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Positive baryon numbers (A>0) and positive lepton numbers (L>0) characterize matter particles while negative baryon numbers and negative lepton numbers characterize antimatter particles. Matter particles and antimatter particles belong to two distinct classes of particles. Matter neutral particles are particles characterized by both zero baryon number and zero lepton number. This third class of particles includes mesons formed by a quark and an antiquark pair (a pair of matter particle and antimatter particle) and bosons which are messengers of known interactions (photons for electromagnetism, W and Z bosons for the weak interaction, gluons for the strong interaction). The antiparticle of a matter particle belongs to the class of antimatter particles, the antiparticle of an antimatter particle belongs to the class of matter particles. The antiparticle of a matter neutral particle belongs to the same class of matter neutral particles. A truly neutral particle is a particle identical with its antiparticle; it belongs necessarily to the class of matter neutral particles. All known interactions of the Standard Model conserve baryon number and lepton number; matter cannot be created or destroyed via a reaction governed by these interactions. Conservation of baryon and lepton number parallels conservation of atoms in chemistry; the number of atoms of a particular species in the reactants must equal the number of those atoms in the products. These laws of conservation valid for interaction involving matter particles are indeed valid for any particles (matter particles characterized by positive numbers, antimatter particles characterized by negative numbers, and matter neutral particles characterized by zero). Interactions within the framework of the Standard Model which conserve both matter and charge at the microscopic level cannot explain the observed asymmetry of our Universe. The strong interaction was introduced to explain the stability of nuclei: there must exist a powerful force to compensate the electromagnetic force which tends to cause protons to fly apart. The weak interaction with laws of conservation different from electromagnetism and the strong interaction was postulated to explain beta decay. Our observed material and neutral universe would signify the existence of another interaction that did conserve charge but did not conserve matter.

To date, no evidence of ββ0ν decay has been found despite tremendous experimental efforts. In contrast, ββ2ν decay has been clearly and definitely observed in several nuclei. These experimental facts question the reality of ββ0ν decay. This ββ0ν decay which violates lepton number conservation can only occur if the neutrino is massive and is its own antiparticle or in other words is a truly neutral particle. The observation of this decay implies then that the neutrino is a truly neutral particle and it has a non-zero mass. But the absence of ββ0ν decay implies only that at least one of the two necessary conditions is not fulfilled. Since the truly neutral character of neutrino is a necessary condition, it is important to provide objective criteria of truly neutral particles. We propose a generalized Gell-Mann and Nishijima formula which provides naturally the criteria of truly neutral particles. According to these criteria n and ν are different from their antiparticles for symmetric reason. The absence of ββ0ν decay could then be simply understood. Indeed a truly neutral particle could be more generally defined as a neutral particle with respect to all charges and is its own antiparticle. The Dirac character of the neutrino does not contradict any experimental fact.

The energy difference between members of the Pairing Triplet could be understood in the framework of charge independence. In the case of two-nucleon analogue stretched states, an estimation more refined than the addition rule is suggested to calculate the energy of pn or 2p states when the energy of 2n states is known. εc, defined as the difference between the residual energies of 2n and 2p states, could be interpreted as the Coulomb interaction between the two protons of the pair. The mean distances between the two nucleons, coupled to their minimum spin value and to their maximum spin value, could then be deduced illustrating the Pauli principle. Mirror members of an isospin triplet have similar lifetime and branching ratios, while the Tz=0 member has quite different properties due to the nonconservation of isospin in electromagnetic interaction. The [Formula: see text] state of the Tz=0 nuclei should decay through M1 transition of about 3 MeV to the [Formula: see text] state, and should have a short lifetime of about 1 fs. Charge independence could be tested by populating high-spin two-nucleon stretched states with 36Ar as the projectile. Proton-rich beam would be of interest to form mirror compound nucleus. Both compound nucleus and mirror compound nucleus would preferentially evaporate protons.

