The low energy behaviour of Quantum Chromodynamics makes unreliable an expansion in terms of its coupling strength, since nothing guarantees the convergence of such expansion. To overcomer such difficulty one resorts to Lattice QCD or Effective Field Theories. In this thesis we compute hadronic processes at low energies, using Resonance Chiral Lagrangians as the effective theory of QCD. The processes we study are important background on the search for Lepton Flavor Violation, Lepton Universality Violation, Lepton Number Violation, Second Class Currents and study the Hadronic light-by-light contribution to the Anomalous Magnetic Moment of the muon. All such processes are of great interest since all of them are to be studied with an increased precision in the very near future by different experiments.
Zero temperature properties of an (axial-) vector meson extended linear sigma model are discussed, concerning on the possible different realizations of the axial anomaly term. The different anomaly terms are compared with each other on the basis of a chi^2 minimalization process. It is found that there is no essential difference among the different realizations. This means that any of them can be equally used from phenomenological point of view.
The so-called extended linear sigma model is a chiral model with (pseudo)scalar and (axial-)vector mesons. It is based on the requirements of (global) chiral symmetry and dilatation invariance. The purpose of this model is the description of the hadron phenomenology up to 1.7 GeV. We present the latest theoretical results, which show a good agreement with the experiment.
The light-front wavefunction for mesons predicted by holographic light-front QCD is used to obtain the light-cone distribution amplitudes for the light vector mesons and the transition form factors for B and $B_s$ decays to $ρ$, $K^*$ and $ϕ$ mesons. Here, I present some of our predictions as compared to lattice QCD, OCD sum rules and the available experimental data.
In the framework of the $U(2)_{R}\times U(2)_{L}$ symmetric linear sigma model with (axial)vector mesons generalized by including a dilaton field we study the phenomenology of the scalar-isoscalar resonances below 2 GeV. It turns out that, in our favoured scenario, the resonance $f_{0}(1370)$ is predominantly a $\bar{q}q$ state and $f_{0}(1500)$ is predominantly a glueball state. Additionally we are able to calculate the value of the gluon condensate, which is in agreement with lattice QCD results.
In this work, we perform a covariant treatment of quark-antiquark systems. We calculate the spectra and wave functions using a formalism based on the Covariant Spectator Theory (CST). Our results not only reproduce very well the experimental data with a very small set of global parameters, but they also allow a direct test of the predictive power of covariant kernels.
We report on a successful extraction of the twist-2 and twist-3 Distribution Amplitudes (DAs) of the rho meson using the HERA data on diffractive rho photoproduction. We extract these DAs using several Colour Glass Condensate (CGC) inspired and a Regge inspired dipole models. All our extracted DAs are consistent with Sum Rules and lattice predictions.
The firm understanding of standard quark-antiquark states (including excited states) is necessary to search for non-conventional mesons with the same quantum numbers. In this work, we study the phenomenology of two nonets of excited vector mesons, which predominantly correspond to radially excited vector mesons with quantum numbers $n$ $^{2S+1}L_{J}=2$ $^{3}S_{1}$ and to orbitally excited vector mesons with quantum numbers $n$~ $^{2S+1}L_{J}=1$ $^{3}D_{1}$. We evaluate the decays of these mesons into two pseudoscalar mesons and into a pseudoscalar and a ground-state vector meson by making use …
We discuss the phenomenology of the axial-vector mesons within a three-flavour Linear Sigma Model containing scalar, pseudoscalar, vector and axial-vector degrees of freedom.
We review how quark models are able to describe the phenomenology of the charm meson sector. The spectroscopy and decays of charmonium and open charm mesons are described in a particular quark model and compared with the data and the results of other existing models in the literature. A quite reasonable global description of the heavy meson spectra is reached. A new assignment of the $ψ(4415)$ resonance as a 3D state leaving aside the 4S state to the X(4360) is tested through the analysis of the resonance structure in $e^{+}e^{-}$ exclusive reactions around the $ψ(4415)$ energy region. We make…
We study the vacuum properties of the pseudoscalar glueball and charmed mesons by using the so-called extended Linear Sigma Model (eLSM). This model includes scalar and pseudoscalar mesons, as well as vector and axial-vector mesons. We calculate the mesonic and baryonic decays of the pseudoscalar glueball, where we fixed its mass to $2.6$ GeV, as predicted by lattice-QCD simulations, and take a closer look at the scalar-isoscalar decay channel. As a second step, we enlarge the so-called extended linear Sigma model (eLSM) by including the charm quark to a global $U(4)_r\times U(4)_l$ chiral sym…
We construct the three-flavor Lorentz-invariant meson-baryon chiral Lagrangians at the order $p^4$, with which a full one-loop investigation may be performed. One obtains 540 independent terms. The processes with the minimal number of mesons and photons that this order Lagrangians may contribute to are also presented.
