Physics Of Neutrinos And Applications To Astrophysics Pdf

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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. In the last few years, particle astrophysics has emerged as a new field at the frontier between high energy astrophysics, cosmology, and particle physics. A spectacular achievement of this new field in the last decade has been the establishment of neutrino astronomy with the detection of solar neutrinos by two independent experiments and the spectacular observation of the neutrinos from the supernova SNA.

In addition, the field has produced tantalizing hints of new physics beyond the standard models of astrophysics and particle physics, generating enthusiastic attempts to confirm these potential effects. The next decade promises to be even more productive.

Extrapolating within the present conceptual framework, we expect the next ten years to bring fascinating results on the following issues:. The elucidation of the nature of dark matter, especially if it is made of nonbaryonic particles. The explanation of the solar neutrino puzzle and if a supernova explodes in our own galaxy, a detailed account of the explosion mechanism by the analysis of the emerging neutrinos.

The possible confirmation of the existence of point sources of energetic particles leading to the production of gamma rays, neutrinos and maybe new particles at energies as high as 10 14 eV. The understanding of the origin of cosmic rays, including the physical processes responsible for their synthesis and acceleration on a wide variety of scales. It is even more likely that as yet unsuspected phenomena will be discovered, that entirely new concepts will be tested and that the deep link between particle physics, the early universe and the high energy astrophysical processes will be extended beyond what we can imagine today!

In contrast with more mature observational fields, particle astrophysics is likely in the next decade to still be based on the succession of experiments which will increasingly sharpen their scientific focus. We see, therefore, the evolution of the field as governed by a number of decision points occurring in the next decade when the information from previous experiments or technological development becomes available:.

The highest priority at the moment is the rapid implementation of the presently approved program of observations on the ground and in space. Within this program, existing neutrino detectors should be coordinated and maintained to provide an efficient supemova watch. The technology is now available to tackle the question of the extragalactic origin of cosmic rays with the study of their spectrum at 10 20 eV.

We recommend that the high resolution Fly's Eye be supported, contingent on a favorable detailed technical review. We foresee important funding decisions to be made in a few years when the required information will be available. If the feasibility of the cryogenic technologies can be demonstrated, it is clear that a full scale search for nonbaryonic dark matter will have very high priority. If the large extensive air shower detectors currently being deployed confirm the claims for localized gamma ray sources above 10 14 eV, understanding these unsuspected acceleration mechanisms and the new particle physics if the claimed anomalous muon content is substantiated would require more powerful detectors.

The results of current solar neutrino detectors may steer the field into new observational directions. Finally, if the early promise of gamma ray astronomy at 10 12 eV is fulfilled, then larger installations will surely be required. The preparation for these decisions appearing on the horizon demands a strong development of new detection techniques: we emphasize in particular the cryogenic particle detectors for dark matter searches, the new solar neutrino schemes, and the test of the water Cerenkov technique for the detection of extensive air showers.

Such a complex and fundamentally multidisciplinary enterprise requires a strong theoretical activity and a variety of coordination mechanisms. Our main recommendation here is the establishment of a particle astrophysics. Particle detection techniques have been essential to the development of high energy astrophysics since the first cosmic ray investigations in the early years of this century.

Their role has been greatly expanded during the past decade as a variety of large experiments have begun to address fundamental astrophysical questions. Two of the most recent and important advances in astronomy have been made by the direct detection of neutrinos. Two independent experiments measured the solar neutrino flux using totally different techniques, and neutrinos from the supernova A have been directly detected by experiments designed to observe proton decay.

Moreover, observation of the electromagnetic spectrum from astrophysical objects has been extended above 10 11 eV using ground based Cerenkov detectors. Evidence obtained with air shower arrays suggests that gamma radiation in excess of 10 14 eV may also have been observed from astrophysical objects.

Cosmic rays have been detected up to 10 20 eV but their nature and origin at these energies remains a mystery, as does the means of their acceleration. In parallel, progress in the understanding of particle physics has suggested that the missing matter in the universe may consist of as yet undiscovered elementary particles, which are relics of the very earliest phases of the formation of the universe.

It also appears that quantum fluctuations and topological singularities generated in phase transitions occurring at very high temperature in the early universe could have played a fundamental role in the formation of large scale structure. In addition, it is now well understood how the properties of neutrinos could be responsible for the solar neutrino puzzle, and the powerful acceleration mechanisms evidenced by the highest energy cosmic rays may require new particle physics.

The discoveries and activities described above have been mostly carried out by an unconventional breed of "astronomers" whose backgrounds have been in particle or nuclear physics. The nature of the research ranges from solid experiments with well defined systematic goals to investigations which test speculative ideas or follow on experimental hints.

