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With a data sample containing 1.1 x lo5 J/$ -+ /L+/L-decays reconstructed with 16 M~V / C ' rms mass resolution, we have measured the differential cross sections versus Feynman-x, rapidity, and p~ for the production of J/$ and 4' in 800 GeVlc p A u collisions. Our results are compared with leading-order QCD predictions and with previous measurements. While the shapes of the cross sections are in qualitative agreement with QCD predictions, the magnitudes disagree by factors of 7 ( J / 4 ) and 25 (4'). Assuming an appropriate form for the differential cross sections in regions not measured, we derive a total J/+ production cross section a ( p + N + J/$ + X) = 442 f 2 i 88 nb/nucleon and a (model-dependent) total 4' cross section u(p + N + $' + X) = 75 f 5 f 22 nblnucleon. For J/$ produced at central rapidity, du(p + N + J/$ + X)/dyly=o = 230 i 5 f 46 nb/nucleon. PACS number(s): 13.85. Ni, 24.85.+p, 25.40.Ve

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Measurements of the D͑ p, g͒ 3 He and p͑ d, g͒ 3 He reactions below E p,d 80 keV are compared to the results of calculations based on correlated hyperspherical harmonic wave functions obtained from realistic interactions with full inclusion of Coulomb distortion in the initial continuum state, and a nuclear current operator with one-and two-body components. Dramatic effects due to the tensor force and the associated two-body (meson-exchange) interaction currents are observed in the vector and, to some extent, tensor analyzing powers for the first time. The extrapolation to zero energy leads to an S-factor value of S͑E 0͒ 0.165 6 0.014 eV b, in reasonable agreement with theory. [S0031-9007(96)00008-7] PACS numbers: 25.40. Lw, 21.45.+v, 24.70.+s, 27.10.+h Weak and radiative capture reactions on few-nucleon systems at very low energies have great astrophysical importance in relation to studies of stellar structure and evolution [1]. Two such aspects are as follows: (1) the mechanism for the energy and neutrino production in main sequence stars, in particular, the determination of the solar neutrino flux; and (2) the process of protostellar evolution toward the main sequence. A quantity of interest in the latter area is the zero-energy astrophysical S factor for D( p, g) 3 He, whose currently accepted value was first determined over 30 years ago by extrapolating low energy cross-section data using a direct capture model [2].Besides their astrophysical relevance, these reactions are very interesting from the aspect of the many-body theory of strongly interacting systems since they are sensitive to ground-and scattering-state wave functions and the full nuclear electroweak transition operators. Indeed, calculations of the D(n,g) 3 H and 3 He(n,g) 4 He capture cross sections at thermal neutron energies carried out with realistic wave functions and a single-nucleon electromagnetic current, the so-called impulse approximation (IA), predict only about 50% [3,4] and 10% [5] of the corresponding empirical values. This is because the IA transition operator cannot connect the main S-state components of the deuteron and 3 H, or 3 He and 4 He, wave functions. Hence, the calculated cross section in IA is small since the reaction must proceed through the small components of the wave functions. Two-body currents, however, can connect the dominant S-state components, and the associated matrix elements are exceptionally large in comparison to those obtained in IA [3][4][5].The data of this paper, some of which were reported recently [6], were obtained using a polarized proton beam at 80 keV in a study of the D͑ p, g͒ 3 He reaction, along with a tensor-polarized deuteron beam at 80 keV to measure the tensor analyzing power T 20 ͑u͒ for the p͑ d, g͒ 3 He reaction. The polarized beams were produced by the Triangle Universities Nuclear Laboratory (TUNL) atomic beam polarized ion source, with typical beam currents of 30 mA on target. Fast spin flip (10 Hz) was employed for both measurements. In the case of the vector analyzing power A ...

The differential cross sections da/dxF for J/y produced inclusively in 800 GeV/c p-Cu and p-Be collisions have been measured in the kinematic range 0.30~xF~0.95 through the decay mode I/Itt it+It . They are compared with the predictions of the semilocal duality model for several sets of parton density functions. No evidence for a suggested intrinsic charm contribution to the cross section is observed. The ratio of the differential cross sections for Cu and Be targets confirms the suppression of J/y production in heavy nuclei at large xr.