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Register a new user$mathcal O(alpha^{3}alpha_s)$ Study on the yields and polarizations of $J/psi(Upsilon)$ within the framework of non-relativistic QCD via $gammagamma to J/psi(Upsilon)+gamma+X$ at CEPC
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Within the framework of the non-relativistic QCD (NRQCD), we make a systematical study of the yields and polarizations of $J/psi$ and $Upsilon$ via $gamma gamma to J/psi(Upsilon)+gamma+X$ in photon-photon collisions at the Circular Electron Positron Collider (CEPC), up to $mathcal O(alpha^{3}alpha_s)$. We find that this process at CEPC is quite clean, namely the direct photoproduction absolutely dominate over the single- and double- resolved processes, at least 2 orders of magnitude larger. It is found that the next-to-leading order (NLO) QCD corrections will significantly reduce the results due to that the virtual corrections to $^3S_1^1$ is large and negative. For $J/psi$, as $p_t$ increases, the color octet (CO) processes will provide increasingly important contributions to the total NLO results. Moreover the inclusion of CO contributions will dramatically change the polarizations of $J/psi$ from toally transverse to longitudinal, which can be regarded as a distinct signal for the CO mechanism. However, for the case of $Upsilon$, the effects of the CO processes are negligible, both for yields and polarizations. For $J/psi$, the dependence of the yields on the value of the renormalization scale $mu_r$ is moderate, while significant for the polarization. The impact of the variation of $mu_{lambda}$ is found to be relatively slight. As for the case of $Upsilon$, the uncertainties of $mu_{r}$ and $mu_{lambda}$ just bring about negligible effects. The future measurements on this semi-inclusive photoproductions of $J/psi(Upsilon)+gamma+X$, especially on the polarization parameters of $J/psi$, will be a good laboratory for the study of heavy quarkonium production mechanism and helpful to clarify the problems of the $J/psi$ polarization puzzle.
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We study $J/psi$ and $eta_c$ inclusive production in $Upsilon$ decay within the framework of nonrelativistic-QCD (NRQCD) factorization. In the latter case, for which no experimental data exist so far, we also include the $h_c$ feed-down contribution. We calculate the short distance coefficients completely through $mathcal{O}(alpha_s^5)$. The NRQCD predictions for the branching fraction $mathcal{B}(Upsilonto J/psi+X)$ via direct production, evaluated with different sets of long-distance matrix elements (LDMEs), all agree with the experimental data in a reasonable range of renormalization scale. Using $eta_c$ and $h_c$ LDMEs obtained from $J/psi$ and $chi_c$ ones via heavy-quark spin symmetry, we find that the bulk of $mathcal{B}(Upsilontoeta_c+X)$ via prompt production arises from the $cbar{c}({}^3!S_1^{[8]})$ Fock state. The experimental study of this decay process would, therefore, provide a particularly clean probe of the color octet mechanism of heavy-quarkonium production.
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 study sub-threshold heavy quarkonium ($J/psi$ and $Upsilon$) photo-productions in $gamma A$ collisions as an independent test of the universality of the nucleon-nucleon short range correlation (SRC) in nuclear scattering processes. Just below the $gamma p$ threshold, the cross section is dominated by the mean field contribution of nucleons inside the nucleus. The SRC contributions start to dominate at lower photon energies, depending on the fraction of the SRC pairs in the target nucleus. We give an estimate of the cross sections in the sub-threshold region both for $J/psi$ and $Upsilon$. This may be helpful for future measurements at JLab as well as at the Electron-Ion Collider in the U.S., and especially in China.
We calculate the photoproduction of double $J/psi$ ($Upsilon$) to leading order based on the nonrelativistic quantum chromodynamics factorization framework at the Large Hadron Collider with forward proton tagging. The numerical results of double $J/psi$ photoproduction pp $rightarrow$ p$gamma$p $rightarrow$ $J/psi$ + $J/psi$ with different forward detector acceptances ($xi$) are presented. The total cross section of double $J/psi$ photoproduction is less than 200 fb with 0.1 $<$ $xi$ $<$ 0.5, but can reach about 1.37(1.27) pb with 0.0015 $<$ $xi$ $<$ 0.5 ( 0.0015 $<$ $xi$ $<$ 0.15 ). The double $J/psi$ photoproduction may have the potential to be detected and provide an interesting signature, thus is useful for studying the mechanism of heavy quarkonium production. We also predict the double $Upsilon$ photoproduction and find they are, unfortunately, small (with less than 10 fb).
We study the $e^+e^-togammaomega J/psi$ process using $11.6 ~rm fb^{-1}$ $e^+ e^-$ annihilation data taken at center-of-mass energies from $sqrt{s}=4.008~rm GeV$ to $4.600~rm GeV$ with the BESIII detector at the BEPCII storage ring. The $X(3872)$ resonance is observed for the first time in the $omega J/psi$ system with a significance of more than $5sigma$. The relative decay ratio of $X(3872)toomega J/psi$ and $pi^+pi^- J/psi$ is measured to be $mathcal{R}=1.6^{+0.4}_{-0.3}pm0.2$, where the first error is statistical and the second systematic (the same hereafter). The $sqrt{s}$-dependent cross section of $e^+e^-togamma X(3872)$ is also measured and investigated, and it can be described by a single Breit-Wigner resonance, referred to as the $Y(4200)$, with a mass of $4200.6^{+7.9}_{-13.3}pm3.0~{rm MeV}/c^2$ and a width of $115^{+38}_{-26}pm12~{rm MeV}$. In addition, to describe the $omega J/psi$ mass distribution above $3.9~rm GeV/c^2$, we need at least one additional Breit-Wigner resonance, labeled as $X(3915)$, in the fit. The mass and width of the $X(3915)$ are measured to be $3926.4pm2.2pm1.2~rm MeV/c^2$ and $3.8pm7.5pm2.6~rm MeV$, or $3932.6pm8.7pm4.7~rm MeV/c^2$ and $59.7pm15.5pm3.7~rm MeV$, respectively, depending on the fit models. The resonant parameters of the $X(3915)$ agree with those of the $Y(3940)$ in $Bto Komega J/psi$ and of the $X(3915)$ in $gammagammatoomega J/psi$ by the Belle and BABAR experiments within errors.
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