The electromagnetic processes of annihilation of $(e^+ e^-)$ pairs,

generated in high-energy nucleus-nucleus and hadron-nucleus collisions,

into heavy flavor lepton pairs are

theoretically studied in the one-photon approximation, using the technique of

helicity amplitudes . For the process $e^+e^- \rightarrow \mu^+\mu^-$, it is

shown that -- in the case of the unpolarized electron and positron -- the final

muons are also unpolarized but their spins are strongly correlated. For the

final $(\mu^+ \mu^-)$ system, the structure of triplet states is analyzed and

explicit expressions for the components of the spin density matrix and

correlation tensor are derived. It is demonstrated that here the spin correlations

of muons have the purely quantum character, since one of the Bell-type

incoherence inequalities for the correlation tensor components is always violated

( i.e. there is always one case when the modulus of sum of two diagonal components

exceeds unity ). Besides, the additional contribution of the weak interaction of lepton

neutral currents through the virtual $Z^0$ boson is considered in detail, and

it is established that, when involving the weak interaction contribution, the

qualitative character of the muon spin correlations does not change.

On the other hand, the theoretical investigation of spin structure for the

processes of lepton pair production by pairs of photons ( which, in particular,

may be emitted in relativistic heavy-ion and hadron-nucleus collisions ) is

performed as well. For the two-photon process $\gamma \gamma \rightarrow

e^+ e^-$, it is found that -- quite similarly to

the process $e^+ e^-

\rightarrow \mu^+ \mu^-$ -- in the case of unpolarized photons the final electron

and positron remain unpolarized, but their spins prove to be strongly correlated.

Explicit expressions for the components of the correlation tensor and for

the relative fractions of singlet and triplet states of the final $(e^+ e^-)$

system are derived. Again, here one of the Bell-type incoherence inequalities

for the correlation tensor components is always violated and, thus, spin

correlations of the electron and positron have the strongly pronounced quantum

character.

Analogous analysis can be wholly applied as well, respectively, to the annihilation process

$e^+ e^- \rightarrow \tau^+ \tau^-$ and to the two-photon processes $\gamma \gamma \rightarrow \mu^+ \mu^-$, $\gamma \gamma \rightarrow \tau^+ \tau^-$,

which become possible at considerably higher energies.