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How Large is the Contribution of Excited Mesons in Coupled-Channel Effects?

Yu Lu; Muhammad Naeem Anwar; Bing-Song ZouSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

We study the excited B mesons' contributions to the coupled-channel e ects under the framework of the 3P0 model for the bottomonium. Contrary to what has been widely accepted, the contributions of P wave B mesons are generally the largest, and to some extent, this result is independent of the potential parameters. We also push the calculation beyond B(1P) and carefully analyze the contributions of B(2S). A form factor is a key ingredient to suppress the contributions of B(2S) for low lying bottomonia. However, this suppression mechanism is not e cient for highly excited bottomonia, such as (5S) and (6S). We give explanations why this di culty happens to the 3P0 model and suggest analyzing the ux-tube breaking model for the full calculation of coupled-channel e ects. |

Modeling Charmonium-η Decays of JP C = 1−− Higher Charmonia

Muhammad Naeem Anwar; Yu Lu; Bing-Song ZouSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

We propose a new model to create a light meson in the heavy quarkonium transition, which is inspired by the Nambu−Jona-Lasinio (NJL) model. Hadronic transitions of JPC = 1−− higher char-monia with the emission of an η meson are studied in the framework of the proposed model. The model shows its potential to reproduce the observed decay widths and make predictions for the unobserved channels. We present our predictions for the decay width of Ψ → J/ η and Ψ → hc(1P )η, where Ψ are higher S and D wave vector charmonia, which provide useful references to search for higher char-monia and determine their properties in forthcoming experiments. The predicted branching fraction B( (4415) → hc(1P )η) = 4.62 × 10−4 is one order of magnitude smaller than the J/ η channel. Esti-mates of partial decay width Γ(Y → J/ η) are given for Y (4360), Y (4390) and Y (4660) by assuming them as cc¯ bound states with quantum numbers 33D1, 33D1 and 53S1, respectively. Our results are in favor of these assignments for Y (4360) and Y (4660). The corresponding experimental data for these Y states has large statistical errors which do not provide any constraint on the mixing angle if we introduce S −D mixing. To identify Y (4390), precise measurements on its hadronic branching fraction are required which are eagerly awaited from BESIII. |

Effects of Zb states and bottom meson loops on γ(4S)→γ(1S, 2S)π+π− transitions

Yun-Hua Chen; Martin Cleven; Johanna T. Daub; Feng-Kun Guo; Christoph Hanhart; Bastian Kubis; Ulf-G. Mei遪er; Bing-Song ZouSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

We study the dipion transitions (4S) → (nS)π+π− (n = 1, 2). In particular, we consider the effects of the two intermediate bottomoniumlike exotic states Zb(10610) and Zb(10650) as well as bottom meson loops. The strong pion–pion final-state interactions, especially including channel coupling to K ¯K in the S-wave, are taken into account modelindependently by using dispersion theory. Based on a nonrelativistic effective field theory we find that the contribution from the bottom meson loops is comparable to those from the chiral contact terms and the Zb-exchange terms. For the (4S) → (2S)π+π− decay, the result shows that including the effects of the Zb-exchange and the bottom meson loops can naturally reproduce the two-hump behavior of the ππ mass spectra. Future angular distribution data are decisive for the identification of different production mechanisms. For the (4S) → (1S)π+π− decay, we show that there is a narrow dip around 1GeV in the ππ invariant mass distribution, caused by the final-state interactions. The distribution is clearly different from that in similar transitions from lower states, and needs to be verified by future data with high statistics. Also we predict the decay width and the dikaon mass distribution of the (4S) → (1S)K+K− process. |

Coupled-Channel Effects for the Bottomonium with Realistic Wave Functions

Yu Lu; Muhammad Naeem Anwar; Bing-Song ZouSubjects: Physics >> Nuclear Physics

With Gaussian expansion method (GEM), realistic wave functions are used to calculate coupled-channel effects for the bottomonium under the framework of 3P0 model. The simplicity and accuracy of GEM are explained. We calculate the mass shifts, probabilities of the B meson continuum, S−D mixing angles, strong and dielectric decay widths. Our calculation shows that both S−D mixing and the B meson continuum can contribute to the suppression of the vector meson's dielectric decay width. We suggest more precise measurements on the radiative decays of Υ(10580) and Υ(11020) to distinguish these two effects. The above quantities are also calculated with simple harmonic oscillator (SHO) wave function approximation for comparison. The deviation between GEM and SHO indicates that it is essential to treat the wave functions accurately for near threshold states. |

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