Search

We have measured angular distributions of differential cross sections and analyzing powers ( A y ) of the reaction p p → d π + at six incident proton energies between 1.3 and 2.4 GeV. They confirm the rapid variations at √ s = 2.65 GeV suggested by earlier experiments. Deviations from a monotonic behavior are also found in the excitation functions of the differential cross section at t = 0 or where Θ π + (c.m.) = 0°. Structures clearly appear at √ s = 2.4 and 2.65 GeV, in some coefficients of the associated Legendre function expansions of A y .

Inelastic scattering of 340 MeV and 480 MeV α-particles has been measured on 58 Ni, 116 Sn and 208 Pb up to 60 MeV excitation energy. Consistent background subtraction and multipole analysis has provided the repartition of multipole strength for all three nuclei. The so-obtained response functions show the already known low-energy giant resonances in a detailed way, as well as new giant resonances at high energy.

Seven differential cross sections of the reaction $p+d\ensuremath{\rightarrow}^{3}\mathrm{He}+\ensuremath{\gamma}$ have been measured at ${T}_{p}=450 \mathrm{and} 550$ MeV between 52\ifmmode^\circ\else\textdegree\fi{} and 92\ifmmode^\circ\else\textdegree\fi{} (${\ensuremath{\theta}}_{\ensuremath{\gamma}}$ c.m.). $^{3}\mathrm{He}$'s were analyzed by the SPES I spectrometer in coincidence with photons detected by Cherenkov counters. The results are about twice the cross sections of the inverse reaction measured recently by Hegerath et al. and by Argan et al. The data are consistent, however, with the $\ensuremath{\gamma}+^{3}\mathrm{He}\ensuremath{\rightleftarrows}p+d$ data of Heusch et al.

First results for the (d,p) reaction on /sup 6/Li, /sup 9/Be, and /sup 16/O are presented for a scattering energy T/sub d/=698 MeV at momentum transfers 2< or =q< or =5 fm/sup -1/. Simple distorted-wave Born-approximation and rescattering calculations stress the need for a more comprehensive analysis by explicitly including both the stripping amplitude and mesonic degrees of freedom.

Cross sections for the /sup 12/C(p,p') reaction leading to the 1/sup +/ states at 15.1 MeV(T = 1) and 12.7 MeV(T = 0) were measured at a bombarding energy of 402 MeV. These data, covering a range of momentum transfer q from 0.45 to 2.65 fm/sup -1/ (0.6 --3.7m/sub ..pi../) provide a test of the effects, precursor to a pion condensate, predicted to be important for the T = 1 state near q = 2--3m/sub ..pi../. The cross sections for the two 1/sup +/ states are very similar fro large q, perhaps indicating that the precursor effects are small.

Differential cross sections have been measured for p+d\ensuremath{\rightarrow}\ensuremath{\gamma}${+}^{3}$He at ${T}_{\mathrm{p}}$(lab)=300, 350, 400, 425, 450, 470, and 500 MeV for ${\mathrm{theta}}_{\ensuremath{\gamma}}$(c.m.) near 60\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{}. Measurements were also made for d+p\ensuremath{\rightarrow}\ensuremath{\gamma}${+}^{3}$He at ${T}_{\mathrm{d}}$=376 MeV for ${\mathrm{theta}}_{\ensuremath{\gamma}}$(c.m.)=84\ifmmode^\circ\else\textdegree\fi{}, 98\ifmmode^\circ\else\textdegree\fi{}, and 113\ifmmode^\circ\else\textdegree\fi{}, and at ${T}_{\mathrm{d}}$=600 MeV for ${\mathrm{theta}}_{\ensuremath{\gamma}}$=96\ifmmode^\circ\else\textdegree\fi{} and 105\ifmmode^\circ\else\textdegree\fi{}. Our results are in agreement with those of the inverse reaction, \ensuremath{\gamma}${+}^{3}$He\ensuremath{\rightarrow}p+d of Sober et al., as is expected from time-reversal invariance. Our data agree with the latest results of Cameron et al. The older radiative capture measurements of Heusch et al. and the photodisintegration measurements made at other laboratories differ significantly from our results. Our data are compared with three theoretical models; the one proposed by Maximon and Prats comes closest to describing the data.

