在$k_T$ -因子分解方法的框架下研究了高能下$Υ(2S)$的产生和极化.我们的考虑是基于非相对论QCD形式主义的束缚态的形成和离壳生产振幅硬部分子过程。考虑了直接产生机制、辐射$χ_b(3P)$和$χ_b(2P)$衰变的反馈贡献以及$Υ(3S)$衰变的贡献。由Ciafaloni-Catani-Fiorani-Marchesini演化方程和Kimber-Martin-Ryskin公式导出了质子中与横动量有关的胶子密度。用多极辐射理论处理非微扰色八重态跃迁,从CMS和ATLAS合作组在LHC能量$\sqrt s = 7$和$13$ TeV下测量的$Υ(2S)$横动量分布和LHCb合作组在$\sqrt s = 7$和$8$ TeV下测量的相对产生率$R^{χ_b(2P)}_{Υ(2S)}$的组合拟合中,我们提取了相应的$Υ(2S)$和$χ_b(2P)$介子的非微扰矩阵元。然后,我们应用提取的值来研究偏振参数$λ_θ$,$λ_ϕ$和$λ_{θϕ}$,这决定了$Υ(2S)$自旋密度矩阵。我们的预测有一个很好的协议与目前可用的数据在理论和实验的不确定性。
英文摘要:
The $Υ(2S)$ production and polarization at high energies is studied in the framework of $k_T$-factorization approach. Our consideration is based on the non-relativistic QCD formalism for bound states formation and off-shell production amplitudes for hard partonic subprocesses. The direct production mechanism, feed-down contributions from radiative $χ_b(3P)$ and $χ_b(2P)$ decays and contributions from $Υ(3S)$ decays are taken into account. The transverse momentum dependent gluon densities in a proton were derived from the Ciafaloni-Catani-Fiorani-Marchesini evolution equation as well as from the Kimber-Martin-Ryskin prescription. Treating the non-perturbative color octet transitions in terms of the mulitpole radiation theory, we extract the corresponding non-perturbative matrix elements for $Υ(2S)$ and $χ_b(2P)$ mesons from a combined fit to $Υ(2S)$ transverse momenta distributions measured by the CMS and ATLAS Collaborations at the LHC energies $\sqrt s = 7$ and $13$ TeV and from the relative production rate $R^{χ_b(2P)}_{Υ(2S)}$ measured by the LHCb Collaboration at $\sqrt s = 7$ and $8$ TeV. Then we apply the extracted values to investigate the polarization parameters $λ_θ$, $λ_ϕ$ and $λ_{θϕ}$, which determine the $Υ(2S)$ spin density matrix. Our predictions have a good agreement with the currently available data within the theoretical and experimental uncertainties.
In this work, we present the calculation of the production cross sections of bottomonia states using Non-Relativistic Quantum Chromodynamics (NRQCD) formalism. The direct production cross-section of a resonance can be factorised in terms of short distance Quantum Chromodynamics (QCD) cross sections and long distance matrix elements (LDMEs) under NRQCD. We use a large set of measured $Υ$(nS) production data at Tevatron and LHC energies in both central and forward rapidity regions to extract the LDMEs with better precision. The feed down contributions from the higher states including the $χ_{b}$…
The universal fragmentation functions of gluon into the flavored quarkonia $B_c$ and (polarized) $B_c^*$ are computed within NRQCD factorization framework, at the lowest order in velocity expansion and strong coupling constant. It is mandatory to invoke the DGLAP renormalization program to render the NRQCD short-distance coefficients UV finite in a point-wise manner. The calculation is facilitated with the sector decomposition method, with the final results presented with high numerical accuracy. This knowledge is useful to enrich our understanding toward the large-$p_T$ behavior of $B_c^{(*)}…
