| Autor: |
T. Vidnovic, K. Gollwitzer, M. M. Obertino, S. Bagnasco, J. Streets, M. M. Macri, G. Cibinetto, Roger Rusack, J. L. Rosen, M. Hu, A. Buzzo, W. Marsh, M. Lo Vetere, P. Rumerio, M. Martini, E. Menichetti, Mirco Andreotti, M. Mandelkern, C. Patrignani, Wander Baldini, P. F. Dalpiaz, I. Uman, S. Jin, S. J. Werkema, P. Maas, R. Mussa, A. Hahn, D. Joffe, Roberto Calabrese, J. Kasper, Giulio Stancari, N. Pastrone, Matteo Negrini, K. K. Seth, W. Roethel, Marco Pallavicini, Giorgio Borreani, G. Lasio, R. Cester, T. K. Pedlar, S. H. Seo, A. Santroni, Z. Metreveli, X. Fan, M. Stancari, J. Schultz, S. Pordes, Eleonora Luppi, G. Zioulas, Stefano Argiro, Matt W. Graham, Amiran Tomaradze, Enrico Robutti, M. Ambrogiani, Mauro Marinelli, D. Bettoni, Gabriele Garzoglio, F. Marchetto, P. Zweber |
| Rok vydání: |
2005 |
| Předmět: |
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| Zdroj: |
Physics Letters B. 610:177-182 |
| ISSN: |
0370-2693 |
| Popis: |
We present the first measurement of the angular distribution for the exclusive process p ¯ p → ψ ( 2 S ) → 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 d N d cos θ ∗ ∝ 1 + λ cos 2 θ ∗ , 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 ( 2 S ) helicity 0 formation amplitude in p ¯ p , comparable to what is observed in J / ψ decays to baryon pairs. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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