arXiv subjects

Ali Kheirandish

Publications and source records attributed to Ali Kheirandish.

At least 37 records · Page 2Linked to original sources

arXiv2021

High-Energy Neutrinos from Magnetized Coronae of Active Galactic Nuclei and Prospects for Identification of Seyfert Galaxies and Quasars in Neutrino Telescopes

Particles may be accelerated in magnetized coronae via magnetic reconnections and/or plasma turbulence, leading to high-energy neutrinos and soft gamma rays. We evaluate the detectability of neutrinos from nearby bright Seyfert galaxies identified by X-ray measurements. In the disk-corona model, we find that NGC 1068 is the most promising Seyfert galaxy in the Northern sky, where IceCube is the most sensitive, and show prospects for the identification of aggregated neutrino signals from Seyfert galaxies bright in X-rays. Moreover, we demonstrate that nearby Seyfert galaxies are promising targets for the next generation of neutrino telescopes such as KM3NeT and IceCube-Gen2. For KM3NeT, Cen A can be the most promising source in the Southern sky if a significant fraction of the observed X-rays come from the corona, and it could be identified in few years of KM3NeT operation. Our results reinforce the idea that hidden cores of supermassive black holes are the dominant sources of the high-energy neutrino emission and underlines the necessity of better sensitivity to medium-energy ranges in future neutrino detectors for identifying the origin of high-energy cosmic neutrinos.

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arXiv2021

Searching for time-dependent high-energy neutrino emission from X-ray binaries with IceCube

X-ray binaries are long-standing source candidates of Galactic cosmic rays and neutrinos. The compact object in a binary system can be the site for cosmic-ray acceleration, while high-energy neutrinos can be produced by the interactions of cosmic rays in the jet of the compact object, the stellar wind, or the atmosphere of the companion star. We report a time-dependent study of high-energy neutrinos from X-ray binaries with IceCube using 7.5 years of muon neutrino data and X-ray observations. In the absence of significant correlation, we report upper limits on the neutrino fluxes from these sources and provide a comparison with theoretical predictions.

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arXiv2021

Dark Matter Annihilation to Neutrinos

We review the annihilation of dark matter into neutrinos over a range of dark matter masses from MeV$/c^2$ to ZeV$/c^2$. Thermally-produced models of dark matter are expected to self-annihilate to standard model products. As no such signal has yet been detected, we turn to neutrino detectors to constrain the ``most invisible channel.'' We review the experimental techniques that are used to detect neutrinos, and revisit the expected contributions to the neutrino flux at current and upcoming neutrino experiments. We place updated constraints on the dark matter self-annhilation cross section to neutrinos $\langle σv \rangle$ using the most recently available data, and forecast the sensitivity of upcoming experiments such as Hyper-Kamiokande, DUNE, and IceCube Gen-2. Where possible, limits and projections are scaled to a single set of dark matter halo parameters for consistent comparison. We consider Galactic and extragalactic signals of $s$, $p$, and $d$-wave annihilation processes directly into neutrino pairs, yielding constraints that range from $\langle σv \rangle \sim 2.5\times10^{-26}~{\rm cm}^3 {\rm s}^{-1}$ at 30 MeV$/c^2$ to $10^{-17}~{\rm cm}^3{\rm s}^{-1}$ at 10$^{11}$ GeV$/c^2$. Experiments that report directional and energy information of their events provide much stronger constraints, outlining the importance of making such data public.

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arXiv2021

Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos

We show that the high-energy cosmic neutrinos seen by the IceCube Neutrino Observatory can be used to probe interactions between neutrinos and the dark sector that cannot be reached by current cosmological methods. The origin of the observed neutrinos is still unknown, and their arrival directions are compatible with an isotropic distribution. This observation, together with dedicated studies of Galactic plane correlations, suggest a predominantly extragalactic origin. Interactions between this isotropic extragalactic flux and the dense dark matter (DM) bulge of the Milky Way would thus lead to an observable imprint on the distribution, which would be seen by IceCube as 1) slightly suppressed fluxes at energies below a PeV and 2) a deficit of events in the direction of the Galactic center. We perform an extended unbinned likelihood analysis using the four-year high-energy starting event dataset to constrain the strength of DM-neutrino interactions for two model classes. We find that, in spite of low statistics, IceCube can probe regions of the parameter space inaccessible to current cosmological methods.

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arXiv2020

$χ$aro$ν$: a tool for neutrino flux generation from WIMPs

Indirect searches for signatures of corpuscular dark matter have been performed using all cosmic messengers: gamma rays, cosmic rays, and neutrinos. The search for dark matter from neutrinos is of particular importance since they are the only courier that can reach detectors from dark matter processes in dense environments, such as the core of the Sun or Earth, or from the edge of the observable Universe. In this work, we introduce $χ$aro$ν$, a software package that, in the spirit of its mythological Greek namesake $χ\acuteαρων$, bridges the dark sector and Standard Model by predicting neutrino fluxes from different celestial dark matter agglomerations. The flux at the point of production is either computed internally by $χ$aro$ν$ or is taken from user supplied tables. $χ$aro$ν$ then propagates this flux through vacuum or dense media and returns the expected neutrino yield at an observer's location. In developing $χ$aro$ν$, we have revisited and updated the production of neutrinos in dense media, updated the propagation of high-energy neutrinos, and studied the sources of uncertainty in neutrino transport. This package is coupled to a new calculation that includes electroweak corrections resulting in the most up-to-date and complete repository of neutrino fluxes from dark matter decay and annihilation over the energy range of 1 GeV to 10 PeV coming from the Earth, the Sun, and the Galactic halo.

