A. Khodjamirian
I discuss recent applications of QCD light-cone sum rules to various form factors of pseudoscalar mesons. In this approach both soft and hard contributions to the form factors are taken into account. Combining QCD calculation with the analyticity of the form factors, one enlarges the region of accessible momentum transfers.
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Demanding the analyticity of hadronic observables (calculated in terms of power series of the running coupling) as a {\it whole}, we show that they are free of the Landau singularity. Employing resummation and dispersion-relation techniques, we compute in a unifying way power corrections to two different hard-scattering functions in perturbative QCD: the electromagnetic pion form factor to leading order and the inclusive cross section of the Drell-Yan process. In the second case, the leading nonperturbative power correction in $bΛ_{\rm QCD}$ gives rise to a Sudakov-like exponential factor in t…
A theoretical framework is presented to treat hadronic observables within analytic perturbative QCD beyond the leading order of the coupling and for more than one single large momentum scale. The approach generalizes and extends the pioneering work of Shirkov and Solovtsov on an analytic strong running coupling. Some applications to hadronic observables at the partonic level are also discussed.
The total $τ$ hadronic width can be accurately calculated using analyticity and the operator product expansion. The theoretical analysis of this observable is updated to include all available perturbative and non-perturbative corrections. The experimental determination of $α_s(M_τ^2)$ and its actual uncertainties are discussed.
Hadron masses show a specific dependence on the quark masses. Therefore, the variation of these masses can cause a resonance in a hadronic scattering amplitude to become a bound state. Consequently, the amplitude exhibits a non-analytic behavior at this transition. Crossed amplitudes, where the resonance can be exchanged in the t-channel, can be shown to exhibit the same phenomenon by s-->t analytic continuation. This entails possible kinks in lattice quark mass extrapolations needed to compute hadronic observables.
Reconciling hadronic and partonic analyticity in $b\to s\ell\ell$ transitions
研究通过b→sℓℓ过渡的稀有B介子衰变，探讨解析性在粒子物理中的应用，利用运算微分展开约束非本地矩阵元，验证部分子计算与Hadronic自由度的一致性。
The status of hadron-hadron interactions is reviewed, with emphasis on the forward and near-forward scattering regions. From analyticity, Finite Energy Sum Rules are introduced from which new analyticity constraints are derived that exploit the many very accurate low energy experimental cross sections, i.e., they constrain the values of the asymptotic cross sections and their derivatives at low energies just above the resonance regions, allowing us new insights into duality. A new robust fitting technique is introduced in order to `clean up' large data samples that are contaminated by outliers…
The removal of unphysical singularities in the perturbatively calculable part of the pion form factor--a classic example of a three-point function in QCD--is discussed. Different ``analytization'' procedures in the sense of Shirkov and Solovtsov re examined in comparison with standard QCD perturbation theory. We show that demanding the analyticity of the partonic amplitude as a \emph{whole}, as proposed before by Karanikas and Stefanis, one can make infrared finite not only the strong running coupling and its powers, but also cure potentially large logarithms (that first appear at next-to-lead…
The two-pion low-energy contribution to the anomalous magnetic moment of the muon, $a_μ\equiv(g-2)_μ/2$, expres sed as an integral over the modulus squared of the pion electromagnetic form fac tor, brings a relatively large contribution to the theoretical error, since the low accuracy of experimental measurements in this region is amplified by the drastic increase of the integration kernel. We derive stringent constraints on the two-pion contribution by exploiting analyticity and unitarity of the pion electromagnetic form factor. To avoid the poor knowledge of the modulus of this function, we …
Using recent precise hadronic tau-decay data on the V-A spectral function and general properties of QCD such as analyticity, the operator product expansion and chiral perturbation theory, we get accurate values for the QCD chiral order parameters L_10 and C_87. At order p^4 we obtain L_10^r(M_rho)=-(5.22+-0.06)10^-3, whereas at order p^6 we get L_10^r(M_rho)=-(4.06+-0.39)10^-3 and C_87^r(M_rho) = (4.89+-0.19)10^-3 GeV^-2.
