Evidence for B+→hcK+ and observation of ηc(2

Abstract

A search for the decays B þ → h c K þ and B 0 → h c K 0 S is performed. Evidence for the decay B þ → h c K þ is found; its significance is 4.8σ. No evidence is found for B 0 → h c K 0 S. The branching fraction for B þ → h c K þ is measured to be ð3.7 þ1.0 −0.9 þ0.8 −0.8 Þ × 10 −5 ; the upper limit for the B 0 → h c K 0 S branching fraction is 1.4 × 10 −5 at 90% C.L. In addition, a study of the ppπ þ π − invariant mass distribution in the channel B þ → ðppπ þ π − ÞK þ results in the first observation of the decay η c ð2SÞ → ppπ þ π − with 12.1σ significance. The analysis is based on the 711 fb −1 data sample collected by the Belle detector at the asymmetric-energy e þ e − collider KEKB at the ϒð4SÞ resonance.

First search for the ηc2(1D) in B decays at Belle

“…Recently the Belle collaboration found evidence for the decay B + → h c K + [16]. Its final state is very similar to that of the B + → η c2 (1D)K + decay.…”

“…Thus, the analysis method used in ref. [16] can be applied to the η c2 (1D) search with minor modifications. Here we present a search for the η c2 (1D) using the decays…”

“…The η decay to π + π − π 0 was also used in ref. [16]. Initially, this JHEP05(2020)034 channel was also reconstructed here, but it was found that including it does not improve the expected sensitivity.…”

“…The channel h c → ppπ + π − was used in ref. [16], but it cannot be used here because the mass resolution is not sufficient to fully distinguish the χ c1 and h c peaks in the ppπ + π − mass spectrum; thus, this channel may contain a peaking background from the process B → ψ 2 (1D)(→ χ c1 (→ ppπ + π − )γ)K. The η c2 (1D) candidates are reconstructed in the channel η c2 (1D) → h c γ; their invariant mass is not restricted.…”

“…These two stages are performed exactly in the same way as in ref. [16]. The resolution is parameterized by the function (12) a (y 1 ) + N G1 G (21) a (x 2 )G (22) a (y 2 ) + N G2 G (31) a (x 3 )G (32) a (y 3 ),…”