Table of contents

We review here theoretical models for describing various types of reactions involving light nuclei on the driplines. Structure features to be extracted from the analysis of such reaction data, as well as those that need to be incorporated in the reaction models for an adequate description of the processes, are also under focus. The major unsolved theoretical issues are discussed, along with some suggestions for future directions of the field.

The model dependence of the development of extensive air showers generated by high-energy cosmic-ray particles in the atmosphere is studied. The increase of proton–proton and proton–air inelastic cross sections and values for the elasticity are varied in the hadronic interaction model QGSJET. Using the CORSIKA simulation program, the impact of these changes is investigated on air shower observables such as the average depth of the shower maximum X_max and the number of muons and electrons at ground level. Calculating the mean logarithmic mass from experimental X_max values, it is found that a moderate logarithmic increase of the proton–proton inelastic cross section from σ^inel_pp = 51 mb at E₀ = 10⁶ GeV to σ^inel_pp = 64 mb at E₀ = 10⁸ GeV, and an elasticity, additionally increased by 10%–15%, describe the data best. Using these parameters, the mean logarithmic mass ⟨ln A⟩ derived from X_max measurements is compatible with the extrapolations of the results of direct measurements to high energies using the poly-gonato model.

We investigate the potential of 3 kiloton-years (kTy) of KamLAND data to further constrain the Δm² and tan²θ values compared to those presently allowed by existing KamLAND and global solar data. We study the extent, dependence and characteristics of this sensitivity in and around the two parts of the LMA region that are currently allowed. Our analysis with 3 kTy simulated spectra shows that KamLAND spectrum data by itself can constrain Δm² with high precision. Combining the spectrum with global solar data further tightens the constraints on allowed values of tan²θ and Δm². We also study the effects of future neutral current data with a total error of 7% from the Sudbury Neutrino Observatory. We find that these future measurements offer the potential of considerable precision in determining the oscillation parameters (specially the mass parameter).

Laser spectroscopy has been used to measure the isotope shifts of ¹⁴⁶Ce and ¹⁴⁸Ce relative to ¹⁴⁴Ce, Z = 58. The new data, in combination with existing optical data on the stable isotopes and radioactive ¹⁴⁴Ce isotope, permits a study of charge radii variations for the even-N Ce nuclei from N = 78 to N = 90. This range covers both the N = 82 shell closure and the N = 88 shape transition region. A marked increase in deformation occurs at N = 88 for elements with Z ⩾ 60 but not for those with Z ⩽ 56. The new data for Ce (Z = 58) show an intermediate behaviour, resulting in a smooth increase in deformation with Z in the N = 88, 90 region.

We consider the evolution of a parton system which is formed in the central region just after a relativistic heavy ion collision. The parton consists of mostly gluons, minijets, which are produced by elastic scattering between constituent partons of the colliding nuclei. We assume that the system can be described by a semi-classical Boltzmann transport equation, which we solve by means of the test particle Monte Carlo method including retardation. The partons proliferate via secondary radiative gg → ggg processes until the thermalization is reached for some assumptions. The extended system is thermalized at about t = 1.6 fm c⁻¹ with T = 570 MeV and remains in kinetic equilibrium for about 2 fm c⁻¹ with breaking temperature T = 360 MeV in the rapidity central region.

Unique because of their super-light masses and tiny interaction cross sections, neutrinos combine fundamental physics on the scale of the miniscule with macroscopic physics on the scale of the cosmos. Starting from the ignition of the primal p-p chain of stellar and solar fusion reactions that signal star-birth, these elementary leptons (neutrinos) are also critical players in the life-cycles and explosive deaths of massive stars and the production and disbursement of heavy elements. Stepping beyond their importance in solar, stellar and supernova astrophysics, neutrino interactions and properties influence the evolution, dynamics and symmetries of the cosmos as a whole. Further, they serve as valuable probes of its material content at various levels of structure from atoms and nuclei to valence and sea quarks.

In the light of the multitude of physics phenomena that neutrinos influence, it is imperative to enhance our understanding of neutrino interactions and properties to the maximum. This is accentuated by the recent evidence of finite neutrino mass and flavour mixing between generations that reverberates on the plethora of physics that neutrinos influence. Laboratory experiments using intense neutrino fluxes would allow precision measurements and determination of important neutrino reaction rates. These can then complement atmospheric, solar and reactor experiments that have enriched so valuably our understanding of the neutrino and its repertoire of physics applications. In particular, intermediate energy neutrino experiments can provide critical information on stellar and solar astrophysical processes, along with advancing our knowledge of nuclear structure, sub-nuclear physics and fundamental symmetries.

