arXiv subjects

Ya-jin Zhou

Publications and source records attributed to Ya-jin Zhou.

At least 19 recordsLinked to original sources

arXiv2026

Azimuthal decorrelation in diffractive dijet production

We calculate the azimuthal angular decorrelation of diffractive dijets in ultra-peripheral heavy-ion, $ep$, and $eA$ collisions to probe non-perturbative diffractive transverse momentum-dependent distributions. Focusing on the dominant semi-inclusive channel with an unobserved semi-hard gluon, we perform an all-order resummation of soft gluon emissions for the transverse energy-energy correlator observable, accounting for both initial and final state radiation. We also analyze heavy-quark pair production and demonstrate the sensitivity of the decorrelation to the jet axis definition. Finally, we provide numerical predictions for relevant kinematics at LHC UPCs, HERA, and the future EIC. Our results demonstrate that the acoplanarity of diffractive dijet production could serve as a promising probe of diffractive transverse momentum-dependent distributions.

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arXiv2025

Azimuthal asymmetry in $J/ψ+γ$ and $J/ψ+J/ψ$ production in ultraperipheral heavy-ion collisions at LHC

Two-photon collision in ultraperipheral heavy-ion collisions (UPCs) provides a unique and powerful platform for probing QCD with linearly polarized quasi-real photons. While photon polarization effects have been recognized in dilepton and even in light hadrons production, their consequences for heavy quarkonium production remain unexplored. In this work we investigate for the first time the $γγ\to J/ψ+γ(J/ψ)$ channels in Pb-Pb UPCs at the Large Hadron Collider (LHC), by integrating the non-relativistic QCD (NRQCD) factorization approach with the transverse-momentum-dependent (TMD) photon distributions. Based on the helicity amplitudes at lowest order in strong coupling and velocity expansion, we predict sizable $\cos(2ϕ)$ and $\cos(4ϕ)$ azimuthal asymmetries arising from the interference of linearly polarized photon states. These azimuthal-dependent observables, defined as the ratios of weighted to unweighted cross sections, are expected to be stable against including the higher-order radiative corrections and varying nonperturbative NRQCD matrix elements, thus offering a fresh test of quarkonium production mechanism and the photon TMD structure in the ultrarelativistic limit.

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arXiv2025

Semi-inclusive deep inelastic scattering off a tensor-polarized spin-1 target

We investigate the semi-inclusive deep inelastic scattering off a tensor-polarized spin-1 target, focusing on the production of an unpolarized hadron. The complete differential cross section is expressed in terms of 23 structure functions, which depend on the spin states of the target and the azimuthal modulations of the final-state hadron. Within the transverse momentum dependent (TMD) factorization framework, we derive the hadronic tensor using quark-quark correlators and quark-gluon-quark correlators up to twist-3. At tree-level, 21 nonvanishing structure functions are obtained at the leading and subleading twist, expressed as convolutions of TMD parton distribution functions and TMD fragmentation functions. The measurement of these nonzero structure functions can be utilized to explore the tensor-polarized structure of spin-1 particles, offering insights into their internal dynamics.

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arXiv2025

Azimuthal Modulations in Photon-Induced Processes

We review recent theoretical developments and experimental measurements of azimuthal modulations in photon-induced processes, covering both ultra-peripheral heavy-ion collisions (UPCs) and $e^+e^-$ colliders. The azimuthal asymmetries $\cos(nϕ)$ ($n=1,2,3,4$) serve as precision diagnostics that probe the linear polarization of coherent photons, final-state soft radiation effects, and quantum interference phenomena at the femtometer scale. In UPCs, we discuss dilepton production, diffractive dijet and vector meson production, where theoretical predictions show excellent agreement with STAR, ALICE, and CMS measurements. The unique double-slit interference effect in nucleus-nucleus collisions plays a crucial role in describing experimental observations. At $e^+e^-$ colliders, $γγ\toππ$ azimuthal asymmetries enable the direct extraction of helicity amplitude phases, with important implications for hadronic light-by-light scattering and the muon anomalous magnetic moment. Azimuthal modulations establish a powerful tool for multi-dimensional nuclear imaging and precision QED/QCD tests.

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arXiv2025

Novel azimuthal observables from two-photon collision at $e^+e^-$ colliders

In this work we advocate a set of novel azimuthal-angle-related observables associated with exclusive hadron production from two-photon fusion at $e^+ e^-$ colliders, taking the $γγ\to ππ$ as a benchmark process. As a direct consequence of the linearly polarized quasi-real photons emitted off the electron and positron beams, the $\cos 2ϕ$ azimuthal asymmetry in dipion production is predicted within the transverse-momentum-dependent (TMD) factorization framework. In numerical analysis, we take the helicity amplitudes of $γγ\to ππ$ determined from the partial wave solutions in dispersion relation as input, and find that the predicted $\cos2ϕ$ azimuthal modulation may reach 40\% for the typical kinematical setup of {\tt Belle 2} and {\tt BESIII} experiments. Future accurate measurement of this azimuthal asymmetry may facilitate the direct extraction of the relative phase between two helicity amplitudes with photon helicity configurations $++$ and $+-$. This knowledge provides a valuable input for the dispersive determination of the hadronic light-by-light (Hlbl) contributions.

