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The strong force, which binds quarks and gluons together in hadrons, is commonly attributed to the color charge, a property of quarks and gluons only, which is analogous to the electric charge responsible for the electromagnetic force. In analogy to the electromagnetic force which is thought to be mediated by the exchange of virtual photons, the strong force is thought to be mediated by the exchange of gluons. At femtometer distances the strong force is much stronger than the Coulombic repulsion and increases with distance, a behavior called colorconfinement. At shorter distances the strong force becomes weaker, a behavior known as asymptotic freedom. The residual strong force, which keeps protons and neutrons bound in nuclei, is typically a factor of 100 weaker than the strong force. It is thought to be analogous to the van der Waals forces in chemistry which originate from the Coulombic forces but are much weaker due to charge screening. A similar type of color charge screening is thought to make the residual strong interaction (energies of ∼ 5 MeV ) much weaker than the strong force itself (energies of ∼ 500 MeV ). A first disappointment for the newcomer is that there is no simple expression, such as Coulomb’s or Newton’s law, allowing for fast computation of the strong force between two particles. The current theory of the strong force is quantum chromodynamics (QCD) and one of its predictions is that for energies below ∼ 200 MeV, frequently termed QCD scale, the quark-gluon plasma condenses to form hadrons, i.e. baryons and mesons.

Is the strong force simply relativistic gravity? The very good, semiquantitative agreement shown in Table 1.1 and in Chaps. 7–10 between experiment and the Bohr-type rotating neutrino model described in Chap. 6 and summarized in Table 1.1 or 7.1 provides strong support to a positive answer. This is of course at the beginning quite counterintuitive since we have always been taught that strong force and gravity are the strongest and weakest forces, respectively, in nature. Their coupling constants differ by some forty to sixty orders of magnitude, and it is generally but rather vaguely anticipated that these coupling constants will merge, together with the electrostatic coupling constant, at distances of the order of the Planck length (∼10−35 m) and energies of the order of the Planck mass energy (∼1019 GeV ). A quantitative examination of the coupling constant behavior of relativistic gravity, assisted by the rotating neutrino hadron model, may thus provide useful and perhaps conclusive information.

The majority of nuclear reactions in astrophysics involve unstable nuclei which are not yet fully accessible by experiments. Therefore, there is high demand for reliable predictions of cross sections and reaction rates by theoretical means. The majority of reactions can be treated in the framework of the statistical model (Hauser-Feshbach). The global parameterizations of the nuclear properties needed for predictions far off stability probe our understanding of the strong force and take it to its limit The sensitivity of astrophysical scenarios to nuclear inputs is illustrated in the framework of a detailed nucleosynthesis study in type II supernovae. Abundances resulting from calculations in the same explosion model with two different sets of reaction rates are compared. Key reactions and required nuclear information are identified.

As can be seen from the results summarized in the previous section, the behavior of the Hamiltonian in the region of strong interactions for which short range correlations exist fits the results of the experiment better than the results in the weak interaction (corresponding to the constant interaction) regime. Especially one should note the shape of the conductance peak spacing and the value of the correlation flux. The strong interaction behavior of these quantum dots is the result of their low density. The fact that these quantum dots are strongly coupled Coulomb systems can be seen from the results of recent transport measurements, which cannot be explained in the weak interaction limit.

