Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userInterpretation of structure in the di-$J/psi$ spectrum
109
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Structure in the di-$J/psi$ mass spectrum observed by the LHCb experiment around 6.9 and 7.2 GeV is interpreted in terms of $J^{PC}=0^{++}$ and $2^{++}$ resonances between a $cc$ diquark and a $bar c bar c$ antidiquark, using a recently confirmed string-junction picture to calculate tetraquark masses. The main peak around 6.9 GeV is likely dominated by the $0^{++}(2S)$ state, a radial excitation of the $cc$-$bar c bar c$ tetraquark, which we predict at $6.871pm 0.025$ GeV. The dip around 6.75 GeV is ascribed to the opening of the Swave di-$chi_{c0}$ channel, while the dip around 7.2 GeV could be correlated with the opening of the di-$eta_c(2S)$ or $Xi_{cc} bar Xi_{cc}$ channel. The low-mass part of the di-$J/psi$ structure appears to require a broad resonance consistent with a predicted $2^{++}(1S)$ state with invariant mass around $M_{rm inv} = 6400$ MeV. Implications for $bb bar b bar b$ tetraquarks are discussed.
rate research
Read More
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 interactions. 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.
In the framework of a nonrelativistic potential quark model (NRPQM) for heavy quark system, we investigate the mass spectrum of the $P$-wave tetraquark states of $ccbar{c}bar{c}$ and $bbbar{b}bar{b}$. The Hamiltonian contains a linear confinement potential and parameterized one-gluon-exchange potential which includes a Coulomb type potential and spin-dependent potentials. The full-heavy tetraquark system is solved by a harmonic oscillator expansion method. With the same parameters fixed by the charmonium and bottomonium spectra, we obtained the full spectra for the $S$ and $P$-wave heavy tetraquark states. We find that the narrow structure around 6.9 GeV recently observed at LHCb in the di-$J/psi$ invariant mass spectrum can be naturally explained by the $P$-wave $ccbar{c}bar{c}$ states. Meanwhile, the observed broad structure around $6.2sim 6.8$ GeV can be consistently explained by the $S$-wave states around 6.5 GeV predicted in our previous work. Some contributions from those suppressed low-lying $P$-wave states around 6.7 GeV are also possible. Other decay channels are implied in such a scenario and they can be investigated by future experimental analysis. Considering the large discovery potential at LHCb, we give our predictions of the $P$-wave $bbbar{b}bar{b}$ states which can be searched for in the 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 mass 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.
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 rescattering 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.
We suggest that the J/psi phi structures observed by LHCb can be fitted in two tetraquak multiplets, the S-wave ground state and the first radial excitation, with composition [cs][cbar sbar]. When compared to the previously identified [cq][cbar qbar] multiplet, the observed masses agree with what expected for a multiplet with q -->s. We propose the X(4274), fitted by LHCb with a single 1^++ resonance, to correspond rather to two, almost degenerate, unresolved lines with J^PC = 0^++, 2^++. Masses of missing particles in the 1S and 2S multiplets are predicted.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