Particle-particle correlations are studied for large- and small-angle separations for the reactions 312 and 680 MeV $^{40}\mathrm{Ar}$${+}^{\mathrm{nat}}$Ag. The spectral shapes and angular ansiotropies allow a characterization of the effective temperatures and spin zones of the hot nuclear emission sources. Small-angle correlations are compared to reaction simulations that employ various parametrizations for the emission time scales. We conclude that the initial lifetime scale for $^{1,2,3}\mathrm{H}$ particle evaporation is of the order of ${10}^{\mathrm{\ensuremath{-}}22}$ s. These times are so short as to suggest a breakdown of the concept of ``sequential evaporation,'' for which a new ansatz is explored.

Large and small angle correlation measurements are reported for [sup 1]H-[sup 1]H, [sup 4]He-[sup 4]He, and [sup 2]H-[sup 4]He pairs from 7.8[ital A] and 17[ital A] MeV [sup 40]Ar+[sup nat]Ag. These measurements are interpreted with the aid of trajectory calculations designed to simulate evaporationlike emission of particles and fragments. The most important physical parameter needed to fit the correlation function peaks is the fractional yield of unstable fragments ([sup 8]Be or [sup 6]Li) compared to independently evaporated particles ([sup 4]He-[sup 4]He) or ([sup 2]H-[sup 4]He). In this approach, the peaks in the simulated correlation functions contain essentially no information concerning the space-time extent of the emitter source. Nevertheless, these simulations can account for the data very well.

Particle-particle coincidence measurements have been made for the reactions 312 and 680 MeV {sup 40}Ar+{sup nat}Ag. The large-angle correlation data indicate essentially complete energy thermalization even for 680 Mev {sup 40}Ar+{sup nat}Ag. They also allow for an assignment of {approx}64{h bar} for the rms spin and {approx}4.3 MeV for the average initial temperature of the composite nuclei formed by incomplete fusion. The small-angle correlation data for {sup 1}H-{sup 1}H and {sup 2}H-{sup 2}H are consistent with phase-space, statistical-model predictions of the evaporation lifetimes. This result implies that energy mixing and evaporation particle emission steps occur with intervals of {approx}10{sup {minus}22} s, a time period comparable to the traversal time for a projectile velocity of 17 MeV/nucleon.

The conservation of electric charge Q is a universal law in the sense that it should be conserved in any interaction, known or yet unknown. However, Q should not be considered as a simple number but as the half sum of two irreducible quantities, the baryon lepton asymmetric number BAL = A-L (where A is the baryonic number and L is the leptonic number) and total flavor TF. Conservation of electric charge implies obviously conservation of Q (considered as a simple number) but also BAL and TF. We verify that electromagnetism and strong interaction which conserve Q, A and L and all individual flavors conserve obviously BAL and TF; that weak interaction which conserves Q, A and L conserves also BAL and TF. However, conservation of BAL does not necessarily imply conservation of A and L. In effect Δ BAL = 0 has another solution ΔA = ΔL = ±1 which points to a possible solution to explain how a material and neutral universe could arise evolving from an A = 0, L = 0, Q = 0 state to an A > 0, Q = 0 state through a process which would conserve BAL and TF without conserving separately A and L.

The criteria of true neutrality would infer that the neutrino is not a truly neutral particle and thus would imply that ββoν decay is forbidden, in agreement with the absence of any evidence of this process so far. Any fundamental interaction admits at least one truly neutral particle as messenger. Materialization through SM interactions corresponds to the creation of a pair of baryon antibaryon or lepton antilepton. These pairs have the same quantum numbers as those of the neutral messenger responsible for their creation. No net change of baryon number or lepton number could be obtained through materialization. But, we know that our present Universe is composed of matter and is electrically neutral. This implies that the number of protons is strictly equal to the number of electrons. A possible scenario is put forward to account for these two fundamental experimental facts. The principle of complementarity would explain the exact balance of protons and electrons. Baryogenesis and leptogenesis would be the two faces of the same phenomenon. This scenario is compatible with the absence of ββoν decay and of proton decay and it does not require the unification of forces. This model could explain the asymmetric but nevertheless electrically neutral Universe; however, it could not account for the numerical value of the tiny excess of matter over antimatter in the early Universe. This value would be incidental. MC force with a structure analogous to that of weak force would ensure the neutrality of our Universe without requiring the strict matter-antimatter symmetry, rendering thus the concept of anti-Universe superfluous.

