Ablikim, Medina N.Achasov, M. N.Adlarson, PatrikAhmed, ShakeelAlbrecht, Malte2022-11-082022-11-082022Ablikim, M., Achasov, M. N., Adlarson, P., Ahmed, S., Albrecht, M., Aliberti, R., . . . (BESIII Collaboration). (2022). First observation of the direct production of the χc1 in e+e- annihilation. Physical Review Letters, 129(12) doi:10.1103/PhysRevLett.129.122001https://doi.org/10.1103/PhysRevLett.129.122001https://hdl.handle.net/20.500.12713/3281We study the direct production of the JPC=1++ charmonium state ?c1(1P) in electron-positron annihilation by carrying out an energy scan around the mass of the ?c1(1P). The data were collected with the BESIII detector at the BEPCII collider. An interference pattern between the signal process e+e-??c1(1P)??J/????+?- and the background processes e+e-??ISRJ/???ISR?+?- and e+e-??ISR?+?- is observed by combining all the data samples. The ?c1(1P) signal is observed with a significance of 5.1?. This is the first observation of a C-even state directly produced in e+e- annihilation. The electronic width of the ?c1(1P) resonance is determined to be ?ee=(0.12-0.08+0.13) eV, which is of the same order of magnitude as theoretical calculations. © 2022 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 SCOAP3.eninfo:eu-repo/semantics/closedAccessArticle12912WOS:0008887598000052-s2.0-85138917856Q110.1103/PhysRevLett.129.122001N/A