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arXiv2025

The Sivers asymmetry of vector meson production in semi-inclusive deep inelastic scattering

The transverse single-spin asymmetry for $ρ^0$ production in semi-inclusive deep inelastic scattering was recently reported by the COMPASS Collaboration. Using the Sivers functions extracted from pion and kaon productions, we perform a calculation of the Sivers asymmetry within the transverse momentum dependent factorization. Our results are consistent with the COMPASS data, confirming the universality of the Sivers functions within current experimental uncertainties. While various global analyses of Sivers functions can equally well describe the current data, we obtain very different predictions on the Sivers asymmetry of $ρ$ and $K^*$ productions at electron-ion colliders, which therefore are expected to provide further constraints.

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arXiv2025

Suppression of Spin Transfer to $Λ$ Hyperon in Deep-Inelastic Scattering

We investigate $Λ$ production in semi-inclusive deep-inelastic scattering using a polarized lepton beam and find that the spin transfer is significantly suppressed by target fragmentation. As further demonstrated by a model estimation, experimental data can be well described once the target fragmentation is taken into account, which alleviates the tension with calculations solely based on current fragmentation. Our findings suggest that, at the energies of existing fixed-target experiments, the separation of current and target fragmentation regions is not distinct. Spin transfer as well as other spin effects offers a sensitive probe into the origin of the produced hadron.

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arXiv2025

Azimuthal modulation in light-by-light scattering from ultraperipheral collisions at LHC

Elastic light-by-light(LbL) scattering, one of the most fascinating processes in the Standard Model(SM), has recently been observed in the ultraperipheral collisions(UPCs) of relativistic heavy ions in the Atlas and CMS experiments at the Large Hadron Collider LHC. Recognizing that the incident quasi-real photons in LbL scattering are strongly linearly polarized, we re-investigate the LbL scattering in UPCs by incorporating the joint dependence of the impact parameter and transverse momenta of the incident photons. We show that the linear polarization of incident photons generates a sizable $\cos2ϕ$-type azimuthal modulation, which awaits the test in future LHC and EIC experiments.

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arXiv2024

Polarization analysis of two baryons with various spin combinations produced in electron-positron annihilation

We developed a method to analyze the polarization correlations of two baryons $B_{1}\bar{B}_{2}$ with various spin combinations in the annihilation process. We established spin density matrices for arbitrary spins in standard and Cartesian forms, and demonstrated their application in the helicity formalism. This paper provides parametrization schemes for the helicity amplitudes and details the analysis of two baryons with spin combinations of (1/2, 1/2), (1/2, 3/2), and (1/2, 5/2). We also illustrated methods for determining the spin and parity of the excited baryon $\barΞ^{*+}$ using the $e^{+}e^{-} \rightarrow γ^*/ψ\rightarrow Ξ^{-}\barΞ^{*+}$ process as an example. Our research offers broad opportunities for exploring the baryon spectrum and transition form factors in electron-positron annihilation.

hep-ph↗

arXiv2024

Azimuthal angular correlations in lepton pair production in ultra-peripheral heavy ion collisions

The coherent photons induced by relativistic heavy ions are highly linearly polarized, in close analogy to the linear polarization of gluons in a large nucleus. We proposed to measure the photon polarization through azimuthal asymmetries in dilepton production in ultra-peripheral collisions. Our prediction for the asymmetries were soon confirmed by the STAR experiment with high precision. We refined our analysis recently by including the final state soft photon radiation effect beyond the double leading logarithm approximation. The azimuthal asymmetries and acoplanarity at relatively high transverse momentum provide unique opportunities to test the resummation formalism thanks to the extremely high photon flux in UPCs. Our results clearly show the feasibility to access the sub-leading resummation effects in UPCs at the RHIC and LHC.

hep-ph↗

arXiv2024

Semi-inclusive production of spin-3/2 hadrons in deep inelastic scattering

We investigate the production of spin-3/2 hadrons in semi-inclusive deep inelastic lepton-nucleon scatterings. The complete differential cross section is derived through the kinematic analysis and expressed in terms of 288 structure functions, corresponding to all polarization configurations and azimuthal modulations. For an unpolarized lepton beam, half of the 192 structure functions have nonzero leading order contributions in the parton model, among which 42 are from rank-3 tensor polarized fragmentation functions of the hadron. For a polarized lepton beam, one third of the 96 structure functions contribute at the leading order and 14 of them are from rank-3 tensor polarized fragmentation functions. In addition to the formalism, we perform a model estimation of the spin transfer to a $S_{hLLL}$ polarized hadron and sizable asymmetry is expected. Therefore, these newly defined observables for the production of a spin-3/2 hadron in a deep inelastic scattering process can be explored in future experiments to understand nucleon spin structures and spin-dependent fragmentation functions.

