Browsing by Author "Neill, N. A."

The phenomenon of neutrino flavor oscillations motivates searches for sterile neutrinos in a broad range of masses and mixing-parameter values. A sterile neutrino 𝑁 that mixes predominantly with the 𝜏 neutrino is particularly challenging experimentally. To address this challenge, we propose a new method to search for a 𝜈𝜏-mixing 𝑁 that is lighter than the 𝜏 lepton. The method uses the large 𝑒+⁢𝑒−→𝜏+⁢𝜏− samples collected at 𝐵-factory experiments to produce the 𝑁 in 𝜏-lepton decays. We exploit the long lifetime of a sterile neutrino in this mass range to suppress background and apply kinematic and vertexing constraints that enable measuring the sterile-neutrino mass. Estimates for the sensitivities of the BABAR, Belle, and Belle II experiments are calculated and presented.

We study the current estimates of Bc→Bsπ to extract the fragmentation fraction fc/fs at the LHCb. A rather robust estimate of Br(Bc→Bsπ) based on factorization and lattice results for the form factor gives fc/fs∼0.056 with a 16% error. We also revisit the extraction of fs/fd using B→Dπ instead of the theoretical cleaner but more suppressed channel B→DK. We also find a tension on the predictions of Br(Bc→J/ψπ) and Br(Bc→Bsπ) considering the measurements of these modes at LHCb, and find that, within a 23% uncertainty, only the lower end of the current prediction range Br(Bc→J/ψ)∼0.4%−1.7% would be consistent with the LHCb measurements.