Recent experiments by the CLEO III detector at CESR indicate that the $\jpsi$ spectrum produced in $Υ$ decay is in conflict with Non-Relativistic QCD (NRQCD) calculations. The measured $\jpsi$ momentum distribution is much softer than predicted by the color-octet mechanisms. The expected peak at the kinematic limit is not observed in the data. However it has recent been pointed out that NRQCD calculations break down near the kinematic endpoint due to large perturbative and non-perturbative corrections. In this paper we combine NRQCD with soft collinear effective theory to study the color-octet contribution to the $Υ\to \jpsi + X$ decay in this region of phase space. We obtain a spectrum that is significantly softened when including the correct degrees of freedom in the endpoint region, giving better agreement with the data than previous predictions.
We give predictions of $\jpsi$ and $\psits$ yields and polarizations in prompt production at hadron colliders based on non-relativistic QCD factorization formula. We calculate short-distance coefficients of all important color-octet intermediate channels as well as color-singlet channels up to $\mathcal{O}(α_S^4)$, i.e. next-to-leading order in $α_S$. For prompt $\jpsi$ production, we also take into account feeddown contributions from $χ_{cJ}$(J=0,1,2) and $\psits$ decays. Color-singlet long-distance matrix elements (LDMEs) are estimated by using potential model, and color-octet LDMEs are extr…
We study the $η_c$ photoproduction in $ep$ collisions in this paper. The short-distance coefficients for $c\bar{c}(^1S_0^{[1]})$, $c\bar{c}(^1S_0^{[8]})$, $c\bar{c}(^3S_1^{[8]})$, and $c\bar{c}(^1P_1^{[8]})$ photoproductions are evaluated at leading order in $α_s$ expansion, where the color-singlet contribution is achieved for the first time. We have carefully analyzed different kinematic distributions of the cross sections and found that the color-singlet contribution is considerably suppressed comparing with the color-octet parts. This feature renders the $η_c$ photoproduction process an ide…
Recently unpolarized and polarized $J/ψ\,(Υ)$ production at the Electron-Ion Collider (EIC) has been proposed as a new way to extract two poorly known color-octet NRQCD long-distance matrix elements: $\langle0\vert{\cal O}_{8}^{J/ψ}(^{1}S_{0})\vert0\rangle$ and $\langle0\vert{\cal O}_{8}^{J/ψ}(^{3}P_{0})\vert0\rangle$. The proposed method is based on a comparison to open heavy-quark pair production ideally performed at the same kinematics. In this paper we analyze this proposal in more detail and provide predictions for the EIC based on the available determinations of the color-octet matrix el…
The observation of unpolarized quarkonium production in high energy pp collisions, at mid rapidity, implies a significant violation of the non-relativistic QCD (NRQCD) velocity scaling rules. A precise experimental confirmation of this picture could definitely rule out the current formulation of the factorization expansion. This conclusion relies on current perturbative determinations of the short-distance kinematic factors and may be reverted if improved calculations would modify, in a very specific way, their transverse momentum dependences. That solution would result, however, in a full deg…
彩色八隅标量，如果在TeV的规模，将产生大量的大型强子对撞机。我们详细讨论了（8，2）_{1/2}表象中标量的现象学，最近Manohar和Wise将其确定为标准模型Higgs扇区的一个补充，符合最小味违反原则。这个多重态与希格斯玻色子的耦合提升了其状态之间的质量简并，可能允许较重的色标量到较轻的色标量和规范玻色子的两体衰变。我们执行这些耦合的重整化群分析，并发现Tevatron搜索的限制留下这些衰变的空间很小。这一事实，以及最小的味道违反的假设，导致我们研究的情况下，八隅体衰变到最重的运动学上可访问的费米子对。专注于对生产事件导致（t t-bar t t-bar），（b b-bar b b-bar）和（b b-bar t t-bar）的最终状态，我们发现在大型强子对撞机的发现应该是可能的质量超过1 TeV。
We have studied color-octet contributions for $J/ψ$ inclusive production at B factories, i.e., $e^+e^-\to J/ψ(^3P_J^{[8]},^1S_0^{[8]}) + X_{\mathrm{non}-c\bar c}$, using the soft gluon factorization (SGF) approach, in which the $J/ψ$ energy spectrum is expressed in a form of perturbatively calculable short-distance hard parts convoluted with one-dimensional soft gluon distributions (SGDs). The series of velocity corrections originated from kinematic effect can be naturally resummed in this approach. Short-distance hard parts have been calculated analytically to next-to-leading order in $α_s$. …
Centrality, rapidity, and transverse-momentum dependence of gluon shadowing and antishadowing on $J/ψ$ production in $d$Au collisions at $\sqrt{s}$=200 GeV
