Observation of e e- → ηΥ(2S) and search for e e- → ηΥ(1S), γXbat √s near 10.75 GeV

I Adachi; L Aggarwal; H Ahmed; Y Ahn; H Aihara; N Akopov; S Alghamdi; M Alhakami; A Aloisio; N Althubiti; K Amos; M Angelsmark; NA Ky; C Antonioli; DM Asner; H Atmacan; T Aushev; V Aushev; M Aversano; R Ayad; V Babu; H Bae; NK Baghel; S Bahinipati; P Bambade; S Banerjee; S Bansal; M Barrett; M Bartl; J Baudot; A Baur; A Beaubien; F Becherer; J Becker; JV Bennett; FU Bernlochner; V Bertacchi; M Bertemes; E Bertholet; M Bessner; S Bettarini; V Bhardwaj; B Bhuyan; F Bianchi; T Bilka; D Biswas; A Bobrov; D Bodrov; A Bondar; G Bonvicini; A Boschetti; A Bozek; M Bračko; P Branchini; RA Briere; TE Browder; A Budano; S Bussino; Q Campagna; L Cao; G Casarosa; C Cecchi; MC Chang; P Cheema; L Chen; BG Cheon; C Cheshta; H Chetri; K Chilikin; J Chin; K Chirapatpimol; HE Cho; K Cho; SJ Cho; SK Choi; S Choudhury; JA Colorado-Caicedo; I Consigny; L Corona; JX Cui; E De La Cruz-Burelo; SA De La Motte; G de Marino; G De Nardo; G De Pietro; R de Sangro; M Destefanis; S Dey; A Di Canto; J Dingfelder; Z Doležal; ID Jiménez; TV Dong; X Dong; M Dorigo; K Dugic; G Dujany; P Ecker; D Epifanov; J Eppelt

Journal article

Observation of e e- → ηΥ(2S) and search for e e- → ηΥ(1S), γXbat √s near 10.75 GeV

I Adachi, L Aggarwal, H Ahmed, Y Ahn, H Aihara, N Akopov, S Alghamdi, M Alhakami, A Aloisio, N Althubiti, K Amos, M Angelsmark, NA Ky, C Antonioli, DM Asner, H Atmacan, T Aushev, V Aushev, M Aversano, R Ayad Show all

Physical Review D | American Physical Society (APS) | Published : 2026

DOI: 10.1103/9f61-rmvx

Open access

Abstract

We present an analysis of the processes e+e- → ηΥ(1S), ηΥ(2S), and γXb with Xb → π+ π- χbJ, χbJ → γΥ(1S) (J = 1, 2) reconstructed from γγπ+π- ℓ+ℓ- (ℓ = e, μ) final states in 19.6 fb-1 of Belle II data collected at four energy points near the peak of the Υ(10753) resonance. Here, Xb is a hypothetical bottomonium-sector partner of the X(3872). In the process e+e- → ηΥ(2S), we observe a signal with a significance that exceeds 6.0σ when all energy points are combined. A signal with a significance of 4.2σ is observed at a center-of-mass energy of 10.653 GeV, close to the B*B* threshold. At this energy, we measure σ(ηΥ(2S))/σ(π+π- Υ(2S)) > 23 at the 90% confidence level, indicating a strong violat..

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