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arXiv2024

Revisiting azimuthal angular asymmetries in diffractive di-jet production

We explore the impact of initial state soft gluon radiations on the azimuthal angle asymmetries in photo-production of hard di-jet via coherent diffraction in ultraperipheral heavy ion collisions, as well as in electron-proton ($ep$) and electron-nucleus ($eA$) collisions. The primary production mechanism is identified as the diffractive production of two hard jets, accompanied by a collinear gluon emission along the beam direction. In contrast, the diffractive exclusive di-jet production, where the initial state radiation is absent, is suppressed due to color transparency. Our analysis shows that azimuthal asymmetries, traditionally attributed to final state gluon emissions, are reduced by the presence of initial state radiations. The sensitivity of azimuthal asymmetries to both initial and final state radiations suggests that they could provide novel insights into the mechanisms of di-jet production in diffractive processes.

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arXiv2023

Refined analysis of $Ω^{-} \barΩ^{+}$ polarization in electron-positron annihilation process

We investigate the production of spin-3/2 hyperon pairs, $Ω^- \barΩ^+$, in electron-positron annihilation within the helicity amplitude formalism. A refined selection of helicity basis matrices is proposed to relate polarization expansion coefficients and spin density matrix elements and to illuminate their inherent physical interpretations and symmetrical properties. With a novel parametrization scheme of helicity amplitudes, we perform an analysis of polarization correlation coefficients for double-tag $Ω^- \barΩ^+$ pairs. We present three sets of expressions to describe the decay of $Ω^{-}$ hyperons, and further address the existing tension in the measurements of its decay parameters, particularly $ϕ_Ω$. The method and the framework developed in this paper can also be applied to studies of the production and decay mechanisms of other spin-3/2 particles.

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arXiv2022

Inclusive and semi-inclusive production of spin-3/2 hadrons in $e^+e^-$ annihilation

We investigate the inclusive and semi-inclusive productions of spin-3/2 hadrons, such as $Ω$, in unpolarized $e^+ e^-$ annihilation. The general differential cross sections are expressed in terms of structure functions in accordance to the polarization of the hadron and the azimuthal modulations. We derive a complete definition of quark transverse momentum dependent (TMD) fragmentation functions (FFs) to spin-3/2 hadrons for the first time from the decomposition of the quark-quark correlation matrix at leading twist, 14 of which are newly defined corresponding to rank-3 tensor polarized hadron. The collinear FFs are obtained from the $k_T$-integrated correlation matrix, and only two TMD FFs with rank-3 tensor polarization have nonvanishing collinear counterparts. Then we perform a leading order calculation of the unpolarized differential cross sections. In the single-hadron inclusive production, only two structure functions are found nonzero and none of the rank-3 tensor polarized FFs contributes. For the nearly back-to-back two-hadron production, half of the 48 structure functions are found nonzero even if the spin of the second hadron is not analyzed, and ten of the rank-3 tensor polarized TMD FFs contribute. Therefore, one can study the rank-3 tensor polarized FFs via the production of a spin-3/2 hadron and an unpolarized hadron in unpolarized $e^+ e^-$ collision experiments. These newly defined FFs can be further applied in semi-inclusive deep inelastic scattering processes for the study of nucleon structures.

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arXiv2022

Energy evolution of T-odd gluon TMDs at small $x$

We study the energy or TMD evolution of the three leading twist dipole type T-odd gluon TMDs inside a transversely polarized nucleon, all of which at small $x$ dynamically originate from the spin dependent odderon. Their energy dependence presents a unique opportunity to study the polarization dependent TMD evolution in the small-$x$ region, where the distributions are identical up to a normalization constant at tree level. We further propose to study their evolution via azimuthal asymmetries in virtual photon-jet production in polarized proton-proton collisions at RHIC. We present model predictions for the asymmetries as functions of the large jet or photon transverse momentum and $Q^2$ which set the hard scales in this process.

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arXiv2022

Probing the gluon tomography in photoproduction of di-pions

A sizable $\cos 4ϕ$ azimuthal asymmetry in exclusive di-pion production near $ρ^0$ resonance peak in ultraperipheral heavy ion collisions recently has been reported by STAR collaboration. We show that both elliptic gluon Wigner distribution and final state soft photon radiation can give rise to this azimuthal asymmetry. The fact that the QED effect alone severely underestimates the observed asymmetry might signal the existence of the nontrivial correlation in quantum phase distribution of gluons.

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arXiv2020

Coulomb nuclear interference effect in dipion production in ultraperipheral heavy ion collisions

We study exclusive $π^+ π^-$ pair production near $ρ^0$ resonance peak in ultraperipheral heavy ion collisions. Pion pair can either be produced via two photon fusion process or from the decay of $ρ^0$ in photon-nuclear reaction. At very low pair transverse momentum, the electromagnetic and nuclear amplitudes become comparable. We show that the Coulomb nuclear interference amplitude gives rise to sizable $\cos ϕ$ and $\cos 3ϕ$ azimuthal asymmetries, which can be used to constrain the phase of the dipole-nucleus scattering amplitude.

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arXiv2020

Studying Coulomb correction at EIC and EicC

We study the gauge link contribution to the dipole type transverse momentum dependent distributions of coherent photons, which is conventionally referred to as the Coulomb correction. We further propose to search for the evidence of the Coulomb correction in the Bethe-Heitler process in eA collisions at EIC and EicC.

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