Therefore, such a field is a vital and exciting one, with new ideas, new practitioners, and the certainty of scientific progress. It may well be that the cosmos is providing us with the first evidences for physics beyond the standard models of astrophysics and particle physics.

We review first the essential scientific questions being tackled and the present experimental program, before turning to priorities and institutional questions. The physics of the early universe is intimately related to particle physics at the very highest energies and it is not possible to distinguish them in the quest for the answer to the fundamental questions of cosmology: What is the nature of the ubiquitous dark matter?

What is the origin of the predominance of matter over antimatter? What is the explanation for the smoothness, flatness, and old age of the universe? What is the origin of the primeval inhomogeneities that triggered the formation of structure and eventually galaxies in the universe? Conversely, the cosmological observations provide essential constraints in the construction of unified theories of particle interactions and may be the only source of information on physics at the very highest energies up to the Planck scale - 10 19 GeV.

Physics at these energies is difficult to probe in terrestrial laboratories and so, at the same time the early universe provides a natural laboratory in which physics at the most fundamental level can be studied. The past decade has seen the consolidation of two standard models: the Su 3 xSU 2 xU 1 gauge theory of particle interactions and the Hot Big Bang model.

The former provides a fundamental theory of the elementary particles and their interactions at distances down to 10 cm energies up to 10 3 GeV , while the latter provides an accurate accounting of the history of the Universe from about 10 -2 sec after the origin of the universe. Encouraged by these impressive successes, particle physicists and cosmologists have begun to extrapolate to earlier times and attempted to answer the fundamental questions outlined above.

The origin of the matter-antimatter asymmetry seems. At very early times 10 sec? For instance, inflation provides a very attractive explanation for the flatness and old age of the universe and of the primeval density inhomogeneities. In addition, many theories that go beyond the particle physics standard model, such as supersymmetry, predict the existence of stable relic elementary particles that are left over from the early moments after the Big Bang and that may constitute dark matter.

Combining such cold dark matter which could also be made of condensed astrophysical objects or primordial black holes with the Harrison-Zel'dovitch spectrum of adiabatic density fluctuations predicted by the simplest models of inflation, it has been possible to obtain a fair first approximation to a theory of the formation of galaxies and clusters of galaxies. Alternatively, it is possible that cosmic strings or other topological defects associated with an early phase transition or with inflation, may be at least partly responsible for structure formation; in this case, there are indications that hot dark matter e.

After more than a decade of intense theoretical work which has produced these fascinating ideas, the time is ripe for strengthened experimentation and observation. The main problems are easily identified:. Determination of the basic cosmological parameters. We are still lacking a definitive determination of the Hubble parameter which enters in most cosmology calculations. The age of the universe is still uncertain.

The combination of these three parameters would allow us to determine the spatial curvature of the universe testing therefore the inflation paradigm and the value of the cosmological constant, the small value of which remains a mystery.

Measurement of primordial abundances : This will allow us to test in more detail the standard Hot Big Bang model of primordial nucleosynthesis and determine the average density of ordinary baryonic matter.

Study of diffuse backgrounds : The primordial fluctuations that presumably lead to the formation of structure in the universe must be reflected in small anisotropies of the 2.

When these are finally detected, they will provide a firm foundation for theories of structure formation and will point back to the processes that gave rise to these fluctuations in the early universe. Timing measurements of the millisecond pulsars place the most stringent bounds on the density of the stochastic gravitational wave background and help to constrain models such as cosmic strings. Mapping of the universe. The systematic measurement of the galaxy density and velocity fields on increasingly larger scales will help to reveal the initial conditions and basic evolutionary processes in the universe.

Search for dark matter. The nature of dark matter remains a mystery but begins to be accessible to observations: condensed astrophysical baryonic objects may be detectable by micro-lensing, relic particles by direct detection via elastic scattering in the laboratory and primordial black holes by the gamma ray bursts they should generate. Although the needed observational evidence involves a wide variety of observational fields of astrophysics, most of which are not covered by this panel, it is important to stress the importance of all these observations in order to understand the role of particle physics in the early universe.

Dark matter currently is probably the best example of the interpenetration of particle physics and cosmology. Based upon decades of astronomical and cosmological observations we are certain that most of the matter in the Universe is nonluminous and transparent. Various cosmological and astrophysical arguments suggest that the dark matter may not be ordinary matter baryons , and that the most likely candidate is a relic elementary particle.

