Suchergebnisse

The production of the heaviest elements in fusion-evaporation reactions is substantially limited by very low cross sections, as fusion cross sections (including fusion-fission) are greatly reduced by the competing quasifission mechanism. Using the Australian National University Heavy Ion Accelerator Facility and CUBE detector array, fission fragments from the 48Ti + 204,208Pb and 50Ti + 206,208Pb reactions have been measured, with the aim to investigate how the competition between quasifission and fusion-fission evolves with small changes in entrance-channel properties associated mainly with the nuclear structure. Analysis of mass-distribution widths of strongly mass-angle-correlated fission fragments within the framework of the compound-nucleus fission theory demonstrates significant differences in quasifission (and therefore fusion) probabilities among the four reactions. The impact of nuclear structure on fusion highlights the importance of future radioactive beams. ; The authors acknowledge the support of Australian Research Council research grants DE140100784, DP140101337, DP160101254, DP170102318, DP170102423, German Academic Exchange Service (DAAD) via funds of the German Federal Ministry of Education and Research (BMBF). The Australian Federal Government NCRIS program is acknowledged for support of operations of the ANU Heavy Ion Accelerator Facility.

Spanish Center for Particle Physics, Astroparticle and Nuclear Physics (CPAN) ; regional government (Generalitat Valenciana) ; Heidelberg University ; IFIC (U. Valencia/CSIC) ; This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of first-principle QCD calculations to yield a precise description of the substructure of jets and study the accuracy of state-of-the-art Monte Carlo tools. Limitations of the experiments' ability to resolve substructure are evaluated, with a focus on the impact of additional (pile-up) proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt from jet substructure analyses in searches for new physics in the production of boosted top quarks.