Mechanical activation process and mechanochemical activation of the solid matter resulting from this process are represented by a new scientific discipline, developed within the physics of a solid body. This multidisciplinary scientific discipline is currently dealt mainly by the research scientists investigating the new materials technologies. Technologies of mechanoactivation are based on the activity of mechanical energy applied on certain material. A thorough study in this area imposes a need to define thermodynamically, mechanical physical and physicochemical processes occurring within the material, comminuting to Micronics dimensions under influence of mechanical energy. The main principles lying behind mechanoactivating technologies rely on changed energy properties of processed solid materials, i.e. on gravitational and electromagnetic properties. These properties are changed due to a changed energy condition of the solid matter, induced by the activity of mechanical energy. Mechanical activation of material is the process accompanied by the energy changes within the processed grains. Mechanical activation process is the system, which comprises the fields of the active forces, devices and mineral grains, in which the centrifugal acceleration may exceed gravitational acceleration by 100 times. In the centrifugal field, mineral grains are brought together by a strong force, whereby the gravitational force acting within a narrow space around particles exceeds weight of the grains by several tenths times. Such a loading of material results in elastic and plastic modifications, changing the shape, volume and surface density of the grains. The energy properties induced by mechanical force are best expressed in the change of the grain inertia. In this paper, the possibility of the grain inertia measurement by means of automatic grain counter is presented.

Quantum Chromodynamics (QCD) is the theory of the strong interaction. The strong force is felt by hadrons, such as the proton, neutron, kaon, but is not felt by leptons, such as the electron, neutrino, muon. It is a local gauge theory, similar to Quantum Electrodynamics (QED) but with a non-Abelian interaction.

Many Cerium, Ytterbium and Uranium systems exhibit a heavy fermion behaviour due to the Kondo effect and, in the case of a lattice, there is a strong interaction between the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida (RKKY) indirect interaction. In this paper, we discuss the competition between the Kondo effect and magnetism in both the Kondo-lattice and Anderson-lattice models and we present a “revisited” version of the Doniach diagram with a drastically reduced Kondo temperature for the lattice. Then, we discuss very briefly the multichannel Kondo effect and the case of Uranium compounds where a coexistence between the Kondo effect and magnetism seems to occur.

By the mid seventies, the search for the triplet of weak bosons W± and Z had become the obvious and highest priority goal of experimental particle physics. After decades of unsuccessful searching, neutral currents had been evidenced in neutrino interactions [1], at last giving experimental support to the ideas of Glashow, Salam and Weinberg [2] about the unification of electromagnetic and weak interactions. With the work of t’ooft [3], soon followed by the advent of quantum chromodynamics in the strong interaction sector [4], the essential role played in Nature by non-abelian gauge theories had become apparent. Moreover, the classification of quarks and leptons in terms of SU(2) doublets had been clearly established [5]. Following this, an experimenter not aware of the utmost importance and urgency of producing and detecting the weak bosons simply had no excuse. However, their masses, expected in a range between 50 and 100 GeV/c 2, were too high to make their production possible using existing accelerators. The problem was therefore to design a collider of sufficiently high energy: many physicists got busy trying to solve it.

I describe our understanding of the strong interactions at the end of the 1960’s and the impact of the experiments on deep inelastic scattering. I recall the steps that lead from the attempts to understand these experiments to the discovery of asymptotic freedom in 1973, the notion of confinement and the subsequent rapid emergence, development and acceptance of the non-Abelian gauge theory of color (QCD) as the theory of the strong interactions. I end with a discussion of the implications of asymptotic freedom.

In 1986, E. Ruska was awarded the Nobel Physics Prize for his pioneering work of building the world’s first transmission electron microscope (TEM) in the late 1920s. The TEM was originally based on the physical principle that charged particles can be focused by magnetic lenses. The strong interaction of incident electrons with electrons and nuclei in crystals makes it feasible to analyze structures of solids based on electron micrographs. The rapid development of TEM techniques in the last 30 years has made it possible to image crystal structures at atomic resolution. Thus TEM has become one of the key research tools in characterizing condensed matter.

The nonequilibrium time evolution of the hot hadronic plasma produced in a relativistic heavy ion collision is studied in the O(N) linear sigma model to leading order in the large N expansion. The chiral phase transition to the broken symmetry phase as the plasma expands and cools is described by the evolution of the order parameter . In order to create a large domain of disoriented chiral condensate (DCC) long wavelength fluctuations must become and remain unstable for times longer than the characteristic strong interaction time scale of a few fm/c. Numerical evidence is presented that such instabilities survive for proper times that are at most 3 fm/c, and hence do not give rise to a substantial signal of DCC in the coherence of the final state pions. The large N development of time-dependent field equations described in this work is quite general and should be applicable to the electroweak phase transition, bubble wall propagation, and baryogenesis problems as well.

