Measurement of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>−</mml:mo></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:mi>η</mml:mi><mml:mi>J</mml:mi><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi></mml:math> cross section from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>3.808</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi></mml:math> to 4.951 GeV
M. Ablikim, М. Н. Ачасов, P. Adlarson, X. C. Ai, R. Aliberti, A. Amoroso, M. R. An, Qi An, Yunfei Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, Angela B. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Çetin, J. F. Chang, T. T. Chang, W. L. Chang, G. R., G. Chelkov, C. Chen, Chao Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, S. L. Chen, S. M. Chen, T. Chen, X. R. Chen, X. T. Chen, Y. B. Chen, Y. Q. Chen, Z. J. Chen, S. K. Choi, X. Chu, G. Cibinetto, S. C. Coen, F. Cossio, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, B. Ding, X. X. Ding, Y. Ding, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, M. C. Du, S. X. Du, Z. H. Duan, P. Egorov, Y. H. Fan, J. Fang, S. S. Fang, W. X. Fang, Y. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, Jianghe Feng, Y. T. Feng, K. M. Fischer, M. Fritsch, C. D. Fu, J. Fu, Y. W. Fu, Hongjun Gao, Y. N. Gao, Yang Gao, S. Garbolino
Abstract
Using data samples with an integrated luminosity of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mn>22.42</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:msup><a:mi>fb</a:mi><a:mrow><a:mo>−</a:mo><a:mn>1</a:mn></a:mrow></a:msup></a:math> collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msup><c:mi>e</c:mi><c:mo>+</c:mo></c:msup><c:msup><c:mi>e</c:mi><c:mo>−</c:mo></c:msup><c:mo stretchy="false">→</c:mo><c:mi>η</c:mi><c:mi>J</c:mi><c:mo>/</c:mo><c:mi>ψ</c:mi></c:math> process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mi>ψ</f:mi><f:mo stretchy="false">(</f:mo><f:mn>4040</f:mn><f:mo stretchy="false">)</f:mo></f:math>, two additional resonances, and a nonresonant component are performed. The mass and width of the first additional state are <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mo stretchy="false">(</j:mo><j:mn>4219.7</j:mn><j:mo>±</j:mo><j:mn>2.5</j:mn><j:mo>±</j:mo><j:mn>4.5</j:mn><j:mo stretchy="false">)</j:mo><j:mtext> </j:mtext><j:mtext> </j:mtext><j:mi>MeV</j:mi><j:mo>/</j:mo><j:msup><j:mi>c</j:mi><j:mn>2</j:mn></j:msup></j:math> and <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mo stretchy="false">(</n:mo><n:mn>80.7</n:mn><n:mo>±</n:mo><n:mn>4.4</n:mn><n:mo>±</n:mo><n:mn>1.4</n:mn><n:mo stretchy="false">)</n:mo><n:mtext> </n:mtext><n:mtext> </n:mtext><n:mi>MeV</n:mi></n:math>, respectively, consistent with the <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"><r:mi>ψ</r:mi><r:mo stretchy="false">(</r:mo><r:mn>4230</r:mn><r:mo stretchy="false">)</r:mo></r:math>. For the second state, the mass and width are <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mo stretchy="false">(</v:mo><v:mn>4386</v:mn><v:mo>±</v:mo><v:mn>13</v:mn><v:mo>±</v:mo><v:mn>17</v:mn><v:mo stretchy="false">)</v:mo><v:mtext> </v:mtext><v:mtext> </v:mtext><v:mi>MeV</v:mi><v:mo>/</v:mo><v:msup><v:mi>c</v:mi><v:mn>2</v:mn></v:msup></v:math> and <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:mo stretchy="false">(</z:mo><z:mn>177</z:mn><z:mo>±</z:mo><z:mn>32</z:mn><z:mo>±</z:mo><z:mn>13</z:mn><z:mo stretchy="false">)</z:mo><z:mtext> </z:mtext><z:mtext> </z:mtext><z:mi>MeV</z:mi></z:math>, respectively, consistent with the <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:mi>ψ</db:mi><db:mo stretchy="false">(</db:mo><db:mn>4360</db:mn><db:mo stretchy="false">)</db:mo></db:math>. The first uncertainties are statistical, and the second ones are systematic. The statistical significance of <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" display="inline"><hb:mi>ψ</hb:mi><hb:mo stretchy="false">(</hb:mo><hb:mn>4040</hb:mn><hb:mo stretchy="false">)</hb:mo></hb:math> is <lb:math xmlns:lb="http://www.w3.org/1998/Math/MathML" display="inline"><lb:mn>8.0</lb:mn><lb:mi>σ</lb:mi></lb:math> and those for <nb:math xmlns:nb="http://www.w3.org/1998/Math/MathML" display="inline"><nb:mi>ψ</nb:mi><nb:mo stretchy="false">(</nb:mo><nb:mn>4230</nb:mn><nb:mo stretchy="false">)</nb:mo></nb:math> and <rb:math xmlns:rb="http://www.w3.org/1998/Math/MathML" display="inline"><rb:mi>ψ</rb:mi><rb:mo stretchy="false">(</rb:mo><rb:mn>4360</rb:mn><rb:mo stretchy="false">)</rb:mo></rb:math> are more than <vb:math xmlns:vb="http://www.w3.org/1998/Math/MathML" display="inline"><vb:mn>10.0</vb:mn><vb:mi>σ</vb:mi></vb:math>. Published by the American Physical Society 2024