We present differential cross sections for p+ d → 3He + π0 at Tp = 300, 350, 400, 425, 450, 470 and 500 MeV, and for p + d → 3H + π+ at 500 MeV, mostly near θπ (c.m.) = 48° and 98°. The ratio dσ(pd → 3H π+)/dσ(pd → 3Heπ0) for identical four momentum transfer at 500 MeV is found to be 2.21 ± 0.17 to 2.57 ± 0.34, depending on angle. The dependence of the invariant matrix element squared |M|2 on the relativistic invariants t and s is examined; for a given value of t, |M|2 is almost independent of s for Tp between 350 and 800 MeV.

Negative-pion production leading to discrete excitation levels of the residual nucleus has been investigated on /sup 9/Be and /sup 12/C targets with 613-MeV protons. On the first seen spectra of /sup 13/O a strong excited peak is observed at 2.82 minus-or-plus 0.24 MeV in excitation energy. The resulting cross sections are found to be far below previously published theoretical predictions.

The knock-out reaction A( p , p)X has been used to search for narrow p -nucleus states. The experiment was performed using the 600 MeV/ c antiproton beam at LEAR and the high-resolution and large-acceptance magnetic spectrometer SPES II. The A -dependence of the annihilation-induced proton spectra has been studied on 2 H, 6 Li, 12 C, 63 Cu, 208 Pb and 209 Bi. The quasi-free elastic p p scattering observed in the lighter targets, and the comparison with the free p p scattering, also observed in this experiment, determine an effective proton number N eff for 1s- and 1p-shell protons. No evidence for narrow bound or resonant p -nucleus states could be found. Upper limits for their production are one order of magnitude lower than certain theoretical predictions, but consistent with the properties of the p -nucleus interaction, as established from recent elastic and inelastic scattering as well as from studies of antiprotonic atoms.

Proton-induced pion production at intermediate energies, leaving the final nucleus in discrete, resolved states, has been measured at the Saclay Synchrotron Saturne I, using the high resolution spectrometer facility SPES I. The (p, π+) reaction has been investigated on 9Be at proton energies of 410 and 605 MeV, and on 10B at incident energies of 320,410, 483 and 605 MeV. These data are presented and analysed in a coherent way, together with previous results at intermediate energies, by means of a pion exchange model. It is found that all the characteristic features of the data are reproduced satisfactorily.

The ( 3 He, d) reaction was studied on all stable Zr isotopes. Twenty-three unbound analog states in the Nb isotopes were populated. The observed cross sections were analyzed using two different methods for DWBA calculations of stripping to unbound analog states. The deduced proton spectroscopic factors are compared to the neutron spectroscopic factors obtained for the parent states from the (d, p) reaction studies. The agreement is generally good, except for the 97 Zr- 97 Nb isotope pair. The difference in the sensitivity to the transferred angular momentum between the (d, p) reaction and the ( 3 He, d) reaction to the analog states is discussed. The good agreement leads us to conclude that the ( 3 He, d) reaction to analog states may be used in nuclear spectroscopy for the study of levels in the parent states which are populated through large angular momentum transfer.

The reactions 95, 97 Mo(p, d) 94, 96 Mo were studied at a proton energy of 26 MeV. Angular distributions were measured from 11° to 40° and compared with distorted-wave Born approximation calculations; l -values and spectroscopic factors were extracted for the low-lying states of 94 Mo and 96 Mo. The angular distributions of these states have a characteristic l = 2 shape. The ratios of the summed spectroscopic factors to the 0 + , 2 + and 4 + states are in good agreement with the (2 d 5 2 ) n neutron configurations. The 2 + strength is strongly fractionated in both 94 Mo and 96 Mo. The 4 + strength in 94 Mo is split among two states, whereas in 96 Mo it is concentrated in the second 4 + state.