The quest for understanding the structure and interaction of hadrons has been the main motivation of strong interaction physics for decades. The advent of Quantum Chromodynamics (QCD) has led to a theoretical description of the strong interaction in terms of the fundamental constituents, quarks and gluons. However, we are still a long way from having the general theoretical framework in place to understand the strong force as it is manifest in the structure of complex hadronic systems such as baryons. At very high energies, perturbative methods have proven very effective. At low energies, simulations on the QCD lattice have generated remarkable results about the static properties of hadrons. Even calculations of electromagnetic form-factors have been possible at low momentum transfers. However, for light quark baryons such as nucleons, the small quark masses are difficult to implement, and crude approximations have been necessary.

One of the challenges of modern heavy ion physics is the extraction of the equation of state for extremely excited nuclear matter. In particular, the creation and study of hadron matter at high net baryon density has received much attention recently. Not much is known about the strenght of the mean fields at large baryon densities. It is expected that the momentum dependence of the nuclear forces1, the excitation into resonance matter2 and the phase transition into the QGP3 will playa crucial role for the created mean fields. In particular, QCD — as the accepted theory of strong interaction — contains chiral symmetry (in the limit of massless quarks) which is spontaneously broken in its groundstate, the QCD vacuum (see e.g. recent lattice calculations4). A rapid restoration of this symmetry with increasing baryon density is predicted by all approaches which embody this fundamental aspect of QCD5,6 Therefore, nucleus-nucleus collisions in the bombarding energy region of baryon stop- ping could be favorable in order to study such medium effects as compared to ultrahigh energies, for which the two colliding nuclei may become transparent to each other. Transport calculations based on hadronic excitations and rescattering like the RQMD approach (strings, resonances)7 or the ARC model (resonances)8 predict that beam energies between 10 to 15 AGeV — as studied experimentally at the BNL-AGS 9, 10, 11 — are well suited to create the desired high stopping and baryon densities.

The field of strong interaction physics has become a common focus ofnuclear and particle physics: it is the place where the long-range properties of quantum chromodynamics (QCD) are expected to play their decisive but,as yet, quantitatively not well-understood role. Once the role of the quarks in hadronic interactions began to be well established, it was quite natural to consider their effects in nuclei. That is the reason why during the last few years many traditional questions of nuclear physics became again the subject of intensive investigations.

In this talk, I wish to describe the method of QCD sum rules as a means of taking into account strong interaction effects in physical phenomena in which strong interactions, as described by quantum chromodynamics (QCD) among quarks and gluons, play an important role. The determination of the isovector and isoscalar axial coupling constants, g A and g A S , via the method of QCD sum rules is used to illustrate the method. The determination of the neutron-proton mass difference from the method serves as another interesting example. Our present efforts focus on the possibility of employing the method to treat nonleptonic weak interaction problems, including parity-violating πNN, ρNN, and ωNN couplings, decays of heavy mesons or of heavy baryons, etc. Throughout the present talk, I shall discuss primarily the issues related to the nucleon structure.

