F. Sarazin

The Pierre Auger Collaboration has reported evidence for anisotropies in the arrival directions of cosmic rays with energies larger thanEth = 55 EeV. There is a correlation above the isotropic expectation with nearby active galaxies and the largest excess is in a celestial region around the position of the radio galaxy Cen A. If these anisotropies are due to nuclei of charge Z, the protons accelerated in those sources are expected, under reasonable assumptions, to lead to excesses in the same regions of the sky at energies above Eth/Z. We here report the lack of anisotropies at these lower energies for illustrative values of Z = 6, 13 and 26. These observations set stringent constraints on the allowed proton fraction at the sources.

In this Letter, we report a new mass for 11Li using the trapping experiment TITAN at TRIUMF's ISAC facility. This is by far the shortest-lived nuclide, t_{1/2}=8.8 ms, for which a mass measurement has ever been performed with a Penning trap. Combined with our mass measurements of ;{8,9}Li we derive a new two-neutron separation energy of 369.15(65) keV: a factor of 7 more precise than the best previous value. This new value is a critical ingredient for the determination of the halo charge radius from isotope-shift measurements. We also report results from state-of-the-art atomic-physics calculations using the new mass and extract a new charge radius for 11Li. This result is a remarkable confluence of nuclear and atomic physics.

The masses of 31 neutron-rich nuclei in the range $A\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}29--47$ have been measured. The precision of 19 masses has been significantly improved and 12 masses were measured for the first time. The neutron-rich Cl, S, and P isotopes are seen to exhibit a change in shell structure around $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}28$. Comparison with shell model and relativistic mean field calculations demonstrate that the observed effects arise from deformed prolate ground state configurations associated with shape coexistence. Evidence for shape coexistence is provided by the observation of an isomer in ${}^{43}\mathrm{S}$.

A new approach to the production and detection of bound neutron clusters is presented. The technique is based on the breakup of beams of very neutron-rich nuclei and the subsequent detection of the recoiling proton in a liquid scintillator. The method has been tested in the breakup of intermediate energy (30--50 MeV/nucleon) ${}^{11}\mathrm{Li},$ ${}^{14}\mathrm{Be},$ and ${}^{15}\mathrm{B}$ beams. Some six events were observed that exhibit the characteristics of a multineutron cluster liberated in the breakup of ${}^{14}\mathrm{Be},$ most probably in the channel ${}^{10}\mathrm{Be}{+}^{4}n.$ The various backgrounds that may mimic such a signal are discussed in detail.