arXiv subjects

C. W. James

Publications and source records attributed to C. W. James.

At least 55 records · Page 3Linked to original sources

arXiv2022

Search for solar atmospheric neutrinos with the ANTARES neutrino telescope

Solar Atmospheric Neutrinos (SA$ν$s) are produced by the interaction of cosmic rays with the solar medium. The detection of SA$ν$s would provide useful information on the composition of primary cosmic rays as well as the solar density. These neutrinos represent an irreducible source of background for indirect searches for dark matter towards the Sun and the measurement of their flux would allow for a better assessment of the uncertainties related to these searches. In this paper we report on the analysis performed, based on an unbinned likelihood maximisation, to search for SA$ν$s with the ANTARES neutrino telescope. After analysing the data collected over 11 years, no evidence for a solar atmospheric neutrino signal has been found. An upper limit at 90\% confidence level on the flux of solar atmospheric neutrinos has been obtained, equal to 7$\times$$10^{-11}$ [TeV$^{-1}$cm$^{-2}$s$^{-1}$] at E$_ν=$ 1 TeV for the reference cosmic ray model assumed.

astro-ph.HE↗

arXiv2022

Search for non-standard neutrino interactions with 10 years of ANTARES data

Non-standard interactions of neutrinos arising in many theories beyond the Standard Model can significantly alter matter effects in atmospheric neutrino propagation through the Earth. In this paper, a search for deviations from the prediction of the standard 3-flavour atmospheric neutrino oscillations using the data taken by the ANTARES neutrino telescope is presented. Ten years of atmospheric neutrino data collected from 2007 to 2016, with reconstructed energies in the range from $\sim$16 GeV to $100$ GeV, have been analysed. A log-likelihood ratio test of the dimensionless coefficients $\varepsilon_{μτ}$ and $\varepsilon_{ττ} - \varepsilon_{μμ}$ does not provide clear evidence of deviations from standard interactions. For normal neutrino mass ordering, the combined fit of both coefficients yields a value 1.7$σ$ away from the null result. However, the 68% and 95% confidence level intervals for $\varepsilon_{μτ}$ and $\varepsilon_{ττ} - \varepsilon_{μμ}$, respectively, contain the null value. Best fit values, one standard deviation errors and bounds at the 90% confidence level for these coefficients are given for both normal and inverted mass orderings. The constraint on $\varepsilon_{μτ}$ is among the most stringent to date and it further restrains the strength of possible non-standard interactions in the $μ- τ$ sector.

hep-ex↗

arXiv2022

Comparison of the Parkes and FAST FRB DM Distribution

We model the Fast Radio Burst (FRB) dispersion measure (DM) distribution for the Five-hundred-meter Aperture Spherical Telescope (FAST) and compare this with the four FRBs published in the literature to date. We compare the DM distribution of Parkes and FAST, taking advantage of the similarity between their multibeam receivers. Notwithstanding the limited sample size, we observe a paucity of events at low DM for all evolutionary models considered, resulting in a sharp rise in the observed cumulative distribution function (CDF) in the region of $1000\lesssim\mathrm{DM}\lesssim2000$ pc cm$^{-3}$. These traits could be due to statistical fluctuations ($0.12 \le p \le 0.22$), a complicated energy distribution or break in an energy distribution power law, spatial clustering, observational bias or outliers in the sample (e.g., an excessive DM_${HOST}$ as recently found for FRB 20190520B). The energy distribution in this regime is unlikely to be adequately constrained until further events are detected. Modelling suggests that FAST may be well placed to discriminate between redshift evolutionary models and to probe the helium ionisation signal of the IGM.

astro-ph.HE↗

arXiv2022

Search for secluded dark matter towards the Galactic Centre with the ANTARES neutrino telescope

Searches for dark matter (DM) have not provided any solid evidence for the existence of weakly interacting massive particles in the GeV-TeV mass range. Coincidentally, the scale of new physics is being pushed by collider searches well beyond the TeV domain. This situation strongly motivates the exploration of DM masses much larger than a TeV. Secluded scenarios contain a natural way around the unitarity bound on the DM mass, via the early matter domination induced by the mediator of its interactions with the Standard Model. High-energy neutrinos constitute one of the very few direct accesses to energy scales above a few TeV. An indirect search for secluded DM signals has been performed with the ANTARES neutrino telescope using data from 2007 to 2015. Upper limits on the DM annihilation cross section for DM masses up to 6 PeV are presented and discussed.

