Juliet Wilson

Results are presented of a search for a heavy Majorana neutrino Image 1 decaying into two same-flavor leptons ℓ (electrons or muons) and a quark-pair jet. A model is considered in which the Image 1 is an excited neutrino in a compositeness scenario. The analysis is performed using a sample of proton-proton collisions at s=13fb−1. The data are found to be in agreement with the standard model prediction. For the process in which the Image 1 is produced in association with a lepton, followed by the decay of the Image 1 to a same-flavor lepton and a quark pair, an upper limit at 95% confidence level on the product of the cross section and branching fraction is obtained as a function of the Image 1 mass Image 2 and the compositeness scale Λ. For this model the data exclude the existence of Image 3 (Image 4) for Image 2 below 6.0 (6.1) TeV, at the limit where Image 2 is equal to Λ. For Image 5, values of Λ less than 20 (23) TeV are excluded. These results represent a considerable improvement in sensitivity, covering a larger parameter space than previous searches in Image 6 collisions at 13 TeV.

Prompt and delayed γ-ray spectroscopy of the neutron-rich 94Kr was performed, as part of the fission campaign at the ALTO facility of the IPN Orsay, using the fast-neutron-induced fission reaction 238U(n,f) in combination with the ν-Ball array, a novel hybrid γ spectrometer for energy and lifetime measurements. Several new yrast and nonyrast transitions were observed for the first time, extending the previously known level scheme. Additionally, we report on the observation of a new short-lived isomer at 3444 keV with a half-life of 32(3) ns. The analysis of the Nilsson orbitals obtained from Gogny cranked Hartree-Fock-Bogoliubov calculations suggests a (9−) spin and an oblate deformation for this isomer corresponding to a two-quasineutron state, indicating an isomeric structure very similar to that of the neighboring isotones 96Sr and 92Se

We report on spectroscopic information and lifetime measurements of even-even neutron-rich Te isotopes. Excited states were populated in fast-neutron induced fission of ²³⁸U at the ALTO facility of IJCLab with the LICORNE neutron source and detected using the hybrid ν-ball spectrometer. We provide first results on lifetimes of the 6+1 state in ¹³⁶Te and the (6+1), (4+1), and (2+1) states in ¹³⁸ Te and discuss the results in the context of large-scale shell-model calculations. The level schemes of ¹³⁶Te and ¹³⁸Te are revised in terms of lifetimes of their 2+1 , 4+1 states and updated information on the (4+2) state in ¹³⁶Te is presented. In addition, previously reported data on spectroscopy and lifetimes in ¹³⁴Te are reexamined. This work provides new insights into the evolution of collectivity for Te isotopes with N = 82, 84, 86.

The reaction of a pulsed 18O beam on a self-supporting and gold-backed isotopically-enriched 164Dy target of thickness 6.3 mg/cm2 at separate primary beam energies of 71, 76 and 80 MeV was studied at the accelerator at the ALTO facility of the IPN Orsay. The γ rays produced were detected using the newly-constructed ν-Ball spectrometer which comprised of HPGe and LaBr3(Ce) detectors. This conference paper describes the methodology and effectiveness of multiplicity/sum-energy gating, for channel selection between fusion evaporation events and lower multiplicity/energy events from inelastic nuclear scattering and Coulomb excitation of the target, and from two-neutron transfer reactions to 166Dy.