Prompt double-$J/ψ$ production at high-energy hadron colliders can be considered as a golden channel to probe double parton scatterings (DPS) --in particular to study gluon-gluon correlations inside the proton-- and, at the same time, to measure the distribution of linearly-polarised gluons inside the proton. Such studies however require a good control of both single and DPS in the respective regions where they are carried out. In this context, we have critically examined two mechanisms of single parton scatterings (SPS) that may be kinematically enhanced where DPS are thought to be dominant, …
We calculate the next-to-leading order (NLO) radiative correction to the color-octet $h_c$ inclusive production in $e^+e^-$ annihilation at Super $B$ factory, within the nonrelativistic QCD factorization framework. The analytic expression for the NLO short-distance coefficient (SDC) accompanying the color-octet production operator $\mathcal{O}_8^{h_c}(^1S_0)$ is obtained after summing both virtual and real corrections. The size of NLO correction for the color-octet production channel is found to be positive and substantial. The NLO prediction to the $h_c$ energy spectrum is plagued with unphys…
The prompt $J/ψ$ photoproduction within the non-relativistic QCD (NRQCD) framework at the future Circular Electron Positron Collider (CEPC) is studied, including the contributions from both direct and resolved photons. Employing different sets of long distance matrix elements, the total cross section is dominated by the color-octet channel. We present different kinematic distributions of $J/ψ$ production and the results show there will be about 50 $J/ψ$ events when the transverse momentum of $J/ψ$ is up to 20 GeV. It renders that the $J/ψ$ photoprodution at the CEPC is a well laboratory to tes…
Exclusive decay of $1^{- -}$ heavy quarkonium into photon and two pions
研究了$1^{--}$重夸克偶素在运动学区域内唯一衰变为一个光子和两个π介子的过程，其中两π介子系统具有一个远小于重夸克偶素质量的不变质量.在忽略重夸克质量的倒数所抑制的影响下，衰变振幅可以分解为与重夸克偶素有关的非微扰效应用非相对论QCD矩阵元表示，与两个π介子有关的非微扰效应用等π介子对中两个胶子的分布振幅表示.通过采取渐近形式的分布振幅，并通过使用手征微扰理论，我们能够获得数值预测的衰减。计算结果表明，在BEPC和CESR上都能观察到$\jpsi$的衰变.在BEPC和CESR上对这一过程的实验观测，可以提供胶子如何转化为双π介子的信息，并可能为研究$ I = 0$ s波$ππ$散射提供一种独特的途径。
本文提出了一个辐射跃迁衰变光子谱的理论预言。部分光谱已经被理解，但对端点区域的理解仍然难以捉摸。在本文中，我们提供了缺失的部分，并解决了文献中的一个争议。我们在软共线有效理论（SCET）的框架内处理Upperdam-> X γ衰变的终点区域。在这种方法中，自然地产生了Upperdum结构函数，并且通过使用重整化群方程运行算子来求和运动学方程。在以前的论文中，我们研究了色八隅体的衰变贡献。在这里，我们处理的颜色单态的贡献。我们将我们的结果与以前的结果相结合，以获得Upperdance-> X伽马谱。我们发现，在端点的颜色单重态的贡献给出了一个结果，这是在更好的协议比领先的顺序预测的数据。
We consider the prompt double $J/ψ$ production in $pp$ collisions at the LHC in the framework of $k_T$-factorization QCD approach. Using the fragmentation mechanism, we evaluate the color octet contributions to the production cross sections taking into account the combinatorial effects of multiple gluon radiation in the initial state driven by the Ciafaloni-Catani-Fiorani-Marchesini evolution equation. We demonstrate the importance of these contributions in a certain kinematical region covered by the CMS and ATLAS measurements. On the other hand, the experimental data taken by the LHCb Collabo…
We present the first study of the QCD corrections to the color-singlet (CS) $J/ψ$ production in deeply inelastic $ep$ scattering at HERA. The $K$-factor ranges from $0.85$ to $2.38$ in the kinematic regions we study. In low transverse momentum regions, the $K$-factors is even smaller, and close to 1, which indicates good convergence of the perturbative expansion. With the QCD corrections, the CS cross section is still below the data. At least at QCD next-to-leading order, the color-octet mechanism is necessary to describe the data.
We present the analytic expressions for the two-loop form factors for the production or decay of pseudo-scalar quarkonia, in a scheme where the quarks are produced at threshold. We consider the two-loop amplitude for the process $γγ\leftrightarrow {^1S_0^{[1]}}$, that was previously known only numerically, as well as for the processes $gg \leftrightarrow {^1S_0^{[1]}}$, $γg \leftrightarrow {^1S_0^{[8]}}$ and $gg \leftrightarrow {^1S_0^{[8]}}$, which have not been computed before. The two-loop corrections to $gg \leftrightarrow {^1S_0^{[1]}}$ are the last missing ingredients for a full NNLO cal…
In this article, we investigate the $\cos2ϕ_t$ azimuthal asymmetry in $e ~p\rightarrow e ~J/ψ~Jet~ X$, where the $J/ψ$-jet pair is almost back-to-back in the transverse plane, within the framework of the generalized parton model(GPM). We use non-relativistic QCD(NRQCD) to calculate the $J/ψ$ production amplitude and incorporate both color singlet(CS) and color octet(CO) contributions to the asymmetry. We estimate the asymmetry using different parameterizations of the gluon TMDs in the kinematics that can be accessed at the future electron-ion collider (EIC) and also investigate the impact of t…