astro-ph.HE↗

arXiv2022

Search for Magnetic Monopoles with ten years of the ANTARES neutrino telescope

This work presents a new search for magnetic monopoles using data taken with the ANTARES neutrino telescope over a period of 10 years (January 2008 to December 2017). Compared to previous ANTARES searches, this analysis uses a run-by-run simulation strategy, with a larger exposure as well as a new simulation of magnetic monopoles taking into account the Kasama, Yang and Goldhaber model for their interaction cross-section with matter. No signal compatible with the passage of relativistic magnetic monopoles is observed, and upper limits on the flux of magnetic monopoles with $β$ = v/c $\geq$ 0.55, are presented. For ultra-relativistic magnetic monopoles the flux limit is $\sim$ 7$\times$$10^{-18}$ $\rm cm^{-2} s^{-1} sr^{-1}$.

astro-ph.HE↗

arXiv2021

Studying Bioluminescence Flashes with the ANTARES Deep Sea Neutrino Telescope

We develop a novel technique to exploit the extensive data sets provided by underwater neutrino telescopes to gain information on bioluminescence in the deep sea. The passive nature of the telescopes gives us the unique opportunity to infer information on bioluminescent organisms without actively interfering with them. We propose a statistical method that allows us to reconstruct the light emission of individual organisms, as well as their location and movement. A mathematical model is built to describe the measurement process of underwater neutrino telescopes and the signal generation of the biological organisms. The Metric Gaussian Variational Inference algorithm is used to reconstruct the model parameters using photon counts recorded by the neutrino detectors. We apply this method to synthetic data sets and data collected by the ANTARES neutrino telescope. The telescope is located 40 km off the French coast and fixed to the sea floor at a depth of 2475 m. The runs with synthetic data reveal that we can reliably model the emitted bioluminescent flashes of the organisms. Furthermore, we find that the spatial resolution of the localization of light sources highly depends on the configuration of the telescope. Precise measurements of the efficiencies of the detectors and the attenuation length of the water are crucial to reconstruct the light emission. Finally, the application to ANTARES data reveals the first precise localizations of bioluminescent organisms using neutrino telescope data.

physics.ao-ph↗

arXiv2021

Murchison Widefield Array rapid-response observations of the short GRB 180805A

Here we present stringent low-frequency 185MHz limits on coherent radio emission associated with a short gamma-ray burst (SGRB). Our observations of the short GRB 180805A were taken with the upgraded Murchison Widefield Array (MWA) rapid-response system, which triggered within 20s of receiving the transient alert from Swift, corresponding to 83.7s post-burst. The SGRB was observed for 30m, resulting in a 3sigma persistent flux density upper-limit of 40.2mJy/beam. Transient searches were conducted at the Swift position of this GRB on 0.5s, 5s, 30s, and 2m timescales, resulting in 3sigma limits of 570-1830, 270-630, 200-420, and 100-200mJy/beam, respectively. We also performed a dedispersion search for prompt signals at the position of the SGRB with a temporal and spectral resolution of 0.5s and 1.28MHz, resulting in a 6sigma fluence upper-limit range from 570Jyms at DM=3000pc/cm^3 (z~2.5) to 1750Jyms at DM=200pc/cm^3 (z~0.1). We compare the fluence prompt emission limit and the persistent upper-limit to SGRB coherent emission models assuming the merger resulted in a stable magnetar. Our observations were not sensitive enough to detect prompt emission associated with the alignment of magnetic fields of a binary neutron star just prior to the merger, from the interaction between the relativistic jet and the interstellar medium or persistent pulsar-like emission from the spin-down of the magnetar. However, in the case of a more powerful SGRB (a gamma-ray fluence an order of magnitude higher than GRB 180805A and/or a brighter X-ray counterpart), our MWA observations may be sensitive enough to detect coherent radio emission from the jet-ISM interaction and/or the magnetar remnant. Finally, we demonstrate that of all current low-frequency radio telescopes, only the MWA has the sensitivity and response times capable of probing prompt emission models associated with the initial SGRB merger event.

astro-ph.HE↗

arXiv2021

Search for neutrinos from the tidal disruption events AT2019dsg and AT2019fdr with the ANTARES telescope

