Transverse momentum and energy correlations in the equilibrium system from high-energy nuclear collisions

The so-called Φ parameter, which measures the transverse momentum or energy correlations (fluctuations) in high-energy collisions independently of the particle multiplicity, is computed for the equilibrium ideal gas. As expected, Φ vanishes for the particles obeying Boltzmann statistics but is finite for the quantum particles, positive for bosons and negative for fermions. Φp⊥, which is found for the pions gas, significantly exceeds the value of Φp⊥ measured by the NA49 experiment. The discrepancy is discussed.