The representation for infinite sum of higher twists (HT) tower in DIS implied by analyticity of virtual Compton amplitude is suggested. Its simplest realization allows to describe the Bjorken sum rule at all momentum transfers. It is stressed that TMDs accommodate the infinite tower of HT similar to non-local vacuum condensates for the case of vacuum matrix element. The D-term in hadronic GPDs bears some similarity to vacuum cosmological constant. The negative sign of D-term may be understood as a similarity between inflation and annihilation via the graviton exchange.
Detailed and precise background predictions are the backbone of large parts of high-energy collider phenomenology. This requires to embed precision QCD calculations into detailed event generators, to produce comprehensive software simulations. Only continued progress in this direction will allow us to exploit the full potential of measurements at the Large Hadron Collider, or at a future Electron-Ion Collider. This work presents a method to combine third-order QCD calculations for hadronic scattering processes with Monte-Carlo event generators, thus enabling a new generation of precision predi…
The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| can be extracted from the rate for the semi-leptonic decay B -> pi + l + antineutrino_l, with little theoretical uncertainty, provided the hadronic form factor for the B -> pi transition can be measured from some other B decay. In here, we suggest using the decay B -> pi Jψ. This is a color suppressed decay, and it cannot be properly described within the usual factorization approximation; we use instead a simple and very general phenomenological model for the b d Jψvertex. In order to relate the hadronic form factors in the B -> pi Jψand B ->…
We show how to obtain the leading energy dependence of hadronic total cross sections, in the framework of the nonperturbative approach to soft high-energy scattering based on Wilson-loop correlation functions, if certain nontrivial analyticity assumptions are satisfied. The total cross sections turn out to be of "Froissart" type, $σ_{\rm tot}^{(hh)}(s) \mathop\sim B\log^2 s$ for ${s \to \infty}$. We also discuss under which conditions the coefficient $B$ is universal, i.e., independent of the hadrons involved in the scattering process. In the most natural scenarios for universality, $B$ can be…
Dispersion relations---a corollary of unitarity and analyticity---are among the few methods which can be employed to study low energy processes in QCD. In this work we critically revisit the calculation of decay widths of a hypothetical light scalar boson into pions and kaons. Strong interactions of the mesons in the final state affect these decays significantly. We argue that applications of the dispersion relations to the calculation of these decay widths, which are present in the literature, rely on an uncontrollable approximation of the reduced S-matrix. When a limited number of initial an…
The total $τ$ hadronic width can be accurately calculated using analyticity and the operator product expansion. The theoretical analysis of this observable is updated to include all available perturbative and non-perturbative corrections. The experimental determination of $α_s(M_τ^2)$ and its actual uncertainties are discussed.
Using our present knowledge on effective hadronic theories, short-distance QCD information, the $1/N_C$ expansion, analyticity and unitarity, we derive an expression for the pion form factor, in terms of $m_π, m_K, M_ρ$ and $f_π$. This parameter-free prediction provides a surprisingly good description of the experimental data up to energies of the order of 1 GeV.