The nuclear structure of 50 Sc is investigated through the 48 Ca( 3 He, p) 50 Sc reaction using 3 He ions accelerated to 18.5 MeV in a cyclotron and semiconductor detectors. Data are obtained on the excitation energies and the spins and parities of a large number of levels in 50 Sc up to 6.62 MeV. The experimental data are compared with DWBA calculations using various wave functions obtained in the framework of the shell model with different degrees of sophistication as to the orbits considered. A reasonable agreement is obtained up to 3.5 MeV excitation energy in 50 Sc for the most complex wave functions. Above 3.5 MeV, the results indicate the existence of strong L = 2 transitions in the ( 3 He, p) reaction, which are not explained by current models, and also a new and previously unidentified collective mode of excitation in 50 Sc.

A systematic study of collective states excited in 44 MeV α-particle inelastic scattering by nuclei near closed shells with 28 neutrons, 20, 28, 50 and 82 protons is presented. The nuclei studied are 40Ca, 46, 48, 50Ti, 52Cr, 54, 56, 58Fe 58, 60, 62, 64Ni, 112, 114, 116, 118, 120, 122, 124Sn and 208Pb. The theoretical analysis has been performed with the Austern-Blair model. The deformation lengths and transition probabilities obtained are compared with several experimental and theoretical data. A discussion of the two-phonon states is given.

The doubly odd nuclei 48 Sc, 50 V, 52 Mn and 54 Co have been studied by the charge exchange reaction ( 3 He, t) on 48 Ca, 50 Ti, 52 Cr and 54 Fe enriched targets. In addition to the analogue state of the target ground state, we observed a great number of low-lying energy levels, especially those which can be described by the [( f 7 2 ) p ( f 7 2 ) n −1 ] configuration. For these levels we got angular distributions from 10° to 70° c.m. We observed that these angular distributions show a typical pattern for each value of the total transferred angular momentum J as shown by levels of 48 Sc, 52 Mn and 54 Co for which spins are already known. This property allowed us to propose J -values for the more excited levels. Thus, most of the components of the [( f 7 2 ) p ( f 7 2 ) n −1 ] multiplet have been identified in 48 Sc, 50 V and 52 Mn. For 48 Sc, angular distributions are practically identical at 18.5 and 30.2 MeV. It seems that the ( 3 He, t) reaction at 30.2 MeV on N = 28 targets proceeds through an apparently quite simple mechanism.

A study of single-particle proton strengths in odd-mass Tc isotopes was performed using the (3He, d) reaction. Angular distributions were measured from 8° to 70° and compared with calculations using the distorted-wave Born approximation. The l-values and spectroscopic factors were extracted and compared with (d, n) results. Proton configurations for the ground states of 92,94Mo and 96Mo were deduced from the analysis. Symmetry energies were extracted from the energy difference between the centroids of the T> and T< states. Various methods for DWBA calculations for unbound states are discussed.

We describe an experimental study of (α, t), (α,3He) reactions at 44 MeV using a solid-state identifier, on the target nuclei 54Fe and 58, 60, 62, 64Ni. A critical study of optical-model and distorted-wave analysis has been performed. We show the complementarity of different transfer reactions, the ambiguity of the spectroscopic factors and the importance of the problem of the reaction mechanism.

The reactions 203,205 Tl(α, t) 204,206 Pb were investigated at an incident energy of 44 MeV, the reactions products being momentum analysed in a double ΔE + E particle identification system with semiconductor counters. The resulting energy resolution was 120 keV. Transitions were observed to the ground state and the lowest 2 + state of 204,206 Pb and to a number of states at higher excitation energies, starting at about 2.9 MeV in 204 Pb and about 2.6 MeV in 206 Pb. Angular distributions were measured for the triton groups corresponding to the ground and first excited states of 204 Pb. The distributions have a forward peaked shape which can be reproduced well by a DWBA calculation assuming a simple proton stripping process.

