arXiv subjects

Yi-Jie Li

Publications and source records attributed to Yi-Jie Li.

12 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.

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arXiv2026

Rare Radiative Decays of Z boson into S- and P-wave Charmonium within the Bethe-Salpeter Model

We employ the Bethe-Salpeter (BS) model to investigate radiative decays of the Z boson into charmonium. Within the instantaneous approximation of the BS equation, we analyze the relevant decay channels for S-wave charmonium states ($ψ(nS)$, $η_{c}(nS)$, $n=1,2,3$) and P-wave charmonium states ($χ_{c0}(mP)$, $χ_{c1}(mP)$, $h_{c}(mP)$, $m=1,2$). We compute all branching fractions using leading-order Feynman diagrams. For the $J/ψ$ channel, our BS calculations suggest that prior theoretical results were likely underestimated, making our prediction more promising for future experimental measurements.

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arXiv2026

Rare Exclusive Decays of the Z-boson into S-wave Quarkonia within the Bethe-Salpeter Formalism

This paper investigates the rare decays of the Z boson into S-wave quarkonia within the Bethe-Salpeter formalism. Both the production of double S-wave quarkonia and radiative decays into single S-wave quarkonium are analyzed. For double quarkonia production, i.e., $Z\to VV$ and $Z\to VP$ (where $V$ and $P$ represent vector and pseudoscalar quarkonia, respectively), we consider the leading order contribution from both QCD as well as electromagnetic transition via virtual photon (QED) amplitudes. The heavy quark limit is adopted to simplify calculations. Additionally, we have introduced another possible leading order channel for Z-boson decays to double S-wave quarkonia, where the Z boson decays into bottomonium plus charmonium via QED amplitude. Such processes may include $Z\to J/ψ+Υ(1S)$, $Z\toη_{b}+J/ψ$ and $Z\toη_{c}+Υ(1S)$. Moreover, we have also studied radiative Z boson decays to S-wave quarkonium, namely $Z\to X(Q\bar{Q})γ$, where $X(Q\bar{Q})=J/ψ$, $Υ$, $η_{c}$, and $η_{b}$. Interestingly, for double charmonium and radiative charmonium production, our results are larger than the NRQCD finding, while for the bottomonium case, our findings are comparatively smaller. This shows that charmonium is a relativistic particle, while bottomonium is a non-relativistic particle.

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arXiv2026

Associated Production of Charmonia-Bottomonia with Color-Octet Channels at the Z Factory, CEPC and FCC-ee

Within the nonrelativistic QCD (NRQCD) framework, we investigate the associated production of charmonia+bottomonia at future super $Z$ factory and at the CEPC/FCC-ee. The color-octet(CO) channels in the $γ^*/Z^0$-propagated process are considered besides the color-singlet(CS) channels. We find that the contributions of the CO states to the total cross section are dominant for almost all processes from the production threshold to the $Z^0$ mass. Thus, the comparison between the theoretical results and future data may give constraints to the CO matrix elements. In addition, we calculate the relativistic corrections to both the CS and CO channels, which decrease the cross sections significantly, with the $K$ factor $\simeq0.5$. The predicted events of ($J/ψ+Υ$, $Υ+η_c$) production, with $J/ψ, Υ$ reconstructed by lepton pair and $η_c$ reconstructed by hadronic decays, are (1,1) and (13,10) at the CEPC(2-yr) and FCC-ee(4-yr), respectively.

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arXiv2025

Relativistic corrections to double $B_c$ meson production in $e^+e^-$ annihilation

Within the framework of nonrelativistic QCD (NRQCD) factorization, we investigate the relativistic corrections to the production of double $B_c$ mesons in $e^+e^-$ annihilation. The study covers center-of-mass energies from the production threshold up to $2m_Z$, considering both the photon and $Z^0$-boson propagated processes. We find that the relativistic corrections are significant, with the corresponding $K$ factors of approximately 0.6. The azimuthal asymmetry, angular distribution, and transverse momentum distribution are also presented.

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arXiv2025

Order-$v^4$ corrections to heavy quark fragmentation to S-wave heavy quarkonium

Within the framework of nonrelativistic quantum chromodynamics (NRQCD) factorization, we compute the $\mathcal{O}(v^{4})$ relativistic corrections to the fragmentation of a heavy quark into the color-singlet $^{1}S_{0}^{[1]}$ and $^{3}S_{1}^{[1]}$ quarkonium states. Using the Collins--Soper definition of the fragmentation function, we reproduce the known $\mathcal{O}(v^{2})$ results. We find that the $\mathcal{O}(v^{4})$ correction gives a positive contribution relative to the leading order result over a wide range of the light-cone momentum fraction $z$, while its magnitude remains much smaller than that of the $\mathcal{O}(v^{2})$ correction. This behavior indicates a good convergence of the NRQCD relativistic expansion in this process. We further extend the calculation to the fragmentation functions in the unequal-mass case at $\mathcal{O}(v^{4})$ and obtain the corresponding analytical expressions.

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arXiv2016

Study of Color Octet Matrix Elements Through $J/ψ$ Production in $e^{+}e^{-}$ Annihilation

In this paper, the color-octet long distance matrix elements are studied though the inclusive $J/ψ$ production in $e^{+}e^{-}$ annihilation within the non-relativistic QCD frame. The calculations are up-to next-to-leading order with the radiative corrections and relativistic corrections at the B-factory energy region and the near-threshold region of $4.6\sim5.6~{\rm GeV}$. A constraint of the long distance matrix elements ($\langle^1S_0^{8}\rangle$, $\langle^3P_0^{8}\rangle$) is obtained. Through our estimation, the P-wave color-octet matrix element ( $\langle0|^3P^8_0|0\rangle$ ) should be the order of $0.005m_c^2~{\rm GeV}^3$ or less. The constraint region is not compatible with the values of the long distance matrix elements fitted at hadron colliders.

