceedings (ISSN 2666-4003). 11 pages, 3 Figures. Short
overview of HAWC and TeV Halos objects until 202
The High-Altitude Water Cherenkov (HAWC) Observatory in M\'exico: The Primary Detector
The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation
continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC
observatory and its analysis techniques build on experience of the Milagro
experiment in using ground-based water Cherenkov detectors for gamma-ray
astronomy. HAWC is located on the Sierra Negra volcano in M\'exico at an
elevation of 4100 meters above sea level. The completed HAWC observatory
principal detector (HAWC) consists of 300 closely spaced water Cherenkov
detectors, each equipped with four photomultiplier tubes to provide timing and
charge information to reconstruct the extensive air shower energy and arrival
direction. The HAWC observatory has been optimized to observe transient and
steady emission from sources of gamma rays within an energy range from several
hundred GeV to several hundred TeV. However, most of the air showers detected
are initiated by cosmic rays, allowing studies of cosmic rays also to be
performed. This paper describes the characteristics of the HAWC main array and
its hardware.Comment: Accepted for publications in Nuclear Inst. and Methods in Physics
Research, A (2023) 168253 (
https://www.sciencedirect.com/science/article/abs/pii/S0168900223002437 ); 39
pages, 14 Figure
- …