We derive lower bounds for the combination of light quark masses m_s +m_u and m_d +m_u. The derivation is based on first principles: the analyticity properties of two-point functions of local current operators and the positivity of the corresponding hadronic spectral functions. The bounds follow from the restriction of the sum over all possible hadronic states which can contribute to the hadronic spectral functions to those with the lowest invariant mass. These hadronic contributions are well known phenomenologically, either from experiment or from chiral perturbation theory calculations. The …
Model-independent constraints on hadronic form factors, in particular those describing exclusive semileptonic decays, can be derived from the knowledge of field correlators calculated in perturbative QCD, using analyticity and unitarity. The location of poles corresponding to below-threshold resonances, i.e., stable states that cannot decay into a pair of hadrons from the crossed channel of the form factor, must be known a priori, and their effect, accounted for through the use of Blaschke factors, is to reduce the strength of the constraints in the semileptonic region. By contrast, above-thre…
Extrapolating semileptonic form factors using Bayesian-inference fits regulated by unitarity and analyticity
提出基于幺正性和解析性的模型无关贝叶斯推断框架，用于拟合强子形状因子数据，并外推至整个物理范围，已应用于 $B_s\to K\ell\nu$ 和 $B \to D^*\ell\nu$ 衰变。
Bayesian inference for form-factor fits regulated by unitarity and analyticity
提出一种基于幺正性和解析性的贝叶斯框架，用于模型无关地拟合强子形状因子数据，并应用于$B_s\to K \nu$衰变，预测$|V_{ub}|$等物理量。
Dispersive approaches for the HVP and HLbL contributions to $(g-2)_μ$
该研究介绍了基于矩阵元解析性质的色散方法在约束μ子反常磁矩的强子真空极化、强子光光散射两类强子贡献中的近期应用，涉及强子截面解析约束、辐射修正与同位旋破缺效应。
We present a new general dispersive formalism for evaluating the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. In the suggested approach, this correction is related to the imaginary part of the muon's electromagnetic vertex function. The latter may be directly related to measurable hadronic processes by means of unitarity and analyticity. As a test we apply the introduced formalism to the case of meson pole exchanges and find agreement with the direct two-loop calculation.
We perform a new calculation of the hadronic contributions, $a({\rm Hadronic})$ to the anomalous magnetic moment of the muon, $a_μ$. For the low energy contributions of order $α^2$ we carry over an analysis of the pion form factor $F_π(t)$ using recent data both on $e^+e^-\toπ^+π^-$ and $τ^+\to \barν_τπ^+π^0$. In this analysis we take into account that the phase of the form factor is equal to that of $ππ$ scattering. This allows us to profit fully from analyticity properties so we can use also experimental information on $F_π(t)$ at spacelike $t$. At higher energy we use QCD to supplement expe…
We review the current status of theoretical calculations of the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment. Different approaches and related issues such as OPE constraints and large breaking of chiral symmetry are discussed. Combining results of different models with educated guesses on the errors we come to the estimate $$a^{\rm HLbL}=(10.5\pm 2.6)\times 10^{-10}.$$ The text is prepared as a contribution to the {\it Glasgow White Paper on the present status of the Muon Anomalous Magnetic Moment}.
A new method for combining QCD matrix elements and parton showers in Monte Carlo simulations of hadronic final states is outlined. The aim is to provide at least a leading-order description of all hard multi-jet configurations together with jet fragmentation to next-to-leading logarithmic accuracy, while avoiding the most serious problems of double counting.
I elaborate on the implementation of analyticity of hadronic quantities at the amplitude level and show that it amounts to the extension of Analytic Perturbation Theory of Shirkov and Solovtsov to non-integer (fractional) powers of the strong running coupling. I give evidence that at the NLO of the factorized pion's electromagnetic form factor this framework diminishes the uncertainty due to the renormalization-scheme choice and nearly removes the dependence on both the renormalization and the factorization scale. I supplement this discussion by considering effects caused by retaining transver…