The observation of the lowest excited state of the nucleon, the Δ-resonance, by Fermi and collaborators1 in 1952–55 was the first experimental evidence for an internal structure of the nucleon. It took another 15 years until Friedman, Kendall and Taylor2 discovered quarks and gluons as constituents of the nucleon in their pioneering experiments on deeply inelastic electron scattering. As any composite system the nucleon can be excited to a rich excitation energy spectrum. The excited states of the nucleon can be characterized by their mass, spin J, parity P, and isospin I. Fig. 1 shows the excitation spectrum up to a total mass of 1.7 GeV/c2. The excited states of the nucleon decay by the strong interaction into a nucleon in its ground state and one or several mesons with lifetimes of about 5 · 10−24 s, corresponding to a typical width of roughly 100 MeV. Because of their large widths the excited states are often called resonances. While all excited states have a strong decay branch into the pion + nucleon channel, only the S11(1535) resonance (J=1/2, I=1/2) with a mass of 1535 MeV is strongly coupled to the η meson. The observation of an η meson is thus a selective signal for the excitation of the S11(1535) resonance.

After Anderson’s great discovery of the positron, or positive electron, by no means did the search for ever more fundamental particles stop. Instead, things got ever more complex. The list of particles continued to swell and some of them soon began to exhibit very peculiar properties which often contradicted known theory.

The atomic nucleus is a quantum system consisting of a limited number of protons and neutrons. Although the strong interaction between the nucleons is not yet precisely known, there exist many theoretical models which describe to a certain extent the structure of the nuclei at low excitation energies. However, already above 1 or 2 MeV there are experimentally and theoretically many open questions. Experimental investigations and theoretical models provide in addition to microscopic descriptions also statistical information. These statistical interpretations can reveal essential new features of the nuclei and of the various models. Such studies concern regular and chaotic dynamics which relate averages and fluctuations in nuclei1, level densities, the K-quantum number, pairing and other problems. A basic prerequisite for these investigations are complete level schemes2 including spin and parity information.

Let us briefly review the properties of the four forces before we return to the unification attempts. The four forces of nature show a large variation in properties, their effective range and strength.

As we have seen, the strong nuclear force is responsible for the formation of quark-containing nuclear particles of matter such as baryons and mesons. However, all of the particles we have analyzed—created in reactions due to cosmic radiation in the upper earth’s atmosphere, but mainly in high-energy particle accelerators—decay shortly after creation, except for the proton (which is stable) and the neutron only as part of the nucleus of atoms. Free neutrons decay in approximately 15 minutes into a proton, electron, and electron-antineutrino.

At present, we have QCD for the strong force, the SU(2) × U(l) standard model for the electroweak force and general relativity for the gravitational force. Together, they seem to give us a satisfactory description of the physical world. However, there remains the puzzle of missing symmetry: These three theories are all based on symmetry. Yet, most of the symmetry quantum numbers are not conserved.

The end of the sixties and the beginning of the seventies were marked by a tremendous progress in elementary particle physics: the strong interaction theory (quantum chromodynamics) was created and the universal theory of electroweak interaction was proposed. Although there are no doubts about basic points of quantum chromodynamics and electroweak interaction theory, both of them possess a number of important problems which are so far unclear.

Introduction: In this essay I review in qualitative terms the present understanding of the vacuum structure and how it interplays with the general understanding of the physical laws. I discuss in turn: (The) Quantum Vacuum, The Electric Vacuum, The Confining Strong Interaction Vacuum, The Known and Unknown Higgs Vacuum, The Gravitating Vacuum and present at the end Historical Highlights

It is widely believed that Quantum Chromodynamics is the correct underlying theory of the strong interaction. Such belief exists despite our rather limited ability to investigate the long wavelength limit, where the poorly understood effects of confinement set in. In fact, the very structure of the QCD vacuum remains a mystery, and it is hoped that a better understanding of this vacuum will shed considerable light on the nature of the confinement mechanism.

