First Study of Antihyperon-Nucleon Scattering Λ[over ¯]p→Λ[over ¯]p and Measurement of Λp→Λp Cross Section

• Published in: Physical review letters 2024-06, Vol.132 (23), p.231902, Article 231902
• Main Authors: Ablikim, M, Achasov, M N, Adlarson, P, Afedulidis, O, Ai, X C, Aliberti, R, Amoroso, A, An, Q, Bai, Y, Bakina, O, Balossino, I, Ban, Y, Bao, H-R, Batozskaya, V, Begzsuren, K, Berger, N, Berlowski, M, Bertani, M, Bettoni, D, Bianchi, F, Bianco, E, Bortone, A, Boyko, I, Briere, R A, Brueggemann, A, Cai, H, Cai, X, Calcaterra, A, Cao, G F, Cao, N, Cetin, S A, Chang, J F, Che, G R, Chelkov, G, Chen, C, Chen, C H, Chen, Chao, Chen, G, Chen, H S, Chen, H Y, 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, Z Y, Choi, S K, Cibinetto, G, Cossio, F, Cui, J J, Dai, H L, Dai, J P, Dbeyssi, A, de Boer, R E, Dedovich, D, Deng, C Q, Deng, Z Y, Denig, A, Denysenko, I, Destefanis, M, De Mori, F, Ding, B, Ding, X X, Ding, Y, Dong, J, Dong, L Y, Dong, M Y, Dong, X, Du, M C, Du, S X, Duan, Z H, Egorov, P, Fan, Y H, Fang, J, Fang, S S, Fang, W X, Fang, Y, Fang, Y Q, Farinelli, R, Fava, L, Feldbauer, F, Felici, G, Feng, C Q, Feng, J H, Feng, Y T, Fritsch, M, Fu, C D, Fu, J L, Fu, Y W, Gao, H, Gao, X B, Gao, Y N, Gao, Yang
• Format: Article
• Language: English
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.132.231902

Using (10.087±0.044)×10^{9} J/ψ events collected with the BESIII detector at the BEPCII storage ring, the processes Λp→Λp and Λ[over ¯]p→Λ[over ¯]p are studied, where the Λ/Λ[over ¯] baryons are produced in the process J/ψ→ΛΛ[over ¯] and the protons are the hydrogen nuclei in the cooling oil of the beam pipe. Clear signals are observed for the two reactions. The cross sections in -0.9≤cosθ_{Λ/Λ[over ¯]}≤0.9 are measured to be σ(Λp→Λp)=(12.2±1.6_{stat}±1.1_{syst}) and σ(Λ[over ¯]p→Λ[over ¯]p)=(17.5±2.1_{stat}±1.6_{syst})  mb at the Λ/Λ[over ¯] momentum of 1.074  GeV/c within a range of ±0.017  GeV/c, where the θ_{Λ/Λ[over ¯]} are the scattering angles of the Λ/Λ[over ¯] in the Λp/Λ[over ¯]p rest frames. Furthermore, the differential cross sections of the two reactions are also measured, where there is a slight tendency of forward scattering for Λp→Λp, and a strong forward peak for Λ[over ¯]p→Λ[over ¯]p. We present an approach to extract the total elastic cross sections by extrapolation. The study of Λ[over ¯]p→Λ[over ¯]p represents the first study of antihyperon-nucleon scattering, and these new measurements will serve as important inputs for the theoretical understanding of the (anti)hyperon-nucleon interaction.