  The so-called "strange metal phase" [1] of high temperature (high Tc)
superconductors remains at the heart of the high Tc mystery. Better
experimental data and insightful theoretical work would improve our
understanding of this enigmatic phase. In particular, the recent advance in
angle resolved photoelectron spectroscopy (ARPES) [2, 3], incorporating low
photon energies (about 7 eV), has given a much more refined view of the many
body interaction in these materials. Here, we report a new ARPES feature of
Bi2Sr2CaCu2O8+d that we demonstrate to have the key ability to distinguish
between different classes of theories of the normal state. This feature---the
anomaly in the nodal many body density of states (nMBDOS)---is clearly observed
in the low energy ARPES data, but also observed in more conventional high
energy ARPES data, when a sufficient temperature range is covered. We show that
key characteristics of this anomaly are explained by a strong electron
correlation model; the electron-hole asymmetry and the momentum dependent self
energy emerge as key required ingredients.
