Research output: Contribution to journal › Article › peer-review
Test of CP Symmetry in the Neutral Decays of Λ via J=ψ → ΛΛ¯. / BESIII Collaboration ; Ачасов, Михаил Николаевич; Мучной, Николай Юрьевич et al.
In: Physical Review Letters, Vol. 136, No. 25, 251802, 23.06.2026.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Test of CP Symmetry in the Neutral Decays of Λ via J=ψ → ΛΛ¯
AU - BESIII Collaboration
AU - Ачасов, Михаил Николаевич
AU - Мучной, Николай Юрьевич
AU - Николаев, Иван Борисович
N1 - The authors thank Professor Jusak Tandean for helpful discussion. The BESIII Collaboration thanks the staff of BEPCII ([57]), the IHEP computing center, and the supercomputing center of the University of Science and Technology of China (USTC) for their strong support. This work is supported in part by National Key R&D Program of China under Contracts No. 2023YFA1609400, No. 2023YFA1606000, and No. 2023YFA1606704; National Natural Science Foundation of China (NSFC) under Contracts No. 11635010, No. 11935015, No. 11935016, No. 11935018, No. 12025502, No. 12035009, No. 12035013, No. 12061131003, No. 2192260, No. 12192261, No. 12192262, No. 12192263, No. 12192264, No. 12192265, No. 12221005, No. 12225509, No. 12235017, No. 12361141819, No. 12122509, No. 12105276; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the Strategic Priority Research Program of Chinese Academy of Sciences under Contract No. XDA0480600; CAS under Contract No. YSBR-101; 100 Talents Program of CAS; The Institute of Nuclear and Particle Physics (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; ERC under Contract No. 758462; German Research Foundation DFG under Contract No. FOR5327; Istituto Nazionale di Fisica Nucleare, Italy; Knut and Alice Wallenberg Foundation under Contracts No. 2021.0174 and No. 2021.0299; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Research Foundation of Korea under Contract No. NRF-2022R1A2C1092335; National Science and Technology fund of Mongolia; Polish National Science Centre under Contract No. 2024/53/B/ST2/00975; STFC (United Kingdom); Swedish Research Council under Contract No. 2019.04595; U.S. Department of Energy under Contract No. DE-FG02-05ER41374. This work is also supported by the Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contract No. U2032111 and the Beijing Natural Science Foundation of China (BNSF) under Contract No. IS23014.
PY - 2026/6/23
Y1 - 2026/6/23
N2 - Using ð10 087 44Þ × 106 J=ψ events collected with the BESIII detector, a full angular analysis is carried out on the process J=ψ → ΛΛ¯ → nπ0p¯ πþ þ c:c. The decay parameters α0 for Λ → nπ0 and α¯ 0 for Λ¯ → n¯π0 are measured to be 0.668 0.007 0.002 and −0.677 0.007 0.003, respectively, yielding the most precise test for CP symmetry of neutral decays of Λ, A0 CP ¼ðα0 þ α¯ 0Þ=ðα0 − α¯ 0Þ, to be −0.006 0.007 0.002. The ratios α0=α− and α¯ 0=αþ are determined to be 0.884 0.013 0.006 and 0.885 0.013 0.004, where α− and αþ are the decay parameters of Λ → pπ− and Λ¯ → p¯ πþ, respectively. The ratios, found to be smaller than unity by more than 5σ, confirm the presence of the ΔI ¼ 3=2 transition in the Λ and Λ¯ decays, which is expected to improve the theoretical calculations for isospin amplitudes, and ACP, in hyperon decays. In all results, the first and second uncertainties are statistical and systematic, respectively.
AB - Using ð10 087 44Þ × 106 J=ψ events collected with the BESIII detector, a full angular analysis is carried out on the process J=ψ → ΛΛ¯ → nπ0p¯ πþ þ c:c. The decay parameters α0 for Λ → nπ0 and α¯ 0 for Λ¯ → n¯π0 are measured to be 0.668 0.007 0.002 and −0.677 0.007 0.003, respectively, yielding the most precise test for CP symmetry of neutral decays of Λ, A0 CP ¼ðα0 þ α¯ 0Þ=ðα0 − α¯ 0Þ, to be −0.006 0.007 0.002. The ratios α0=α− and α¯ 0=αþ are determined to be 0.884 0.013 0.006 and 0.885 0.013 0.004, where α− and αþ are the decay parameters of Λ → pπ− and Λ¯ → p¯ πþ, respectively. The ratios, found to be smaller than unity by more than 5σ, confirm the presence of the ΔI ¼ 3=2 transition in the Λ and Λ¯ decays, which is expected to improve the theoretical calculations for isospin amplitudes, and ACP, in hyperon decays. In all results, the first and second uncertainties are statistical and systematic, respectively.
KW - Hadronic decays
KW - Baryons
KW - Strange quark
KW - CP symmetry
KW - Polarization
KW - Lepton colliders
UR - https://www.scopus.com/pages/publications/105043821322
U2 - 10.1103/5x9g-82jg
DO - 10.1103/5x9g-82jg
M3 - Article
C2 - 42430625
VL - 136
JO - Physical Review Letters
JF - Physical Review Letters
SN - 0031-9007
IS - 25
M1 - 251802
ER -
ID: 80165094