So where should we look for such intense neutrino sources?

Spallation neutron facilities by their design are sources of intense neutrino pulses that are produced as a by-product of neutron spallation. These neutrino sources could serve as unique laboratories to enrich our knowledge of neutrino physics and the multifaceted science it interfaces. In fact, the neutrino energy spectra expected at spallation neutron facilities overlap remarkably with those emanating from distant supernovae and these sources seem `made to order' for terrestrial studies of supernova reactions. They are also in a suitable energy regime to pursue neutrino-mediated studies of nuclear structure, fundamental symmetries and solar reactions.

Recent research indicates neutrino-nuclear reactions may be even more influential in supernova dynamics and detection than hitherto believed. The need for in-depth understanding of the individual neutrino-nuclear reactions that collectively have dramatic effects on the large-scale dynamics of evolving stars points to laboratory measurements of neutrino reactions on various nuclei as a premier requirement of neutrino-nuclear astrophysics. Such experimental data can improve our input to the extensive modelling projects that investigate the evolutionary stages of exploding supernovae and further our understanding of their internal physics.

State-of-the-art simulations exploring the neutrino-reheating phases fail to produce explosions---yet clearly nature explodes her supernovae. Matters pertaining to the galactic abundance of very p-rich nuclei and the various isotope ratios are by no means well defined and demand further research, as do the intricacies of the nucleo-synthesis channels. Neutrino-nuclear experiments are also essential for proper development and calibration of appropriate supernova detectors.

Solar neutrino research and detection have contributed vastly to our current understanding of neutrino science and have helped to validate the standard solar model. The chapter is by no means closed and experiments with intense neutrino fluxes could enrich valuably our understanding of both neutrino and solar physics.

Neutrino nuclear reactions are not only important for their role in nuclear astrophysics, but also for the insight they provide on nuclear structure and the theoretical models used to calculate nuclear excitations by neutrinos. They can also provide better precision for the elastic axial form factor and serve as effective probes of the strangeness content of nuclei.

Neutrino interactions with charged leptons can add significantly to our understanding of electroweak physics and neutrino-electron elastic cross sections measured at intense pulsed sources can provide precision constraints on the electroweak parameters.

The intrinsic properties of the neutrino, including mass values and oscillations, form a subject of critical current interest and research. The parameter space for neutrino oscillations and studies of electroweak interactions that could be accessed at spallation neutron sources would complement the research undertaken at higher energy neutrino facilities and neutrino factories.

The following collection of articles highlights the physics research that could be undertaken with neutrinos at spallation neutron facilities. It addresses open questions that need research and some of the experimental aspects and detector features associated with conducting that research. We feel this will be an effective and timely enterprise in the light of renewed international interest in spallation neutron sources (one is under construction at Oak Ridge, TN, USA and others are being considered in Europe and Japan), and the critical role of intermediate energy neutrino physics in particle, nuclear and astrophysics. The collection is by no means exhaustive or complete, but we hope it will provide a unique and valuable compendium for reference and guidelines as nuclear, particle and condensed matter scientists join hands for basic research at shared facilities.

We would like to take this opportunity to thank the authors who have taken time from their various commitments to contribute to this special section and A Mezzacappa and W R Hix for providing the cover image displaying the interplay between microscopic neutrino-nuclear processes and the macroscopic supernova dynamics. We would also like to thank Journal of Physics G: Nuclear and Particle Physics for hosting this section and apologize for any errors or credits that we may have missed.

This article provides a brief review of neutrino research at LAMPF and at ISIS, including the early history of both programmes. The techniques adopted for the characterization of the neutrino fluxes, and a description of the neutrino experimental programmes at both facilities are given.

In this brief review we explore the role of neutrino–nucleus interactions in core-collapse supernovae and discuss open questions. In addition implications of neutrino mass and mixings in such environments are summarized.

