The critical phenomena of liquid 4He in the vicinity of upper Λ-point

The analysis of specific heat data of liquid 4He in the vicinity of the upper lambda point is presented, in which a trial function with a correction term to the leading singularity is used. The universal amplitude ratios, A/A' = 1.086 +- 0.007 and D/D' = 0.95 +- 0.20 were obtained, but a systematic derivation was also observed. D/D' = 0.95 +- 0.20 implies that the irrelevant variable has the similar effect on Csub(p) in the normalfluid and superfluid regions within experimental errors. (orig.)