The double differential thick target neutron yields (TTNY) for 500 MeV/u 9 Be ions incident on a lead target were measured at emission angles from 0 degrees to 75 degrees using the time-of-flight (TOF) method with organic liquid scintillators. The angular distribution of neutron yields was obtained by integrating the neutron energy spectrum above the detection threshold. The experimental data were then compared with results calculated using the Monte Carlo simulation codes GEANT4, PHITS, and FLUKA with different physics models. The results show that the neutron energy spectrum in the forward direction exhibits a broad peak centered around 60-70% of the incident particle energy per nucleon and spread up to nearly twice the projectile energy per nucleon. All calculations overestimate the neutron yields near this broad peak except at 0 degrees, and overestimate the neutron energy corresponding to the peak center at all angles. The GEANT4 results show good agreement with the experimental data from a few tens of MeV to around 100 MeV at angles from 5 degrees to 60 degrees, while PHITS and FLUKA results slightly overestimate the yields. Regarding the angular distribution, the predictions from GEANT4, PHITS, and FLUKA differ from the experimental data by less than a factor of 2 except at 75 degrees.
The study of t+t cluster states in 6 He provides valuable insights into exotic nuclear structures and the behavior of fermionic cluster systems. This study shows rich cluster resonant structures above the threshold, observed experimentally and investigated theoretically. The excitation energy spectrum above the t+t threshold in 6 He is measured via the fragmentation excitation process during the breakup reaction of 9 Li on a 208 Pb target at an incident energy of 32.7 MeV/nucleon. The resonant states are reconstructed from the final state coincident particles t+t using the invariant mass method, while the non-resonant background is estimated using the event mixing method. Two structures are observed at excitation energies of Ex=14.0 +/- 0.3 and 15.0 +/- 0.3 MeV, both located above the t+t threshold at Ex similar or equal to 12.31 MeV. Microscopic cluster model calculations exploring the t+t resonant states in 6He yield theoretical energy spectra which are then compared with the current experimental results. The calculated reduced width amplitudes (RWA) of the t+t channels further support the presence of t+t clustering in the observed resonant structures.
We report new experimental cross sections for the 183 W(n, n' gamma ) and 183 W(n, 2n gamma ) reactions. This work aims to expand the experimental knowledge on neutron scattering reactions on tungsten isotopes, which are relevant for nuclear applications, including fusion reactor design. The results presented here were obtained using the GRAPhEME setup, located at the JRC-Geel GELINA facility. The measurement relies on prompt gamma -ray spectroscopy combined with neutron energy determination by time-of-flight. A full Monte Carlo analysis was employed, for the first time for a GRAPhEME data set, to obtain comprehensive uncertainties and covariance matrices. We compare the experimental cross sections with theoretical predictions from reaction model calculations. The data set presented here is significant for the understanding of nuclear reactions, and completes a previous similar study on 182,184,186 W.
The photon flux-weighted average cross-sections of natGd(γ,xn)151,153,159Gd reactions were measured at bremsstrahlung end-point energies of 30, 40, 50, and 60 MeV using a combination of activation techniques and off-line γ-ray spectrometry. The measurements were conducted at the LUE−75 linear electron accelerator facility of the A.I. Alikhanyan National Science Laboratory (AANL) in Yerevan, Armenia. To complement the experimental data, theoretical calculations of the natGd(γ,xn)151,153,159Gd reactions weighted average cross-section as a function of bremsstrahlung end-point energy were carried out using the TALYS 2.0 and EMPIRE 3.2 codes. The results from the experimental measurements were compared with the predictions from these models, as well as with available experimental data from the literature. For 151Gd, experimental data on the weighted average cross-section are reported for the first time, thereby providing new reference values for this isotope. Highlights
We employ the QCD sum rule method to study the semileptonic weak decay of the single bottom baryon Omega b & lowast; with spin 32 into the single charmed baryon Omega c & lowast; with spin 32 , corresponding to a 32 -> 32 weak transition. A three-point correlation function is calculated in both the physical and theoretical sides to derive the sum rules for the form factors of the transition. The analysis incorporates both the perturbative and non-perturbative contributions up to mass dimension six. After determining the working regions of the auxiliary parameters and performing numerical calculations of the sum rules of the form factors, we extract the q2 -dependent fit functions for the form factors. The obtained fit functions are then applied to compute the decay widths of the Omega b & lowast;->Omega c & lowast;& ell;nu & strns;& ell; transition in all lepton channels. Our results may serve as useful theoretical benchmarks for future experimental investigations of the semileptonic Omega b & lowast;->Omega c & lowast;& ell;nu & strns;& ell; weak decays and the weak dynamics of excited heavy baryons.
