Nucleus-nucleus potential from identical-particle interference

Based on the quantum interference between two-identical-nucleus scattering at energies around the Coulomb barrier, the barrier positions for $^{58}$Ni+$^{58}$Ni and $^{16}$O+$^{16}$O are extracted from Mott oscillations in the angular distributions around 90$^{\circ}$ for the first time. The angle separation of pairs of Mott scattering valleys around 90$^{\circ}$ has a direct relationship with the closest distance between two nuclei in elastic scattering. Together with the barrier height from fusion excitation function, the extracted barrier position provides a sensitive probe to constrain the model predictions for the nucleus-nucleus potential barrier.Comment: 4 figures, accepted for publication in Phys. Lett.

AeDet: Azimuth-invariant Multi-view 3D Object Detection

Recent LSS-based multi-view 3D object detection has made tremendous progress, by processing the features in Brid-Eye-View (BEV) via the convolutional detector. However, the typical convolution ignores the radial symmetry of the BEV features and increases the difficulty of the detector optimization. To preserve the inherent property of the BEV features and ease the optimization, we propose an azimuth-equivariant convolution (AeConv) and an azimuth-equivariant anchor. The sampling grid of AeConv is always in the radial direction, thus it can learn azimuth-invariant BEV features. The proposed anchor enables the detection head to learn predicting azimuth-irrelevant targets. In addition, we introduce a camera-decoupled virtual depth to unify the depth prediction for the images with different camera intrinsic parameters. The resultant detector is dubbed Azimuth-equivariant Detector (AeDet). Extensive experiments are conducted on nuScenes, and AeDet achieves a 62.0% NDS, surpassing the recent multi-view 3D object detectors such as PETRv2 (58.2% NDS) and BEVDepth (60.0% NDS) by a large margin. Project page: https://fcjian.github.io/aedet.Comment: Tech repor

Influence of entrance-channel magicity and isospin on quasi-fission

The role of spherical quantum shells in the competition between fusion and quasi-fission is studied for reactions forming heavy elements. Measurements of fission fragment mass distributions for different reactions leading to similar compound nuclei have been made near the fusion barrier. In general, more quasi-fission is observed for reactions with non-magic nuclei. However, the 40Ca+ 208Pb reaction is an exception, showing strong evidence for quasi-fission, though both nuclei are doubly magic. Time-dependent Hartree-Fock calculations predict fast equilibration of N/Z in the two fragments early in the collision. This transfer of nucleons breaks the shell effect, causing this reaction to behave more like a non-magic one in the competition between fusion and quasi-fission. Future measurements of fission in reactions with exotic beams should be able to test this idea with larger N/Z asymmetries

Insights into the mechanisms and time-scales of breakup of 6,7 Li

Using a back-angle detector array covering 117° to 167°, coincidence measurements of breakup fragments at sub-barrier energies have enabled the complete characterisation of the breakup processes in the reactions of 6,7Li with 208Pb. Those breakup proce

Predominance of transfer in triggering breakup in sub-barrier reactions of 6,7Li with 144Sm, 207,208Pb, and 209Bi

Coincidence measurements of breakup fragments were carried out for the 7Li+144Sm and 6,7Li+207,208Pb,209Bi reactions at sub-barrier energies. Breakup modes in reactions of 6,7Li were identified through the reaction Q values, and the time-scales of each p

Mapping quasifission characteristics and timescales in heavy element formation reactions

Background: The formation of superheavy elements by fusion of two massive nuclei is severely inhibited by the competing quasifission process. Purpose: Through extensive mass-angle distribution measurements, we map out the systematic dependence of quasifi