A. De Rújula

Demythification of electroproduction local duality and precocious scaling

In an effort to develop a quantitative check of asymptotically free color-gauge theories, we analyze the logarithmic corrections to ξ-scaling coming from anomalous dimensions and coefficient functions of twist-two operators and compare with electroproduction data for 1 ⩽ Q^2 ⩽ 16 GeV^2. Excellent agreement is obtained using g^2(2 GeV)4π^2 = 0.17 for the effective quark-gluon coupling in the color-gauge theory. Effects of higher-twist operators are suppressed by powers of M_0^2Q^2. We use data from the resonance region to show M_0 ⋍ 400 MeV, in agreement with theoretical expectations. Our fit to νW_2 in the scaling region also describes the resonance region in the sense of Bloom-gilman local duality. We show that local duality is a consequence of the moment predictions obtained from the operator-product expansion in quantum chromodynamics. We resolve a paradox associated with local duality and spin-zero targets. Present measurements of R = σLσT at large x and Q^2 are systematically higher than our predictions.

NEUTRINO OSCILLATION PHYSICS WITH A NEUTRINO FACTORY

Abstract Data from atmospheric and solar neutrinos indicate that there are at least three neutrino types involved in oscillation phenomena. Even if the corresponding neutrino mass scales are very different, the inevitable reference to mixing between more than two neutrino types has profound consequences for the planning of the accelerator experiments suggested by these results. We discuss the measurement of mixing angles and CP phases in the context of the neutrino beam emanating from a neutrino factory: the straight sections of a muon storage ring. We emphasize the importance of charge identification. The appearance of wrong-sign muons in a long baseline experiment may provide a powerful test of neutrino oscillations in the mass-difference range indicated by atmospheric-neutrino observations.

The self-couplings of vector bosons: does LEP-1 obviate LEP-2?

Abstract Theories beyond the standard model (“meta-theories”) are severely constrained by the current body of data and must necessarily respect the standard gauge symmetry. We analyze the constraints on two generic types of meta-theory, in which fundamental scalar do or do not exist. The novel low-energy effects can be comprehensively described by grafting onto the standard lagrangian new operators that - in the sense of a Taylor expansion - form a complete set. Completeness calls for consideration of previously discarded operators, and for a thorough exploitation of the equations of motion. We illustrate the current strictures by focusing on the allowed range of departures from the most crucial, untested, precise standard prediction: the size and structure of the triple gauge-boson vertices. We conclude that their direct measurement at LEP-2, while phenomenologically very interesting, is, alas, unlikely to provide new information.

A Matter-Antimatter Universe?

We ask whether the universe can be a patchwork consisting of distinct regions of matter and antimatter. We demonstrate that, after recombination, it is impossible to avoid annihilation near regional boundaries. We study the dynamics of this process to estimate two of its signatures: a contribution to the cosmic diffuse γ-ray background and a distortion of the cosmic microwave background. The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter-antimatter symmetric universe is empirically excluded.

An antimatter spectrometer in space

Abstract We discuss a simple magnetic spectrometer to be installed on a satellite or space station. The purpose of this spectrometer is to search for primordial antimatter to the level of antimatter/matter ≈10 −9 , improving the existing limits obtained with balloon flights by a factor of 10 4 to 10 5 . The design of the spectrometer is based on an iron-free, NdFeB permanent magnet, scintillation counters, drift tubes, and silicon or time projection chambers. Different design options are discussed. Typically, the spectrometer has a weight of about 2 tons and an acceptance of about 1.0 m 2 sr. The availability of the new NdFeB material makes it possible for the first time to put a magnet into space economically and reliably.

Charged dark matter

Abstract We propose that dark matter is made of CHAMPs, charged massive particles that survive annihilation in the early Universe. We constrain champs to be matter-antimatter symmetric, to provide critical mass density, and to constitute the non-baryonic halo of galaxies such as ours. We show that the window of allowed champ mass extends from 20 to 1000 TeV. Champs of charge + 1 should now appear as super-heavy isotopes of hydrogen. While some of their antiparticles could bind to 4He nuclei somewhat after primordial nucleosynthesis (also to appear today in the disguise of super-heavy hydrogen), we argue that negative champs overwhelmingly bind to protons to pose as super-heavy stable neutrons. En route to detectors, these bound champs suffer nuclear reactions that change their ultimate appearance. By the time they come to rest, negative champs have recombined with larger nuclei to form various super-heavy isotopes. We discuss how and where to search for relic champs.

Radiative corrections to high-energy neutrino scattering

Abstract Motivated by precise neutrino experiments, we reconsider the electromagnetic radiative corrections to the data. We investigate the usefulness and demonstrate the simplicity of the “leading log” approximation: the calculation to order α ln ( Q / μ ), α ln ( Q / m q ). Here Q is an energy scale of the overall process, μ is the lepton mass and m q is a hadronic mass, the effective quark mass in a parton model. We identify those questions the answers to which do not depend on unknown hadron parameters like quark masses. The leading log radiative corrections to d δ /d y distributions and to suitably interpreted d δ /d x distributions are quark-mass independent. We improve upon the conventional leading log approximation and compute explicitly the largest terms that lie beyond the leading log level. In practice this means that our model-independent formulae, though approximate, are likely to be excellent estimates everywhere except at low energy or very large y . We point out that radiative corrections to measurements of deviations from the Callan-Gross relation and to measurements of the “sea” constituency of nucleons are gigantic. The QCD inspired study of deviations from scaling is of particular interest. We compute, beyond the leading log level, the radiative corrections to the QCD predictions.

Calorimetric measurements of 163holmium decay as tools to determine the electron neutrino mass

Abstract We compute the spectrum of “calorimetric” energy in the electron capture decay of 163 Ho. A calorimetric experiment would yield an excellent determination of the ( 163 Ho, 163 Dy) mass difference. The proximity of the spectral endpoint to an atomic resonance makes the fraction of events that are sensitive to a non-zero neutrino mass superior in 163 Ho decay than in tritium decay.

A fresh look at neutrino oscillations

Abstract We analyze the present experimental situation on neutrino oscillations in the standard weak interaction theory with three neutrinos. Sizeable oscillations νe ⇌ ντ are compatible with, and perhaps indicated by, present data.

Neutrinoless double electron capture as a tool to measure the electron neutrino mass

A nucleus (Z, A) may capture two atomic electrons to become (Z − 2, A). For Majorana neutrinos this may occur with no neutrino emission, the process is a virtual mixing of the parent atom and the daughter atom with two electron holes. The process becomes real as the daughter atom de-excites. In some cases where the daughter nucleus is excited, the neutrinoless decay may be enhanced by its proximity to a virtual resonance. We identify the 112Sn → 112Cd transition as a good case. The no-neutrino lifetime for mν = 30 eV ranges from 1022 to 1027 years as a function of the insufficiently well determined distance to resonance. The signatures of the two- or no-neutrino modes are very different.