In recent decades, the spin and transverse momentum of quarks and gluons were found to play integral roles in the structure of the nucleon. Simultaneously, the onset of gluon saturation in hadrons and nuclei at high energies was predicted to result in a new state of matter dominated by classical gluon fields. Understanding both of these contributions to hadronic structure is essential for current and future collider phenomenology. In this Dissertation, we study the combined effects of transverse spin and gluon saturation using the Glauber-Gribov-Mueller / McLerran-Venugopalan model of a heavy …
The two-pion contribution from low energies to the muon magnetic moment anomaly, although small, has a large relative uncertainty since in this region the experimental data on the cross sections are neither sufficient nor precise enough. It is therefore of interest to see whether the precision can be improved by means of additional theoretical information on the pion electromagnetic form factor, which controls the leading order contribution. In the present paper we address this problem by exploiting analyticity and unitarity of the form factor in a parametrization-free approach that uses the p…
The form factors of the light pseudoscalar mesons are investigated in a dispersive formalism based on hadronic unitarity, analyticity and the OPE expansion of the QCD Green functions. We propose generalizations of the original mathematical techniques, suitable for including additional low energy information provided by experiment or Chiral Perturbation Theory (CHPT). The simultaneous treatment of the electroweak form factors of the $π$ and $K$ mesons allows us to test the consistency with QCD of a low energy CHPT theorem. By applying the formalism to the pion electromagnetic form factor, we de…
We introduce parametrizations of hadronic three-body $B$ and $D$ weak decay amplitudes that can be readily implemented in experimental analyses and are a sound alternative to the simplistic and widely used sum of Breit-Wigner type amplitudes, also known as the isobar model. These parametrizations can be particularly useful in the interpretation of CP asymmetries in the Dalitz plots. They are derived from previous calculations based on a quasi-two-body factorization approach in which two-body hadronic final state interactions are fully taken into account in terms of unitary $S$- and $P$-wave $π…
Analyticity of gluon and Faddeev--Popov ghost propagators and their form factors on the complex momentum-squared plane is exploited to continue analytically the ultraviolet asymptotic form calculable by perturbation theory into the infrared non-perturbative solution. We require the non-perturbative multiplicative renormalizability to write down the renormalization group equation. These requirements enable one to settle the value of the exponent characterizing the infrared asymptotic solution with power behavior which was originally predicted by Gribov and has recently been found as approximate…
We analyze how the recent precise hadronic tau-decay data on the V-A spectral function and general properties of QCD such as analyticity, the operator product expansion and chiral perturbation theory (ChPT), can be used to improve the knowledge of some of the low-energy constants of ChPT. In particular we find the most precise values of L_{9,10} (or equivalently l_{5,6}) at order p^4 and p^6 and the first phenomenological determination of C_87 (c_50).
Recent ALEPH/OPAL data on the V-A spectral functions from hadronic tau decays are used for fixing the QCD continuum threshold at which the first and second Weinberg sum rules should be satisfied in the chiral limit, and for predicting the values of the low-energy constants f_π,~m_{π^+}-m_{π^0} and {L}_{10}. Some DMO-like sum rules and the $τ$-total hadronic widths R_{τ,V-A} are also used for extracting the values of the D=6,~8 QCD vacuum condensates and the corresponding (in the chiral limit) electroweak kaon penguin matrix elements Q^{3/2}_{8,7}\ra_{2π},, where a deviation from the vacuum sat…
Using recent CLEO III results for the cross section for $e^+e^- \to {\rm hadrons}$ at seven centre-of-mass energies between 6.964 and 10.538 GeV, we derive a value for the strong coupling constant $α_s(M_Z^2)=0.110_{-0.012}^{-0.010}{}_{-0.011}^{+0.010}$ where the uncertainties are uncorrelated and correlated, respectively. Our result differs significantly from the one derived by CLEO III, as a consequence of inclusion of quark mass effects and the proper matching between the effective theories with four and five flavours. Combining this new result with an analysis based on earlier cross sectio…