Inelastic scattering of 480 MeV and 340 MeV α particles on 208Pb, 116Sn and 58Ni has been used in a search for high excitation energy giant multipole resonances, up to E* = 60 MeV for 208Pb and E* = 45 MeV for 116Sn and 58Ni. Above the well known quadrupole and monopole resonances, there is clear evidence for a very wide set of negative parity modes (including the already known high energy octupole), followed and mixed with another very wide set of positive parity resonances, extending up to the limits of the experimental spectra.

The angular distributions of the inelastic scattering of antiprotons for a few collective states of 12C and 18O have been measured. They exhibit a diffractive pattern, typical of strong absorption. Coupled channel analysis of these data has been carried out. The derived multipole moments agree fairly well with those obtained with other probes. Microscopic calculations performed in the framework of the DWIA formalism, using either the Paris or the Dover-Richard NN interaction are in good agreement with the data for the low-lying collective states. The present status of the experimental study of the unnatural parity levels is discussed.

Angular distributions for elastic scattering of antiprotons from nuclei are analyzed in terms of a fuzzy black disk model. Data from /sup 12/C, /sup 16/O, /sup 18/O, and /sup 40/Ca at incident antiproton energies of 47 and 180 MeV are analyzed. The obtained fits are qualitatively good concerning the slope and position of the extrema, but are too deep in the minima.

The angular distribution for elastic scattering of 179.3 MeV antiprotons by deuterium has been measured. The data should provide further constraints on the elementary p-n amplitudes.

Angular distributions of cross section, and A y and A yy analysing powers were measured for polarised deuteron elastic scattering from 16 O at 200, 400 and 700 MeV. The data at 200 MeV bear evidence of the nuclear rainbow phenomenon while those at 400 and 700 MeV are reminiscent of the proton scattering results at equivalent energies. The data were analysed in terms of the optical model. The real central potential shape changes from an attractive Woods-Saxon form at 200 MeV to a wine-bottle-bottom form with a repulsive interior at 700 MeV. The total reaction cross sections deduced display a clear nuclear transparency effect in the present energy domain in agreement with predictions from the Glauber theory optical limit. Comparison with previous results for 40 Ca and 58 Ni targets is made.

Thanks to an experimentation, this research studies the effects of two broadcast sponsorships on implicit attitude toward a new brand. This brand sponsors two quasi-identical broadcasts differentiated only by their emotional content. To be ecologically valid, the experiment records the attitudinal effects one week later when the subjects don't remember the exposition phase any more and cannot explicitly recognize the brand. The attitude is then implicit. The impact of humorous broadcast sponsorship (with two exposures) on implicit attitude toward the brand is manifest and positive. The sad broadcast has no implicit effects: this type of TV sponsorship has been inefficient. The results are explained with the familiarity-misattribution model. At least, practical suggestions are proposed.

Antiproton-carbon elastic and inelastic scattering cross sections have been measured at 46.8 MeV over an angular range 6° ⩽ θ ⩽ 59° with a magnetic spectrometer. Fits to the elastic and inelastic 4.44 MeV excited state cross sections put realistic limits on the strengths of the real and imaginary parts of the antiproton-carbon optical potential. The continuum cross section due to carbon break-up appears to be smaller than it is for corresponding proton data.

Elastic scattering of 288,340,480 and 699 MeV Alpha -particles was measured on 208 Pb, 116 Sn and 58 Ni. The data were analysed in terms of a phenomenological optical model. The optical potentials obtained were found to vary consistently with the target nucleus and the incident energy. The radial zone where the potentials are well determined was studied in detail. The data for 208 Pb were also analysed with a folding model. The energy dependence of the strong-absorption radius and of the reaction cross section shows that the nuclear surface becomes slightly transparent for incident energies above 150 MeV per nucleon.