arXiv subjects

Meng-Kun Jia

Publications and source records attributed to Meng-Kun Jia.

7 recordsLinked to original sources

arXiv2026

Resonance-continuum interference with a possible tensor $X(6900)$ in radiative double-charmonium production at $\sqrt{s}=10.58~{\rm GeV}$

We study radiative double-charmonium production, $e^+e^-\to HHγ$ with $H=J/ψ$ and $η_c$, at $\sqrt{s}=10.58~{\rm GeV}$, including a possible tensor contribution from the fully charmed state $X(6900)$. The nonresonant amplitudes are calculated within the color-singlet non-relativistic QCD framework, while the $J^{PC}=2^{++}$ resonance is combined coherently with the continuum. We find that continuum--resonance interference significantly modifies the invariant-mass distributions near $M_{HH}\simeq M_X$. The $J/ψJ/ψγ$ channel exhibits a pronounced phase-dependent resonant structure, with a near-resonance cross section of $0.038$--$0.111~{\rm fb}$. In contrast, the $η_cη_cγ$ channel is continuum dominated and shows only a localized interference effect with an extremely suppressed production rate, rendering its experimental observation extremely challenging. These channel-dependent features arise from the different effective decay structures and demonstrate the importance of an amplitude-level treatment of the $X(6900)$ contribution.

hep-ph↗

arXiv2026

Exclusive process $γγ\rightarrow J/ψ+γ$ production in ultraperipheral proton and nuclear collisions at the HL-LHC and FCC

We present a next-to-leading-order (NLO) analysis of exclusive $J/ψ+γ$ production via photon-photon fusion in ultraperipheral collisions at the High-Luminosity Large Hadron Collider (HL-LHC) and the Future Circular Collider (FCC). The study is performed within the NRQCD factorization framework for proton-proton, proton-nucleus, and nucleus-nucleus collisions, with nuclear species spanning a wide range of nuclear charges (O, Ca, Ar, Kr, Xe, and Pb), enabling a systematic investigation of nuclear effects on the production cross sections. The photon fluxes are modeled using an electric-dipole form factor, with the impact-parameter dependence strictly enforced to ensure the exclusivity of the process. We present predictions for total cross sections and kinematic distributions at leading order and NLO. With a transverse momentum cut of $p_T > 2\,\mathrm{GeV}$, the NLO corrections reduce the cross section by approximately $35\%$ at the central scale. The associated theoretical uncertainties are systematically estimated via renormalization scale variations. Despite this suppression, the cross sections remain sizable and indicate that exclusive $J/ψ+ γ$ production serves as a sensitive probe of photon-induced quarkonium production mechanisms. We thus present the corresponding event yields predicted for the HL-LHC and the FCC.

hep-ph↗

arXiv2022

Investigating the color-suppressed decays $Λ_b\rightarrow Λψ$ in the perturbative QCD approach

The nonleptonic two-body $Λ_b\rightarrow Λψ$ decays with $ψ=J/ψ$ or $ψ(2S)$ are investigated based on the perturbative QCD approach. These are color-suppressed processes in which the nonfactorizable contributions are confirmed to be dominant. Angular momentum conservation allows us to describe the concerned decays by four independent complex helicity amplitudes. It is observed that the negative-helicity states for the $Λ$ baryon are preferred as expected in the left-handed nature of the charged-current interaction. The obtained results for the helicity amplitudes are used to compute the branching ratios and various observable parameters, which are then compared to the existing theoretical predictions and experimental data. In particular, we predict the ratio $\mathcal{R}=\frac{\mathcal{B}(Λ_b\rightarrowΛψ(2S))}{\mathcal{B}(Λ_b\rightarrowΛJ/ψ)}=0.47^{+0.02}_{-0.00}$ in comparison with $0.508\pm 0.023$ from the Particle Data Group at the level of 1 standard deviation. We also briefly explore the long-distance contributions to the semileptonic $Λ_b \rightarrow Λl^+l^-$ decays in the kinematic regions where the dilepton invariant masses are around the $J/ψ$ and $ψ(2S)$ resonances.

hep-ph↗

arXiv2022

Nonleptonic two-body decays of $Λ_b\rightarrow Λ_c π, Λ_cK$ in the perturbative QCD approach

