Measurements of the Electric and Magnetic Form Factors of the Neutron for Timelike Momentum Transfer

• Published in: Physical review letters 2023-04, Vol.130 (15), p.151905-151905, Article 151905
• Main Authors: Ablikim, M, Achasov, M N, Adlarson, P, Aliberti, R, Amoroso, A, An, M R, An, Q, Bai, Y, Bakina, O, Balossino, I, Ban, Y, Batozskaya, V, Begzsuren, K, Berger, N, Bertani, M, Bettoni, D, Bianchi, F, Bianco, E, Bloms, J, Bortone, A, Boyko, I, Briere, R A, Brueggemann, A, Cai, H, Cai, X, Calcaterra, A, Cao, G F, Cao, N, Cetin, S A, Chang, J F, Chang, T T, Chang, W L, Che, G R, Chelkov, G, Chen, C, Chen, Chao, Chen, G, Chen, H S, Chen, M L, Chen, S J, Chen, S M, Chen, T, Chen, X R, Chen, X T, Chen, Y B, Chen, Y Q, Chen, Z J, Cheng, W S, Choi, S K, Chu, X, Cibinetto, G, Coen, S C, Cossio, F, Cui, J J, Dai, H L, Dai, J P, Dbeyssi, A, de Boer, R E, Dedovich, D, Deng, Z Y, Denig, A, Denysenko, I, Destefanis, M, De Mori, F, Ding, B, Ding, Y, Dong, J, Dong, L Y, Dong, M Y, Dong, X, Du, S X, Duan, Z H, Egorov, P, Fan, Y L, Fang, J, Fang, S S, Fang, W X, Fang, Y, Farinelli, R, Fava, L, Feldbauer, F, Felici, G, Feng, C Q, Feng, J H, Fischer, K, Fritsch, M, Fritzsch, C, Fu, C D, Fu, Y W, Gao, H, Gao, Y N, Gao, Yang, Garbolino, S, Garzia, I, Ge, P T, Ge, Z W, Geng, C, Gersabeck, E M, Gilman, A
• Format: Article
• Language: English
• Subjects: Form factors; Physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Strong interaction
• ISSN: 0031-9007; 1079-7114; 1079-7114
• DOI: 10.1103/PhysRevLett.130.151905

We present the first measurements of the electric and magnetic form factors of the neutron in the timelike (positive q^{2}) region as function of four-momentum transfer. We explored the differential cross sections of the reaction e^{+}e^{-}→n[over ¯]n with data collected with the BESIII detector at the BEPCII accelerator, corresponding to an integrated luminosity of 354.6  pb^{-1} in total at twelve center-of-mass energies between sqrt[s]=2.0-2.95  GeV. A relative uncertainty of 18% and 12% for the electric and magnetic form factors, respectively, is achieved at sqrt[s]=2.3935  GeV. Our results are comparable in accuracy to those from electron scattering in the comparable spacelike region of four-momentum transfer. The electromagnetic form factor ratio R_{em}≡|G_{E}|/|G_{M}| is within the uncertainties close to unity. We compare our result on |G_{E}| and |G_{M}| to recent model predictions, and the measurements in the spacelike region to test the analyticity of electromagnetic form factors.