On October 1, 2019, the IceCube Collaboration detected a muon track neutrino with high probability of being of astrophysical origin, IC191001A. After a few hours, the tidal disruption event (TDE) AT2019dsg, observed by the Zwicky Transient Facility (ZTF), was indicated as the most likely counterpart of the IceCube track. More recently, the follow-up campaign of the IceCube alerts by ZTF suggested a second TDE, AT2019fdr, as a promising counterpart of another IceCube muon track candidate, IC200530A, detected on May 30, 2020. These are the second and third associations between astrophysical sources and high-energy neutrinos after the compelling identification of the blazar TXS 0506+056. Here, the search for ANTARES neutrinos from the directions of AT2019dsg and AT2019fdr using a time-integrated approach is presented. As no significant evidence for space clustering is found in the ANTARES data, upper limits on the one-flavour neutrino flux and fluence are set.

astro-ph.HE↗

arXiv2021

Measurement of the atmospheric $ν_e$ and $ν_μ$ energy spectra with the ANTARES neutrino telescope

This letter presents a combined measurement of the energy spectra of atmospheric $ν_e$ and $ν_μ$ in the energy range between $\sim$100 GeV and $\sim$50 TeV with the ANTARES neutrino telescope. The analysis uses 3012 days of detector livetime in the period 2007--2017, and selects 1016 neutrinos interacting in (or close to) the instrumented volume of the detector, yielding shower-like events (mainly from $ν_e+\overline ν_e$ charged current plus all neutrino neutral current interactions) and starting track events (mainly from $ν_μ+ \overline ν_μ$ charged current interactions). The contamination by atmospheric muons in the final sample is suppressed at the level of a few per mill by different steps in the selection analysis, including a Boosted Decision Tree classifier. The distribution of reconstructed events is unfolded in terms of electron and muon neutrino fluxes. The derived energy spectra are compared with previous measurements that, above 100 GeV, are limited to experiments in polar ice and, for $ν_μ$, to Super-Kamiokande.

hep-ex↗

arXiv2021

The fast radio burst population evolves, consistent with the star-formation rate

Fast radio bursts (FRBs) are extremely powerful sources of radio waves observed at cosmological distances. We use a sophisticated model of FRB observations -- presented in detail in a companion paper -- to fit FRB population parameters using large samples of FRBs detected by ASKAP and Parkes, including seven sources with confirmed host galaxies. Our fitted parameters demonstrate that the FRB population evolves with redshift in a manner consistent with, or faster than, the star-formation rate (SFR), ruling out a non-evolving population at 99.9\% C.L. Our estimated maximum FRB energy is $\log_{10} E_{\rm max} [{\rm erg}] = 41.84_{-0.18}^{+0.49}$ (68\% C.L.) assuming a 1\,GHz emission bandwidth, with slope of the cumulative luminosity distribution $γ=-1.16_{-0.12}^{+0.11}$. We find a log-mean host DM contribution of $145_{-60}^{+64}$\,pc\,cm$^{-3}$ on top of a typical local (ISM and halo) contribution of $\sim80$\,pc\,cm$^{-3}$, which is higher than most literature values. These results are consistent with the model of FRBs arising as the high-energy limit of magnetar bursts, but allow for FRB progenitors that evolve faster than the SFR.

astro-ph.HE↗

arXiv2021

An Ultra-High Time Resolution Cosmic Ray Detection Mode for the Murchison Widefield Array

The radio-wavelength detection of extensive air showers (EAS) initiated by cosmic-ray interactions in the Earth's atmosphere is a promising technique for investigating the origin of these particles and the physics of their interactions. The Low Frequency Array (LOFAR) and the Owens Valley Long Wavelength Array (OVRO-LWA) have both demonstrated that the dense cores of low frequency radio telescope arrays yield detailed information on the radiation ground pattern, which can be used to reconstruct key EAS properties and infer the primary cosmic-ray composition. Here, we demonstrate a new observation mode of the Murchison Widefield Array (MWA), tailored to the observation of the sub-microsecond coherent bursts of radiation produced by EAS. We first show how an aggregate 30.72 MHz bandwidth (3072x 10 kHz frequency channels) recorded at 0.1 ms resolution with the MWA's voltage capture system (VCS) can be synthesised back to the full bandwidth Nyquist resolution of 16.3 ns. This process, which involves `inverting' two sets of polyphase filterbanks, retains 90.5% of the signal-to-noise of a cosmic ray signal. We then demonstrate the timing and positional accuracy of this mode by resolving the location of a calibrator pulse to within 5 m. Finally, preliminary observations show that the rate of nanosecond radio-frequency interference (RFI) events is 0.1 Hz, much lower than that found at the sites of other radio telescopes that study cosmic rays. We conclude that the identification of cosmic rays at the MWA, and hence with the low-frequency component of the Square Kilometre Array, is feasible with minimal loss of efficiency due to RFI.

