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Longjie Chen

Publications and source records attributed to Longjie Chen.

5 recordsLinked to original sources
arXiv2026

Extension of the non-pole technique to the twist-3 gluon distribution contribution in $pp$ collisions

It is known that the Sivers effect is described as a twist-3 effect within the collinear factorization framework and has the characteristic feature that it arises from the pole contribution in a hard parton scattering. The calculation formalism that focuses only on the pole part was established in the 2000s and SSAs were calculated for many processes in $ep$ and $pp$ collisions. On the other hand, there also exists a contribution from twist-3 fragmentation functions regarded as the Collins effect. The Collins effect arises from the nonpole part of the hard scattering and its calculation is formulated in a somewhat different manner from that for the Sivers effect. In recent years, some attempts have been made to revisit the Sivers effect by applying the ``nonpole'' formalism developed for the Collins effect. For $ep$ collisions, this approach has successfully reproduced the known results. For $pp$ collisions, however, the presence of both initial-state-interaction and final-state-interaction makes the calculation more complicated and the known results have not yet been reproduced. In this paper, we provide a solution to this problem and develop the nonpole method so that it can be applied to the Sivers effect in any process.

hep-ph↗
arXiv2026

Two photon decay width of the fully charmed tetraquarks: revisiting prospects for ultraperipheral collisions

We discuss the role of fully heavy tetraquarks in ultraperipheral collisions $AA\to AA\, J/\psi J/\psi$ and $AA \to AA\, \gamma \gamma$. Two-photon couplings to scalar and tensor tetraquarks are considered. We use relatively recent results of four-body calculation of fully heavy tetraquark wave function within the extended relativized quark model. The corresponding radiative decay widths for different tetraquark states are evaluated using NRQCD factorisation, with LDMEs extracted from the four-body wave functions at the origin. The results are collected in tables. The cross sections for production of pairs of $J/\psi$ mesons and diphotons in UPC of $^{208}Pb + {^{208}Pb}$ collisions are presented. While the couplings for $T_{4c}\left(0^{++}, 2^{++}\right) \to \gamma \gamma$ are calculated based on the model wave functions, simplified couplings are used for $T_{4c}\left(0^{++}, 2^{++}\right) \to J/\psi J/\psi$. When calculating the energy dependence of the resonant $\gamma \gamma \to J/\psi J/\psi$ and $\gamma \gamma \to \gamma \gamma$ cross section, we employ the total decay widths measured at $\Gamma_{\rm{tot}}=0.446\,\rm{GeV}$ for $X(6600)$ while $\Gamma_{\rm{tot}}=0.135\,\rm{GeV}$ for $X(6900)$ in latest CMS data. The resonant terms are compared with continuum contributions for both considered channels. While for the $J/\psi J/\psi$ channel the resonant contributions are larger than continuum ones, for the $\gamma \gamma$ channels the situation is reversed. The latter result is in clear disagreement with the result obtained from the n\"aive use of vector dominance picture.

hep-ph↗
arXiv2026

The twist-3 gluon contribution to $A_N$ in $J/\psi$ production in $pp$ collisions

We present our results for the twist-3 gluon contribution to the single transverse-spin asymmetry(SSA) in $J/\psi$ production in proton-proton collisions. Although the data were reported by the RHIC experiment more than a decade ago, a theoretical calculation based on rigorous collinear factorization has remained unavailable for the dominant gluonic contribution. Our results show that only the $C$-even type twist-3 gluon distribution, which has a direct relationship with the gluon TMD distribution function, contributes to the $J/\psi$ SSA. Therefore, this observable serves as a key probe to understand the three-dimensional motion of gluons inside the proton. We also perform numerical simulations of the $J/\psi$ SSA at RHIC and LHC energies. Our simulations indicate that a sizable SSA could be generated through a mechanism different from that responsible for the SSA in light hadron and $D$-meson production.

hep-ph↗
arXiv2023

The twist-3 gluon contribution to Sivers asymmetry in $J/\psi$ production in semi-inclusive deep inelastic scattering

We carry out the first calculation for the twist-3 gluon contribution to the single transverse-spin asymmetry(SSA) in $J/\psi$ production in semi-inclusive deep inelastic scattering. Our result shows that the $J/\psi$ SSA is an ideal observable to pin down the $C$-even type twist-3 gluon distribution that has a direct relationship with the gluon transverse-momentum-dependent distribution function. We also perform some numerical simulations of the $J/\psi$ SSA for the kinematics accessible at the future electron-ion-collider experiment. For color-singlet contribution, the hadronization effect of $J/\psi$ is completely canceled at the level of the SSA and the spin-dependent structure functions directly reflect the behavior of the $C$-even twist-3 gluon distribution.

hep-ph↗