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arXiv2020

Identifying Galactic Sources of High-Energy Neutrinos

High-energy neutrinos present the ultimate signature for a cosmic ray accelerator. Galactic sources responsible for acceleration of cosmic ray up to the knee in cosmic ray spectrum will provide a guaranteed, albeit subdominant, contribution to the high-energy cosmic neutrino flux. In this review, we discuss the the prospects for identification of high-energy neutrinos from sources of the very high energy gamma ray emission in the Milky Way. We present the status of the search for point-like and extended emission from these sources, and describe how the results of these studies indicate that neutrino telescopes are closing in on identifying Galactic sources of high-energy neutrinos.

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arXiv2020

IceCube Search for Galactic Neutrino Sources based on Very High Energy Gamma-ray Observations

Galactic cosmic rays reach energies of at least several PeV, and their interactions should generate $γ$-rays and neutrinos from decay of secondary pions. Therefore, Galactic sources have a guaranteed contribution to the total high-energy cosmic neutrino flux observed by IceCube. Assuming that the highest energy $γ$-rays are pionic, promising neutrino source candidates have been identified based on their spectra, and observing them is likely over the lifetime of the IceCube experiment. Here, we present the search for Galactic sources of high-energy cosmic neutrinos by focusing on sources identified by HAWC's very high energy $γ$-ray survey.

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arXiv2019

Observing EeV neutrinos through the Earth: GZK and the anomalous ANITA events

Tau neutrinos are unique cosmic messengers, especially at extreme energies. When they undergo a charged-current interaction, the short lifetime of the produced tau gives rise to secondary tau neutrinos that carry a significant fraction of the primary neutrino energy. This effect, known as tau neutrino regeneration, has not been applied to its full potential in current generation neutrino experiments. In this work, we present an updated calculation of tau neutrino regeneration, and explore its implications for two scenarios: the recent anomalous ANITA events and the cosmogenic neutrino flux. For the former, we investigate the idea of localized emission and find that the maximum secondary neutrino flux allowed by IceCube measurements implies a primary flux that is incompatible with the ANITA observation, regardless of the assumed source energy spectrum. For the latter, we study the prospect of detecting the cosmogenic neutrino flux of regenerated PeV neutrinos with current and next generation neutrino detectors.

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arXiv2019

Search for Dark Matter Annihilation to Neutrinos from the Sun

Weakly interacting massive particles (WIMPs) can be gravitationally captured by the Sun and trapped in its core. The annihilation of those WIMPs into Standard Model particles produces a spectrum of neutrinos whose energy distribution is related to the dark matter mass. In this work, we present the theoretical framework for relating an observed neutrino flux to the WIMP-nucleon cross section and summarize a previous solar WIMP search carried out by IceCube. We then outline an ongoing updated solar WIMP search, focusing on improvements over the previous search.

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arXiv2019

Searches for neutrinos from fast radio bursts with IceCube

Although IceCube has discovered a diffuse astrophysical neutrino flux, the underlying sources of these neutrinos remain unknown. Transient astrophysical objects, such as fast radio bursts (FRBs), could explain a large percentage of the measured flux. We present the analysis techniques of IceCube searches for MeV to TeV neutrinos from FRBs. As no significant correlation between IceCube neutrinos and FRBs has been found, we present the first limit on MeV neutrino emission from FRBs and the most constraining limits for neutrinos with GeV to TeV energies. We also describe the prospects for future IceCube neutrino searches coinciding with FRB detections from next generation radio interferometers.

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arXiv2019

IceCube Search for Galactic Neutrino Sources based on HAWC Observations of the Galactic Plane

We present a search in IceCube data for neutrino emission from Galactic TeV gamma-ray sources detected by the HAWC gamma-ray observatory. HAWC serves as the excellent instrument to complement IceCube with its energy range extending to very high energies. Assuming that the highest energy photons originate from the decay of pions, rather than from accelerated leptons, the very high energy gamma-rays observed by HAWC are expected to be correlated with neutrinos. Using eight years of IceCube data, we report on two analyses that investigate a possible neutrino--gamma ray correlation. The first is a stacked analysis of identified HAWC point sources and the second is a template method which accounts for the full morphology of HAWC sources, including their measured extension.

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arXiv2019

Searching for High-Energy Neutrino Emission from TeV Pulsar Wind Nebulae

Pulsar wind nebulae (PWNe) are main gamma-ray emitters in the Galactic plane. Although the leptonic scenario is able to explain most PWNe emission well, a hadronic contribution cannot be excluded. High-energy emission raises the possibility that gamma-rays are hadronically produced which inevitably leads to the production of neutrinos. We report a stacking analysis to search for neutrino emission from 35 PWNe that are very-high-energy gamma-ray emitters and the results using 9.5 years of all-sky IceCube data. In the absence of any significant correlation, we set upper limits on the total neutrino emission from those PWNe and constraints on the hadronic component.