astro-ph.IM↗

arXiv2021

ANTARES upper limits on the multi-TeV neutrino emission from the GRBs detected by IACTs

The first gamma-ray burst detections by Imaging Atmospheric Cherenkov Telescopes have been recently announced: GRB 190114C, detected by MAGIC, GRB 180720B and GRB 190829A, observed by H.E.S.S. A dedicated search for neutrinos in space and time coincidence with the gamma-ray emission observed by IACTs has been performed using ANTARES data. The search covers both the prompt and afterglow phases, yielding no neutrinos in coincidence with the three GRBs studied. Upper limits on the energetics of the neutrino emission are inferred. The resulting upper limits are several orders of magnitude above the observed gamma-ray emission, and they do not allow to constrain the available models.

astro-ph.HE↗

arXiv2021

Search for neutrino counterparts of gravitational-wave events detected by LIGO and Virgo during run O2 with the ANTARES telescope

An offline search for a neutrino counterpart to gravitational-wave (GW) events detected during the second observation run (O2) of Advanced-LIGO and Advanced-Virgo performed with ANTARES data is presented. In addition to the search for long tracks induced by $ν_μ$ ($\barν_μ$) charged current interactions, a search for showering events induced by interactions of neutrinos of any flavour is conducted. The severe spatial and time coincidence provided by the gravitational-wave alert allows regions above the detector horizon to be probed, extending the ANTARES sensitivity over the entire sky. The results of this all-neutrino-flavour and all-sky time dependent analysis are presented. The search for prompt neutrino emission within $\pm$500~s around the time of six GW events yields no neutrino counterparts. Upper limits on the neutrino spectral fluence and constraints on the isotropic radiated energy are set for each GW event analysed.

astro-ph.HE↗

arXiv2020

The Fast Radio Burst Dispersion Measure Distribution

We compare the dispersion measure (DM) statistics of FRBs detected by the ASKAP and Parkes radio telescopes. We jointly model their DM distributions, exploiting the fact that the telescopes have different survey fluence limits but likely sample the same underlying population. After accounting for the effects of instrumental temporal and spectral resolution of each sample, we find that a fit between the modelled and observed DM distribution, using identical population parameters, provides a good fit to both distributions. Assuming a one-to-one mapping between DM and redshift for an homogeneous intergalactic medium (IGM), we determine the best-fit parameters of the population spectral index, $\hatα$, and the power-law index of the burst energy distribution, $\hatγ$, for different redshift evolutionary models. Whilst the overall best-fit model yields $\hatα=2.2_{-1.0}^{+0.7}$ and $\hatγ=2.0_{-0.1}^{+0.3}$, for a strong redshift evolutionary model, when we admit the further constraint of $α=1.5$ we favour the best fit $\hatγ=1.5 \pm 0.2$ and the case of no redshift evolution. Moreover, we find no evidence that the FRB population evolves faster than linearly with respect to the star formation rate over the DM (redshift) range for the sampled population.

astro-ph.CO↗

arXiv2020

ANTARES search for point-sources of neutrinos using astrophysical catalogs: a likelihood stacking analysis

A search for astrophysical point-like neutrino sources using the data collected by the ANTARES detector between January 29, 2007 and December 31, 2017 is presented. A likelihood stacking method is used to assess the significance of an excess of muon neutrinos inducing track-like events in correlation with the location of a list of possible sources. Different sets of objects are tested in the analysis: a) a sub-sample of the \textit{Fermi} 3LAC catalog of blazars, b) a jet-obscured AGN population, c) a sample of soft gamma-ray selected radio galaxies, d) a star-forming galaxy catalog , and e) a public sample of 56 very-high-energy track events from the IceCube experiment. None of the tested sources shows a significant association with the sample of neutrinos detected by ANTARES. The smallest p-value is obtained for the radio galaxies catalog with an equal weights hypothesis, with a pre-trial p-value equivalent to a $2.8 \, σ$ excess, equivalent to $1.6 \, σ$ post-trial. In addition, the results of a dedicated analysis for the blazar MG3 J225517+2409 are also reported: this source is found to be the most significant within the \textit{Fermi} 3LAC sample, with 5 ANTARES events located at less than one degree from the source. This blazar showed evidence of flaring activity in \textit{Fermi} data, in space-time coincidence with a high-energy track detected by IceCube. An \emph{a posteriori} significance of $2.0\, σ$ for the combination of ANTARES and IceCube data is reported.