In this NATO Advanced Study Institute many different problems of large-scale molecular systems were discussed. The range of topics covered in this ASI is immensely broad. In view of the very nature of this ASI, what I addressed in lecture and elaborated further here is only a subset of all the large-scale molecular systems discussed in the Proceedings. I am primarily concerned with irreversible processes (relaxation) in correlated systems in which some identical constituents, molecules, ions, or their analogues, are interacting in either the quantum or classical mechanical sense, whichever is appropriate. Additional randomness caused by possible factors such as the presence of not identical constituents and fluctuations of local environments makes the problem even more complex. Correlated systems with additional complications such as distribution and randomness will be referred to as complex correlated systems. I am interested in the dynamics of irreversible processes in these systems which require solutions to these many body problems that give the time developments of either macroscopic (e.g. stress, strain, and electric polarization) or microscopic (e.g. orientation of tagged molecules, center-of-mass vector of a probe polymer chain in a polymer matrix) dynamical variables. When interactions between the constituents are strong, the system becomes highly correlated and solution is extremely difficult. In this paper I shall focus on three examples of such highly correlated systems. These are: (1) a glass forming viscous liquid that is made up of molecular units that are densely packed together and hence interacting strongly with each other (e.g. (O-terphenyl, 1,3,5 trinaphthalbenzene, and toulouene); (2) a vitreous ionic conductor (e.g. the alkali oxide trisilicate and triborate glasses, Na2O-3SiO2 and Li2O-3B2O3 respectively and also defect crystalline ionic conductors (e.g. Na β-alumina) that contain a propensity of interacting ions; and (3) polymer melts of long linear or star branched macromolecules that are fully entangled with each other and noncrossability of these densely packed macromolecules implies strong interaction.

The pionic X-ray spectra of 181Ta, natRe, natPt, 197Au, 208Pb, 209Bi and 237Np have been investigated to obtain data which provide for a systematical investigation of the pionic 3d and 4f levels. Special attention was paid to experimental methods for obtaining clearly improved results as compared to earlier experiments, by using an array of Compton suppression BGO-shields and by using neutron time-of-flight discrimination to reduce background. Also to explore X-rays populating deeply bound pionic 1s-levels in 24Mg, 27A1, 28Si and 2p-orbits in 93Nb, natRu, respectively, coincidence techniques in combination with these high resolution Ge-BGO Compton suppression spectrometers were applied. Only deviations in the width of the pionic 3d-levels are observed. They are narrower by a factor 1.5 as compared to theoretical predictions. The same deviation as for Γ0(3d) is found for the strong interaction quadrupole shift, e2, for both the 4f- and 3d-orbits. An explanation for the difference in Γ0(3d) can be found by adding an isovector absorption term to the optical potential with a negative value for the parameters ImB1 or ImC1.

The study of antiprotonic atoms in low-pressure gas targets became possible through the intense low-energy beams at LEAR. Strong interaction effects and the pressure dependence of the atomic cascade have been measured in the elementary systems pH and pHe [1–8]. The deexcitation of very high atomic states and even molecular effects became visible in the spectra of antiprotonic noble gases [9] and CnHm compounds [10].

Strong interaction corrections to the decay rates and the production cross sections of the minimal standard model Higgs boson are discussed for the processes which are relevant to LEPI and SLC experiments.

Ion flow through membranes is not favored because it involves movement of charge through a low dielectric constant medium. The strong interaction between ions and the highly polarizable fluid, water, means that a great deal of energy is needed to remove ions from water. The low polarizability of the lipid environment in the membrane does not interact strongly with ions and therefore acts as a good barrier to ion flux. For these reasons, ion flux through membranes must be facilitated by a transport process or some polar defect in the membrane.

The subject of string theory originates from the study of the strong interaction. It starts with Regge poles, duality and Veneziano formalizm. Several important issues in string theory can be illustrated by reviewing the original motivation that lead to a dual resonance model of relativistic strings.

While the study of perturbative QCD has yielded important insights into the nature of the strong force at least in the high energy/momentum region, there are still outstanding problems in the low energy sector. For example, the Bloch-Nordsieck mechanism for cancellation of infra-red(IR) divergences doesn’t in general work in QCD (unlike QED)2 unless one is looking at ‘suitably’ inclusive cross sections. The main reason for this is the presence of interacting massless particles which typically give rise to infra-red or collinear singularities. It has been suggested that if we could do perturbation theory about a different vacuum which has no interacting massless particles then such problems could be ameliorated.

