Measurement of the angular distribution in p̄p→ψ(2S) →e+e-

M. Ambrogiani, M. Andreotti, S. Argiro, S. Bagnasco, W. Baldini, D. Bettoni, G. Borreani, A. Buzzo, R. Calabrese, R. Cester, G. Cibinetto, P. Dalpiaz, X. Fan, G. Garzoglio, K. E. Gollwitzer, M. Graham, A. Hahn, M. Hu, S. Jin, D. JoffeJ. Kasper, G. Lasio, M. Lo Vetere, E. Luppi, P. Maas, M. Macrí, M. Mandelkern, F. Marchetto, M. Marinelli, W. Marsh, M. Martini, E. Menichetti, Z. Metreveli, R. Mussa, M. Negrini, M. M. Obertino, M. Pallavicini, N. Pastrone, C. Patrignani*, T. K. Pedlar, S. Pordes, E. Robutti, W. Roethel, J. Rosen, P. Rumerio, R. Rusack, A. Santroni, J. Schultz, S. H. Seo, K. K. Seth, G. Stancari, M. Stancari, J. Streets, Amiran Tomaradze, I. Uman, T. Vidnovic, S. Werkema, G. Zioulas, P. Zweber

*Corresponding author for this work

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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 languageEnglish (US)
Pages (from-to)177-182
Number of pages6
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume610
Issue number3-4
DOIs
StatePublished - Mar 24 2005

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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    Ambrogiani, M., Andreotti, M., Argiro, S., Bagnasco, S., Baldini, W., Bettoni, D., Borreani, G., Buzzo, A., Calabrese, R., Cester, R., Cibinetto, G., Dalpiaz, P., Fan, X., Garzoglio, G., Gollwitzer, K. E., Graham, M., Hahn, A., Hu, M., Jin, S., ... Zweber, P. (2005). Measurement of the angular distribution in p̄p→ψ(2S) →e+e-. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 610(3-4), 177-182. https://doi.org/10.1016/j.physletb.2005.01.093