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arXiv · 2602.09652

First observation of the $\eta_{c}\to\Xi^{0} \bar{\Xi}^{0}$ decay

BESIII Collaboration·M. Ablikim·M. N. Achasov·P. Adlarson·X. C. Ai·C. S. Akondi·R. Aliberti·A. Amoroso·Q. An·Y. H. An·Y. Bai·O. Bakina·H. R. Bao·X. L. Bao·V. Batozskaya·K. Begzsuren·N. Berger·M. Berlowski·M. B. Bertani·D. Bettoni·F. Bianchi·E. Bianco·A. Bortone·I. Boyko·R. A. Briere·A. Brueggemann·D. Cabiati·H. Cai·M. H. Cai·X. Cai·A. Calcaterra·G. F. Cao·N. Cao·S. A. Cetin·X. Y. Chai·J. F. Chang·T. T. Chang·G. R. Che·Y. Z. Che·C. H. Chen·Chao Chen·G. Chen·H. S. Chen·H. Y. Chen·M. L. Chen·S. J. Chen·S. M. Chen·T. Chen·W. Chen·X. R. Chen·X. T. Chen·X. Y. Chen·Y. B. Chen·Y. Q. Chen·Z. K. Chen·J. Cheng·L. N. Cheng·S. K. Choi·X. Chu·G. Cibinetto·F. Cossio·J. Cottee-Meldrum·H. L. Dai·J. P. Dai·X. C. Dai·A. Dbeyssi·R. E. de Boer·D. Dedovich·C. Q. Deng·Z. Y. Deng·A. Denig·I. Denisenko·M. Destefanis·F. De Mori·X. X. Ding·Y. Ding·Y. X. Ding·Yi. Ding·J. Dong·L. Y. Dong·M. Y. Dong·X. Dong·Z. J. Dong·M. C. Du·S. X. Du·Shaoxu Du·X. L. Du·Y. Q. Du·Y. Y. Duan·Z. H. Duan·P. Egorov·G. F. Fan·J. J. Fan·Y. H. Fan·J. Fang·Jin Fang·S. S. Fang·W. X. Fang·Y. Q. Fang·L. Fava
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Abstract

Using $(10087\pm 44)\times 10^6$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider, we report the first observation of the decay $\eta_{c} \to \Xi^{0} \bar{\Xi}^{0}$. The interference between $J/\psi\to\gamma\eta_c\to\gamma\Xi^0\bar{\Xi}^0$ and $J/\psi\to\gamma\Xi^0\bar{\Xi}^0|_{\rm non-resonance}$ is considered in the $\Xi^0 \bar{\Xi}^0$ mass spectrum fits. The branching fractions are measured to be $B(\eta_c \to \Xi^0 \bar{\Xi}^0)=(1.33 \pm 0.03 \pm 0.18) \times 10^{-3}$ for the constructive interference and $B(\eta_c \to \Xi^0 \bar{\Xi}^0)=(1.63 \pm 0.04 \pm 0.21) \times 10^{-3}$ for the destructive interference, where the first uncertainties are statistical and the second are systematic.

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BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, C. S. Akondi, R. Aliberti, A. Amoroso, Q. An, Y. H. An, Y. Bai, O. Bakina, H. R. Bao, X. L. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. B. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, D. Cabiati, H. Cai, M. H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, X. Y. Chai, J. F. Chang, T. T. Chang, G. R. Che, Y. Z. Che, C. H. Chen, Chao Chen, G. Chen, H. S. Chen, H. Y. Chen, M. L. Chen, S. J. Chen, S. M. Chen, T. Chen, W. Chen, X. R. Chen, X. T. Chen, X. Y. Chen, Y. B. Chen, Y. Q. Chen, Z. K. Chen, J. Cheng, L. N. Cheng, S. K. Choi, X. Chu, G. Cibinetto, F. Cossio, J. Cottee-Meldrum, H. L. Dai, J. P. Dai, X. C. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, C. Q. Deng, Z. Y. Deng, A. Denig, I. Denisenko, M. Destefanis, F. De Mori, X. X. Ding, Y. Ding, Y. X. Ding, Yi. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, Z. J. Dong, M. C. Du, S. X. Du, Shaoxu Du, X. L. Du, Y. Q. Du, Y. Y. Duan, Z. H. Duan, P. Egorov, G. F. Fan, J. J. Fan, Y. H. Fan, J. Fang, Jin Fang, S. S. Fang, W. X. Fang, Y. Q. Fang, L. Fava. 2026-02-10. First observation of the $\eta_{c}\to\Xi^{0} \bar{\Xi}^{0}$ decay. https://arxiv.org/abs/2602.09652

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