Unraveling the Structure of Λ Hyperons with Polarized Λ Λ ¯ Pairs
Year: 2025
Type: article
Abstract: With data collected in a dedicated energy scan from 2.3864 up to 3.0800 GeV, the BESIII Collaboration provides the first complete energy-dependent measurements of the Λ electromagnetic form factors in the timelike region. By combining double-tag and single-tag events from the e^{+}e^{-}→ΛΛ[over ¯]→pπ^{-}p[over ¯]π^{+} reaction, we achieve a complete decomposition of the spin structure of the reaction at five energy points, with high statistical and systematic precision. Our data reveal that while the modulus of the ratio between the electric and magnetic form factor, R(q^{2})=|G_{E}(q^{2})/G_{M}(q^{2})|, remains fairly constant across the considered energy range, the relative phase ΔΦ(q^{2})=Φ_{E}(q^{2})-Φ_{M}(q^{2}) changes by more than 90° between 2.396 and 2.6544 GeV. Using a fit to our data based on dispersion relations, the complex form factor ratio is determined as a function of q^{2}, and the preferred solution has multiple zero-crossings in the complex plane. From the derivative of the ratio at q^{2}=0, the root-mean-squared charge radius of the Λ is obtained. The two most probable solutions yield a negative root-mean-squared charge radius, indicating an asymmetric charge distribution where the ds quark pair lies close to the center of the Λ hyperon.
Source: Physical Review Letters
DOI: 10.1103/9f1h-fl4k
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Institutions: Institute of High Energy Physics, Siberian Branch of the Russian Academy of Sciences, Budker Institute of Nuclear Physics, Uppsala University, Zhengzhou University, Johannes Gutenberg University Mainz, Istituto Nazionale di Fisica Nucleare, Istituto Nazionale di Fisica Nucleare, Sezione di Torino, University of Turin, University of Science and Technology of China, Southeast University, Joint Institute for Nuclear Research, Peking University, Chinese Academy of Sciences, University of Chinese Academy of Sciences, National Centre for Nuclear Research, Mongolian Academy of Sciences, Institute of Physics and Technology, Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Carnegie Mellon University, University of Münster, Wuhan University, Lanzhou University, Istinye University, Nankai University, China University of Geosciences, Soochow University, Henan University, North China Electric Power University, Nanjing University, Tsinghua University, Institute of Modern Physics, Jilin University, Sun Yat-sen University, Hunan University, Chung-Ang University, Fudan University, Shandong University, Yunnan University, Helmholtz Institute Mainz, Ruhr University Bochum, University of South China, University of Jinan, Liaoning University, Inner Mongolia University, Henan Normal University, Università degli Studi del Piemonte Orientale “Amedeo Avogadro”, Nanjing Normal University, University of Ferrara, University of Manchester, University of Oxford, GSI Helmholtz Centre for Heavy Ion Research, Guangxi University, Shandong Normal University, Indiana University Bloomington, Indiana University, University of Hawaiʻi at Mānoa, University of Hawaii System, Suranaree University of Technology, South China Normal University, University of the Punjab, Hangzhou Normal University, Huangshan University, University of Tarapacá, University of Groningen, Indian Institute of Technology Madras, Justus-Liebig-Universität Gießen, Liaoning Normal University, Qufu Normal University, Renmin University of China, Hebei University, China Center of Advanced Science and Technology, Sichuan University, Guangxi Normal University, Shanxi University, Central China Normal University, Henan University of Science and Technology, Henan University of Technology, Central South University, Zhejiang University, COMSATS University Islamabad, University of Perugia, Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Hunan Normal University, Shanghai Jiao Tong University, Near East University, Beihang University, Yantai University, University of Bristol, Shanxi Normal University, University of Science and Technology Liaoning
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,750
Funders: Institute of Nuclear and Particle Physics, Shanghai Jiao Tong University, U.S. Department of Energy, Istituto Nazionale di Fisica Nucleare Sezione di Padova, Mongolian Foundation for Science and Technology, Deutsche Forschungsgemeinschaft, Swedish Foundation for International Cooperation in Research and Higher Education, National Natural Science Foundation of China, Chinese Academy of Sciences, National Research Foundation of Korea, Knut och Alice Wallenbergs Stiftelse, Narodowe Centrum Nauki, Vetenskapsrådet, Kalkinma Bakanliği, CAS Center for Excellence in Particle Physics, Shanghai Key Laboratory for Particle Physics and Cosmology, National Key Research and Development Program of China
Awards: Measurement of charmed baryon-antibaryon asymmetry at LHCb, G1580621639, BESIII上正反超子对关联产生及其衰变的实验研究, G2505060883, G2777307501, G328816031, G333704919, G3427629783, BESIII上胶球的寻找和轻介子谱的研究, G3534486373, G3790219004, G3829643926, New insights into the tetrapod terrestrialisation revealed by 3D high-resolution imaging, G4883783264, G5170186115, UNDERSTANDING QCD IN THE LIGHT MESON SECTOR (WITH EMPHASIS ON MAPPING GLUONIC EXCITATIONS)..., G6119985531, G6165130261, 北京谱仪III上Ds衰变的实验研究, G6371861488, 北京正负电子对撞机BESIII实验上粲重子Λc研究, G6746531785, G6845169765, G6927153966, 北京谱仪III上奇异介子和奇异夸克偶素的实验研究, G7692396955, G783835211, G8146335776, G8158558910, G8396383697, G8644667100, G904559116, G945438540, G965723986
OpenAlex ID: W4415899232