  We investigate the structure of Kubo - Martin - Schwinger (KMS) states on
some extension of the universal enveloping algebra of SL(2,C}. We find that
there exists a one-to-one correspondence between the set of all covariant KMS
states on this algebra and the set of all probability measures d\mu on the real
half-line, which decrease faster than any inverse polynomial. This problem is
connected to the problem of KMS states on square of white noise algebra.