I would like to attempt to get two important points across in this necessarily superficial and incomplete theoretical review1 of polarization experiments: a) I would like to emphasize their versatility and their relevance to a large variety of aspects of hadron physics. I will discuss polarization measurements as tests of basic symmetries (parity, time reversal ......) a probe of strong interaction dynamics (e.g. in inclusive reactions) a tool for doing hadron spectroscopy (N* spectra, baryonium and di-baryon resonances, multiquark (?) states .....). b) I would like to present a qualitative picture of the wealth of experimental data on polarization parameters in pp and np scattering in the Regge language and in the diffraction language, emphasizing the overlap in basic assumption of the two approaches once the veil of their different language has been lifted. More important, both approaches agree that polarization data at medium energy do reveal the structure of the high energy diffractive amplitudes.

We live in interesting times. We have a theory, at last, of strong, weak, and electromagnetic interactions. Many new accelerators are ahuilding to test our theory.

Monte Carlo simulation of statistical systems is a well established technique of the condensed matter physicist. In the last few years, particle theorists have rediscovered this method and are having a marvelous time applying it to quantized gauge field theories. The main result has been strong numerical evidence that the standard SU(3) non-Abelian gauge theory of the strong interaction is capable of simultaneously confining quarks into the physical hadrons and exhibiting asymptotic freedom, the phenomenon of quark interactions being small at short distances.

The aim of this talk is to convince people that grand unified theories give a very nice and plausible explanation of a whole lot of different and at first sight unrelated phenomena, and they definitely have the merit and right to be taken seriously. A detailed analysis of many of the things that I mention here may be found in Ref. 1, which the interested reader may consult. I’ll try to argue in simple words that a grand synthesis (unification) of strong-electromagnetic and weak interactions beyond aesthetic appeal and conceptual satisfaction may be a necessity if for example we want to understand charge quantization. Such a picture has made many successful predictions1 such as sin2θW ≃ 0.20, ms ≃ 0.5 GeV and mb ≃ 5 GeV and for the first time it is possible to explain the absence of appreciable accumulations of antimatter in the universe, and directly and successfully estimate the baryon to photon ratio in the universe in terms of observable parameters of elementary particle physics. Then a with a lifetime not far above present lower bounds. Since the calculations of the proton lifetime have the usual theoretical uncertainties, we would like to urge experimentalists to improve measurements on the proton lifetime, because we believe that the decay of the proton will be the most dramatic confirmation of a grand synthesis of all elementary particle forces.

Differential scattering of Cs atoms from 4He clusters indicates strong interaction at all relative velocities between 140 and 350 m/s. Quantum fluid properties seem to be masked by the particular dynamics at the surface of the 4He clusters.

Electron-positron annihilation at high energy is giving some of the most significant results for our understanding of particle physics. Besides the discovery and detailed study of new quark flavors, they provide an important testing ground for electromagnetic, weak and strong interaction theories. Most of these central results will he covered in H. Lynch lectures, hut I shall try and show that there exists a wealth of less known results, either older, or new (or even futuristic), which deserve attention.

Within the conventional framework of a spontaneously broken gauge theory, general principles establish that the electroweak symmetry is broken by a new force that may be weak with associated new quanta below 1 TeV or strong with quanta above 1 TeV. The SSC parameters, \( \sqrt s= 40 \) TeV and ℒ = 1033 cm-2 s-1, define a minimal facility with assured capability to observe the signals of symmetry breaking by a strong force above 1 TeV. Foreseeable luminosity upgrades would not be able to compensate a much lower collider energy for these physics signals. If the strong WW scattering signal were seen at the SSC in the 1990’s it would provide a clear imperative for a collider with the physics reach of the ELOISATRON to begin detailed studies of the new force and quanta early in the next century.

