We present the first measurement of the angular distribution for the exclusive process p̄p→ψ(2S)→e+e- based on a sample of 6844 events collected by the Fermilab E835 experiment. We find that the angular distribution is well described by the expected functional form dNd/cosθ* ∝1+λcos2θ*, where θ* is the angle between the antiproton and the electron in the center of mass frame, with λ=0.67±0.15(stat)±0.04(sys). The measured value for λ implies a small but non-zero ψ(2S) helicity 0 formation amplitude in p̄p, comparable to what is observed in J/ψ decays to baryon pairs.
|Original language||English (US)|
|Number of pages||6|
|Journal||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|State||Published - Mar 24 2005|
ASJC Scopus subject areas
- Nuclear and High Energy Physics