Search for: All records

Abstract Scattering of high energy particles from nucleons probes their structure, as was done in the experiments that established the non-zero size of the proton using electron beams 1 . The use of charged leptons as scattering probes enables measuring the distribution of electric charges, which is encoded in the vector form factors of the nucleon 2 . Scattering weakly interacting neutrinos gives the opportunity to measure both vector and axial vector form factors of the nucleon, providing an additional, complementary probe of their structure. The nucleon transition axial form factor, F A , can be measured from neutrino scattering from free nucleons, ν μ n  →  μ − p and $${\bar{\nu }}_{\mu }p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n , as a function of the negative four-momentum transfer squared ( Q 2 ). Up to now, F A ( Q 2 ) has been extracted from the bound nucleons in neutrino–deuterium scattering 3–9 , which requires uncertain nuclear corrections 10 . Here we report the first high-statistics measurement, to our knowledge, of the $${\bar{\nu }}_{\mu }\,p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n cross-section from the hydrogen atom, using the plastic scintillator target of the MINERvA 11 experiment, extracting F A from free proton targets and measuring the nucleon axial charge radius, r A , to be 0.73 ± 0.17 fm. The antineutrino–hydrogen scattering presented here can access the axial form factor without the need for nuclear theory corrections, and enables direct comparisons with the increasingly precise lattice quantum chromodynamics computations 12–15 . Finally, the tools developed for this analysis and the result presented are substantial advancements in our capabilities to understand the nucleon structure in the weak sector, and also help the current and future neutrino oscillation experiments 16–20 to better constrain neutrino interaction models. 

Isolated MgSiO3 and Mg2SiO4 molecules are shown here to exhibit bright infrared (IR) features that fall close to unattributed astronomical lines observed toward objects known to possess crystalline enstatite and forsterite, minerals of the same respective empirical formulae. These molecules are therefore tantalizing candidates for explaining the origin of such features. Furthermore, the C2v monomer minima of each formula set have dipole moments on the order of 10.0 D or larger making them desirable candidates for radioastronomical observation as enabled through rotational spectroscopic data further provided in this high-level CCSD(T)-F12/cc-pVTZ-F12 quantum chemical study. Astrophysical detection of these molecules could inform the build-up pathways for creating nanocrystals from small molecules in protoplanetary discs or could show the opposite in explaining the destruction of enstatite and forsterite minerals in supernovae events or other high-energy stellar processes. This work also shows that the lowest energy isomers for molecules containing the geologically necessary elements Mg and Si have oxygen bonded between any of the other heavier elements making oxygen the glue for pre-mineralogic chemistry.