Electronic excitations near the Brillouin zone boundary of ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$

Based on angle resolved photoemission spectra measured on different systems at different dopings, momenta, and photon energies, we show that the anomalously large spectral linewidth in the $(\pi ,0)$ region of optimal doped and underdoped ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ has significant contributions from the bilayer band splitting, and that the scattering rate in this region is considerably smaller than previously estimated. This picture of the electronic excitation near $(\pi ,0)$ puts additional experimental constraints on various microscopic theories and data analyses.