Located at the South Pole, the IceCube Neutrino Observatory is the world largest neutrino telescope, instrumenting one cubic kilometre of Antarctic ice at a depth between 1450m to 2450m. In 2013 IceCube reported the first observations of a diffuse astrophysical high-energy neutrino flux. Although the IceCube Collaboration has identified more than 100 high-energy neutrino events, the origin of this neutrino flux is still not known. Blazars, a subclass of Active Galactic Nuclei and one of the most powerful classes of objects in the Universe, have long been considered promising sources of high energy neutrinos. A blazar origin of this high-energy neutrino flux can be examined using stacking methods testing the correlation between IceCube neutrinos and catalogs of hypothesized sources. Here we present the results of a stacking analysis for 1301 blazars from the third catalog of hard \textit{Fermi}-LAT sources (3FHL). The analysis is performed on 8 years of through-going muon data from the Northern Hemisphere, recorded by IceCube between 2009 and 2016. No excess of neutrinos from the blazar position was found and first limits on the neutrino production of these sources will be shown.
We obtained Calar Alto identification spectra for six cataclysmic variable candidates, and studied archival observations at a range of wavelengths. Two sources were too faint to allow for easy identification by their spectra, and the other four are likely to be dwarf novae. No periodicity was detected for any of the sources on the basis of CRTS data.
Several projects are concentrating their efforts on opening the high energy neutrino window on the Universe with km-scale detectors. The detection principle relies on the observation, using photomultipliers, of the Cherenkov light emitted by charged leptons induced by neutrino interactions in the surrounding detector medium. In the Northern hemisphere, while the pioneering Baikal telescope, has been operating for 10 years, most of the activity now concentrates in the Mediterranean sea. Recently, the Antares collaboration has completed the construction of a 12 line array comprising ~ 900 photom…
I further test the theory that the Cosmic Background Radiation (CBR) is made of photons with a weak U(1) component. Tipler (2005) has previously argued that the consistency of the Standard Model (SM) with the Second Law of Thermodynamics requires the early universe CBR to be composed mainly of an SU(2) gauge field. The U(1) field would be suppressed. One of the consequences of this approach is that the Ultra High Energy Cosmic Rays (UHECR) would be able to propagate much further than conventionally accepted, as an SU(2) dominant CBR would be largely unable to couple with right handed fermions.…
The Telescope Array (TA) is the largest ultrahigh energy (UHE) cosmic ray observatory in the northern hemisphere TA is a hybrid experiment with a unique combination of fluorescence detectors and a stand-alone surface array of scintillation counters. We will present the spectrum measured by the surface array alone, along with those measured by the fluorescence detectors in monocular, hybrid, and stereo mode. The composition results from stereo TA data will be discussed. Our report will also include results from the search for correlations between the pointing directions of cosmic rays, seen by …
The IceCube Collaboration has recently reported evidence for a high-energy extraterrestrial neutrino flux. During two years of operation 28 events with energies between 30 TeV and 1.2 PeV were observed while only 10.6 events were expected from conventional atmospheric backgrounds. The hadronic interactions responsible for this IceCube excess will also produce a flux of high-energy gamma-rays that can serve as a probe of source direction and distance. We show that existing TeV to PeV diffuse gamma-ray limits support the interpretation that the IceCube excess is mostly of extragalactic origin. H…
We present the results of time-integrated searches for astrophysical neutrino sources in both the northern and southern skies. Data were collected using the partially-completed IceCube detector in the 40-string configuration between 2008 April 5 and 2009 May 20, totaling 375.5 days livetime. An unbinned maximum likelihood ratio method is used to search for astrophysical signals. The data sample contains 36,900 events: 14,121 from the northern sky, mostly muons induced by atmospheric neutrinos and 22,779 from the southern sky, mostly high energy atmospheric muons. The analysis includes searches…
