  Core-collapse supernova (CCSN) provides a unique astrophysical site for
studying neutrino-matter interactions. Prior to the shock-breakout neutrino
burst during the collapse of the iron core, a preshock $\nu_e$ burst arises
from the electron capture of nuclei and it is sensitive to the low-energy
coherent elastic neutrino-nucleus scattering (CE$\nu$NS) which dominates the
neutrino opacity. Since the CE$\nu$NS depends strongly on the non-standard
neutrino interactions (NSI) which are completely beyond the standard model and
yet to be determined, the detection of the preshock burst thus provides a clean
way to extract the NSI information. Within the spherically symmetric
general-relativistic hydrodynamic simulation for the CCSN, we investigate the
NSI effects on the preshock burst. We find that the NSI can maximally enhance
the peak luminosity of the preshock burst almost by a factor of three, reaching
a value comparable with that of the shock-breakout burst. Future detection of
the preshock burst will have critical implications on astrophysics, neutrino
physics and physics beyond the standard model.
