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arXiv · 2104.08754

Observation of a near-threshold enhancement in the $\Lambda\bar{\Lambda}$ mass spectrum from $e^+e^-\to\phi\Lambda\bar{\Lambda}$ at $\sqrt{s}$ from 3.51 to 4.60 GeV

M. Ablikim·M. N. Achasov·P. Adlarson·S. Ahmed·M. Albrecht·R. Aliberti·A. Amoroso·M. R. An·Q. An·X. H. Bai·Y. Bai·O. Bakina·R. Baldini Ferroli·I. Balossino·Y. Ban·K. Begzsuren·N. Berger·M. Bertani·D. Bettoni·F. Bianchi·J. Bloms·A. Bortone·I. Boyko·R. A. Briere·H. Cai·X. Cai·A. Calcaterra·G. F. Cao·N. Cao·S. A. Cetin·J. F. Chang·W. L. Chang·G. Chelkov·D. Y. Chen·G. Chen·H. S. Chen·M. L. Chen·S. J. Chen·X. R. Chen·Y. B. Chen·Z. J Chen·W. S. Cheng·G. Cibinetto·F. Cossio·X. F. Cui·H. L. Dai·X. C. Dai·A. Dbeyssi·R. E. de Boer·D. Dedovich·Z. Y. Deng·A. Denig·I. Denysenko·M. Destefanis·F. De Mori·Y. Ding·C. Dong·J. Dong·L. Y. Dong·M. Y. Dong·X. Dong·S. X. Du·Y. L. Fan·J. Fang·S. S. Fang·Y. Fang·R. Farinelli·L. Fava·F. Feldbauer·G. Felici·C. Q. Feng·J. H. Feng·M. Fritsch·C. D. Fu·Y. Gao·Y. G. Gao·I. Garzia·P. T. Ge·C. Geng·E. M. Gersabeck·A Gilman·K. Goetzen·L. Gong·W. X. Gong·W. Gradl·M. Greco·L. M. Gu·M. H. Gu·Y. T. Gu·C. Y Guan·A. Q. Guo·L. B. Guo·R. P. Guo·Y. P. Guo·A. Guskov·T. T. Han·W. Y. Han·X. Q. Hao·F. A. Harris·K. L. He
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Abstract

The process $e^+ e^- \to \phi \Lambda \bar{\Lambda}$ is studied using data samples collected with the BESIII detector at the BEPCII collider at center-of-mass energies $\sqrt{s}$ ranging from $3.51$ to $4.60~{\rm GeV}$ . An intermediate resonance structure is observed near the threshold of $\Lambda \bar{\Lambda}$. It has a mass of $(2262 \pm 4 \pm 28)~{\rm{MeV}}/c^{2}$ and a width of $(72 \pm 5 \pm 43)~\rm{MeV}$, where the quoted uncertainties are statistical and systematic, respectively. The $J^{PC}$ quantum numbers of $0^{-+}$ and $0^{++}$ are rejected, while other $J^{PC}$ hypotheses are possible, according to the helicity angle study. The energy-dependent cross section of the $e^+ e^- \to \phi \Lambda \bar{\Lambda}$ process is measured for the first time in this energy region, and contributions from excited $\psi$ states and vector charmonium-like $Y$-states are investigated.

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M. Ablikim, M. N. Achasov, P. Adlarson, S. Ahmed, M. Albrecht, R. Aliberti, A. Amoroso, M. R. An, Q. An, X. H. Bai, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, K. Begzsuren, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, W. L. Chang, G. Chelkov, D. Y. Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, X. R. Chen, Y. B. Chen, Z. J Chen, W. S. Cheng, G. Cibinetto, F. Cossio, X. F. Cui, H. L. Dai, X. C. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, C. Dong, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, S. X. Du, Y. L. Fan, J. Fang, S. S. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, M. Fritsch, C. D. Fu, Y. Gao, Y. G. Gao, I. Garzia, P. T. Ge, C. Geng, E. M. Gersabeck, A Gilman, K. Goetzen, L. Gong, W. X. Gong, W. Gradl, M. Greco, L. M. Gu, M. H. Gu, Y. T. Gu, C. Y Guan, A. Q. Guo, L. B. Guo, R. P. Guo, Y. P. Guo, A. Guskov, T. T. Han, W. Y. Han, X. Q. Hao, F. A. Harris, K. L. He. 2021-04-18. Observation of a near-threshold enhancement in the $\Lambda\bar{\Lambda}$ mass spectrum from $e^+e^-\to\phi\Lambda\bar{\Lambda}$ at $\sqrt{s}$ from 3.51 to 4.60 GeV. https://doi.org/10.1103/physrevd.104.052006

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