Hadronic photon correction to $γ^{\ast} γ\to f_{2}(1270)$ at next-to-leading order
该研究在光锥求和规则框架下，计算了$\gamma^*\u03b3 \to f_2(1270)$跃迁形状因子的强子光子修正，建立次领头阶因子化公式并重求和大对数，结合QCD共线因子化给出三个螺旋度形状因子的更新理论预言及不确定性估计。
We provide hadronic input for the $B$-meson semileptonic transitions to a light pseudoscalar meson at large recoil. The $B_s\to K$ form factor calculated from QCD light-cone sum rule is updated, to be used for a $|V_{ub}|$ determination from the $B_s\to K \ell ν$ width. Furthermore, we calculate the hadronic input for the binned observables of $B \to π\ell^+ \ell^-$ and $B \to K \ell^+ \ell^-$. In addition to the form factors, the nonlocal hadronic matrix elements are obtained, combining QCD factorization and light-cone sum rules with hadronic dispersion relations. We emphasize that, due to no…
PINNing the pion: conformal deep learning for $F_π(s)$ and the $(g-2)_μ$ hadronic contribution
提出一种嵌入共形 z 平面的物理信息神经网络，直接从第一性原理构建 pion 电磁形状因子，避免模型依赖，并给出电荷半径、ρ 极点参数及 muon 反常磁矩双 pion 贡献的模型无关估计。
We propose studying the mechanism of factorization in exclusive decays of the form B->D(*)X by examining the differential decay rate as a function of the invariant mass of the light hadronic state X. If factorization works primarily due to the large N_c limit then its accuracy is not expected to decrease as the X invariant mass increases. However, if factorization is mostly a consequence of perturbative QCD then the corrections should grow with the X invariant mass. Combining data for hadronic tau decays and semileptonic B decays allows tests of factorization to be made for a variety of final …
We consider the transverse-momentum ($q_T$) distribution of $Z$ bosons produced in hadronic collisions. At small values of $q_T$, we perform the analytic resummation of the logarithmically enhanced QED contributions up to next-to-leading logarithmic accuracy, including the mixed QCD-QED contributions at leading logarithmic accuracy. Resummed results are consistently matched with the next-to-leading fixed-order results (i.e. $\mathcal{O}(α^2)$) at small, intermediate and large values of $q_T$. We combine the QED corrections with the known QCD results at next-to-next-to-leading order ($\mathcal{…
We present a model for the decay $D^+\to K^-π^+π^+$. The weak interaction part of this reaction is described using the effective weak Hamiltonian in the factorisation approach. Hadronic final state interactions are taken into account through the $Kπ$ scalar and vector form factors fulfilling analyticity, unitarity and chiral symmetry constraints. Allowing for a global phase difference between the $S$ and $P$ waves of $-65^\circ$, the Dalitz plot of the $D^+\to K^-π^+π^+$ decay, the $Kπ$ invariant mass spectra and the total branching ratio due to $S$-wave interactions are well reproduced.
In line with some previous works, we study in this paper the meson spectrum in the framework of a second order quark-antiquark Bethe-Salpeter formalism which includes confinement. An analytic one loop running coupling constant alpha_s(Q), as proposed by Shirkov and Sovlovtsov, is used in the calculations. As for the quark masses, the case of a purely phenomenological running mass for the light quarks in terms of the c. m. momentum is further investigated. Alternatively a more fundamental expression m_P(Q) is introduced for light and strange quarks, combining renormalization group and analytici…
The analysis on the hadron-hadron scattering at high energies in the framework of holographic QCD is presented. Combining the Pomeron exchange kernel and the hadron-Pomeron couplings which are obtained from the bottom-up AdS/QCD models, we calculate the total cross sections. Our calculation for the nucleon-nucleon scattering is consistent with the experimental data including the recent ones measured by the TOTEM collaboration at the LHC. Within the framework, one can consider other processes involving other hadrons. As examples to show this feature of the model, the resulting total cross secti…
We present results of calculations of the hadronic vacuum polarisation contribution to the muon anomalous magnetic moment. Specifically, we focus on controlling the infrared regime of the vacuum polarisation function. Our results are corrected for finite-size effects by combining the Gounaris-Sakurai parameterisation of the timelike pion form factor with the Lüscher formalism. The impact of quark-disconnected diagrams and the precision of the scale determination is discussed and included in our final result in two-flavour QCD, which carries an overall uncertainty of 6%. We present preliminary …
