We study proton-antiproton annihilation into $Λ_c \barΛ_c$ pairs within the generalized parton picture. Our starting point is the double handbag diagram which is shown to factorize into soft generalized parton distributions for the $p \to Λ_c$ (and $\bar{p} \to \barΛ_c$) transition and a hard subprocess amplitude for $u \bar{u} \to c \bar{c}$. Thereby the mass of the charm quark is taken as the hard scale so that our results are not restricted to large scattering angles and/or incredibly large energies. Modelling the generalized parton distributions for the $p\to Λ_c$ transition by an overlap of simple quark-diquark light-cone wave functions we make first predictions for $p\to Λ_c$ transition form factors and unpolarized $p\bar{p} \to Λ_c \barΛ_c$ cross sections. Our findings may become interesting in view of forthcoming experiments at FAIR in Darmstadt.
We present a partonic picture for diffractive onium-nucleus scattering in the large-number-of-color limit from which the distribution of rapidity gaps in a certain kinematic region can be deduced. This picture allows us to draw a parallel between diffractive dissociation and the genealogy of partonic evolution, the latter being essentially similar to a branching-diffusion process in which the branching is the parton splitting, and the diffusion occurs in the transverse momenta of the partons. In particular, we show that the rapidity gap distribution corresponds to the distribution of the split…
In this paper, I will explain in as simple and intuitive physical terms as possible what generalized parton distributions are, what new information about the structure of hadrons they convey and therefore what picture of the hadron will emerge. To develop this picture, I will use the example of deeply virtual Compton scattering (DVCS) and exclusive meson electroproduction processes. Based on this picture, I will make some general predictions for these processes.
The Froissart (\F) asymptotic behavior of high energy cross-sections, if considered in a parton picture, is usually represented as a kind of behavior that occurs in the process of a collision of two almost black disks, filled with partons, when radiuses of these \F - disks grow proportional to log's of there energies. In this article we briefly summarize the main asymptotic properties of \F - disks that one can expect in QCD. ~~Then we consider if it is possible to guarantee the boost-invariance of transparency $T(s,b) = 1 - σ_{in}(s,b)$, where $σ_{in}(s,b)$ is the total inelastic cross-sectio…
We report progress on the development of Perturbative Integral Representation Ansätze to compute the nucleon Faddeev Wave function, using an explicit quark-diquark picture. Our formalism is able to handle non-pointlike diquark and to mimic the strong, dynamical correlations observed when solving the Faddeev Equation. We then project the wave function in order to compute the leading-twist Parton Distribution Amplitude.
Single-parton scattering versus double-parton scattering in the production of two $c \bar c$ pairs and charmed meson correlations at the LHC
比较了单部分子散射（SPS）和双部分子散射（DPS）对$c \bar c c \bar c$产生和$D$介子关联的精确计算结果。SPS计算是在共线近似下进行的，对$g g \to c \bar c c \bar c$和$q \bar q \to c \bar c c \bar c$子过程采用精确矩阵元。结果表明，胶子-胶子过程的贡献比夸克-反夸克湮灭的贡献大50倍左右。新的结果进行了比较与以前的计算结果与近似矩阵元的$g g \to c \bar c c \bar c$在高能近似。仅当两个$c$夸克（或两个$\bar c$反夸克）的不变质量和快度差很小时，本文精确计算的截面才较大。我们比较了两个$c$（或两个$\bar c$）的DPS和SPS贡献的快速相关性。最后，我们比较了我们对$D$介子的预测与最近的LHCb合作的结果的不变质量，介子之间的快度距离和二介子不变质量。预测的形状与测量的形状相似，但是，似乎缺乏一些强度。我们的新计算清楚地证实了DPS在产生具有双重魅力的事件中的主导地位。
We propose a partonic picture for high-mass diffractive dissociation events in onium-nucleus scattering, which leads to simple and robust predictions for the distribution of the sizes of gaps in diffractive dissociation of virtual photons off nuclei at very high energies. We show that the obtained probability distribution can formally be identified to the distribution of the decay time of the most recent common ancestor of a set of objects generated near the edge of a branching random walk, and explain the physical origin of this appealing correspondence. We then use the fact that the diffract…
Parton showers have become a standard component in the description of high-energy collisions. Nowadays most final-state ones are of the dipole character, wherein a pair of partons branches into three, with energy and momentum preserved inside this subsystem. For initial-state showers a dipole picture is also possible and commonly used, but the older global-recoil strategy remains a valid alternative, wherein larger groups of partons share the energy--momentum preservation task. In this article we introduce and implement a dipole picture also for initial-state radiation in PYTHIA, and compare w…
We calculate cross section for production of $D$ mesons and $Λ_c$ baryons in proton-proton collisions at the LHC. The cross section for production of $c \bar c$ pairs is calculated within $k_T$-factorization approach with the Kimber-Martin-Ryskin unintegrated gluon distributions obtained on the basis of modern collinear gluon distribution functions. We show that our approach well describes the $D^0$, $D^+$ and $D_s$ experimental data. We try to understand recent ALICE and LHCb data for $Λ_c$ production with the $c \to Λ_c$ independent parton fragmentation approach. The Peterson fragmentation f…
We present a selection of results from our recent study of $pp\to t\bar{t}W^\pm$ production matched to partons showers at NLO QCD at the LHC. Theoretical predictions are obtained at perturbative orders $\mathcal{O}(α_s^3α)$ and $\mathcal{O}(α_sα^3)$, where the different contributions are studied first separately at the inclusive level before being combined within a realistic two same-sign lepton signature. We investigate in detail uncertainties originating from missing higher-order corrections and from the parton-shower matching scheme employed.
These lecture notes on Generalised Parton Distributions aim at providing a general picture of the field on the theoretical and phenomenological sides to master and Ph.D. students. They go along with the lecture given at the Baryon International School of Physics in 2021.
Double charm production in single- and double-parton scattering
我们讨论了在LHC中质子-质子碰撞中两对$c \bar c$的产生。分析中包括了部分子散射（DPS）和部分子散射（SPS）的贡献。DPS的每一步都是在$k_t$ -因子分解方法中计算的，该方法有效地包括一些次领先阶次校正。所讨论的机制必然会导致介子对的产生：$D_i D_j$（每个都包含$c$夸克）或$\bar D_i \bar D_j$（每个都包含$\bar c$反夸克）。我们计算了$(D^0 D^0$ + $\bar D^0 \bar D^0)$生产的相应微分分布。在大的理论不确定性的预测DPS横截面是相当相似的横截面测量最近的LHCb合作。我们还提出了第一个结果的$2 \to 4$单部分子散射$g g \to c \bar c c \bar c$子过程的第一次完全在$k_t$ -因子分解方法。在这个计算中，我们使用了一个离壳矩阵元素平方计算使用最近开发的技术。我们的结果进行了比较，较早的结果内的共线方法。仅获得比共线方法的情况稍大的横截面，但SPS机制的贡献仍然比DPS机制的贡献小得多。包含胶子进入硬过程的横动量导致$c c$和$\bar c \bar c$之间的方位角解相关比共线因子分解方法强得多。双部分子散射（DPS）的预测结果和LHCb数据的比较强烈表明，两个完全独立的DPS（$g g \to c \bar c \otimes g g \to c \bar c$）的假设…
