The CFHHM (Correlation Function Hyperspherical Harmonic Method) is a method of direct solution of the Schroedinger equation of the few-body problem. The method has been initially proposed by V.B. Mandelzweig, further developed together with M.I. Haftel of the Naval Research Laboratory in Washington, and is currently being developed in a Slovenian-Israeli collaboration between the J. Stefan Institute in Ljubljana and The Racah Institute of Physics of the Hebrew University of Jerusalem.

CFHHM has been applied to several atomic physics three-body problems, including the Helium atom, the positronium negative ion, muonic molecules relevant for muon-catalyzed fusion, and the muonic Helium atom. The extension to the four-body problem is in progress. The method is especially suitable for the calculation of expectation values of singular operators. This is possible because the CFHHM wave function is a true (numerical) solution of the Schroedinger equation and therefore has accurate local properties and uniform accuracy over a finite region of the configuration space.

The main achievements have been the then best value of the annihilation rate of the positronium negative ion (1993), the confirmation that the Lamb shift discrepancy between theory and experiment for the first excited state of Helium atom is not caused by possible bad convergence of the variational wave functions (1994), the best values of the sticking probability and fusion rate from the ground state of the muonic deuteron-triton molecule (1995), and the best values of the hyperfine splitting in the muonic Helium atom, exposing the unreliability of the formulas for relativistic and other corrections (1997-1998). (See the bibliography.)

The CFHHM code is about 400 pages long and possibly the code with the largest efficiency around (up to 70%), measured by using hardware counters.