We explore the detectability of the neutrino flux from the entire Galactic Plane or from a part of it with IceCube. We calculate the normalization and the spectral index of the neutrino power law spectrum from different regions of the Galactic plane, based on the observed spectral characteristics of the pion decay gamma-ray diffuse emission observed by the Fermi/LAT telescope in the energy band above 100 GeV. We compare the neutrino flux calculated in this way with the sensitivity of IceCube for the detection of extended sources. Assuming a binned extended source analysis method, we find that …
Recent observations of the gamma-ray source HAWC J2227+610 by Tibet AS+MD and LHAASO confirm the special interest of this source as a galactic PeVatron candidate in the northern hemisphere. HAWC J2227+610 emits Very High Energy (VHE) gamma-rays up to 500 TeV, from a region coincident with molecular clouds and significantly displaced from the nearby pulsar J2229+6114. Even if this morphology favours an hadronic origin, both leptonic or hadronic models can describe the current VHE gamma-ray emission. The morphology of the source is not well constrained by the present measurements and a better ch…
We present new results of searches for neutrino point sources in the northern sky, using data recorded in 2007-08 with 22 strings of the IceCube detector (approximately one-fourth of the planned total) and 275.7 days of livetime. The final sample of 5114 neutrino candidate events agrees well with the expected background of atmospheric muon neutrinos and a small component of atmospheric muons. No evidence of a point source is found, with the most significant excess of events in the sky at 2.2 sigma after accounting for all trials. The average upper limit over the northern sky for point sources …
Point source searches with neutrino telescopes like IceCube are normally restricted to one hemisphere, due to the selection of up-going events as a way of rejecting the atmospheric muon background. In this work we show that the down-going region above the horizon can be included in the search by suppressing the background through energy-sensitive selection procedures. This approach increases the reach to the EeV regime of the signal spectrum, which was previously not accessible due to the absorption of neutrinos with energies above a PeV inside the Earth. We present preliminary results of this…
Using commissioning data from the first year of operation of the Canadian Hydrogen Intensity Mapping Experiment's (CHIME) Pulsar backend system, we conduct a systematic analysis of the Faraday Rotation Measure (RM) of the northern hemisphere pulsars detected by CHIME. We present 55 new RMs as well as obtain improved RM uncertainties for 25 further pulsars. CHIME's low observing frequency and wide bandwidth between 400-800 MHz contribute to the precision of our measurements, whereas the high cadence observation provide extremely high signal-to-noise co-added data. Our results represent a signif…
IceCube has reported the detection of a diffuse TeV-PeV neutrino emission, for which the flat spectrum radio quasars (FSRQs) have been proposed to be the candidate sources. Here we assume that the neutrino flux from FSRQs is proportional to their gamma-ray ones, and obtain the gamma-ray/neutrino flux ratio by the diffuse gamma-ray flux from Fermi-LAT measurement of FSRQs and the diffuse neutrino flux detected by IceCube. We apply this ratio to individual FSRQs and hence predict their neutrino flux. We find that a large fraction of candidate FSRQs from the northern sky in the IceCube point sour…
Encompasing a volume of ~1 km^3 of glacial ice at the South Pole, IceCube is currently the worlds largest neutrino detector. It consists of 5160 optical modules on 86 strings in a depth between 1450m and 2450m, as well as 324 optical modules arranged in 81 stations on the surface to detect charged cosmic rays. A large amount of data has already been acquired with smaller configurations throughout the installation period. Using this data the atmospheric neutrino spectrum in the northern hemisphere has been measured up to 100 TeV. No point sources have been identified in a set of more than 10^5 …
We recently started a systematic search of low-energy counterparts of the unidentified gamma-ray sources (UGSs) listed in the Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) and the Fermi-LAT 2-Year Source Catalog (2FGL).} The main goal of our investigation is to find active galaxies belonging to the blazar class that lie within the positional uncertainty region of the UGSs and thus could be their potential low-energy counterparts. To achieve our aims, we first adopted several procedures based on the peculiar observational properties of blazars in the radio and in the IR. Then we …
