Measurements of Σ+ and Σ− time-like electromagnetic form factors for center-of-mass energies from 2.3864 to 3.0200 GeV
M. Ablikim, М. Н. Ачасов, P. Adlarson, S. Ahmed, M. Albrecht, A. Amoroso, Q. An, Anita, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, K. Begzsuren, J. V. Bennett, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J. Biernat, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, H. Cai, X. Z. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Çetin, J. F. Chang, W. L. Chang, G. Chelkov, D.Y. Chen, G. Chen, H.S. Chen, M.L. Chen, S.J. Chen, X.R. Chen, Yuanbo Chen, W. Cheng, G. Cibinetto, F. Cossio, X. F. Cui, H.L. Dai, J. P. Dai, X. Dai, A. Dbeyssi, R. B. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, C. Dong, J. Dong, L. Y. Dong, M. Y. Dong, S. X. Du, J. Fang, S. S. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, M. Fritsch, C. D. Fu, Y. Fu, X.L. Gao, Y. Gao, Y. Gao, Y. Gao, I. Garzia, E. Gersabeck, A. Gilman, K. Goetzen, L. Gong, W. X. Gong, W. Gradl, M. Greco, L. M. Gu, M. H. Gu, S. Gu, Yi Gu, C. Y. Guan, A. Q. Guo, L. B. Guo, R. P. Guo, Y. P. Guo, Y. P. Guo, A. Guskov, S. W. Han, T. T. Han, T. Z. Han, X. Q. Hao, F. A. Harris
Abstract
The Born cross sections of the e + e − → Σ + Σ ¯ − and e + e − → Σ − Σ ¯ + processes are determined for center-of-mass energy from 2.3864 to 3.0200 GeV with the BESIII detector. The cross section lineshapes can be described properly by a pQCD function and the resulting ratio of effective form factors for the Σ + and Σ − is consistent with 3. In addition, ratios of the Σ + electric and magnetic form factors, | G E / G M | , are obtained at three center-of-mass energies through an analysis of the angular distributions. These measurements, which are studied for the first time in the off-resonance region, provide precision experimental input for understanding baryonic structure. The observed new features of the Σ ± form factors require more theoretical discussions for the hyperons.