HEAVY RESIDUE PRODUCTION IN HEAVY ION INDUCED REACTIONS ON 124 Sn BETWEEN 10 AND 84 MeV/NUCLEON

Heavy residue velocity spectra of 12C, 20Ne, 40Ar + 124Sn reactions induced in the 10-84 MeV/nucleon energy range have been measured between 0° and 10°. Asymmetric incomplete fusion process calculations are in agreement with the data

Neutron-proton bremsstrahlung from intermediate energy heavy-ion reactions as a probe of the nuclear symmetry energy?

Hard photons from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions are examined as a potential probe of the nuclear symmetry energy within a transport model. Effects of the symmetry energy on the yields and spectra of hard photons are found to be generally smaller than those due to the currently existing uncertainties of both the in-medium nucleon-nucleon cross sections and the photon production probability in the elementary process $pn\to pn\gamma$. Very interestingly, nevertheless, the ratio of hard photon spectra $R_{1/2}(\gamma)$ from two reactions using isotopes of the same element is not only approximately independent of these uncertainties but also quite sensitive to the symmetry energy. For the head-on reactions of $^{132}Sn+^{124}Sn$ and $^{112}Sn+^{112}Sn$ at $E_{beam}/A=50$ MeV, for example, the $R_{1/2}(\gamma)$ displays a rise up to 15% when the symmetry energy is reduced by about 20% at $\rho=1.3\rho_0$ which is the maximum density reached in these reactions.Comment: Added new results in Fig. 6 and new references [27.28]. Phys. Lett. B in pres

KNO Scaling in the Neutral Pion Multiplicity Distributions for pi^{-}-proton interactions at 40 and 250 GeV/c

We analysed the binomial multiplicity moments of the neutral pions, using an extension of the generating functional technique for detection losses. We applied this model-independent method to the individual gamma-weights of 10000 events of pi^{-}-proton interactions at 40 GeV/c. We compared the obtained results to those of 250 GeV/c. We used the FRITIOF and a shifted KW distribution to describe the data.Comment: 8pp LaTeX, 1 Postscript Figur

Thermal Bremsstrahlung photons probing the nuclear caloric curve

Hard-photon (E$_{\gamma}>$ 30 MeV) emission from second-chance nucleon-nucleon Bremsstrahlung collisions in intermediate energy heavy-ion reactions is studied employing a realistic thermal model. Photon spectra and yields measured in several nucleus-nucleus reactions are consistent with an emission from hot nuclear systems with temperatures $T\approx$ 4 - 7 MeV. The corresponding caloric curve in the region of excitation energies $\epsilon^\star\approx$ 3{\it A} - 8{\it A} MeV shows lower values of $T$ than those expected for a Fermi fluid.Comment: 13 pages, 3 figures. To appear in Physics Letters

Prompt reactivity determination in a subcritical assembly through the response to a Dirac pulse

The full understanding of the kinetics of a subcritical assembly is a key issue for its online reactivity control. Point kinetics is not sufficient to determine the prompt reactivity of a subcritical assembly through the response to a dirac pulse, in particular in the cases of a large reflector, a small reactor, or a large subcriticality.Taking into account the distribution of intergeneration times, which appears as a robust characteristic of each type of reactor, helps to understand this behaviour.Eventually, a method is proposed for the determination of the prompt reactivity. It provides a decrease rate function depending on the prompt multiplication coefficient Keffp. Fitting a measured decrease rate with this function, calculated once for the reactor, gives the true value of keffp. The robustness of the method is tested. (Elsevier

A direct probe of the in-medium pn scattering cross section

Hard photon production from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions is examined as a probe of the in-medium pn scattering cross section within a transport model. Uncertainty of photon production probability pn-pngamma is cancelled out by using the ratio of hard photon spectra R_{12C+12C/p+n}(gamma) from two reactions. The in medium pn scattering cross section is constrained by using the ratio of hard photon production cross sections of proton-induced reactions p+12C and p+2H. A reduction factor sigma_pn^medium/sigma_pn^free of about 0.5 ~ 0.7 around saturation density is obtained by comparing with the existing experimental data.Comment: 9 pages, 3 figures, accepted by PL