Measurement of the Spin Alignment of &psi(2S) Meson from Prompt Prodcution and B-decay with Run II data

The spin alignment of the &psi' vector meson has been measured using 800 pb-1 of data collected in CDF Run II. We use the decay &psi' &rarr &mu+&mu- and cover the kinematic range 5 GeV/c &le pT(&psi') &le 30 GeV/c for |y| &le 0.6.
The spin alignment is measured using the distribution of the decay angle &theta* which is the angle between the &mu+ direction in the &psi' rest frame and the &psi' direction in the lab frame. We compare the measured cos&theta* distribution to the distribution of realistic Monte Carlo simulations taking account of geometric and kinematic acceptance of the detector as well as the reconstruction efficiency. The data-based dimuon trigger efficiency has been used to simulate the trigger efficiency. The &psi' mesons from prompt production and B-decay have been separated by an impact parameter siginificance cut.

For prompt &psi' production the polarization in the highest pT bin is longitudinal, in contradistinction to the NRQCD prediction of large transverse polarization.

We also report the first measurement of the spin alignment of &psi' mesons from B-hadron decay. The result is &alphaB = 0.28 ± 0.27 ± 0.03.

A complete description of the analysis is available here: ps .






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