arXiv subjects

Rubén Alfaro

Publications and source records attributed to Rubén Alfaro.

6 recordsLinked to original sources

arXiv2025

Dark photon constraints using the UHE gamma-ray emission from galactic sources. A Phenomenological Study

Context: Dark photons (Dph) appear in theories beyond the Standard Model of particles (SM). Under certain conditions, it is possible to have a mixing between SM photons and Dphs that should be observed as anomalies in the spectrum of astrophysical sources. Aim: To either find evidence of, or set constraints on the existence of Dphs with masses in the range of $μ\text{eV}$ using observations of two galactic sources observed at TeV energies. Methods: Using the flux of the Crab Nebula and MGRO J1908+06 at TeV energies reported by HAWC and LHAASO observatories, and assuming a model where Dphs can mix with SM photons in the vacuum; we compute the Test Statistic (TS) to search for evidence of Dphs in the form of variations/attenuation in the observed spectrum. Results: We do not find statistically significant evidence of the existence of $μ\text{eV}$ Dphs. Then, we compute the 68\% C.L. and 95\% C.L. exclusion regions for Dphs with masses in the range from $10^{-8}$ to $10^{-5}~\text{eV}$ and mixing angles with values between 0.01 and 1.0.

astro-ph.HE↗

arXiv2019

Monitoring radio galaxies at TeV energies with HAWC

With an instantaneous field of view of 2 sr and a duty cycle > 95%, the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is a perfect instrument for monitoring variable TeV sources. Because radio galaxies are a type of Active Galactic Nuclei (AGN) with their jets misaligned with respect to our line of sight, they may help us to probe the physics of very-high-energy (VHE) emission processes in these objects. Three out of four radio galaxies that have been detected at TeV energies by other facilities are located within the field of view of the HAWC Observatory: M87, NGC 1275, and 3C 264. A search for TeV gamma rays at their locations yields no statistically significant excess of counts. We present corresponding upper limits for each radio galaxy and light curves covering 3 years of data taken with HAWC.

astro-ph.HE↗

arXiv2017

Observation of radio galaxies with HAWC

The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is an extensive air shower array located in Puebla, Mexico. The closest radio galaxy within the HAWC field of view, M87, has been detected in very high energies. In this work we report upper limits on the TeV γ-ray flux of the radio galaxy M87. At a distance of 16 Mpc, M87 is a supergiant elliptical galaxy located in the Virgo Cluster that has been observed from radio wavelengths to TeV γ-rays. Although a single-zone synchrotron self-Compton model has been successfully used to explain the spectral energy distribution of this source up to a few GeV, the γ-ray spectrum at TeV has been interpreted within different theoretical models. We discuss the implications of these upper limits on the photo-hadronic interactions, as well as the number of neutrino events expected in the IceCube neutrino telescope.

astro-ph.HE↗

arXiv2017

Detection of vertical muons with the HAWC water Cherenkov detectors and its application to gamma/hadron discrimination

The HAWC observatory reconstructs atmospheric showers induced by very high-energy primary cosmic- or gamma-rays. Cosmic-rays with hadronic nature are several orders of magnitude more frequent than primary gammas and therefore it is necessary to perform the best gamma-hadron discrimination for each event to be able to survey the gamma-ray sky. Single vertical muons cause very characteristic signals in the 300 HAWC detectors. Particularly, those events that produce signals in the four PMTs of a tank corresponding to muons traversing the tank in the central region. In such cases exist the correlation that the largest signal is also the earliest to arrive, this due to the geometry of the Cherenkov light emission and the fact that relativistic muons travel faster than the light in the medium. This pattern is different from that of electrons, positrons and low energy gammas showering in the first meter of the tank water, which is typical of electromagnetic showers. In this work, we explored whether in air-showers it is possible to identify muon signals and whether this can help in the gamma/hadron discrimination of the recorded events.

astro-ph.IM↗

arXiv2017

Searching for TeV DM evidence from Dwarf Irregular Galaxies with the HAWC Observatory

The dynamics of dwarf irregular (dIrr) galaxies are observed to be dominated by dark matter (DM). Recently, the DM density distribution has been studied for 31 dIrrs. Their extended DM halo (Burket type profile) makes these objects good candidates for DM searches. Located in Puebla (Mexico), the High Altitude Water Cherenkov (HAWC) Observatory is an optimal in- strument to perform such DM searches, because of its large sky coverage (8.4 sr per day). We analyzed a set of two years of HAWC data and we found no significant DM signal from dIrr galaxies. We present the upper limits for DM annihilation cross-section with dIrr galaxies.

astro-ph.HE↗

arXiv2017

Capability of the HAWC gamma-ray observatory for the indirect detection of ultra-high energy neutrinos

The detection of ultra-high energy neutrinos, with energies in the PeV range or above, is a topic of great interest in modern astroparticle physics. The importance comes from the fact that these neutrinos point back to the most energetic particle accelerators in the Universe, and provide information about their underlying acceleration mechanisms. Atmospheric neutrinos are a background for these challenging measurements, but their rate is expected to be negligible above $\approx$ 1 PeV. In this work we describe the feasibility to study ultra-high energy neutrinos based on the Earth-skimming technique, by detecting the charged leptons produced in neutrino-nucleon interactions in a high mass target. We propose to detect the charged leptons, or their decay products, with the High Altitude Water Cherenkov (HAWC) observatory, and use as a large mass target for the neutrino interactions the Pico de Orizaba volcano, the highest mountain in Mexico. In this work we develop an estimate of the detection rate using a geometrical model to calculate the effective area of the observatory. Our results show that it may be feasible to perform measurements of the ultra-high energy neutrino flux from cosmic origin during the expected lifetime of the HAWC observatory.

astro-ph.IM↗