The application of the crude shell-model to A = 2Z + 2N + 2 (Z = N) nuclei leads to the concept of two-nucleon analogue stretched states in a triplet. Their energies are predicted by a simple addition rule. The pn-pairing is defined by analogy to 2n-pairing and 2p-pairing. These three pairings could be considered as the three members of a pairing triplet. The (36Ar, 34Cl) reaction should preferentially populate the analogue states in A = (2Z + 1, 2N + 1) nuclei.

New levels strongly excited by 112-MeV {sup 12}C ions on even Ni and Zn isotopes are {ital J}{sup {pi}} assigned on kinematical and geometrical arguments, crude shell-model calculations, and distorted-wave Born approximation angular-distribution analysis. These tentative assignments are supported by the Bansal-French model. Because of the contribution of additional collective effects, the two-proton transfer reaction spectra are less selectively fed than those obtained with the analogous two-neutron transfer reactions induced on the same targets in a similar energy range.

Mean square radii of light radioactive projectiles, including exotic isotopes close to the neutron drip line (11Li, 14Be, and 17B), have been deduced from total reaction cross-section measurements, using a simple microscopic model. The isospin dependence of nuclear radii is discussed and compared to other experimental results.

Gamma-ray multiplicities (first and second moments) have been measured, in the 220 MeV 20 Ne + nat Re and 315 MeV 40 Ar+ 165 Ho reactions, as a function of fission fragment masses and centre-of-mass total kinetic energies. The two reactions lead to the same fusion nucleus, 205 At, at the same excitation energy (167 MeV). The experimental critical angular momentum for the fission process in the Ne + Re system (91 ± 3) ℏ is close to l Bf =0 (~80ℏ) while in the Ar + Ho reaction this critical angular momentum (136 ± 4) ℏ is much larger than the l Bf =0 value, favoring the occurrence of the fast fission process. The observed widths of the fission fragment mass distribution: (42 ± 2) u in the Ne + Re system and (56 ± 4) u in the Ar + Ho reaction strengthen this hypothesis. For both compound nucleus fission and fast fission components in Ar + Ho, the total spin values obtained in absolute magnitude and in their dependence on the mass asymmetry are well described by assuming rigid rotation of the fissioning complex and statistical excitation of some collective rotational modes such as “Bending” and “Wriggling” according to the Schmitt-Pacheco model. These modes, however, are not all fully excited, their degrees of excitation are approximately the same for both fission components. From theoretical estimates of equilibration times, one anticipates the “Tilting” mode to be by far the last to be excited, and from its non-excitation in the present data together with the excitation of bending and wriggling, a time interval of about 10 −21 s to 2 × 10 −20 s can be derived for the reaction time of both normal fission and fast fission. The γ-ray multiplicity as a function of the c.m. total kinetic energy decreases in the Ne + Re system, while it increases in the Ar + Ho system even for symmetric splitting, which indicates experimentally for the first time that fast fission populates the whole mass range. This difference between the two reactions is in agreement with the normal-fission-fast-fission distinction in angular momentum space.

Total nuclear reaction cross-sections are determined by means of a 4π-γ method. The results cover a wide span of targets for various stable beams. The validity of the method is shown in a combined systematics including also the results of transmission-type experiments. The data are very well described by the formula developed by Kox et al. The same method is applied to secondary fragment beams produced from a 44 MeV/u22Ne beam on a 332mg/cm2 181Ta target. Using the LISE spectrometer the fragments4, 6He,6–9, 11Li,7, 9–12, 14Be,10–15, 17B11–19C,13–19N,15–21O,18– 21F and20,21 Ne are analyzed and transported to interact with a 199.4 mg/cm2 Cu target surrounded by a 4π-γ counter. The measured total reaction cross-sectionsσ R are discussed in terms of the reduced strong absorption radiusr 0 and compared with other experimental results.

