The next-to-leading order (NLO) evolution of the parton distribution functions (PDF's) in QCD is the "industry standard" in the lepton-hadron and hadron-hadron collider data analysis. The standard NLO DGLAP evolution is formulated for inclusive (integrated) PDFs and is done using inclusive NLO kernels. We report here on the ongoing project, called KRKMC, in which NLO DGLAP evolution is performed for the exclusive multiparton (fully unintegrated) distributions (ePDF's) with the help of the exclusive kernels. These kernels are calculated within the two-parton phase space for bremsstrahlung subset of the Feynman diagrams of the non-singlet evolution, using Curci-Furmanski-Petronzio factorization scheme. The multiparton distribution with multiple use of the exclusive NLO kernels is implemented in the Monte Carlo program simulating multi-gluon emission from single quark emitter. With high statistics tests ($\sim 10^{9}$ events) it is shown that the new scheme works perfectly well in practice and is equivalent at the inclusive level with the traditional inclusive NLO DGLAP evolution. Once completed, this Monte Carlo module is aimed as a building block for the NLO parton shower Monte Carlo, for W/Z production at LHC and for ep scattering, as well as a starting point for other perturbative QCD based Monte Carlo projects.
Monte Carlo modelling of NLO DGLAP QCD Evolution in the fully unintegrated form
现有的微扰QCD计算结合了硬过程矩阵元和Parton Shower Monte Carlo程序,其特点是硬过程矩阵元的计算经常超过首阶(LO),即包括完全的次首阶(NLO),甚至次首阶(NNLO)修正,而Parton Shower只在首阶(LO)。我们在这里报告的工作正在进行中,证明了构建Parton Shower Monte Carlo(PSMC)的可行性,具有完整的非线性光学校正QCD演化相对于对数的因式分解尺度。这项工作目前涵盖了非单态子集的费曼图有助于上述QCD的演变。应该强调的是,我们的方法的非线性QCD演化是唯一的,这是给洞察到完全未整合的相空间。然而,在包容性层面上,我们的实施完全符合NLO DG演变的标准包容性图片。我们的新方法(包括非线性光学单线图后)提供了一个完整的方法相结合的mammed和固定阶微扰QCD计算超出LO的形式适合于MC实现,现有的替代。第一个实际应用将包括在强子-强子对撞机和轻子-强子对撞机中W/Z产生过程的蒙特卡罗发生器。
The $D$-meson production is investigated by considering the unintegrated gluon distribution within the dipole approach in the momentum representation. We analyze the $D$-meson spectrum accounting for the effects of nonlinear behavior of the QCD dynamics which can be accordingly addressed in the dipole framework. The unintegrated gluon distribution is obtained by using geometric scaling property and the results are compared to the Glauber-Gribov framework. The absolute transverse momentum spectra and the nuclear modification ratios are investigated. Predictions are compared with the experimenta…
We investigate open charm meson production in fixed-target LHCb experiment at $\sqrt{s}=86.6$ GeV in $p+^4\!\mathrm{He}$ collisions. Theoretical calculations of charm cross section are done in the framework of the $k_{T}$-factorization approach. Its application in the kinematical range never examined before is carefully discussed. We consider different schemes for the calculations relevant for different unintegrated (transverse momentum dependent) parton densities in a proton. We include in the analysis both CCFM- and DGLAP-based models of unintegrated parton distributions appropriate for the …
The present work is devoted to study the high-energy $QCD$ events, such as the di-jet productions from proton-proton inelastic collisions at the $LHC$ in the forward-center and the forward-forward configurations, using the $unintegrated$ parton distribution functions ($UPDF$) in the $k_t$-factorization framework. The $UPDF$ of $Kimber$ et. al. ($KMR$) and $Martin$ et.al. ($MRW$) are generated in the leading order ($LO$) and next-to-leading order ($NLO$), using the $Harland-Lang$ et al. ($MMHT2014$) $PDF$ libraries. While working in the forward-center and the forward-forward rapidity sectors, o…
The class of semi-hard reactions represents a promising venue where to enhance our knowledge of strong interactions and deepen the aspects related to this theory in kinematical regimes so far unexplored. In particular, the high energies reached in electron-proton and in proton-proton collisions first at HERA and then at the LHC, allow us to study scattering amplitudes of hard and semi-hard processes in perturbative QCD. The structure of this thesis can be considered twofold. On one hand, the possibility to distinguish those channels where at least two final-state particles are emitted with lar…
