Abstract
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) |
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Pages (from-to) | 177-182 |
Number of pages | 6 |
Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |
Volume | 610 |
Issue number | 3-4 |
DOIs | |
State | Published - Mar 24 2005 |
Funding
The authors wish to thank the staffs, engineers and technicians at their respective institutions for their valuable help and cooperation. This research was supported by the US Department of Energy and by the Italian Istituto Nazionale di Fisica Nucleare.
ASJC Scopus subject areas
- Nuclear and High Energy Physics