The /sup 60/Ni nucleus has been studied via the /sup 58/Ni(..cap alpha..,2p..gamma..) reaction at E/sub ..cap alpha../ = 32 MeV using in-beam ..gamma.. spectroscopy techniques. High-spin states up to 10 MeV excitation have been established. Among the five branches depopulating the yrast J/sup ..pi../ = 7/sup -/ state has been found an E3 transition down to the 4/sup +/ state. Comparison with direct reaction results suggests the very likely (..nu..f/sub 5/2/,..nu..g/sub 9/2/)/sub 7/- configuration for the J/sup ..pi../ = 7/sup -/ yrast state at 5349 keV, suggesting then the (..nu..(p/sub 1/2/,p/sub 3/2/,f/sub 5/2/ )/sub 2/+/sup 2/ x (..nu..f/sub 5/2/,..nu..g/sub 9/2/)/sub 7/- /sup 2/)/sub 9/- configuration for the J/sup ..pi../ = 9/sup -/ yrast state. Other high-spin states might be accounted for by the breaking of the /sup 56/Ni core.

Resume By means of the 70 Zn (α, 2 n γ) 72 Ge reaction, levels with spins up to J π = 11 − , 12 + have been established with E x 68–72 Ge obtained through the Zn( α , 2n γ )Ge reactions with the existing theoretical calculations shows that with increasing neutron number the yrast transitions become more and more collective and that the ν g 9 2 shell becomes increasingly important to explain the properties of the low-lying states.

The nucleus $^{70}\mathrm{Ge}$ has been studied via the $^{68}\mathrm{Zn}(\ensuremath{\alpha},2n\ensuremath{\gamma})^{70}\mathrm{Ge}$ reaction at ${E}_{\ensuremath{\alpha}}\ensuremath{\simeq}30$ MeV using different in-beam $\ensuremath{\gamma}$ spectroscopic techniques. Levels up to 5.5 MeV have been identified and spins up to ${8}^{+}$ have been established.

The 66 Ga nucleus has been studied via the reactions 64 Zn( α , pn γ ) at E a = 30 MeV and 63 Cu( α , n γ ) at E a = 18 MeV using different in-beam γ-spectroscopy techniques: excitation functions, electronic timing, angular distributions and γ-γ coincidences. High-spin states up to 4 MeV excitation and 11 + characteristics have been established. They are plainly interpreted in terms of the single-particle shell model from the weak coupling of a 65 Ga core to a g 9 2 neutron.

Yrast levels of /sup 68/Zn have been investigated via measurements of excitation functions and angular distributions of single ..gamma.. rays and of ..gamma..-..gamma.. coincidences following the /sup 65/Cu(..cap alpha..,p ..gamma..)/sup 68/Zn reaction with ..cap alpha.. particle energies between 12--21 MeV. Spins up to 8h were assigned to observed states. (AIP)

Par la méthode d'atténuation de l'effet Doppler-Fizeau (ajustement de la forme de la raie) nous avons tout particulièrement mesuré, dans les noyaux 68Ge, 70Ge et 66Zn obtenus par réaction (α, 2nγ) à Eα = 30 MeV, les durées de vie des états de haut spin. Le fait que la cible soit autoporteuse d'épaisseur finie de 1,2 à 1,5 mg/cm2, permet de déterminer les pouvoirs d'arrêt avec une bonne précision. Les résultats concernent une trentaine de niveaux, en particulier les niveaux de spin élevé (Jmax = 8 dans 70Ge, Jmax = 10 dans 68Ge, J max = (12) dans 66Zn) et font apparaître dans le cas des 68Ge et 70Ge la coexistence de niveaux faiblement et fortement collectifs, indiquant ainsi la mollesse de ces noyaux de transitions.

The different paradigms on which traditional information retrieval systems are built are reused to design Web search engines. However, designers have to innovate in order to adapt to this particular documentary context, which has an important impact on the way tools operate. Through an analysis of French and English scientific literature, and observations made during Web search training sessions, we try to define how far users are taken into account in the design of such systems, by comparing paradigm implementation to recent researches on information needs and the informational process. An analysis of the different steps of an information retrieval process highlights the complexity and the many dimensions of the concept of relevance in document retrieval.