astro-ph.HE↗

arXiv2020

Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope

The ANTARES detector is an undersea neutrino telescope in the Mediterranean Sea. The search for point-like neutrino sources is one of the main goals of the ANTARES telescope, requiring a reliable method to evaluate the detector angular resolution and pointing accuracy. This work describes the study of the Sun "shadow" effect with the ANTARES detector. The shadow is the deficit in the atmospheric muon flux in the direction of the Sun caused by the absorption of the primary cosmic rays. This analysis is based on the data collected between 2008 and 2017 by the ANTARES telescope. The observed statistical significance of the Sun shadow detection is $3.7σ$, with an estimated angular resolution of $0.59^\circ\pm0.10^\circ$ for downward-going muons. The pointing accuracy is found to be consistent with the expectations and no evidence of systematic pointing shifts is observed.

astro-ph.HE↗

arXiv2020

Constraining the contribution of Gamma-Ray Bursts to the high-energy diffuse neutrino flux with 10 years of ANTARES data

Addressing the origin of the astrophysical neutrino flux observed by IceCube is of paramount importance. Gamma-Ray Bursts (GRBs) are among the few astrophysical sources capable of achieving the required energy to contribute to such neutrino flux through p$γ$ interactions. In this work, ANTARES data have been used to search for upward going muon neutrinos in spatial and temporal coincidence with 784 GRBs occurred from 2007 to 2017. For each GRB, the expected neutrino flux has been calculated in the framework of the internal shock model and the impact of the lack of knowledge on the majority of source redshifts and on other intrinsic parameters of the emission mechanism has been quantified. It is found that the model parameters that set the radial distance where shock collisions occur have the largest impact on neutrino flux expectations. In particular, the bulk Lorentz factor of the source ejecta and the minimum variability timescale are found to contribute significantly to the GRB-neutrino flux uncertainty. For the selected sources, ANTARES data have been analysed, by maximising the discovery probability of the stacking sample through an extended maximum-likelihood strategy. Since no neutrino event passed the quality cuts set by the optimisation procedure, 90\% confidence level upper limits (with their uncertainty) on the total expected diffuse neutrino flux have been derived, according to the model. The GRB contribution to the observed diffuse astrophysical neutrino flux around 100 TeV is constrained to be less than 10\%.

astro-ph.HE↗

arXiv2020

Combined search for neutrinos from dark matter self-annihilation in the Galactic Centre with ANTARES and IceCube

We present the results of the first combined dark matter search targeting the Galactic Centre using the ANTARES and IceCube neutrino telescopes. For dark matter particles with masses from 50 to 1000 GeV, the sensitivities on the self-annihilation cross section set by ANTARES and IceCube are comparable, making this mass range particularly interesting for a joint analysis. Dark matter self-annihilation through the $τ^+τ^-$, $μ^+μ^-$, $b\bar{b}$ and $W^+W^-$ channels is considered for both the Navarro-Frenk-White and Burkert halo profiles. In the combination of 2,101.6 days of ANTARES data and 1,007 days of IceCube data, no excess over the expected background is observed. Limits on the thermally-averaged dark matter annihilation cross section $\langleσ_A\upsilon\rangle$ are set. These limits present an improvement of up to a factor of two in the studied dark matter mass range with respect to the individual limits published by both collaborations. When considering dark matter particles with a mass of 200 GeV annihilating through the $τ^+τ^-$ channel, the value obtained for the limit is $7.44 \times 10^{-24} \text{cm}^{3}\text{s}^{-1}$ for the Navarro-Frenk-White halo profile. For the purpose of this joint analysis, the model parameters and the likelihood are unified, providing a benchmark for forthcoming dark matter searches performed by neutrino telescopes.

astro-ph.HE↗