Measurement of J/Psi and Psi(2S) Polarization in ppbar Collisions at sqrt(s) = 1.8 TeV

Abstract

We have measured the polarization of J/Psi and Psi(2S) mesons produced in p\bar{p} collisions at \sqrt{s} = 1.8 TeV, using data collected at CDF during 1992-95. The polarization of promptly produced J/Psi [Psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4[5.5] < P_T < 20 GeV/c and |y| < 0.6. For P_T \gessim 12 GeV/c we do not observe significant polarization in the prompt component.

Figures (3)

• Figure 1: The $J/\psi$ polarization fit to $\cos \theta^{\ast}$ distributions in the 12-15 ${\mathrm GeV}\!/c$ bin. Points: sideband-subtracted data in the SVX short-lived, SVX long-lived and CTC samples. Dashed lines: fit.
• Figure 2: (a) The fitted polarization of prompt $J/\psi$ mesons for $|y^{J/\psi}| < 0.6$. Full error bars denote statistical and systematic uncertainties added in quadrature; ticks denote statistical errors alone. The shaded band shows an NRQCD factorization prediction braaten which includes the contribution from $\chi_c$ and $\psi(2S)$ decays. (b) The fitted polarization of prompt $\psi(2S)$ mesons for $|y^{\psi(2S)}| < 0.6$. Error bars denote statistical and systematic uncertainties added in quadrature. Shaded bands show two NRQCD factorization predictions benkrambraaten.
• Figure 3: Fits to $|\cos \theta^{\ast}|$ distributions in the short-lived $\psi(2S)$ data sample, in the three $P_T$ bins. Points: data, dashed lines: fit. The acceptance extends further out in $|\cos \theta^{\ast}|$ as $P_T$ increases.