Study of the hc(11P1) meson via ψ(2S) → π0hc decays at BESIII

Authors：Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Amoroso, A.; An, Q.; Bai, X. H.; Bai, Y.; Bakina, O.; Ferroli, R. Baldini; Balossino, I; Ban, Y.; Batozskaya, V.; Becker, D.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi, F.; Biernat, J.; Bloms, J.; Bortone, A.; Boyko, I; Briere, R. A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, W. L.; Chelkov, G.; Chen, D. Y.; Chen, G.; Chen, H. S.; Chen, M. L.; Chen, S. J.

Source：Physical Review D, 2022, 106(7): 072007.

DOI：10.1103/PhysRevD.106.072007

• NARROW RESONANCE
• DISCOVERY

Using 448 million psi(2S) events, the spin-singlet P-wave charmonium state h(c)(1(1)P(1)) is studied via the psi(2S) -> pi(0)h(c) decay followed by the h(c) -> gamma eta(c) transition. The branching fractions are measured to be B-Inc(psi(2S) -> pi(0)h(c)) x B-Tag (h(c) -> gamma eta(c)) = (4.22(-0.26)(+0.27) +/- 0.19) x 10(-4), B-Inc (psi(2S) -> pi(0)h(c)) = (7.32 +/- 0.34 +/- 0.41) x 10(-4) , and B-Tag (h(c) -> gamma eta(c)) = (57.66(-3.50)(+3.62) +/- 0.58)%, where the uncertainties are statistical and systematic, respectively. The h(c)(1(1)P(1)) mass and width are determined to be M = (3525.32 +/- 0.06 +/- 0.15) MeV/c(2) and Gamma = (0.78(-0.24)(+0.27)+/- 0.12) MeV. Using the center of gravity mass of the three chi(cJ) (1(3)P(J)) mesons [M(c.o.g.)], the 1P hyperfine mass