  A large body of spectroscopic data on the cuprate high temperature
superconductors (CHTSC) is reviewed in order to determine their order
parameter. ASJ, INS, B2g Raman spectra, optical data, NIS "dips", ARPES "dips"
and ARPES "kinks" all show the same excitation energy (40 meV for OP95
systems), proportional to the superconducting transition temperature, and it is
therefore identified with the order parameter.