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arXiv2015

Interference effects on Higgs mass measurement in $e^+e^-\to H(γγ) Z$ at CEPC

A high luminosity Circular Electron Positron Collider (CEPC) as a Higgs Factory will be helpful to the precision measurement of the Higgs mass. The signal-background interference effect is carefully studied for the Higgs diphoton decay mode in the associated Z boson production at the future $e^+e^-$ colliders at energy $246 {\rm GeV}$. The mass shifts go up from about $20 {\rm MeV}$ to $50 {\rm MeV}$ for the experimental mass resolution ranging from $0.8 {\rm GeV}$ to $2 {\rm GeV}$.

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arXiv2014

$α_sv^2$ corrections to $η_c$ and $χ_{cJ}$ production recoiled with a photon at $e^+e^-$ colliders

We consider the production of the $η_c$ and $χ_{cJ}$ states recoiled with a photon up to $\mathcal{O}(α_s v^2)$ at BESIII and B-factories within the frame of NRQCD factorization. With the corrections, we revisit the numerical calculations to the cross sections for the $η_c(nS)$ and the $χ_{cJ}(mP)$ states. We argue that the search for $XYZ$ states with even charge conjugation such as $X(3872)$, $X(3940)$, $X(4160)$, and $X(4350)$ recoiled with a photon at BESIII may help clarify the nature of these states. For completeness, the production of charmonium with even charge conjugation recoiled with a photon at B factories is also discussed.

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arXiv2013

Search for $C=+$ charmonium and XYZ states in $e^+e^-\to γ+ H$ at BESIII

Within the framework of nonrelativistic quantum chromodynamics, we study the production of $C=+$ charmonium states $H$ in $e^+e^-\to γ~+~H$ at BESIII with $H=η_c(nS)$ (n=1, 2, 3, and 4), $χ_{cJ}(nP)$ (n=1, 2, and 3), and $^1D_2(nD)$ (n=1 and 2). The radiative and relativistic corrections are calculated to next-to-leading order for $S$ and $P$ wave states. We then argue that the search for $C=+$ $XYZ$ states such as $X(3872)$, $X(3940)$, $X(4160)$, and $X(4350)$ in $e^+e^-\to γ~+~H$ at BESIII may help clarify the nature of these states. BESIII can search $XYZ$ states through two body process $e^+e^-\to γH$, where $H$ decay to $J/ψπ^+π^-$, $J/ψϕ$, or $D \bar D$. This result may be useful in identifying the nature of $C=+$ $XYZ$ states. For completeness, the production of $C=+$ charmonium in $e^+e^-\to γ+~H$ at B factories is also discussed.

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arXiv2013

Relativistic Correction to J/psi and Upsilon Pair Production

The relativistic corrections to the productions of double J/psi, double Upsilon, and J/psi+Upsilon at the Tevatron and the LHC were investigated within the frame of nonrelativistic QCD. The ratios of short distance coefficients between relativistic correction and leading order result for color singlet and color octet states in large p_T limit are approximately -1,-11/3, respectively, for pair production. And for J/psi+Upsilon process the ratio is -11/6 for the CO channel. The K factors of relativistic corrections for color singlet and color octet double J/psi production are -0.23 and -0.84 with adopting v^2=0.23. The relativistic corrections significantly dilute the difference between the shape of color-singlet differential cross sections and the color-octet's at leading order. Also our results show that the single parton scattering model may be enough to explain the LHCb data for the J/psi pair production.

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arXiv2013

Relativistic Correction to Color Octet J/psi Production at Hadron Colliders

The relativistic corrections to the color-octet $J/ψ$ hadroproduction at the Tevatron and LHC are calculated up to $\mathcal{O}(v^2)$ in nonrelativistic QCD factorization frame. The short distance coefficients are obtained by matching full QCD with NRQCD results for the partonic subprocess $g+g\to J/ψ({}^1S_0^{[8]},{}^3S_1^{[8]}, {}^3P_J^{[8]})+g$, $q+\bar{q}\to J/ψ({}^1S_0^{[8]},{}^3S_1^{[8]}, {}^3P_J^{[8]})+g$ and $g+q({\bar{q}})\to J/ψ({}^1S_0^{[8]},{}^3S_1^{[8]}, {}^3P_J^{[8]})+q({\bar{q}})$. The short distance coefficient ratios of relativistic correction to leading order for color-octet states ${^1}S_{0}^{[8]}$, ${^3}S_{1}^{[8]}$, and ${^3}P_{J}^{[8]}$ at large $p_T$ are approximately -5/6, -11/6, and -31/30, respectively, for each subprocess, and it is 1/6 for color-singlet state ${^3}S_{1}^{[1]}$. If the higher order long distance matrix elements are estimated through velocity scaling rule with adopting $v^2=0.23$ and the lower order long distance matrix elements are fixed, the leading order cross sections of color-octet states are reduced by about a factor of $20\sim40%$ at large $p_T$ at both the Tevatron and the LHC. Comparing with QCD radiative corrections to color-octet states, relativistic correction is ignored along with $p_T$ increasing. Using long distance matrix elements extracted from the fit to $J/ψ$ production at the Tevatron, we can find the unpolarization cross sections of $J/ψ$ production at the LHC taking into account both QCD and relativistic corrections are changed by about $20\sim50%$ of that considering only QCD corrections. These results indicate that relativistic corrections may play an important role in $J/ψ$ production at the Tevatron and the LHC.

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