Following updates in the compilation of $e^+e^-\rightarrow{\rm hadrons}$ data, this work presents re-evaluations of the hadronic vacuum polarisation contributions to the anomalous magnetic moment of the electron ($a_e$), muon ($a_μ$) and tau lepton ($a_τ$), to the ground-state hyperfine splitting of muonium and also updates the hadronic contributions to the running of the QED coupling at the mass scale of the $Z$ boson, $α(M_Z^2)$. Combining the results for the hadronic vacuum polarisation contributions with recent updates for the hadronic light-by-light corrections, the electromagnetic and th…
Based on analyticity, unitarity, and Lorentz invariance the contribution from hadronic vacuum polarization to the anomalous magnetic moment of the muon is directly related to the cross section of e^+e^- --> hadrons. We review the main difficulties that impede such an approach for light-by-light scattering and identify the required ingredients from experiment. Amongst those, the most critical one is the scattering of two virtual photons into meson pairs. We analyze the analytic structure of the process gamma^* gamma^* --> pi pi and show that the usual Muskhelishvili-Omnes representation can be …
Dispersion relations for the hadronic VVA correlator
本文为强子VVA关联函数推导了两种色散关系，并利用其结合渐近与低能约束，降低了缪子反常磁矩中第一代家族VVA贡献的理论不确定性。
We extend recently developed methods used for determining the electromagnetic charge radius and $a_μ^{ππ}$ to obtain a determination of the electromagnetic form factor of the pion, $F_π^V(t)$, in several significant kinematical regions, using a parametrization-free formalism based on analyticity and unitarity, and with the inclusion of precise inputs from both timelike and spacelike regions. On the unitarity cut, below the first inelastic threshold we use the precisely known phase of the form factor, known from $ππ$ elastic scattering via the Fermi-Watson theorem, and above the inelastic thres…
We developed the new parton model approach for exclusive semileptonic decays of $B$-meson to $D,~D^*$ by extending the inclusive parton model, and by combining with the results of the HQET, motivated by Drell-Yan process. Without the nearest pole dominance ansätze, we {\bf derived} the dependences of hadronic form factors on $q^2$. We also calculated numerically the slope of the Isgur-Wise function, which is consistent with the experimental results.
We propose a dispersive representation of the charged pion vector form factor that is consistent with chiral symmetry and fulfills the constraints imposed by analyticity and unitarity. Unknown parameters are fitted to the very precise data on $τ^-\toπ^-π^0ν_τ$ decays obtained by Belle, leading to a good description of the corresponding spectral function up to a $ππ$ squared invariant mass $s\simeq 1.5$ GeV$^2$. We discuss the effect of isospin corrections, and obtain the values of low energy observables. For larger values of $s$, this representation is complemented with a phenomenological desc…
We present a calculation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment, $a_μ^{\mathrm hvp}$, in lattice QCD employing dynamical up and down quarks. We focus on controlling the infrared regime of the vacuum polarization function. To this end we employ several complementary approaches, including Padé fits, time moments and the time-momentum representation. We correct our results for finite-volume effects by combining the Gounaris-Sakurai parameterization of the timelike pion form factor with the Lüscher formalism. On a subset of our ensembles we have deri…
Combining the recently reported electric dipole moment (EDM) of $^{199}$Hg atom due to breaking of parity and time-reversal symmetries with the improved relativistic atomic calculations, precise limits on the tensor-pseudotensor (T-PT) electron-nucleus (e-N) coupling coefficient and the nuclear Schiff moment (NSM) interactions are determined. Using these limits with the nuclear calculations, we infer limits on the EDMs of neutron and proton as $d_n < 2.2 \times 10^{-26} |e| \rm{cm}$ and $d_p < 2.1 \times 10^{-25} |e| \rm{cm}$, respectively, and on the quantum chromodynamics (QCD) parameter and…
