K. Ackerstaff et al., STUDY OF PHI(1020), D-ASTERISK+ - AND B-ASTERISK SPIN ALIGNMENT IN HADRONIC Z(0) DECAYS/, Zeitschrift fur Physik. C, Particles and fields, 74(3), 1997, pp. 437-449
Measurements of helicity density matrix elements have been made for th
e phi(1020), D(+/-) and B* vector mesons in multihadronic Z(0) decays
in the OPAL experiment at LEP, Results for inclusive phi produced wit
h high energy show evidence for production preferentially in the helic
ity zero state, with rho(00) = 0.54 +/- 0.08, compared to the value of
1/3 expected for no spin alignment. The corresponding element for the
D(+/-) has a value of 0.40 +/- 0.02, also suggesting a deviation fro
m 1/3. The B result, with rho(00) = 0.36 +/- 0.09, is consistent with
no spin alignment. Off-diagonal elements have been measured for the p
hi and D mesons; for the D* the element Re rho(1-1) is non-zero, indi
cating non-independent fragmentation of the primary quarks.