The search for compact components of strong ($S_{int} \ge 5$ Jy at 102.5 MHz) discrete radio sources from the Pushchino catalogue was carried out using the method of interplanetary scintillation. A total of 3620 sources were examined, and 812 of them were found to compact (scintillating) components. Estimates of fluctuations of the flux density of these compact components were derived from the scintillation index ($m_{max}$) corresponding to an elongation of $25^o$. The angular size and compactness of 178 sources with compact components were estimated. Scintillation indices of sources correspo…
Northern hemisphere TeV gamma-ray observatories such as Milagro and Tibet AS$γ$ have demonstrated the importance of all-sky instruments by discovering previously unidentified sources that may be the PeVatrons producing cosmic rays up to the "knee" in the cosmic ray spectrum. We evaluate the potential of IceCube to identify similar sources in the southern sky by detailing an analytic approach to determine fluxes of muons from TeV gamma-ray showers. We apply this approach to known gamma-ray sources such as supernova remnants. We find that, similar to Milagro, detection is possible in 10 years fo…
The extragalactic $γ$-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei (AGNs). Many of the $γ$-ray sources included in Fermi -Large Area Telescope Third Source catalog (3FGL) are classified as a blazar candidate of uncertain type (BCU) because there is no optical spectra available in the literature to confirm their nature. In 2013 we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the Unidentified $γ$-ray Sources. The main goal of our investigation is to confirm the blazar nature of these sources having peculiar …
The hypothesis that high energy cosmic neutrinos are power law distributed is critically analyzed. We propose a model with two components that explains better the observations. The extragalactic component of the high energy neutrino flux has a canonical $E_ν^{-2}$ spectrum while the galactic component has a $E_ν^{-2.7}$ spectrum; both of them are significant. This model has several implications, that can be tested by IceCube and ANTARES in the next years. Moreover, the existence of a diffuse component close to the Galactic plane and that yields (20-30)\% of IceCube's events, is interesting for…
The IceCube Neutrino Observatory measured a flux of high-energy astrophysical neutrinos in several detection channels. The energy spectrum is fitted as unbroken power-law, but different best-fit parameters were obtained in the various analyses covering different energy ranges between few TeV to 10 PeV. Here, we present an update to the analysis of through-going muon-neutrinos from the Northern Hemisphere. It was extended to almost ten years of data and an improved treatment of systematic uncertainties on the atmospheric fluxes was implemented. The updated best-fit parameters for the astrophysi…
Sokolsky and D_Avignon have recently reported an examination of a variety of measurements that relate to the question as to how the mass composition of the highest-energy cosmic-rays evolves with energy. They assert that cosmic rays arriving from the Northern Hemisphere have a different mass composition from those arriving from the Southern Hemisphere, implying a diversity of sources of high-energy cosmic-rays in the two hemispheres. Were this conclusion to be correct, it would have profound implications for theories of cosmic-ray origin and would influence planning of future projects. Their c…
Spectral and anisotropy properties of IceCube astrophysical neutrino signal reveal an evidence for a significant Galactic contribution to the neutrino flux in Southern hemisphere. We check if the Galactic contribution is detectable in the astrophysical muon neutrino flux observed from a low positive declinations region of the Northern sky. Estimating the Galactic neutrino flux in this part of the sky from gamma-ray and Southern sky neutrino data, we find that the Northern sky astrophysical muon neutrino signal shows an excess over the Galactic flux. This points to the presence of an additional…
This paper reports on the observation of the sidereal large-scale anisotropy of cosmic rays using data collected by the ARGO-YBJ experiment over 5 years (2008$-$2012). This analysis extends previous work limited to the period from 2008 January to 2009 December,near the minimum of solar activity between cycles 23 and 24.With the new data sample the period of solar cycle 24 from near minimum to maximum is investigated. A new method is used to improve the energy reconstruction, allowing us to cover a much wider energy range, from 4 to 520 TeV. Below 100 TeV, the anisotropy is dominated by two wid…
