Projectilelike fragments from N14 beams at 15, 25, and 35 MeV/nucleon

Momentum distributions of projectilelike fragments produced in the interaction of 15, 25, and 35 MeV/nucleon N14 beams on targets of C12, Mg24, Al27, Ti48, and Ni58 have been measured. Widths and centroids of the quasielastic component of the distributions have been extracted for fragments ranging from He4 to N13. The widths are compared with published data and several theoretical predictions. The Friedman model correctly predicts the charge and isotope dependence of the widths at the highest beam energy. At 15 MeV/nucleon some deviations from the trend of the published data suggest the possibility of a different reaction mechanism for the projectile-target combinations studied in the present work

Predictions of total and total reaction cross sections for nucleon-nucleus scattering up to 300 MeV

Total reaction cross sections are predicted for nucleons scattering from various nuclei. Projectile energies to 300 MeV are considered. So also are mass variations of those cross sections at selected energies. All predictions have been obtained from coordinate space optical potentials formed by full folding effective two-nucleon (NN) interactions with one body density matrix elements (OBDME) of the nuclear ground states. Good comparisons with data result when effective NN interactions defined by medium modification of free NN t matrices are used. Coupled with analyses of differential cross sections, these results are sensitive to details of the model ground states used to describe nuclei

Binary decay of Ni56 formed in the 32S+24Mg reaction

Fully energy-damped yields from the Mg32 reaction have been measured at center-of-mass energies of Ec.m.=51.6 and 60.5 MeV with the use of an experimental arrangement where both of the resulting heavy fragments could be detected in coincidence. Energy, velocity, and angular distributions of the reaction fragments have been determined. The cross sections prior to secondary light-particle emission have been deduced for the breakup of the compound system into different mass channels. These data are discussed in terms of two possible reaction mechanisms: fusion followed by fission and deep-inelastic orbiting

Fusion of O16 + Ca40 at Elab(16O)=13.4 MeV/nucleon

Mass and velocity distributions have been measured for the evaporation residue and fusion-fission products from the O16+40Ca reaction at 214 MeV. Comparisons of Monte Carlo statistical evaporation simulations to the observed angle and mass dependences of the evaporation-residue velocity distributions were used to set limits on the maximum complete-fusion cross section and to extract information about the magnitude and character of incomplete-fusion processes. The extracted value of the complete fusion evaporation-residue cross section is discussed in the framework of previous results and existing models

Fusion evaporation-residue cross sections for Si28+40Ca at E(28Si)=309, 397, and 452 MeV

Velocity distributions of mass-identified evaporation residues produced in the Si28+40Ca reaction have been measured at bombarding energies of 309, 397, and 452 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate the complete-fusion and incomplete-fusion components. Angular distributions and upper limits for the total evaporation-residue and complete-fusion evaporation-residue cross sections were extracted at all three bombarding energies. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models. The ratios of the complete-fusion evaporation-residue cross section to the total evaporation-residue cross section, along with those measured for the Si28+12C and Si28+28Si systems at the same energies, support the entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process reported earlier

Velocity and angular distributions of evaporation residues from induced32 reactions

Velocity distributions of mass-resolved evaporation residues from reactions of S32 with C12, Mg24, Al27, Si28, and Ca40 have been measured at bombarding energies of 194, 239, and 278 MeV using time-of-flight techniques. In all cases, the observed shifts in the velocity centroids relative to the values expected for complete fusion are consistent with a previously reported parametrization of a threshold for onset of incomplete fusion. Angular distributions were measured and total cross sections extracted for the Mg32 system at all three energies. A comparison with existing results for Mg32 at lower energies, and with other systems leading to the Ni56 compound nucleus, suggests two different types of compound-nuclear limitations to complete fusion at higher energies

Energy dependence of fusion evaporation-residue cross sections in the Si28+12C reaction

Fusion evaporation-residue cross sections for the Si28+12C reaction have been measured in the energy range 18≤Ec.m.≤136 MeV using time-of-flight techniques. Velocity distributions of mass-identified reaction products were used to identify evaporation residues and to determine the complete-fusion cross sections at high energies. The data are in agreement with previously established systematics which indicate an entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models

Energy dependence of fusion evaporation-residue cross sections in the Si28+28Si reaction

Velocity distributions of mass-identified evaporation residues produced in the t28/rSi+28Si reaction have been measured at bombarding energies of 174, 215, 240, 309, 397, and 452 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate the complete-fusion and incomplete-fusion components. Angular distributions and total cross sections were extracted at all six bombarding energies. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with lower energy data and the predictions of existing models

Observation of photon-induced W⁺W⁻ production in pp collisions at √s=13 TeV using the ATLAS detector

This letter reports the observation of photon-induced production of W-boson pairs, γγ→ WW. The analysis uses 139 fb-1 of LHC proton-proton collision data taken at √s=13 TeV recorded by the ATLAS experiment during the years 2015-2018. The measurement is performed selecting one electron and one muon, corresponding to the decay of the diboson system as WW→e±νμ∓ν final state. The background-only hypothesis is rejected with a significance of well above 5 standard deviations consistent with the expectation from Monte Carlo simulation. A cross section for the γγ→ WW process of 3.13±0.31(stat.)±0.28(syst.) fb is measured in a fiducial volume close to the acceptance of the detector, by requiring an electron and a muon of opposite signs with large dilepton transverse momentum and exactly zero additional charged particles. This is found to be in agreement with the Standard Model prediction