The level scheme of 63Cu has been experimentally investigated through the 63Ni(α, pnγ)63Cu reaction using standard on-line γ-ray spectroscopic techniques. An isomeric high-spin yrast state J π = 17 2 + (τ = 6.1 ± 0.6ns; |g| is observed at 4498 keV excitation energy. The resulting 63Cu decay scheme is discussed in the framework of nuclear models. The g 9 2 single-particle shell orbital seems to be essential in the explanation of the high-spin positive-parity states proposed in this work, although these states cannot be simply interpreted by the coupling of a proton g 9 2 with a 62Ni core.

The $^{60}\mathrm{Cu}$ nucleus has been studied via the $^{58}\mathrm{Ni}(\ensuremath{\alpha}, \mathrm{pn}\ensuremath{\gamma})$ reaction using different techniques of in-beam $\ensuremath{\gamma}$ spectroscopy. As in the other odd-odd Cu isotopes, the ${g}_{\frac{9}{2}}$ shell plays an important role for the explanation of observed high-spin states. Some of these (particularly ${6}^{\ensuremath{-}}$ and ${9}^{+}$ states) could be interpreted as two-nucleon states in the framework of a crude shell model.

L'etude de la reaction 31P(p, α) de Ep = 1 MeV a 2,02 MeV et de la diffusion elastique 31P(p, p) aux environs de 2 MeV nous a permis de mettre en evidence et de determiner les caracteristiques de niveaux excites du 32S de 9,8 a 10,8 MeV.

The presence of a strong discontinuity in the free α−α scattering amplitude at 40 MeV is used as a probe for the identification of α clusters in nuclei. The Li6(α,2α) reaction is investigated at 37.5 and 43.5 MeV with the deuteron as spectator in order to produce quasifree scattering conditions. The distributions measured at these two energies are found to be very different in magnitude as well as in structure, and this phenomenon is attributed to the presence of α−α scattering in the α−Li6 collision. Calculations based on the plane-wave impulse approximation are unable to reproduce the distributions even qualitatively. A calculation based on the graph formalism which takes into account the exact phase-shift amplitude of the free α−α collision fits the two distributions with the same set of parameters. One may conclude that these observations are in favor of the existence of α particles inside the Li6 nucleus.

Les distributions angulaires de la reaction 16O(d, p 1)17O* (871 keV) sont analysees par interference de stripping (DWBA) et noyau compose autour des resonances a Ed ~ 0,450, 0,650 et 1 MeV mises en evidence dans un travail anterieur.

Experimental results of the reaction 6 Li(d, α ) have been fitted using the complex eigenvalue theory. We have examined different possible level schemes with the penetration factors defined by (i) Π c = e c 2 k c 2 l and (ii) P c = 1/( F c 2 + G c 2 )| r c = a c . Good fits are obtained with the following level schemes: 0 + (≈ 22.7 MeV) 4 + (≈ 22.7 MeV) 2 + (≈ 25 MeV); 2 + (≈ 22.6 MeV) 4 + (≈ 22.6 MeV) and 2 + (≈ 25.1 MeV). The level scheme 2 + (22.54 MeV) 0 + (24.02 MeV) 2 + (25.23 MeV) suggested by Mani is also possible. Therefore it is impossible to define the best set with the reaction 6 Li(d, α ) only.

The response of photovoltaic cells to heavy ions and fission products have been tested in-beam. Their main advantages are their extremely low price, their low sensitivity to energetic light ions with respect to fission products, and the possibility to cut and fit them together to any shape without dead zone. The time output signals of a charge sensitive preamplifier connected to these cells allows fast coincidences. A resolution of 12 ns (FWHM) has been measured between two cells.

A compilation of a large number of experimental results supporting a crude shell-model description of two-nucleon high-spin states is presented. A simple addition rule is deduced: In even nuclei the energy of a state involving two nucleons coupled to their maximum spin value is simply the sum of the experimental energies of each nucleon in its single-particle state in the neighboring nucleus plus the pairing energy when the two nucleons are identical. This simple model gives predictions in a parameter-free way, all the involved data being extracted from experiments.