In this paper we present a phenomenological analysis of the Partially Aligned Two Higgs Doublet Model (PA-2HDM) by using leptonic decays of mesons and $B^0_{d,s}$-$\bar B^0_{d,s}$ mixing. We focus our attention in a scenario where the leading contribution to FCNC is given by the tree level interaction with the light pseudoscalar $A^0$ ($M_{A^0}\sim 250$ GeV). We show how an underlying flavor symmetry controls FCNC in the quark and lepton couplings with the pseudoscalar, without alignment between Yukawa matrices. Upper bounds on the free parameters are calculated in the context of the leptonic …
The chiral SU(3) Lagrangian with pseudoscalar and vector $D$ mesons and with the octet and decuplet baryons is considered. The leading two-body counter terms involving two baryon fields and two $D$ meson fields are constructed in the open-charm sector. There are 26 terms. A combined expansion in the inverse of the charm quark mass and in the inverse of the number of colors provides sum rules that reduce the number of free parameter down to 5 only. Our result shows the feasibility of a systematic computation of the open-charm baryon spectrum based on coupled-channel dynamics.
The chiral Lagrangians with vector mesons are constructed in different approaches, including the next-to-leading order Lagrangian in the vector-field approach, the next-to-next-to-leading order Lagrangians in the tensor-field and the hidden local symmetry approaches. Some redundant terms are found at the next-to-leading order in the tensor-field and the hidden local symmetry approaches. The corresponding relations between the next-to-next-to-leading order pseudoscalar mesonic low-energy constants and the ones in the hidden local symmetry approach are obtained at tree level. The equivalence bet…
We present a comprehensive discussion of the phenomenology of flavourful axions, including both standard Peccei-Quinn (PQ) axions, associated with the solution to the strong $CP$ problem, and non-standard axion-like particles (ALPs). We give the flavourful axion-fermion and axion-photon couplings and calculate the branching ratios of heavy meson ($K$, $D$, $B$) decays involving a flavourful axion. We also calculate the mixing between axions and heavy mesons $ K^0 $, $ D^0 $, $ B^0 $ and $ B_s^0 $, which affects the meson oscillation probability and mass difference. Mixing also contributes to m…
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））
Meson correlation functions are studied in the model with four-fermion interaction Lagrangian. We demonstrate that despite the singular character of system mean energy and corresponding quark condensate found out the meson observables are finite, quite well identified and compatible with experimental energy scale. It allows one to use the similar model Hamiltonians for describing the nonequilibrium features of quark/hadron systems which reveal themselves in studying ultrarelativistic heavy ion collisions. The analytical results for meson correlation functions in the Keldysh model are given.
As a successive work to [Phys.Rev.D 102 (2020), 034034], we derive the $1/m_Q$ corrections to chiral effective Lagrangian for heavy-light mesons from QCD under proper approximations. The low energy constants in the effective Lagrangian are expressed in terms of the light quark self-energy and heavy quark mass $m_Q$. Numerical results of the low energy constants with $1/m_Q$ corrections are given. We find that the results of pion decay constant and the masses of heavy-light mesons are improved coherently compared to that obtained in the heavy quark limit.
The chiral SU(3) Lagrangian with the baryon octet and decuplet fields is considered. The Q^2 counterterms involving the decuplet fields are constructed. We derive the correlation of the chiral parameters implied by the 1/N_c expansion at leading order in QCD.
We study the phenomenology of the recently proposed modified version of the Soft-Wall model of holographic QCD with a negative dilaton profile. We investigate vector and scalar mesons, evaluating mass spectra, decay constants and two-point correlation functions. We then study chiral symmetry breaking and compute the coupling of a scalar meson with two pseudoscalars. Finally, we compare the results with the ones found in the literature in the positive-dilaton case.
The Higgs discovery and the lack of any other hint for new physics favor a description of non-standard Higgs physics in terms of an effective field theory. We present an implementation of a general Higgs effective Lagrangian containing operators up to dimension six in the framework of FeynRules and provide details on the translation between the mass and interaction bases, in particular for three- and four-point interaction vertices involving Higgs and gauge bosons. We illustrate the strengths of this implementation by using the UFO interface of FeynRules capable to generate model files that ca…
We consider a generic composite Higgs model based on the coset SO(5)/SO(4) and study its phenomenology beyond the leading low-energy effective lagrangian approximation. Our basic goal is to introduce in a controllable and simple way the lowest-lying, possibly narrow, resonances that may exist is such models. We do so by proposing a criterion that we call partial UV completion. We characterize the simplest cases, corresponding respectively to a scalar in either singlet or tensor representation of SO(4) and to vectors in the adjoint of SO(4). We study the impact of these resonances on the signal…
使用Schwinger型质量关系筛选人口过多的等密度张量状态。找到了两种解决方案：一个是胶球是fJ（2220），另一个是胶球分布更广，其中f2（1820）具有最大分量。f2（1565）和fJ（1710）不能被容纳为胶球-（杂化）介子混合物，在没有显着耦合到衰变通道。f2 '（1525）-> pi pi与实验结果一致。fJ（2220）既不民主地衰减味道，也不狭窄。
We investigate capabilities of the effective interaction in a rainbow-ladder truncated meson model of QCD within a covariant Landau-gauge Bethe-Salpeter-equation approach. Based upon past success for the light- as well as heavy-quark domains, we discuss the range of applicability and features of an effort with comprehensive phenomenological claim and goals.