We present a model for the decay D+ --> K- pi+ pi+. The weak interaction part of this reaction is described using the effective weak Hamiltonian in the factorisation approach. Hadronic final state interactions are taken into account through the Kpi scalar and vector form factors fulfilling analyticity, unitarity and chiral symmetry constraints. The model has only two free parameters that are fixed from experimental branching ratios. We show that the modulus and phase of the S wave thus obtained agree nicely with experiment up to 1.55 GeV. We perform Monte Carlo simulations to compare the predi…
We present our analysis on high energy hadron-hadron scattering in the framework of the holographic QCD. Combining the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel and gravitational form factors of the involved hadrons which are obtained by using the bottom-up AdS/QCD models in the five-dimensional AdS space, we calculate the total cross sections at high energies. We show that our calculations for the nucleon-nucleon scattering agree with the experimental data including the recent ones taken by the TOTEM collaboration at the LHC. The present framework is applicable to any high energ…
Inclusive hadronic decay rate of the $τ$ lepton from lattice QCD: the $\bar u s$ flavour channel and the Cabibbo angle
本文利用格点QCD在n_f=2+1+1非微扰精度下计算τ→X_{us}ν_τ单举衰变率，结合实验数据以0.9%精度提取CKM矩阵元|V_{us}|（Cabibbo角）。
We calculate the contribution to the muon anomalous magnetic moment hadronic vacuum polarization from {the} connected diagrams of up and down quarks, omitting electromagnetism. We employ QCD gauge-field configurations with dynamical $u$, $d$, $s$, and $c$ quarks and the physical pion mass, and analyze five ensembles with lattice spacings ranging from $a \approx 0.06$ to~0.15~fm. The up- and down-quark masses in our simulations have equal masses $m_l$. We obtain, in this world where all pions have the mass of the $π^0$, $10^{10} a_μ^{ll}({\rm conn.}) = 637.8\,(8.8)$, in agreement with independe…
Studies of quarkonium spectral functions at finite temperature, based on an approach combining QCD sum rules and the maximum entropy method are briefly reviewed. QCD sum rules for heavy quarkonia incorporate finite temperature effects in form of changing values of gluonic condensates that appear in the operator product expansion. These changes depend on the energy density and pressure at finite temperature, which we extract from quenched lattice QCD calculations. The maximum entropy method then allows us to obtain the most probable spectral function from the sum rules, without having to introd…
One of the advantages of the finite energy sum rules is the fact that every operator in the operator product expansion series can be selected individually by the use of an appropriate kernel function which removes other operator poles. This characteristic is maintained by QCD systems in the presence of external homogeneous magnetic field, providing interesting information about the magnetic evolution of QCD and hadronic parameters. In this work finite energy sum rules are applied on QCD in the light quark sector, combining axial and pseudoscalar channels in the presence of an external homogene…
Non-perturbative thermal QCD at very high temperatures: computational strategy and hadronic screening masses
本文提出结合步进标度与平移边界条件的非微扰热QCD计算策略，首次在1 GeV至160 GeV温度范围计算强子屏蔽谱，并定量计算次领头阶重子屏蔽质量，揭示微扰方法在有限温度下适用性有限。
Background: The transverse densities $ρ_{1, 2}(b)$ describe the distributions of electric charge and magnetic moment at fixed light-front time and connect the nucleon's elastic form factors with its partonic structure. The dispersive representation of the form factors $F_{1, 2}(t)$ expresses the densities in terms of exchanges of hadronic states in the $t$-channel and permits their analysis using hadronic physics methods. Purpose: Compute the densities at peripheral distances $b = \mathcal{O}(M_π^{-1})$, where they are generated predominantly by the two-pion states in the dispersive representa…
We present our model-independent and data-driven method to describe pseudoscalar meson transition form factors in the space- and (low-energy) time-like regions. The method is general and conforms a toolkit applicable to any other form factor, of one and two variables, with the potential to include both high- and low-energy QCD constraints altogether. The method makes use of analyticity and unitary properties of form factors, it is simple, systematic and can be improved upon by including new data. In the present discussion, the method is used to show the impact of experimental data for precisio…
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