We study the color-allowed $Λ_b\rightarrow Λ_c π, Λ_cK$ decays in the perturbative QCD approach (PQCD) to lowest order in strong coupling constant $α_s$. Both the factorizable and nonfactorizable contributions are taken into account in our calculations. It is found that these processes are dominated by the factorizable contributions, while the important nonfactorizable contributions can enhance the branching ratios by about 30$\%$. The decay branching ratios are predicted to be $\mathcal{B}(Λ_b\rightarrow Λ_c π)=6.7^{+4.1}_{-3.8}\times 10^{-3}$ and $\mathcal{B}(Λ_b\rightarrow Λ_c K)=5.0^{+4.0}_{-3.0}\times 10^{-4}$, where the uncertainties arise from the baryon light-cone distribution amplitudes (LCDAs), the heavy charm quark and charmed baryon masses, and the hard scales. It is shown that the asymmetry parameters in the two decays are approximately equal to -1, which is expected as in the heavy quark limit and the soft meson limit. Our predictions are consistent with the recent experimental data within errors. The obtained numerical results are also compared to those in the other theoretical approaches when they are available.

hep-ph↗

arXiv2022

$CP$-violating observables in four-body $B\rightarrow ϕ(\rightarrow K\bar K)K^*(\rightarrow Kπ)$ decays

We analyse the four-body $B\rightarrow ϕ(\rightarrow K\bar K)K^*(\rightarrow Kπ)$ decays in the perturbative QCD approach,where the invariant mass of $K\bar K$($Kπ$) system is limited in a window of $\pm 15$ MeV ($\pm150$ MeV) around the $ϕ(K^*(892))$ mass.In addition to the P wave resonances,two important S wave backgrounds in the selected invariant mass region are also accounted for. Angular momentum conservation allows six helicity amplitudes to contribute,including three P waves, two single S waves,and one double S wave. We calculated the branching ratio for each component and found sizable S wave contributions,coincide with the experimental observation.The obtained branching ratios of $B^{0(+)}\rightarrow ϕK^{*0(+)}$ are comparable with the previous predictions and support the measurements, whereas the predicted $\mathcal{B}(B^0_s\rightarrow ϕ\bar K^{*0})$ is smaller than the world average. The longitudinal polarizations are predicted to be around 0.7,consistent with previous PQCD results but larger than the data. Aside from the direct CP asymmetries,the true and fake triple product asymmetries(TPAs) are calculated in this work. In the case of neutral modes, both direct CP asymmetries and true TPAs are expected to be zero due to the vanishing weak phase difference. The direct CP asymmetries for the $B^+$ mode are predicted to be tiny,since the tree contributions are suppressed with respect to the penguin ones. The true asymmetries have shown no significant deviations from zero.In contrast,large fake asymmetries are observed in these decays,indicating the presence of significant final state interactions.We give the predictions of the S wave induced TPAs for the first time,which is consistent with LHCb data and would be checked with future measurements from Belle and BABAR experiments if the S wave components can be properly taken into account in angular analysis.

hep-ph↗

arXiv2021

$S$-wave contributions to the $B_{(s)}\rightarrow χ_{c1} (ππ,Kπ,KK)$ decays

We make a detailed study of the three-body decays $B_{(s)}\rightarrow χ_{c1} hh'$, where $h^{(')}$ is either a pion or kaon, by taking into account the $S$-wave states in the $hh'$ invariant mass distribution within the perturbative QCD approach. The two meson distribution amplitudes (DAs) are introduced to capture the strong interaction related to the production of the $hh'$ system. We calculate the branching ratios for the $S$-wave components and observe large values of order $10^{-4}$ for some Cabibbo-favored decays, which are accessible to the LHCb and Belle II experiments. The obtained branching ratio $\mathcal{B}(B\rightarrow χ_{c1}K^*_{0}(1430)(\rightarrow K^+π^-))=(5.1^{+0.6}_{-0.8})\times 10^{-5}$ consistent with the data from Belle within errors. Moreover, we also predict the differential distributions in the $hh'$ invariant mass for the decays under consideration, which await the future experimental test. In addition, the corresponding $χ_{c1}(2P)$ channels are also investigated, which are helpful to clarify the nature of the $X(3872)$ state.

hep-ph↗

arXiv2020

Revisiting nonfactorizable contributions to factorization-forbidden decays of $B$ mesons to charmonium

Motivated by the large rates of $B\rightarrow (χ_{c0}, χ_{c2}, h_c)K$ decays observed by the $BABAR$ and Belle collaborations, we investigate the nonfactorizable contributions to these factorization-forbidden decays, which can occur through a gluon exchange between the $c\bar c$ system and the spectator quark. Our numerical results demonstrate that the spectator contributions are capable of producing a large branching ratio consistent with the experiments. As a by-product, we also study the Cabibbo-suppressed decays, such as $B\rightarrow (χ_{c0}, χ_{c2}, h_c)π$ and the U-spin-related $B_s$ decay, which have so far received less theoretical and experimental attention. The calculated branching ratios reach the order of $10^{-6}$, which in within the scope of the Belle-II and LHCb experiments. Further, the $CP$-asymmetry parameters are also calculated for these decays. The obtained results are compared with the available experimental data and numbers from other predictions. We also investigate the sources of theoretical uncertainties in our calculation.

hep-ph↗