  Quantum anomalies are the breaking of a classical symmetry by quantum
fluctuations. They dictate how physical systems of diverse nature, ranging from
fundamental particles to crystalline materials, respond topologically to
external perturbations, insensitive to local details. The anomaly paradigm was
triggered by the discovery of the chiral anomaly that contributes to the decay
of pions into photons and influences the motion of superfluid vortices in
$^3$He-A. In the solid state, it also fundamentally affects the properties of
topological Weyl and Dirac semimetals, recently realized experimentally in
TaAs, Na$_3$Bi, Cd$_3$As$_2$, and ZrTe$_{5}$. In this work we propose that the
most identifying consequence of the chiral anomaly, the charge density
imbalance between fermions of different chirality induced by non-orthogonal
electric and magnetic fields, can be directly observed in these materials with
the existing technology of photoemission spectroscopy. With angle resolution,
the chiral anomaly is identified by a characteristic note-shaped pattern of the
emission spectra, originating from the imbalanced occupation of the bulk states
and a previously unreported momentum dependent energy shift of the surface
state Fermi arcs. We further demonstrate that the chiral anomaly likewise
leaves an imprint in angle averaged emission spectra, facilitating its
experimental detection. Thereby, our work provides essential theoretical input
to foster the direct visualization of the chiral anomaly in condensed matter.