The next-to-leading order (NLO) ($\mathcal{O}(α_s^3)$) corrections for gluon fragmentation functions to a heavy quark-antiquark pair in ${^{3}\hspace{-0.6mm}P_{J}^{[1,8]}}$ states are calculated within the NRQCD factorization. We use integration-by-parts reduction and differential equations to semi-analytically calculate fragmentation functions in full-QCD, and find that infrared divergences can be absorbed by the NRQCD long distance matrix elements. Thus, the NRQCD factorization conjecture is verified at two-loop level via a physical process, which is free of artificial ultraviolet divergence…
Prompt inclusive production of $J/ψ$, $ψ'$ and $χ_{c}$ mesons at the LHC in forward directions within the NRQCD $k_t$-factorization approach - search for the onset of gluon saturation
本文用非线性量子色动力学(NRQCD)$k_t$ -因子化方法,利用Kimber-Martin-Ryskin(KMR)非积分胶子分布(UGDF)讨论了在LHC质子-质子碰撞中$J/ψ$介子的瞬发产生.我们包括直接的颜色单态产生($g g \to J/ψg$)以及从$χ_c \to J/ψγ$和$ψ' \to J/ψX$衰变的反馈。衰变介子($χ_c$或$ψ'$)的产生也是在NRQCD $k_t$ -因子分解方法中计算的。相应的矩阵元素为$g g \to J/ψ$ g,$g g \to ψ'g$和$g g \to χ_c$包括参数的非相对论性空间波函数的夸克在$r = 0$,这是取自潜在的模型在文献中。我们得到的$χ_c(2)$与$χ_c(1)$在中等速度下的相应横截面比最近的分析更接近实验数据。计算了$J/ψ$和$ψ'$的快度和横动量的微分分布,并与ALICE和LHCb合作组的实验数据进行了比较。本文讨论了在前向/后向快度下产生$J/ψ$和$χ_{c}$介子时胶子饱和效应的可能发生。我们表明,这是必要的,以修改标准的KMR UGDF描述ALICE和LHCb数据。有人提出了一种混合的城市发展基金设想。然后,我们可以描述的实验数据$J/ψ$生产模型的不确定性与颜色单态分量。因此,我们的理论结果只留下一个相对较小的空间的颜色八隅体的贡献。
The $Υ(1S)$ meson production and polarization at high energies is studied in the framework of the $k_T$-factorization approach. Our consideration is based on the non-relativistic QCD formalism for a bound states formation and off-shell production amplitudes for hard partonic subprocesses. The direct production mechanism, feed-down contributions from radiative $χ_b(mP)$ decays and contributions from $Υ(3S)$ and $Υ(2S)$ decays are taken into account. The transverse momentum dependent (TMD) gluon densities in a proton were derived from the Ciafaloni-Catani-Fiorani-Marchesini evolution equation an…
Prompt charmonia production and polarization at LHC in the NRQCD with kt-factorization. Part II: $χ_c$ mesons
在kt-因子分解方法的框架下,研究了LHC能区pp碰撞中瞬发$χ_c$介子的产生.我们的考虑是基于硬部分子过程$g^*g^*\toχ_{cJ}$的离壳振幅和束缚态的非相对论QCD形式。质子中与横动量有关的(未积分的)胶子密度是从Ciafaloni-Catani-Fiorani-Marchesini演化方程推导出来的,或者,根据Kimber-Martin-Ryskin公式选择。考虑到色单重态和色八重态的贡献,我们推导出相应的非微扰长距离矩阵元素的拟合最新的ATLAS数据$χ_{c1}$和$χ_{c2}$横向动量分布在$\sqrt s = 7$ TeV。我们发现,这些分布在小和中等pt主要是由颜色单态分量。我们成功地描述了ATLAS、CMS和LHCb合作组提供的微分截面和相对产生率$σ(χ_{c2})/σ(χ_{c1})$的数据。我们发现拟合点是$χ_{c1}$和$χ_{c2}$态的不等波函数。
The $Z$-boson decay provides good opportunities for the research on $Ξ_{bQ'}$ baryon due to large quantity of $Z$ events that can be collected at the high-energy colliders. We performed a completed investigation of the indirect production of the $Ξ_{bc}$ and $Ξ_{bb}$ baryon via $Z$-boson decay $Z\to Ξ_{bQ'}+\bar b +\bar Q'$ with $Q'= (c, b)$ quark according to NRQCD factorizations approach. After considering the contribution of the diquark states $\langle bc\rangle [^3S_1]_{\bar 3/6}$, $\langle bc\rangle [^1S_0]_{\bar 3/6}$, $\langle bb\rangle [^1S_0]_{6}$ and $\langle bb\rangle [^3S_1]_{\bar …
We study the transverse-momentum spectrum of quarkonium production from single light-parton fragmentation mechanism. In the case of semi-inclusive deep inelastic scattering, we observe that there are two possible initiating processes, namely photon-gluon fusion and light-quark fragmentation. For the second case we derive the factorization theorem, which involves a new hadronic quantity: the quarkonium transverse-momentum-dependent fragmentation functions in NRQCD. We calculate their matching onto the non-perturbative long distance matrix elements at the lowest order in the strong-coupling cons…