The aim of these lectures is to give a review of the situation concerning neutrino and antineutrino inelastic scattering and the implication of recent high energy data concerning the number and the properties of quarks.

Nowadays we are accustomed to think of particle interactions in terms of elementary couplings of quarks and leptons. In table 1 we list major steps which have contributed to our present picture. Entries in square brackets refer to theoretical speculations; round bracketed entries are observed phenomena which demonstrate the dynamical reality of quarks, complementing their algebraic reality which emerged from an analysis of the hadron spectrum. In this course we will be mainly concerned with the weak couplings of quarks and leptons.

The question whether the 102 – 1015 GeV big desert is completely wild or contains some oases at intermediate mass scales (IMS) is still open. As we are denied any direct verification (at least for IMS some orders of magnitude away from MW), it behooves us to sharpen any possible motivation and/or consequences of such IMS. Apart from the “classical” emotional (aesthetical) repulsion for a desert which does not present any analog with previous physics, some interest in IMS has been renewed by new trends in particle physics: i) technicolour (including supercolour or technicolour/supersymmetric technicolour scenarios) and the composite models introduce a new fundamental strong interaction, whose scale must be in the TeV region to reproduce the phenomenological weak interaction scale MW (no matter how poor, they represent the only candidates for a dynamical understanding of MW); ii) some standard problems of the fruitful particle physics-cosmology marriage could require a prolonged first order phase transition, thus introducing some physical scale between the grand unification mass (MQU) and MW

Large N QCD is the zeroth order of the 1/N expansion, which is a candidate for a sensible approximation scheme for strong interaction phenomena. Monte Carlo simulations of reduced models reveal properties of this “bare” QCD. Results for static potential, string tension and deconfinement are reviewed, showing that largen QCD confines and that the variation from N=3 to N=∞ is small for \( {T_c}/\sqrt \theta \). The prospect of measuring properties of glueballs and mesons at large N in reduced models is discussed.

The pp atom is a simple system that permits to study NN strong interactions at threshold in depth and to exploit NN annihilations for light and exotic mesons spectroscopy. The study of NN interactions in depth at threshold requires to measure individually all the annihilation channels, to measure the global effects of all open annihilation channels (that reflect in the hadronic width of protonium atomic levels) and to measure the global effects of virtual elastic and charge exchange and of all open virtual annihilation channels (that reflect in the hadronic shift of the atomic levels). Ideally these studies should be done for all JPC states of protonium with L=0 and 1 in order to get the complete picture of the dynamics of the strong interaction and of its dependence on the quantum numbers of the initial state. The search of new mesonic resonances in pp annihilation requires to measure exclusive annihilation channels and the intermediate resonant states. This search and the study of the dynamics of NN annihilations at threshold are one a byproduct of the other. Experimentally two lines of research are open with different requirements from the X-ray detectors used for protonium spectroscopy.

At low temperatures two phenomena of collective behavior of the conduction electrons in metals are known: superconductivity and the Kondo effect. With the system (La, Ce) Al2 we succeeded in demonstrating a strong interaction between these two phenomena as predicted by Muller-Hartmann and Zittartz in 1971.1 The most unusual behavior of this superconducting alloy is the vanishing of superconductivity below a second transition temperature at very low temperatures. This second transition back into the normal state was first observed by Riblet and Winzer2 in an adiabatic demagnetization cryostat with a standard ac mutual inductance technique. Figure 1 shows a typical example of these two transitions. The induction signal of the specimen compared to that of a clean LaAl2 probe of the same size is plotted vs. temperature. This specimen with 0.67 at. % Ce substitution of La in LaAl2 becomes superconducting between 1.5 and 1°K and normal again below 0.5°K. As a consequence of this second transition, the temperature dependence of all the other superconducting properties becomes strange. It is therefore proposed to call such an alloy a “Kondo superconductor.”