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تسجيل مستخدم جديدProducing fully-charm structures in the $J/psi$-pair invariant mass spectrum
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Very recently, the LHCb Collaboration reported the observation of several enhancements in the invariant mass spectrum of a $J/psi$ pair between 6.2 and 7.4 GeV. In this work, we propose the dynamical mechanism to mimic the experimental data of a di-$J/psi$ mass spectrum given by LHCb, which is based on the reactions, where all the possible combinations of a double charmonium directly produced by a proton-proton collision are transferred into a final state $J/psi J/psi$. We find that the LHCb experimental data can be well reproduced. We further extend our framework to study a di-$Upsilon(1S)$ system, and give the line shape of a differential cross section of a partner process in a $bbar{b}$ system on the invariant mass of $Upsilon(1S)Upsilon(1S)$, which shows that there should exist possible enhancements near $m_{Upsilon(1S)Upsilon(1S)}=$19.0, 19.3, 19.7 GeV in the $Upsilon(1S)$-pair invariant mass spectrum. These predictions can be tested in LHCb and CMS, which can be as a potential research issue in near future.
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Motivated by a recent successful dynamical explanation for the newly observed fully-charm structure $X(6900)$ in the mass spectrum of di-$J/psi$ by LHCb [J.~Z.~Wang textit{et al.} arXiv:2008.07430], in this work, we extend the same dynamical rescatte
ring mechanism to predict the line shape of more potential fully-heavy structures in the invariant mass spectrum of $J/psi psi(3686)$, $J/psi psi(3770)$, $psi(3686) psi(3686)$, and $J/psi Upsilon(1S)$ at high energy proton-proton collisions, whose verification in experiments should be helpful to further clarify the nature of $X(6900)$. The above final states of vector heavy quarkonia can be experimentally reconstructed more effectively by a $mu^+mu^-$ pair in the muon detector compared with $Qbar{Q}$ meson with other quantum numbers. Furthermore, the corresponding peak mass positions of each of predicted fully-heavy structures are also given. Our theoretical studies here could provide some valuable information for the future measurement proposals of LHCb and CMS, especially based on the accumulated data after completing Run III of LHC in the near future.
Using proton-proton collision data at centre-of-mass energies of $sqrt{s} = 7$, $8$ and $13mathrm{,TeV}$ recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of $9mathrm{,fb}^{-1}$, the invariant mas
s spectrum of $J/psi$ pairs is studied. A narrow structure around $6.9mathrm{,GeV/}c^2$ matching the lineshape of a resonance and a broad structure just above twice the $J/psi$ mass are observed. The deviation of the data from nonresonant $J/psi$-pair production is above five standard deviations in the mass region between $6.2$ and $7.4mathrm{,GeV/}c^2$, covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow $X(6900)$ structure are measured assuming a Breit--Wigner lineshape.
Partial wave analysis is performed, with effective potentials as dynamical inputs, to scrutinize the recent LHCb data on the di-$J/psi$ invariant mass spectrum. Coupled-channel effects are incorporated in the production amplitude via final state inte
ractions. The LHCb data can be well described. A dynamical generated pole structure, which can be identified as the $X(6900)$ state, is found. Our analysis also provides hints for the existence of three other possible states: a bound state $X(6200)$, a broad resonant state $X(6680)$ and a narrow resonant state $X(7200)$. The $J^{PC}$ quantum numbers of the $X(6680)$ and $X(6900)$ states should be $2^{++}$, while the $X(6200)$ and $X(7200)$ states prefer $0^{++}$. To determine the above states more precisely, more experimental data for the channels, such as $J/psipsi(2S)$, $J/psipsi(3770)$, di-$psi(2S)$, are required.
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