New facilities to measure neutrino–nucleus cross sections, such as those possible in conjunction with spallation neutron sources, could provide an experimental foundation for the many neutrino–nucleus weak interaction rates needed in supernova models. This would enable more realistic supernova models and provide a greatly improved ability to understand the physics fundamental to supernovae by comparison of these models with detailed observations. Charged- and neutral-current neutrino interactions on nuclei in the stellar core play a central role in supernova dynamics and nucleosynthesis as well as being important for supernova neutrino detection. Measurements of these reactions on judiciously chosen targets would provide an invaluable test of the complex theoretical models used to compute the large number of neutrino–nucleus cross sections that are needed.

The neutrinos emitted from supernovae contain information about the physics of stellar collapse and of the nature of the neutrinos themselves. Several large detectors exist that will be capable of observing some subset of those neutrinos. In addition, we have designed OMNIS, the Observatory for Multiflavour NeutrInos from Supernovae. OMNIS will detect the neutrinos from (a) neutral-current interactions from ν_e, ν_μ, , ν_τ and , and (b) charged-current interactions from high-momentum ν_e, with lead nuclei. It will utilize two types of detectors: (1) lead slabs alternating with vertical planes of neutron detectors, in which neutrons produced by neutrino–lead interactions will be detected, and (2) lead perchlorate, in which both the resulting neutrons and Cerenkov light will be detected. OMNIS will measure neutrino masses below 100 eV, provide new information on MSW or vacuum oscillations from ν_μ/ν_τ to ν_e, especially to Θ₁₃, and possibly diagnose the process of collapse to a black hole. It will observe the late-time evolution of the neutrino distributions, and possibly see predicted late-time effects, e.g. a phase transition from neutron-star matter to kaon-condensed matter or quark matter. OMNIS is also sensitive to some modes of nucleon decay that should make it possible to improve significantly on present limits for those modes. Of crucial importance to OMNIS is an experiment, using neutrinos from a stopped pion beam, to determine the flavour and energy-dependent response of lead to neutrinos. This will provide important input into cross section calculations for which few data currently exist. We plan to perform this experiment using one of the lead perchlorate detector modules from OMNIS.

The methods used in the evaluation of the neutrino–nucleus cross section are reviewed. Results are shown for a variety of targets of practical importance. Many of the described reactions are accessible in future experiments with neutrino sources from the pion and muon decays at rest, which might be available at the neutron spallation facilities. Detailed comparison between the experimental and theoretical results would establish benchmarks needed for verification and/or parameter adjustment of the nuclear models. Having a reliable tool for such calculation is of great importance in a variety of applications, e.g. the neutrino oscillation studies, detection of supernova neutrinos, description of the neutrino transport in supernovae and description of the r-process nucleosynthesis.

The standard nuclear physics approach and effective field theory approach for calculations of neutrino–deuteron cross sections for the solar neutrino energies are considered. Their main features, the level of accuracy and problems to be addressed for further developments are discussed.

There are several proposals to build facilities similar to the neutron spallation source (SNS) under construction at the Oak Ridge National Laboratory (ORNL). These are also prolific sources of intermediate energy neutrinos. We have used the parameters of the SNS to compute the spectra, flux and time structure of neutrinos from stopped-pions and muons from protons impinging on a high-Z target. We demonstrate the feasibility of a broad programme of measurements of neutrino–nucleus cross-sections, important in weak interaction nuclear physics and nuclear astrophysics that could be carried out at such facilities.

Standard model predictions for neutrino–electron scattering cross-sections, including effects of electroweak radiative corrections, are reviewed. The sensitivity of these quantities to neutrino dipole moments, Z' bosons and dynamical symmetry breaking is described. Neutrino indices of refraction in matter are also discussed. A perspective on future initiatives with intense neutrino sources, such as from stopped pion decays at a neutron spallation source, superbeams or neutrino factories, is given.

Neutrino electron elastic scattering can be measured with great sensitivity at a spallation neutron source using an oil or water Cerenkov detector. The value of sin²θ_W can be determined to less than 2% at low q² and searches performed for neutrino magnetic moments and several exotic physics processes.

Spallation neutron sources utilizing intense pulsed GeV proton beams on heavy (high Z) targets are ideal for the investigation of neutrino oscillations involving and ν_μ. The fundamentals of neutrino oscillation theory are reviewed. Detailed descriptions of experiments that can be performed in the vicinity of a pulsed 1 GeV, 2 MW source are given. The parameters of the spallation neutron source (SNS) at Oak Ridge National Laboratory are used as an example. The results anticipated from other proposed sources can be scaled from the results presented here. The detector configuration chosen is a 2000 ton scintillating Cerenkov detector.