Study of γγ→γψ(2S) at Belle

Abstract

Using 980 fb −1 of data at and around the ϒðnSÞ (n ¼ 1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy e þ e − collider, the two-photon process γγ → γψð2SÞ is studied from the threshold to 4.2 GeV for the first time. Two structures are seen in the invariant mass distribution of γψð2SÞ: one at M R 1 ¼ 3922.4 AE 6.5 AE 2.0 MeV=c 2 with a width of Γ R 1 ¼ 22 AE 17 AE 4 MeV, and another at M R 2 ¼ 4014.3 AE 4.0 AE 1.5 MeV=c 2 with a width of Γ R 2 ¼ 4 AE 11 AE 6 MeV; the signals are parametrized with the incoherent sum of two Breit-Wigner functions. The first structure is consistent with the Xð3915Þ or the χ c2 ð3930Þ, and the local statistical significance is determined to be 3.1σ with the systematic uncertainties included. The second matches none of the known charmonium or charmoniumlike states, and its global significance is determined to be 2.8σ including the look-elsewhere effect. The production rates are Γ γγ BðR 1 → γψð2SÞÞ ¼ 9.8 AE 3.6 AE 1.3 eV assuming ðJ PC ; jλjÞ ¼ ð0 þþ ; 0Þ or 2.0 AE 0.7 AE 0.2 eV with ð2 þþ ; 2Þ for the first structure and Γ γγ BðR 2 → γψð2SÞÞ ¼ 6.2 AE 2.2 AE 0.8 eV with ð0 þþ ; 0Þ or 1.2 AE 0.4 AE 0.2 eV with ð2 þþ ; 2Þ for the second. Here, the first errors are statistical and the second systematic, and λ is the helicity.

Five-flavor pentaquarks and other light- and heavy-flavor symmetry partners of the LHCb hidden-charm pentaquarks

“…(i.c) Besides this, the mass of the 2 ++ partner of the X(3872) is 4011.6 ± 0.8, which is compatible with the mass and quantum numbers of a 2 ++ resonance recently observed by Belle [54] (M = 4014.3 ± 4.0 ± 1.5 MeV and J = 0 or 2, though the signal has poor statistical significance). This 2 ++ partner, which was conjectured a decade ago [33,34], is a consequence of HQSS: if the X(3872) is indeed a 1 ++ D * D bound state, it should have a 2 ++ D * D * partner state.…”

“…The location of this state is usually predicted at 4012 − 4013 MeV when pion interactions are neglected and 4015 MeV if the effects of the one pion exchange (OPE) potential are included [34]. The width of this state has been previously estimated to be of the order of a few MeV [55] (from 0.9 to 14.0 MeV depending on the assumptions), which is in line with the width measured by Belle [54] (Γ = 4 ± 11 ± 6 MeV). (i.d) We also obtain a D D virtual state close to threshold, which might correspond to the D D bound state found in the lattice, and we predict the Z c and Z cs states as D * D and D * s D virtual states, where the masses are in line with the previous theoretical analyses of Refs.…”

Production of the X(4014) as the Spin-2 Partner of X(3872) in e + e − Collisions

“…respectively, observed in the two-photon fusion process. [15] Although the global significance of the new structure is only 2.8𝜎 (so additional experimental studies would be necessary), the information already collected and con-veyed reveals that the mass of this new structure perfectly matches the prediction for the spin-2 partner of the 𝑋(3872) based on the heavy quark spin symmetry (HQSS). [16,17] In particular, already its residing within just a few MeV from the 𝐷 * D* threshold hints towards its molecular interpretation and makes it more promising candidate for the 𝑋(3872) spin partner than the well established remote state 𝜒𝑐2(3930).…”

“…To summarize, while some hint for the 𝑋2 candidate has been provided by the Belle collaboration in the twophoton fusion process, [15] the substantial uncertainties in its mass and width, as well as the limited statistics, highlight the need for additional theoretical efforts to facilitate further experimental studies of this state. The latter ones, like many other possible searches for hidden-charm exotic states, involve a variety of methods, including their production in prompt 𝑝𝑝 collisions, decays of 𝐵 mesons, and the 𝑒 + 𝑒 − annihilation.…”

Prevalence of resistance mutations associated with integrase inhibitors in therapy-naive HIV-positive patients in Baoding, Hebei province, China

“…Recently, the BESIII Collaboration searched for the 0 + (2 ++ ) state in the D D invariant mass spectrum by the process e + e − → π + π − D D [94], but no obvious signal was found. Very recently, the Belle Collaboration studied the γγ → γψ(2S) [95], and reported a hint of new state (with global significance 2.8σ) with mass and width [m, Γ] = [4014.3 ± 4.0 ± 1.5, 4 ± 11 ± 6] MeV, which was conjectured to be the tensor-isoscalar partner of X(3872) [96][97][98]. The 1 + (1 +− ) state in D * D * system shall correspond to the known Z c (4020) [13].…”