We study effects of the running of the coupling in QCD at small Bjorken-x and in particular the ones related to gluon saturation. After introducing the steps taken to the derivation of the next to leading order nonlinear evolution equation, we discuss the infrared sensitivity of the Pomeron intercept, the energy dependence of the saturation momentum and the appearance of geometrical scaling, and the dominance of the running coupling effects over the ones introduced by loops of Pomerons.
We report on recent experimental and theoretical developments in our understanding of the QCD running coupling α_s in QCD's nonperturbative regime. They allow us to analytically compute the hadron mass spectrum, with Λ_s the only input necessary to this determination. The computed spectra agrees well with experimental data.
The QCD coupling $α_s$ is the most important parameter for achieving precise QCD predictions. By using the well measured effective coupling $α^{g_1}_{s}(Q)$ defined from the Bjorken sum rules as a basis, we suggest a novel and self-consistency way to fix the $α_s$ at all scales: The QCD light-front holographic model is adopted for its infrared behavior, and the fixed-order pQCD prediction under the principle of maximum conformality (PMC) is used for its high-energy behavior. Using the PMC scheme-and-scale independent perturbative series, and by transforming it into the one under the physical $…
A Double-Dilaton Holographic Model of QCD: Running Coupling and Meson Phenomenology
Universitat Autònoma de Barcelona（巴塞罗那自治大学）；Institut de Física d’Altes Energies (IFAE)（高能物理研究所（IFAE））；The Barcelona Institute of Science and Technology (BIST)（巴塞罗那科学技术学院（BIST））
In this article we present REvolver, a C++ library for renormalization group evolution and automatic flavor matching of the QCD coupling and quark masses, as well as precise conversion between various quark mass renormalization schemes. The library systematically accounts for the renormalization group evolution of low-scale short-distance masses which depend linearly on the renormalization scale and sums logarithmic terms of high and low scales that are missed by the common logarithmic renormalization scale evolution. The library can also be accessed through Mathematica and Python interfaces a…
We consider electroweak corrections to the relation between the running $\overline{\mathrm{MS}}$ mass $m_b$ of the $b$ quark in the five-flavor QCD$\times$QED effective theory and its counterpart in the Standard Model (SM). As a bridge between the two parameters, we use the pole mass $M_b$ of the $b$ quark, which can be calculated in both models. The running mass is not a fundamental parameter of the SM Lagrangian, but the product of the running Yukawa coupling $y_b$ and the Higgs vacuum expectation value. Since there exist different prescriptions to define the latter, the relations considered…
We evaluate QCD effects in the neutrinoless double beta ($0νββ$) decay, originating from new physics short-range mechanism in the form of five dimension-9 operators. For this, we employ the one-loop and two-loop renormalization group equations (RGEs) for the corresponding Wilson coefficients, performing the RGE-evolution from the new physics scales (estimated as $Λ~ \sim 10^2$ GeV) to the typical spacelike $0νββ$-scale $Q \sim 0.1$ GeV. Since the latter scale is clearly nonperturbative, we apply various infrared-safe (IR-safe) variants of QCD where the running coupling has no Landau singularit…
Tachyonic AdS/QCD, Determining the Strong Running Coupling and β-function in both UV and IR Regions of AdS Space
Instituto Tecnológico de Aeronáutica（巴西空军理工学院）；Laboratório de Computação Científica Avançada e Modelamento (Lab-CCAM)（高级计算与建模实验室）；University of Coimbra（科英布拉大学）；Universidade Federal de São Carlos（圣卡洛斯联邦大学）；Universidade Federal de Campina Grande（坎皮纳格兰德联邦大学）；Universidade Federal da Paraíba（帕拉伊巴联邦大学）
Starting from the leading Odderon solution of the three gluon system in perturbative QCD we introduce, as a first step towards the transition to the nonperturbative region, an infrared cutoff and use the running QCD coupling constant. In our numerical analysis we find that the fixed cut solution with intercept one persists, hinting at a physical Odderon with intercept one and a small t-slope.
