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We have developed a versatile software package for the simulation of di-electron production in pp and dp collisions at moderate beam kinetic energies (1-2GeV). Particular attention has been paid to incorporate different descriptions of the Dalitz decay $ \Delta$ $ \rightarrow$ Ne e via a common interface. In addition, suitable parameterizations for the virtual bremsstrahlung process NN $ \rightarrow$ NNe e based on one-boson exchange models have been implemented. Such simulation tools with high flexibility of the framework are important for the interpretation of the di-electron data taken with the HADES spectrometer and demonstrates the wide applicability within the field of nuclear and hadronic physics. [ABSTRACT FROM AUTHOR]

Proton-π0 coincidences have been measured at the beam energy of 180 A MeV in the reaction Ar+Ca studied by TAPS at SIS/GSI. In the proton-π0 invariant mass spectrum we observe a significant excess of strength above the background obtained by event mixing. We attribute this signal to the strength distribution NΔ of the Δ baryonic resonance. No correlation is observed in the case of deuteron-π0 coincidences. Assuming isotropic emission of π0 and Δ+ from a midrapidity thermal source and isospin symmetry, we determined the global NΔ/ Nπratio of 0.79 ±0.30(stat) ±0.2(syst). This value indicates that most pions produced at subthreshold energy in heavy-ion reaction are mediated by the Δ-resonance. [ABSTRACT FROM AUTHOR]

This work demonstrates the feasibility of in-beam γ-spectroscopy employing radioactive ion beam species at relativistic energies of E = 210 ∼ 280 A· MeV. Neutron-rich nuclei below 48Ca with neutron number between the two magic numbers 20 and 28 have been investigated. Using a Pb target, single step inelastic excitation originating mainly from Coulomb interaction takes place populating preferentially low-lying low-spin states and enabling the extraction of B(E2) values. On a C target, nucleon removal reactions are dominating and medium-spin states are populated thus offering spectroscopic information in neighboring nuclei. Cross sections of inelastic excitation are determined and compared to coupled-channels calculations. Two new states of the very neutron-rich nucleus 44Ar at 1.78(8) MeV and 2.61(16) MeV are deduced from γ-transitions. [ABSTRACT FROM AUTHOR]

We investigate the beam energy dependence of neutron and proton squeeze-out in collisions ofAu+Au at E/A=400-800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve - independent of beam energy - if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile. [ABSTRACT FROM AUTHOR]

Collective properties ofPb have been investigated with gamma-ray spectroscopy using nuclear and electromagnetic excitation byPb projectiles. From the measurement of particle-particle- γ and particle-particle- γ γ coincidences a new energy level inPb at 5.683 MeV was observed and the data suggest an interpretation as a 2-phonon octupole vibrational state with spin 4 or 6. For this state one finds the same dynamical deformation parameter β as for the first-excited collective 3 state. The results are compared to predictions of models which consider, in particular, the aspects of the quadrupole interaction and the interaction of the 2-particle pairing vibration with the 2-phonon octupole vibration. For thePb+Pb system at 6.2 MeV/u the nuclear potential could be determined from the measured inelastic cross sections. [ABSTRACT FROM AUTHOR]

The production of π and η mesons has been studied in the reactionsNe +Al at 350 MeV/u andAr + Ca at 1.0 GeV/ u. Rapidity distributions and transverse momentum spectra have been measured and are compared to thermal distributions. [ABSTRACT FROM AUTHOR]

The ground-state band ofTb has been Coulomb excited up to spin 23/2 by 151-MeVAr ions. The lifetimes of the 9/2 to 23/2 levels have been determined by combining results obtained with the RD and DSA methods, the E2/ M1 mixing ratios for Δ I=1 transitions have been measured using angular correlation techniques and the branching ratios for the levels up to spin 17/2 have been determined. The energies of the levels and the reduced M1 and E2 transition probabilities for their decay have been compared with the predictions of the rotational model, without and with Δ K=1 admixtures. No satisfactory agreement could be achieved for all available experimental data simultaneously. [ABSTRACT FROM AUTHOR]

Lifetimes of the first 2, 4 and 6 levels inW have been measured by the recoil-distance method based on the Doppler effect, using theGd (Ne, 5 n)W reaction. The following conclusions can be drawn from the results: if there are any deviations from the predictions of the rotational model for the lifetimes of the 4 and 6 states, they are smaller than 8.5 %; if this model accurately describes the nucleusW, the intrinsic quadrupole moment of this nucleus is: Q=5.93±0.06 barns, and its deformation is: β=0.240±0.003. The value of Q is compared with the predictions of various calculations for the tungsten isotopes. [ABSTRACT FROM AUTHOR]

In a joint experiment the TAPS and CERES collaborations have studied the production of the neutral mesons $\pi^\circ,\eta$ and $\omega$ in 450 GeV p-Be and p-Au collisions at the CERN SPS. The mesons were identified by their $\pi^\circ\rightarrow\gamma\gamma$, $\eta\rightarrow\gamma\gamma$, and $\omega\rightarrow\pi^\circ\gamma$ decay modes. The cross sections were measured down to very low $p_T$ ( $\geq$ 20 MeV/c) near mid-rapidity ( $3.0 < y < 4.0$). The $\eta$ and $\omega$ cross sections are smaller than expected from extrapolations of earlier data to low $p_T$. Integrated over all $p_T$, the ratios $\eta/\pi^\circ$ and $\omega$/ $\pi^\circ$ are lower by about 25% compared to previously published values. The reduction may be attributed to the large number of low $p_T$ pions from decays of heavier mesons. In addition, we have studied the dependence of neutral meson production on the mass of the nuclear target and find it in good agreement with previous measurements of charged mesons. [ABSTRACT FROM AUTHOR]

In a joint effort the CERES/NA45 and TAPS collaborations have measured low-mass electron pairs in p–Be and p–Au collisions at 450 GeV/ $c$ at the CERN SPS. In the range covered up to $\approx$ 1.5 GeV/ $c^2$ the mass spectra from p–Be and p–Au collisions are well explained by electron pairs from decays of neutral mesons. For p–Au our result is new. For p–Be, the simultaneously measured electron pair inclusive pair spectrum in which instrumental uncertainties are highly reduced. We confirm the earlier finding of HELIOS-1 with significantly reduced systematic uncertainties of 23% in the mass range below 450 MeV/ $c^2$, and of 28% in the mass range above 750 MeV/ $c^2$ at 90% confidence limit. Any unconventional source of electron pairs is limited by these error margins as the percentage fraction of the hadronic contribution. [ABSTRACT FROM AUTHOR]

The one-neutron transfer reactions d( Xe, p) Xe have been investigated in inverse kinematics with xenon beams incident on deuterium loaded titanium targets. The angular distributions of the protons, measured with a detector array of 100 PIN-photodiodes, have been analyzed using standard DWBA. Generally, good agreement is obtained with results previously obtained in reactions induced by light-ion beams. [ABSTRACT FROM AUTHOR]

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