prediction, and differs by 2.9-4.10* from three recent measurements.:I: 0.0025(stat.) zb 0.0015(sys.) ps"1, which is consistent with the QED rate values consistent with each other. The combined result is Ag : 7.0398 are carried out with two different types of SiO; powder, resulting in decay errors in all the previous experiments. Two independent measurements of the extrapolation, which might have been sources of the main systematic rate can be determined without the ambiguities of the thermalization nor errors. From Eq.(1), the population of o -Ps, N(t), is expected to obey the following entirely new method, which is free from above-mentioned systematicWe report here on a new measurement of the 0 -Ps decay rate with the extrapolation to zero density might be a source of another systematic error.the multiple scattering at the surface of the materials [15]. Therefore the linear materials are conjectured to be more complicated due to the processes such as the one between single rigid balls. However the collisions of the 0 -Ps with the materials is only valid, if the coliision between the 0 -Ps and the material is like the assumption of the linear dependence of Apickojf on the densities of the target unthermalized o-~Ps could result to a large systematic error [13, 14]. Furthermore there seems to exist no concrete evidence to support this assumption, and the yielded the A0, assuming that the velocity of the o -Ps was constant. However, varying densities of the target materials, and the extrapolation to zero densities of the material. In all the previous experiments, the /1.,,;,, 's were measured by pickoff annihilation rate is a function of time, which depends on the properties ultimate thermal energy of about 0.03 eV ('thermalization'), the corresponding eV immediately after formation, and slows down by elastic collisions toward the and to the velocity of the 0 -Ps. Since the 0 -Ps has a. kinetic energy of about 1 materials, and is consequently proportional to the densities of the target materials The /\,,;,,;,.,,·_,· is proportional to the rate at which the 0 -Ps collides with the /\¤¤»·(*) Z Ac + )*p<¤k¤:r(*)( 1) annihilation rate, /\,,,,,;,,,,·,·, i.e.decay rate, /\,,;,,, is the sum of the the intrinsic decay rate, A0, and the pickoff colliding with the atomic electrons of the target material, the observed 0 --PsBecause some portion of 0 -Ps inevitably causes the 'pickoff' annihilation by without any evidence so far [7, 8, 9, 10, 11, 12].to clarify the discrepancy, various exotic decay modes have been searched for, discrepancy, being 6.7, 6.3 and 4.30, is statistically very significant. In an effort ppm) than the theoretical QED calculation corrected up to O(cz2) [4, 5, 6]. This performed, which reported decay rate values much larger (by 1400, 1300 and 920Three precision measurements [1, 2, 3] of the o --Ps decay rate were recently the constituent leptons interact only through the electromagnetic interactions.direct information about quantum electrodynamics(QED), since to higher order decays slowly into three ph...