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arXiv2019

Fundamental physics with high-energy cosmic neutrinos today and in the future

The astrophysical neutrinos discovered by IceCube have the highest detected neutrino energies --- from TeV to PeV --- and likely travel the longest distances --- up to a few Gpc, the size of the observable Universe. These features make them naturally attractive probes of fundamental particle-physics properties, possibly tiny in size, at energy scales unreachable by any other means. The decades before the IceCube discovery saw many proposals of particle-physics studies in this direction. Today, those proposals have become a reality, in spite of astrophysical unknowns. We will showcase examples of doing fundamental neutrino physics at these scales, including some of the most stringent tests of physics beyond the Standard Model. In the future, larger neutrino energies --- up to tens of EeV --- could be observed with larger detectors and further our reach.

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arXiv2019

High-energy neutrino attenuation in the Earth and its associated uncertainties

We describe nuFATE Neutrino Fast Attenuation Through Earth, a very rapid method of accurately computing the attenuation of high-energy neutrinos during their passage through Earth to detectors such as IceCube, ANTARES or KM3Net, including production of secondary neutrinos from $τ^\pm$ lepton decay. We then use this method to quantify the error on attenuation due to uncertainties in the isotropic neutrino spectrum, the composition of the Earth, and the parton distribution functions. We show that these can be as large as 20%, which can significantly impact reconstructed astrophysical neutrino parameters, as well as searches for new physics. An implementation of this algorithm is provided as a public code.

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arXiv2018

On the Neutrino Flares from the Direction of TXS 0506+056

For the first time since the discovery of high-energy cosmic neutrinos by IceCube, a multimessenger campaign identified a distant gamma ray blazar, TXS 0506+056, as the source of a high-energy neutrino. The extraordinary brightness of the blazar despite its distance suggests that it may belong to a special class of sources that produce cosmic rays. Moreover, over the last 10 years of data, the high-energy neutrino flux from the source is dominated by a previous neutrino flare in 2014, which implies that flaring sources strongly contribute to the cosmic ray flux. We investigate the contribution of this subclass of flaring blazars to the high-energy neutrino flux and examine its connection to the very high energy cosmic ray observations. We also study the high energy gamma ray emission accompanying the neutrino flare and show that the sources must be more efficient neutrino than gamma ray emitters. This conclusion is supported by the gamma-ray observations during the 2014 neutrino flare.

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arXiv2017

Gamma-Ray Puzzles in Cygnus X: Implications for High-Energy Neutrinos

The Cygnus X region contains giant molecular cloud complexes and populous associates of massive young stars. The discovery of spatially extended, hard gamma-ray emission in Cygnus X by both Milagro and Fermi indicates that Cygnus X is also a potential source of high-energy Galactic neutrinos. Here, we adapt our single-zone model for cosmic ray interactions in the central molecular zones of starburst galaxies for use in Cygnus X. We calculate the potential neutrino flux corresponding to the hard gamma-ray emission from the "Cygnus Cocoon" and to the soft, diffuse interstellar gamma-ray emission. We check our results by comparing the corresponding gamma-ray emission against the Fermi interstellar emission model and Milagro, ARGO-YBJ, and HAWC observations. In comparing our results against a recent IceCube analysis and the current sensitivity limits, we find that neutrino emission from the Cocoon has a large enough flux that it could plausibly be detected, provided hadronic interactions are occurring at sufficiently high energies. High-energy neutrinos from Cygnus X would provide direct evidence for the presence of as yet unidentified PeV energy accelerators in the Galactic disk.

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arXiv2017

A search for neutrinos from fast radio bursts with IceCube

We present a search for neutrinos in coincidence in time and direction with four fast radio bursts (FRBs) detected by the Parkes and Green Bank radio telescopes during the first year of operation of the complete IceCube Neutrino Observatory (May 2011 through May 2012). The neutrino sample consists of 138,322 muon neutrino candidate events, which are dominated by atmospheric neutrinos and muons but also contain an astrophysical neutrino component. Considering only neutrinos detected on the same day as each FRB, zero IceCube events were found to be compatible with the FRB directions within the estimated 99\% error radius of the neutrino directions. Based on the non-detection, we present the first upper limits on the neutrino fluence from fast radio bursts.

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arXiv2016

Constraining Dark Matter Neutrino Interaction with High Energy Neutrinos

We employ data from the recently observed high-energy neutrino events at the IceCube Neutrino Observatory to constrain interactions between the dark matter (DM) in the Milky Way and the neutrino sector. We construct an extended un-binned likelihood in order to explore the parameter space of allowed interactions. We present results in the specific case of a scalar DM candidate interacting via a scalar mediator, and show that due to the energy dependence of the interaction cross section, this approach can constrain the coupling more strongly than traditional cosmological probes for some regions of the parameter space.

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