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Register a new userUsing High-Energy Neutrinos As Cosmic Magnetometers
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Added by
Mauricio Bustamante
Publication date
2020
fields
Physics
and research's language is
English
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Magnetic fields are crucial in shaping the non-thermal emission of the TeV-PeV neutrinos of astrophysical origin seen by the IceCube neutrino telescope. The sources of these neutrinos are unknown, but if they harbor a strong magnetic field, then the synchrotron energy losses of the neutrino parent particles---protons, pions, and muons---leave characteristic imprints on the neutrino energy distribution and its flavor composition. We use high-energy neutrinos as cosmic magnetometers to constrain the identity of their sources by placing limits on the strength of the magnetic field in them. We look for evidence of synchrotron losses in public IceCube data: 6 years of High Energy Starting Events (HESE) and 2 years of Medium Energy Starting Events (MESE). In the absence of evidence, we place an upper limit of 10 kG-10 MG (95% C.L.) on the average magnetic field strength of the sources.
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This is a summary of a series of lectures on the current experimental and theoretical status of our understanding of origin and nature of cosmic radiation. Specific focus is put on ultra-high energy cosmic radiation above ~10^17 eV, including secondary neutral particles and in particular neutrinos. The most important open questions are related to the mass composition and sky distributions of these particles as well as on the location and nature of their sources. High energy neutrinos at GeV energies and above from extra-terrestrial sources have not yet been detected and experimental upper limits start to put strong contraints on the sources and the acceleration mechanism of very high energy cosmic rays.
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A. Barbano (for the IceCube Collaboration
, the Pierre Augern Collaboration
, the Telescope Array Collaboration
2020
The sources of ultra-high energy cosmic rays (UHECRs) are still one of the main open questions in high-energy astrophysics. If UHECRs are accelerated in astrophysical sources, they are expected to produce high-energy photons and neutrinos due to the interaction with the surrounding astrophysical medium or ambient radiation. In particular, neutrinos are powerful probes for the investigation of the region of production and acceleration of UHECRs since they are not sensitive to magnetic deflections nor to interactions with the interstellar medium. The results of three different analyses that correlate the very high-energy neutrino candidates detected by IceCube and ANTARES and the highest-energy cosmic rays measured by the Pierre Auger Observatory and the Telescope Array will be discussed. The first two analyses use a sample of high-energy neutrinos from IceCube and ANTARES selected to have a significant probability to be of astrophysical origin. The first analysis cross-correlates the arrival directions of these selected neutrino events and UHECRs. The second one is a stacked likelihood analysis assuming as stacked sources the high-energy neutrino directions and looking for excesses in the UHECR data set around the directions of the neutrino candidates. The third analysis instead uses a larger sample of neutrinos selected to look for neutrino point-like sources. It consists of a likelihood method that looks for excesses in the neutrino point-source data set around the directions of the highest-energy UHECRs.
The interaction of cosmic rays with the gas contained in our Galaxy is a guaranteed source of diffuse high energy neutrinos. We provide expectations for this component by considering different assumptions for the cosmic ray distribution in the Galaxy which are intended to cover the large uncertainty in cosmic ray propagation models. We calculate the angular dependence of the diffuse galactic neutrino flux and the corresponding rate of High Energy Starting Events in IceCube by including the effect of detector angular resolution. Moreover we discuss the possibility to discriminate the galactic component from an isotropic astrophysical flux. We show that a statistically significant excess of events from the galactic plane in present IceCube data would favour models in which the cosmic ray density in the inner galactic region is much larger than its local value, thus bringing relevant information on the cosmic ray radial distribution.
High-energy cosmic neutrinos can reveal new fundamental particles and interactions, probing energy and distance scales far exceeding those accessible in the laboratory. This white paper describes the outstanding particle physics questions that high-energy cosmic neutrinos can address in the coming decade. A companion white paper discusses how the observation of cosmic neutrinos can address open questions in astrophysics. Tests of fundamental physics using high-energy cosmic neutrinos will be enabled by detailed measurements of their energy spectrum, arrival directions, flavor composition, and timing.
We explore the joint implications of ultrahigh energy cosmic ray (UHECR) source environments -- constrained by the spectrum and composition of UHECRs -- and the observed high energy astrophysical neutrino spectrum. Acceleration mechanisms producing power-law CR spectra $propto E^{-2}$ are compatible with UHECR data, if CRs at high rigidities are in the quasi-ballistic diffusion regime as they escape their source environment. Both gas- and photon-dominated source environments are able to account for UHECR observations, however photon-dominated sources do so with a higher degree of accuracy. However, gas-dominated sources are in tension with current neutrino constraints. Accurate measurement of the neutrino flux at $sim 10$ PeV will provide crucial information on the viability of gas-dominated sources, as well as whether diffusive shock acceleration is consistent with UHECR observations. We also show that UHECR sources are able to give a good fit to the high energy portion of the astrophysical neutrino spectrum, above $sim$ PeV. This common origin of UHECRs and high energy astrophysical neutrinos is natural if air shower data is interpreted with the textsc{Sibyll2.3c} hadronic interaction model, which gives the best-fit to UHECRs and astrophysical neutrinos in the same part of parameter space, but not for EPOS-LHC.
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