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 p_T(&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 p_T 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 &alpha_B = 0.28 ± 0.27 ± 0.03.

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

Below are the eps and gif versions of all figures meant for downloads.

• Figure 1: The mass fit results for the Prompt &psi(2S)
  
  • P_T(&psi(2S)) 5 - 7 GeV/c (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 7 - 10 GeV/c (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 10 - 30 GeV/c (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 5 - 30 GeV/c (.eps), (.gif), (.jpg)
• Figure 2: The sideband subtracted ct distributions for Prompt &psi(2S) selection
  
  • No impact parameter significance cut (.eps), (.gif), (.jpg)
    
  • With the impact parameter significance cut (.eps), (.gif), (.jpg)
    
• Figure 3: The sideband subtracted ct distribution of B-decay &psi(2S) candidates (.eps), (.gif), (.jpg)
• Figure 4: The polarization fit results for the Prompt &psi(2S) with MC templates.
  *solid red line is the best fit and dotted magenta(green) line is fully transverse(longitudinal) MC template.
  • P_T(&psi(2S)) 5 - 7 GeV/c with fully transverse MC template (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 5 - 7 GeV/c with fully longitudinal MC template (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 7 - 10 GeV/c with fully transverse MC template (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 7 - 10 GeV/c with fully longitudinal MC template (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 10 - 30 GeV/c with fully transverse MC template (.eps), (.gif), (.jpg)
    
  • P_T(&psi(2S)) 10 - 30 GeV/c with fully longitudinal MC template (.eps), (.gif), (.jpg)
    
• Figure 5: The polarization fit results for the &psi(2S) from B decay with MC templates.
  *solid red line is the best fit and dotted magenta(green) line is fully transverse(longitudinal) MC template.
  • The fit result with fully transverse MC template (.eps), (.gif), (.jpg)
    
  • The fit result with fully longitudinal MC template (.eps), (.gif), (.jpg)
    
• Figure 6: Prompt &psi(2S) polarization(&alpha) (.eps), (.gif), (.jpg)
• Figure 7: &psi(2S) polarization from B decay (.eps), (.gif), (.jpg)