The abundance of the candidate relics, their properties, and means of detecting them have been studied, and we are now ready to undertake the most important step: the experimental testing of the particle dark matter hypothesis. Three types of dark matter particles are particularly well motivated: light neutrinos, axions and weakly interacting massive particles.

Light neutrinos of mass of about 30 eV would solve the dark matter problem, although they may complicate the explanation of the formation of large scale structure of the universe. Unfortunately, no experimentally viable method has yet been proposed to detect the cosmological neutrinos directly and we will require laboratory.

The detection of a large number of neutrinos from distant supernovae could eventually provide interesting direct mass limits. The axion , a very light mass of about 10 -3 eV to 10 -6 eV pseudoscalar particle still represents the best solution to a fundamental problem of the standard Particle Physics model the strong CP problem of QCD.

Unfortunately the axion interactions are expected to be very weak, not much stronger than gravitational, and it is a testimony to the talents of the experimentalist involved that the sensitivities of the first generation experiments employing resonant microwave cavities were within about a factor of of that required.

It may be possible to improve the sensitivity by this factor with large cavities in the lower mass region. The fundamental experimental problem remains that present detection schemes are narrow band, and, since the axion mass which leads to closure density is only known to a factor of about , scanning the entire region requires a long time and a large effort.

Recent theoretical work suggests that the mass uncertainty may even be larger as radiation from global strings may be the dominant source of axions. Weakly interacting massive particles WIMPs are another general class of candidates which correspond to the case where heavy dark matter particles were in thermal equilibrium with the rest of matter in the early universe.

Their interaction cross sections can then be estimated from their current density and turn out to be of the order expected for ''Weak Interactions'' in the technical sense. This coincidence may be purely accidental or may be a very precious hint that physics at the W and Z 0 scale e. For instance the lightest supersymmetric particle may constitute dark matter: this particle is the neutralino, sometimes referred to as the photino or higgsino, which are special cases.

In order to test this fairly general hypothesis, we could attempt to detect directly the interaction of halo particles with a laboratory target, in a way complementary to the new particle searches at accelerators LEP, Tevatron and the SSC.

This requires, unfortunately, very sensitive detectors with a good rejection of the radioactive background. Current detectors using ionization techniques have set interesting limits, for instance excluding the possibility that dark matter is made of heavy Dirac neutrinos Fig. But before the neutralino model can be probed, the rejection of backgrounds must be improved by two or three orders of magnitude.

This factor could eventually be reached with emerging technologies based on the detection of phonons or quasiparticles in superconductors which should allow better energy sensitivity and much higher redundancy. Although not sufficient to establish the feasibility of a definitive experiment, the results obtained currently with cryogenic detectors of a few tens of grams are encouraging.

Recent balloon measurements indeed indicate an excess of antiprotons and positrons but the interpretation in terms of dark matter annihilation products now seems less likely than some other possible explanations.

Of these indirect methods, neutrinos originating from the sun may be the least model dependent. Other relic particles may be significant in cosmology even if they do not constitute dark matter recall that the cosmic microwave background contributes less that 10 -4 of the critical density. The observation of relic cosmological neutrinos would of course be of exceptional interest but no good ideas for their detection have been proposed.

Significant relics include superheavy magnetic monopoles, decaying neutrinos, a neutralino species, or decaying axions.

Physics of Neutrinos

JavaScript is disabled for your browser. Some features of this site may not work without it. Astrophysics and Physics of Neutrino Detection. Services Full metadata XML. Title Astrophysics and Physics of Neutrino Detection. Authors Li, Cheng-Hsien.


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This book provides a survey of the current state of research into the physics of neutrinos. It is presented in a form accessible to non-specialists and graduate students, but will also be useful as a handbook for researchers in this field. The reader finds here a global view of the areas of physics in which neutrinos play important roles, including astrophysics and cosmology. The book is intended to be self-contained: Starting from the standard theory of electroweak interactions, the key notions are explained in detail and the fundamental equations are derived explicitly, so that readers can understand their precise content.

The mass of the neutrino is much smaller than that of the other known elementary particles. A neutrino created with a specific flavor has an associated specific quantum superposition of all three mass states. As a result, neutrinos oscillate between different flavors in flight.

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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. In the last few years, particle astrophysics has emerged as a new field at the frontier between high energy astrophysics, cosmology, and particle physics. A spectacular achievement of this new field in the last decade has been the establishment of neutrino astronomy with the detection of solar neutrinos by two independent experiments and the spectacular observation of the neutrinos from the supernova SNA.

Photosensors development and application Yuji Yoshizawa, Hamamatsu Photonics, Japan [view abstract pdf]. Our current and archive events programme. Key dates Paper submission deadline: 30 September

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