TY - JOUR
T1 - Evidence for the Cusp Effect in η′ Decays into ηπ0π0
AU - BESIII Collaboration
AU - Ablikim, M.
AU - Achasov, M. N.
AU - Kalantar-Nayestanaki, N.
AU - Kappert, R.
AU - Kavatsyuk, M.
AU - Messchendorp, J.
AU - Rodin, V.
N1 - Funding Information:
The BESIII Collaboration thanks the staff of BEPCII and the IHEP computing center for their strong support. This work is supported in part by National Key R&D Program of China under Contracts No. 2020YFA0406300, No. 2020YFA0406400; National Natural Science Foundation of China (NSFC) under Contracts No. 11635010, No. 11735014, No. 11835012, No. 11935015, No. 11935016, No. 11935018, No. 11961141012, No. 12005195, No. 12022510, No. 12025502, No. 12035009, No. 12035013, No. 12192260, No. 12192261, No. 12192262, No. 12192263, No. 12192264, No. 12192265, No. 12225509; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contract No. U1832207; CAS Key Research Program of Frontier Sciences under Contract No. QYZDJ-SSW-SLH040; 100 Talents Program of CAS; INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology; ERC under Contract No. 758462; European Union’s Horizon 2020 research and innovation program under Marie Sklodowska-Curie Grant Agreement under Contract No. 894790; German Research Foundation DFG under Contracts No. 443159800, Collaborative Research Center CRC 1044, GRK 2149; Istituto Nazionale di Fisica Nucleare, Italy; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Science and Technology fund; STFC (United Kingdom); The Royal Society, UK under Contracts No. DH140054, No. DH160214; The Swedish Research Council; U.S. Department of Energy under Award No. DE-FG02-05ER41374.
Publisher Copyright:
© 2023 authors. Published by the American Physical Society.
PY - 2023/2/24
Y1 - 2023/2/24
N2 - Using a sample of 4.3×105 η′→ηπ0π0 events selected from the ten billion J/ψ event dataset collected with the BESIII detector, we study the decay η′→ηπ0π0 within the framework of nonrelativistic effective field theory. Evidence for a structure at π+π- mass threshold is observed in the invariant mass spectrum of π0π0 with a statistical significance of around 3.5σ, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the ππ scattering length combination a0-a2 is determined to be 0.226±0.060stat±0.013syst, which is in good agreement with theoretical calculation of 0.2644±0.0051.
AB - Using a sample of 4.3×105 η′→ηπ0π0 events selected from the ten billion J/ψ event dataset collected with the BESIII detector, we study the decay η′→ηπ0π0 within the framework of nonrelativistic effective field theory. Evidence for a structure at π+π- mass threshold is observed in the invariant mass spectrum of π0π0 with a statistical significance of around 3.5σ, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the ππ scattering length combination a0-a2 is determined to be 0.226±0.060stat±0.013syst, which is in good agreement with theoretical calculation of 0.2644±0.0051.
UR - http://www.scopus.com/inward/record.url?scp=85149669098&partnerID=8YFLogxK
U2 - 10.1103/PhysRevLett.130.081901
DO - 10.1103/PhysRevLett.130.081901
M3 - Article
C2 - 36898113
SN - 0031-9007
VL - 130
JO - Physical Review Letters
JF - Physical Review Letters
IS - 8
M1 - 081901
ER -