Point source searches with the IceCube neutrino telescope have been restricted to one hemisphere, due to the exclusive selection of upward going events as a way of rejecting the atmospheric muon background. We show that the region above the horizon can be included by suppressing the background through energy-sensitive cuts. This approach improves the sensitivity above PeV energies, previously not accessible for declinations of more than a few degrees below the horizon due to the absorption of neutrinos in Earth. We present results based on data collected with 22 strings of IceCube, extending i…
In this paper, after a short introduction to the physics of neutrino telescopes, we will report on first performances of the IceCube detector and a selection of preliminary results obtained from data taken while IceCube operated in a partially completed configuration (22 strings and 40 strings). We will emphasize new analysis methods recently developed for the study of the Southern Hemisphere as well as for extended regions. Based on the long term experience of AMANDA and IceCube, the South Pole ice has proven to be an ideal site for astroparticle physics. New ideas and projects about the futu…
Between May 2009 and May 2010, the IceCube neutrino detector recorded 32 billion of atmospheric muons generated in air showers produced by cosmic rays in the TeV energy range. With such high statistics sample it is possible to observe, for the first time in the southern hemisphere, an energy dependence in the Galactic cosmic ray anisotropy up to a few hundred TeV. This study shows that the same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV; the anisotropy observed at 400 TeV shows substantial differences with respect to that at lower energy. In addi…
Telescope Array (TA) is the largest experiment in the Northern Hemisphere studying ultrahigh energy cosmic rays. TA measurements of the cosmic ray spectrum using the surface detector have the best statistical power in the experiment, and observe the ankle of the spectrum and the high energy cutoff. When the data are divided into two declination bands, above and below 24.8 degrees, the cutoff appears at $10^{19.64 \pm 0.04}$ ($10^{19.84 \pm 0.02}$) eV in the lower (higher) band, an energy difference of 58\%. The global significance of the difference is 4.3 standard deviations. The lack of an in…
In this contribution we summarize the selected highlights of IceCube in the domain of high-energy astrophysics and particle physics. We discuss the highest-energy neutrino detection and its interpretation after 4 years of data. The significance is such that the discovery of a non terrestrial component can be claimed but its origin is not yet clarified. The high energy non-atmospheric component is seen also in other analyses with smaller significance, for instance when using muon neutrino induced events coming from the Northern hemisphere. Flavor mixing is probed along cosmic distances in an an…
We review all existing air-fluorescence measurements of the elongation rate of extensive air showers (slope of mean EAS shower maximum (Xmax) vs log of shower energy E) above 1017 eV. We find remarkable agreement for all current and historic experiments over a 30 year period for the energy range from 1017 to 3x1018 eV. The mean elongation rate in this energy interval is near 80 gm/cm2/decade Above this energy, experiments in the Northern hemisphere are in good agreement with an average elongation rate of 48 +/- 10 gm/cm2/decade while Southern hemisphere experiments have a flatter elongation ra…
The IceCube Observatory has collected over 577 billion cosmic-ray induced muon events in its final configuration from May 2011 to May 2020. We used this data set to provide an unprecedented statistically accurate map of the cosmic ray arrival direction distribution in the TeV-PeV energy range scale in the Southern Hemisphere. Such an increase in event statistics makes it possible to extend the sensitivity to anisotropies at higher cosmic ray energies and smaller angular scales. It will also facilitate a more detailed assessment of the observatory stability over both short- and long-time scales…
A clue to finding the long-sought sources of cosmic rays is the recent observation of an astrophysical flux of high-energy neutrinos by the IceCube detector, since these possibly originate in hadronic interactions at cosmic-ray accelerators. While the neutrino sky map shows no significant indication of point sources so far, it is possible to utilize the sensitivity of Imaging Air Cherenkov Telescope (IACT) arrays, such as VERITAS, to search for hadronic gamma-ray emission from the neutrino directions. Over the last 2 years, the positions of neutrino events detected by IceCube have been observe…
