Bottomonium-like States Research Articles

An overview of XYZ new particles

In the past decade, more and more charmoniumlike and bottomoniumlike states have been reported in experiments, which have led us to extensive discussions on the underlying structure of these states. In this review paper, we briefly summarize the experimental and theoretical status of these observed states.

Production of Charged Heavy Quarkonium-Like States at the LHC and Tevatron

We study prompt hadroproduction of the charged bottomonium-like states Zb± (10610) and Zb± (10650), and the charged charmonium-like states Zc±(3900) and Zc±(4020), at the Tevatron and the LHC, provided that these states are S-wave hadronic molecules. Using two Monte Carlo event generators, Herwig and Pythia, to simulate the production of heavy meson pairs, we derive an order-of-magnitude estimate of the production rates for these four particles. Our estimates yield a cross section at the nb level for the Zb (10610) and Zb (10650). The results for the Zc (3900) and Zc (4020) are larger by a factor of 20–30. These cross sections are large enough to be observed, and measurements at hadron colliders in the future will supplement the study using electron-positron collisions, and therefore allow to explore the mysterious nature of these exotic states.

Hadroproduction ofΥ(nS)above theBB¯thresholds and implications forYb(10890)

Based on the nonrelativistic QCD factorization scheme, we study the hadroproduction of the bottomonium states $\ensuremath{\Upsilon}(5S)$ and $\ensuremath{\Upsilon}(6S)$. We argue to search for them in the final states $\ensuremath{\Upsilon}(1S,2S,3S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, which are found to have anomalously large production rates at $\ensuremath{\Upsilon}(5S)$. The enhanced rates for the dipionic transitions in the $\ensuremath{\Upsilon}(5S)$ energy region could, besides $\ensuremath{\Upsilon}(5S)$, be ascribed to ${Y}_{b}(10890)$, a state reported by the Belle Collaboration, which may be interpreted as a tetraquark. The LHC/Tevatron measurements are capable of making a case in favor of or against the existence of ${Y}_{b}(10890)$, as demonstrated here. Dalitz analysis of the $\ensuremath{\Upsilon}(1S,2S,3S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ states from the $\ensuremath{\Upsilon}(5S)/{Y}_{b}(10890)$ decays also impacts directly on the interpretation of the charged bottomonium-like states, ${Z}_{b}(10600)$ and ${Z}_{b}(10650)$, discovered by Belle in these puzzling decays.

Possible JPC =0+− exotic states

We study possible exotic JPC =0+− states using tetraquark interpolating currents with the QCD sum rule approach. The extracted masses are around 4.85 GeV for the charmonium-like states and 11.25 GeV for the bottomonium-like states. There is no working region for the light tetraquark currents, which implies that the light 0+− state may not exist below 2 GeV.

Light hadron, charmonium(-like) and bottomonium(-like) states

Hadron physics represents the study of strongly interacting matter in all its manifestations and understanding its properties and interactions. The interest in this field has been revitalized by the discovery of new light hadrons, charmonium- and bottomonium-like states. In this paper, the most recent experimental results from different experiments are reviewed.

Bottomonium spectrum with coupled-channel effects

We study the bottomonium spectrum in the nonrelativistic quark model with the coupled-channel effects. The mass shifts and valence $b\bar{b}$ component are evaluated to be rather large. We find that the hadronic loop effects can be partially absorbed into a reselection of the model parameters. No bottomonium state except $\Upsilon(5\,^1S_0)$ and $\Upsilon(5\,^3S_1)$ with mass around 10890 MeV is found in the quark models both with and without coupled-channel effects, so we suggest that $Y_{b}(10890)$ is an exotic state beyond the quark model, if it is confirmed to be a new resonance. The predictions for the $\chi_b(3P)$ masses are consistent with the ATLAS measurements. If some new bottomonium-like states are observed at LHCb or SuperB in the future, we can determine whether they are conventional bottomonium or exotic states by comparing their masses with the mass spectrum predicted in our work.

Tetraquark interpretation of the charged bottomonium-like statesZb±(10610)andZb±(10650)and implications

We present a tetraquark interpretation of the charged bottomonium-like states Z+-_b(10610) and Z+-_b(10650), observed by the Belle collaboration in the pi+- Upsilon(nS) (n=1,2,3) and pi+- h_b(mP) (m=1,2) invariant mass spectra from the data taken near the peak of the Upsilon(5S). In this framework, the underlying processes involve the production and decays of a vector tetraquark Y_b(10890), e+e- --> Y_b(10890) --> [Z+-_b(10610)pi-+, Z+-_b(10650)pi-+] followed by the decays [Z+-_b (10610), Z+-_b (10650)] --> pi+- Upsilon(nS), pi+- h_b(mP). Combining the contributions from the meson loops and an effective Hamiltonian, we are able to reproduce the observed masses of the Z+-_b(10610) and Z+-_b(10650). The analysis presented here is in agreement with the Belle data and provides crucial tests of the tetraquark hypothesis. We also calculate the corresponding meson loop effects in the charm sector and find them dynamically suppressed. The charged charmonium-like states Z+-_c(3752) and Z+-_c(3882) can be searched for in the decays of the J^{PC}=1^{--} tetraquark state Y(4260) via Y(4260) --> Z+-_c(3752)pi-+ and Y(4260) --> Z+-_c(3882)pi-+, with the subsequent decays (Z+-_c(3752),Z+-_c(3882)) --> (J/psi, h_c)pi+-.

Radiative transitions fromΥ(5S)to molecular bottomonium

The heavy quark spin symmetry implies that in addition to the recently observed $Z(10610)$ and $Z(10650)$ molecular resonances with ${I}^{G}={1}^{+}$, there should exist two or four molecular bottomonium-like states with ${I}^{G}={1}^{\ensuremath{-}}$. Properties of these $G$-odd states are considered, including their production in the radiative transitions from $\ensuremath{\Upsilon}(5S)$, by applying the same symmetry to the $\ensuremath{\Upsilon}(5S)$ resonance and the transition amplitudes. The considered radiative processes can provide a realistic option for observing the yet hypothetical states.