@article{e6b6f81fcb8c4701a44f41b229ff9226,
title = "Complete Measurement of the Λ Electromagnetic Form Factors",
abstract = "The exclusive process e+e-→Λ{\=Λ}, with Λ→pπ- and {\=Λ}→{\=p}π+, has been studied at s=2.396 GeV for measurement of the timelike Λ electric and magnetic form factors, GE and GM. A data sample, corresponding to an integrated luminosity of 66.9 pb-1, was collected with the BESIII detector for this purpose. A multidimensional analysis with a complete decomposition of the spin structure of the reaction enables a determination of the modulus of the ratio R=|GE/GM| and, for the first time for any baryon, the relative phase Δφ=φE-φM. The resulting values are R=0.96±0.14(stat)±0.02(syst) and Δφ=37°±12°(stat)±6°(syst), respectively. These are obtained using the recently established and most precise value of the asymmetry parameter αΛ=0.750±0.010 measured by BESIII. In addition, the cross section is measured with unprecedented precision to be σ=118.7±5.3(stat)±5.1(syst) pb, which corresponds to an effective form factor of |G|=0.123±0.003(stat)±0.003(syst). The contribution from two-photon exchange is found to be negligible. Our result enables the first complete determination of baryon timelike electromagnetic form factors.",
author = "{(BESIII Collaboration)} and M. Ablikim and Achasov, {M. N.} and P. Adlarson and S. Ahmed and M. Albrecht and M. Alekseev and A. Amoroso and An, {F. F.} and Q. An and Y. Bai and O. Bakina and {Baldini Ferroli}, R. and Y. Ban and K. Begzsuren and Bennett, {J. V.} and N. Berger and M. Bertani and D. Bettoni and F. Bianchi and J. Biernat and J. Bloms and I. Boyko and Briere, {R. A.} and H. Cai and X. Cai and A. Calcaterra and Cao, {G. F.} and N. Cao and Cetin, {S. A.} and J. Chai and Chang, {J. F.} and Chang, {W. L.} and G. Chelkov and Chen, {D. Y.} and G. Chen and Chen, {H. S.} and Chen, {J. C.} and Chen, {M. L.} and Chen, {S. J.} and Chen, {Y. B.} and W. Cheng and G. Cibinetto and F. Cossio and Cui, {X. F.} and Dai, {H. L.} and Dai, {J. P.} and Dai, {X. C.} and A. Dbeyssi and D. Dedovich and Deng, {Z. Y.}",
note = "Publisher Copyright: {\textcopyright} 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP.",
year = "2019",
month = sep,
day = "20",
doi = "10.1103/PhysRevLett.123.122003",
language = "English",
volume = "123",
journal = "Physical Review Letters",
issn = "0031-9007",
publisher = "American Physical Society",
number = "12",
}