We present a novel analysis method for the determination of the neutrino-nucleon Deep Inelastic Scattering (DIS) cross section in the TeV - PeV energy range utilizing neutrino absorption by the Earth. We analyze five years of data collected with the complete IceCube detector from May 2011 to May 2016. This analysis focuses on electromagnetic and hadronic showers (cascades) mainly induced by electron and tau neutrinos. The applied event selection features high background rejection (< 10% background contamination below 60 TeV, background free above 60 TeV) of atmospheric muons and high signal ef…
During the past two decades, experiments in both the Northern and Southern hemispheres have observed a small but measurable energy-dependent sidereal anisotropy in the arrival direction distribution of galactic cosmic rays. The relative amplitude of the anisotropy is $10^{-4} - 10^{-3}$. However, each of these individual measurements is restricted by limited sky coverage, and so the pseudo-power spectrum of the anisotropy obtained from any one measurement displays a systematic correlation between different multipole modes $C_\ell$. To address this issue, we present the preliminary status of a …
The last IceCube catalog of High Energy Starting Events (HESE) obtained with a livetime of 1347 days comprises 54 neutrino events equally-distributed between the three families with energies between 25 TeV and few PeVs. Considering the homogeneous flavors distribution (1:1:1) and the spectral features of these neutrinos the IceCube collaboration claims the astrophysical origin of these events with more than $5σ$. The spatial distribution of cited events does not show a clear correlation with known astrophysical accelerators leaving opened both the Galactic and the extra-Galactic origin interpr…
We report the analysis of the $10-1000$ TeV large-scale sidereal anisotropy of Galactic cosmic rays (GCRs) with the data collected by the Tibet Air Shower Array from October, 1995 to February, 2010. In this analysis, we improve the energy estimate and extend the declination range down to $-30^{\circ}$. We find that the anisotropy maps above 100 TeV are distinct from that at multi-TeV band. The so-called "tail-in" and "loss-cone" features identified at low energies get less significant and a new component appears at $\sim100$ TeV. The spatial distribution of the GCR intensity with an excess (7.…
The very-high-energy gamma-ray sky can be surveyed on a daily basis by particle-detector arrays at high (mountain) elevation. In the northern hemisphere the survey recently conducted by the HAWC gamma-ray observatory significantly enriched our knowledge about TeV gamma-ray sources. In this contribution, we will present an overview on the effort to realise a next-generation gamma-ray survey observatory in the southern hemisphere. We will discuss the unique science case for this observatory and how it will be embedded in the multi-messenger and multi-wavelength census of the non-thermal universe…
We compute the gamma-ray and neutrino diffuse emission of the Galaxy on the basis of a recently proposed phenomenological model characterized by radially dependent cosmic-ray (CR) transport properties. We show how this model, designed to reproduce both Fermi-LAT gamma-ray data and local CR observables, naturally reproduces the anomalous TeV diffuse emission observed by Milagro in the inner Galactic plane. Above 100 TeV our picture predicts a neutrino flux that is about five (two) times larger than the neutrino flux computed with conventional models in the Galactic Center region (full-sky). Exp…
A search for cosmic neutrino point-like sources using the ANTARES and IceCube neutrino telescopes over the Southern Hemisphere is presented. The ANTARES data was collected between January 2007 and December 2012, whereas the IceCube data ranges from April 2008 to May 2011. Clusters of muon neutrinos over the diffusely distributed background have been looked for by means of an unbinned maximum likelihood maximisation. This method is used to search for a localised excess of events over the whole Southern Sky assuming an $E^{-2}$ source spectrum. A search over a pre-selected list of candidate sour…
A recent proposal to associate 60~TeV to 2~PeV IceCube neutrino events with gamma-ray bursts~(GRBs) indicates the Lorentz violation of cosmic neutrinos and leads further to the $CPT$ symmetry violation between neutrinos and antineutrinos. Here we find that another 12 northern hemisphere track events possibly correlated with GRBs from three-year IceCube data satisfy the same regularity at a lower energy scale around 1~TeV. The combined fitting indicates a Lorentz violation scale ${E}_{\rm LV}=(6.4\pm 1.5)\times10^{17}~{ \rm GeV}$ and an intrinsic time difference ${Δ{t}_{\rm in}=(-2.8\pm 0.7)\ti…
