1. Measurements of J/ψ→pp̄
- Author
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J.Z. Bai, Y. Ban, J.G. Bian, X. Cai, J.F. Chang, H.F. Chen, H.S. Chen, H.X. Chen, J. Chen, J.C. Chen, Jun Chen, M.L. Chen, Y.B. Chen, S.P. Chi, Y.P. Chu, X.Z. Cui, H.L. Dai, Y.S. Dai, Z.Y. Deng, L.Y. Dong, S.X. Du, Z.Z. Du, J. Fang, S.S. Fang, C.D. Fu, H.Y. Fu, L.P. Fu, C.S. Gao, M.L. Gao, Y.N. Gao, M.Y. Gong, W.X. Gong, S.D. Gu, Y.N. Guo, Y.Q. Guo, Z.J. Guo, S.W. Han, F.A. Harris, J. He, K.L. He, M. He, X. He, Y.K. Heng, H.M. Hu, T. Hu, G.S. Huang, L. Huang, X.P. Huang, X.B. Ji, Q.Y. Jia, C.H. Jiang, X.S. Jiang, D.P. Jin, S. Jin, Y. Jin, Y.F. Lai, F. Li, G. Li, H.H. Li, J. Li, J.C. Li, Q.J. Li, R.B. Li, R.Y. Li, S.M. Li, W. Li, W.G. Li, X.L. Li, X.Q. Li, X.S. Li, Y.F. Liang, H.B. Liao, C.X. Liu, Fang Liu, F. Liu, H.M. Liu, J.B. Liu, J.P. Liu, R.G. Liu, Y. Liu, Z.A. Liu, Z.X. Liu, G.R. Lu, F. Lu, J.G. Lu, C.L. Luo, X.L. Luo, F.C. Ma, J.M. Ma, L.L. Ma, X.Y. Ma, Z.P. Mao, X.C. Meng, X.H. Mo, J. Nie, Z.D. Nie, S.L. Olsen, H.P. Peng, N.D. Qi, C.D. Qian, H. Qin, J.F. Qiu, Z.Y. Ren, G. Rong, L.Y. Shan, L. Shang, D.L. Shen, X.Y. Shen, H.Y. Sheng, F. Shi, X. Shi, L.W. Song, H.S. Sun, S.S. Sun, Y.Z. Sun, Z.J. Sun, X. Tang, N. Tao, Y.R. Tian, G.L. Tong, G.S. Varner, D.Y. Wang, J.Z. Wang, L. Wang, L.S. Wang, M. Wang, Meng Wang, P. Wang, P.L. Wang, S.Z. Wang, W.F. Wang, Y.F. Wang, Zhe Wang, Z. Wang, Zheng Wang, Z.Y. Wang, C.L. Wei, N. Wu, Y.M. Wu, X.M. Xia, X.X. Xie, B. Xin, G.F. Xu, H. Xu, Y. Xu, S.T. Xue, M.L. Yan, W.B. Yan, F. Yang, H.X. Yang, J. Yang, S.D. Yang, Y.X. Yang, L.H. Yi, Z.Y. Yi, M. Ye, M.H. Ye, Y.X. Ye, C.S. Yu, G.W. Yu, C.Z. Yuan, J.M. Yuan, Y. Yuan, Q. Yue, S.L. Zang, Y. Zeng, B.X. Zhang, B.Y. Zhang, C.C. Zhang, D.H. Zhang, H.Y. Zhang, J. Zhang, J.M. Zhang, J.Y. Zhang, J.W. Zhang, L.S. Zhang, Q.J. Zhang, S.Q. Zhang, X.M. Zhang, X.Y. Zhang, Yiyun Zhang, Y.J. Zhang, Y.Y. Zhang, Z.P. Zhang, Z.Q. Zhang, D.X. Zhao, J.B. Zhao, J.W. Zhao, P.P. Zhao, W.R. Zhao, X.J. Zhao, Y.B. Zhao, Z.G. Zhao, H.Q. Zheng, J.P. Zheng, L.S. Zheng, Z.P. Zheng, X.C. Zhong, B.Q. Zhou, G.M. Zhou, L. Zhou, N.F. Zhou, K.J. Zhu, Q.M. Zhu, Yingchun Zhu, Y.C. Zhu, Y.S. Zhu, Z.A. Zhu, B.A. Zhuang, and B.S. Zou
- Subjects
Quantum chromodynamics ,Physics ,Nuclear and High Energy Physics ,Particle physics ,Angular distribution ,Positron ,Proton ,Branching fraction ,Analytical chemistry ,High Energy Physics::Experiment ,Electron ,Bar (unit) - Abstract
The process J/\psi --> p \bar{p} is studied using 57.7 X 10^6 J/\psi events collected with the BESII detector at the Beijing Electron Positron Collider. The branching ratio is determined to be Br(J/\psi --> p \bar{p})=(2.26 +- 0.01 +- 0.14) X 10^{-3}, and the angular distribution is well described by \frac{dN}{d cos\theta_p}=1+\alpha\cos^2\theta_p with \alpha = 0.676 +- 0.036 +- 0.042, where \theta_p is the angle between the proton and beam directions. The value of \alpha obtained is in good agreement with the predictions of first-order QCD.
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