Yazar "Ahmed, Shakeel" seçeneğine göre listele

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    First observation of the direct production of the ?c1 in e+e- annihilation
    (American Physical Society, 2022) Ablikim, Medina N.; Achasov, M. N.; Adlarson, Patrik; Ahmed, Shakeel; Albrecht, Malte
    We 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.
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    Measurements of the center-of-mass energies of e+e-collisions at BESIII
    (IOP Publishing, 2021) Ablikim, Medina N.; Achasov, M. N.; Adlarson, Patrik; Ahmed, Shakeel; Albrecht, Malte; Kolcu, Onur Buğra
    During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5 fb -1 of e+e- collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e-, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-collection period. © 2021Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.
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    Search for the hyperon semileptonic decay ? ? ? ? 0 e ? ¯¯¯ ? e
    (American Physical Society, 2021) Ablikim, Medina N.; Achasov, M. N.; Adlarson, Patrik; Ahmed, Shakeel; Çetin, Serkant Ali; Kolcu, Onur Buğra
    Using events collected by the Beijing Spectrum III (BESIII) detector at the Beijing Electron Positron Collider II (BEPCII) collider, we search for the hyperon semileptonic decay . No significant signal is observed and the upper limit on the branching fraction is set to be at 90% confidence level. This result is one order of magnitude more strict than the previous best limit. © 2021 Published by the American Physical Society