Anomalous neutron Compton scattering in Nb hydride: Indications of protoncorrelations

Neutron Compton scattering probes properties of matter at time scales of the order of 10-16-$10^{-15}\,{\rm s}$. Very strong anomalies in the cross-sections for protons were observed for scattering on ${\rm NbH}_x$ and ${\rm NbH}_x{\rm D}_y$. The effective proton cross-section was found to vary with the time of observation (first used as a parameter in the present experiments) being reduced by 30% at times around $\rm 10^{-16}\,s$ but reaching its conventional value for times larger than $\rm 2\cdot 10^{-15}\, s$. No conventional explanation for this anomaly (which indicates some kind of very short-lived correlations) is known. A tentative explanation is that during such short time intervals, nearby protons are quantum correlated (even at ambient temperatures) in such a manner that their neutron cross-sections are modified.