We investigate photo-production of vector mesons J/Psi and Upsilon measured both at HERA and LHC, using 2 particular fits of inclusive unintegrated gluon distributions, based on non-linear Balitsky-Kovchegov evolution (Kutak-Sapeta gluon; KS) and next-to-leading order Balitsky-Fadin-Kuraev-Lipatov evolution (Hentschinski-Sabio Vera-Salas gluon; HSS). We find that linear next-to-leading order evolution can only describe production at highest energies, if perturbative corrections are increased to unnaturally large values; rendering this corrections to a perturbative size, the growth with energy …
The dynamical entropy of dense gluonic states in proton-proton collisions at high energies is studied by using phenomenological models for the unintegrated gluon distribution. The corresponding transverse momentum probability distributions are evaluated in terms of rapidity. The dynamical entropy density is obtained in the rapidity range relevant for the collisions at the Large Hadron Collider. The total entropy density for the dense system is computed as a function of the rapidity evolution $ΔY = Y-Y_0$ given an initial rapidity $Y_0$. The theoretical uncertainties are investigated and compar…
We investigate photo-production of vector mesons J/Psi and Psi(2s), based on both HERA and LHC data, using 2 fits of unintegrated gluon distributions. The latter are subject to non-linear Balitsky-Kovchegov evolution (Kutak-Sapeta gluon; KS) and linear next-to-leading order Balitsky-Kuraev-Fadin-Lipatov evolution (Hentschinski-Sabio Vera-Salas; HSS gluon) respectively. Apart from extending previous studies to the case of radially excited charmonium Psi(2s), we further use an improved set of charmonium wave functions and provide an estimate of the uncertainties associated with the HSS gluon. Wh…
The idea that the nuclear matter may posses long range topological order is supported by the theory and the lattice calculations. At high temperature this order is instrumental in producing anomalous phenomena such as the Chiral Magnetic Effect. In the cold nuclear matter it affects the gluon distribution in the nuclear wave function at low $x$. The effect of the topological order is encapsulated in the unintegrated gluon distribution functions which are proportional, at the leading order, to the square of the gluon propagator at finite topological charge density. It is argued that the Electro…
Transverse momentum dependence of the quark helicity distributions and the Cahn effect in double-spin asymmetry $A_{LL}$ in Semi Inclusive DIS
在半包含深度非弹性散射的LO QCD部分子模型$\ell N \to \ell h X$中,利用未积分的夸克分布和碎裂函数,研究了双夸克自旋不对称性$A_{LL}$对$\bfP_{hT}$的依赖性.我们包括1/Q的运动学修正,诱导方位调制的不对称性,类似于在非极化SIDIS的卡恩效应。我们表明,$A_{LL}$和加权DSA $A_{LL}^{\cosϕ_h}$的研究允许提取的横向动量依赖的未积分螺旋度分布函数$g_{1L}^q(x,k_\perp)$ [或$Δq(x, k_\perp)]$。预测,基于一些模型的未知功能,给出了正在进行的COMPASS,HERMES和JLab实验。
In the article, we investigate the diquark-diquark-antiquark type fully-heavy pentaquark states with the spin-parity $J^P={\frac{1}{2}}^-$ via the QCD sum rules, and obtain the masses $M_{cccc\bar{c}}=7.93\pm 0.15\,\rm{GeV}$ and $M_{bbbb\bar{b}}=23.91\pm0.15\,\rm{GeV}$. We can search for the fully-heavy pentaquark states in the $J/ψΩ_{ccc}$ and $ΥΩ_{bbb}$ invariant mass spectrum in the future.
We construct the diquark-diquark-diquark type vector six-quark currents to investigate the vector and scalar hexaquark states in the framework of the QCD sum rules in a consistent way, and make predictions for the hexaquark masses. We can search for the fully-heavy hexaquark states in the di-$ Ω_{ccc}$ and di-$ Ω_{bbb}$ invariant mass spectra in the future. Combined with our previous works on the fully-heavy tetraquark states and pentaquark states, the present predictions can shed light on the nature of the fully-heavy multiquark states.
The presence of geometric scaling within the $p_T$ spectra of produced hadrons at high energy $pp$ collisions using small-$x$ $k_T$-factorization is investigated. It is proposed a phenomenological parameterization for the unintegrated gluon distribution in the scaling range which reproduces the features of the differential cross section both in the saturated and dilute perturbative QCD regimes. As the saturation scale acts as an effective regulator of the infrared region (IR), the extension of the model to quantities usually associated to soft physics is studied. The approach is applied to com…