Its detectors recorded the hit and sent out a public alert. The trail of light left behind by the second particle, a muon, pointed back to an intriguing object 4 billion light-years away: a violent, particle-flinging galaxy called a blazar, powered by a supermassive black hole.
This is the first time scientists have found evidence of the birthplace of an ultra-high-energy cosmic neutrino. And it is the second big result—after an August blockbuster from the Laser Interferometer Gravitational-Wave Observatory and a band of additional experiments—in what scientists are calling a new era of multi-messenger astronomy. Now, seeing neutrinos and gravitational waves from a single source tells us even more.
Because none of these multi-messenger astronomical signals has an electromagnetic charge, all of them travel through the universe unaffected by magnetic fields. Their paths are predictable, meaning scientists can trace them back to where they came from.
Most thorough test to date finds no Lorentz violation in high-energy neutrinos
For about a century, scientists had been collecting detections of ultra-high-energy particles from space—but all of them were charged particles called cosmic rays, not neutrinos. Neutrinos in High Energy and Astroparticle Physics. Selected type: Paperback. Added to Your Shopping Cart. Evaluation Copy Request an Evaluation Copy. This is a dummy description. This self-contained modern textbook provides a modern description of the Standard Model and its main extensions from the perspective of neutrino physics. In particular it includes a thorough discussion of the varieties of seesaw mechanism, with or without supersymmetry.
The suitable theoretical tools which are available, at the time of performing actual calculations in these various scenarios, include:. Naturally, one should also consider astrophysical models of highly energetic processes which generate neutrinos in the field of star models, as well as in cosmology.
In this inaugural letter, I shall try to give a flavor of the sort of questions and motivations which the Journal will welcome. I shall refer to some of the open problems, which I think may have high impact on the field, a choice which obviously represents a small sample of the complete universe of today's problems. Our short list includes the following topics. The list of references is not complete and it is intended to as an introductory bibliography.
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The chain of reactions known as BBN explains the sequence leading to the formation of the light elements. The predicted abundances are in good agreement with the experimental data, with the possible exception of 7 Li [ 1 ]. The theoretical predictions, starting from the neutron beta-decay until freeze-out, are based on nuclear reaction assumptions whose basic ingredients are thermal equilibrium and standard reaction rates and cross sections. The data show a nice agreement, between the calculated and observed abundances, except for 7 Li. For this nucleus, the observed abundance is systematically smaller, by a factor 2 or so, than the calculated one.
Naturally, one may try to fix the difference by using experimental cross sections, for reactions leading to 7 Li. Among the possible explanations of the deficit in the abundance of 7 Li, one may think of astrophysical mechanisms, like the trapping of primordial Li in the interior of stars [ 5 , 6 ], of nuclear reactions involving resonances [ 7 , 8 ], or just errors in the determination of the experimentally extracted values.
While in some recent references, the dominance of astrophysical mechanisms has been advanced [ 5 , 6 ], in some others, the nuclear reaction and nuclear structure sectors of the theory [ 7 , 8 ] have been revisited to include resonances in the reaction channels involving Be, in such a manner that the reduction in the abundance of 7 Li is just the result of decays which deplete the abundance of Be. This is, indeed, a very interesting problem, still unsolved, which may be further explored experimentally by performing measurements of nuclear reactions involving Be and its excited states, and theoretically, by performing nuclear structure calculation in the presence of resonances.
Certainly, this can be achieved, for instance, by using shell model basis or other approximations, adapted to the handling of resonant single particle states. The analysis of the measurements performed by the Wilkinson Microwave Anisotropy Probe WMAP [ 1 ] and by Planck [ 2 ] have constrained rather accurately some relevant cosmological parameters, like the baryon to photon ratio and the effective number of neutrinos. These results are of importance at the time of making a comparison with theoretical models, particularly those which include the mixing between sterile and active neutrinos.
One aspect which is particularly sensitive to the inclusion of sterile neutrinos in the neutrino spectrum is the determination of the neutrino occupation factors, relevant for the calculation of other cosmological observables, like light nuclei abundances.
- Three types of extreme-energy space particles may have unified origin — Eberly College of Science.
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The theoretical models may accommodate one or more sterile neutrino species in interaction with the standard three mass eigenstates, such that the resulting spectrum, which will be dependent on extra mixing angles, may depart from the standard three-flavor scheme [ 9 — 11 ]. This is achieved in two steps, by solving the neutrino eigenvalue problem in presence of sterile neutrino, and then, by using the resulting spectrum in solving the evolution equation for an expanding Universe. The results of the calculations performed so far are rather interesting, since, once again, the calculations have opened the way to a very detailed comparison between observational data, like the ones of WMAP and Planck, with models which take into account different formulations of the cosmological framework by treating different degrees of freedom, as it is the case of models with more than one sterile neutrino species, varying cosmological parameters [ 12 ].
Astroparticle physics with high energy neutrinos: from AMANDA to IceCube - Semantic Scholar
Thus, it would be very interesting to see, in future developments of the cosmological models, if the number of extra sterile neutrinos can be constrained and if their inclusion in leptonic mediated decays and reactions may explained for the data. Along this, one can discuss, for instance, the dependence of WMAP and Planck observables upon extra light- and heavy-mass sterile neutrinos.
The nuclear neutrinoless double beta decay is perhaps the rarest event in nuclear and particle physics. It may proceed by massive Majorana neutrino exchange between nucleons in a nucleus, and because of its kinematics limitations it may be the unique way of determining the absolute scale of the neutrino mass spectrum.
Naturally, because its leading contribution is a second order processes in the electro-weak Hamiltonian, the measurement of the half-life of a nuclear double beta decay emitter, which has a lower limit of the order of 10 25 years [ 3 , 4 ], is a real challenge to the imagination of experimental physicist [ 13 , 14 ]. In parallel to this, the value of the effective neutrino mass, relevant for the double beta decay, cannot be directly extracted, even if the decay is detected, without a precise control of the involved nuclear matrix elements, and, at least, without setting precise limits on each of the possible mechanisms, other than the mass one, which may contribute to the decay.
The activity in this field is very intense, and will continue to be intense in the near future, because of the need to converge to reliable values of the relevant nuclear matrix elements, and because of the possibility of improvements from the experimental side, that is by the way of increasing the sensitivity to masses of the order of tens of meV. Smaller values of the neutrino mass may not be directly accessible by measurements, with the present techniques at least, but they will certainly point out to other scenarios, like super-symmetry SUSY.
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In these models the light neutralino is a combination of super symmetric gauge-fermions and Higgs partners [ 15 ]. Highly energetic neutrinos may originate in micro-quasars, which are binary systems formed by a donor star and a compact object [ 17 ]. The accompanying collimated jets, where particles are accelerated to very high energies, are the source of high energy neutrinos. In this context, the effects of neutrino oscillations, on the neutrino fluxes coming from these astronomical objects, have been studied in the past years, and these studies have shown that the initial neutrino-flavor ratios are indeed very much affected by neutrino oscillations.
The detection of neutrinos from micro-quasars is crucial to investigate the jet-composition and the particle acceleration processes inside the jet. Ice-cube type detectors [ 18 ] or for the sake of the discussion, a cubic Km scale detector , may be sensitive to energies in the range 1— TeV. The formalism, which consists of the expressions for the neutrino-flux as a function of astrophysical parameters, contains elements coming from the reaction sector, like the energy dependence of the proton spectrum, the neutrino sector, like the oscillation parameters and the interactions between the neutrino and the media.