QCD sum rules for pion wave function revisited

We analyze new QCD sum rules for the pion wave function (WF) ?_π (x), obtained recently in [1] in the non-local vacuum condensates method for non-diagonal correlators, and suggest a new approach for extracting WF of the π-meson and the mass and WF of the first resonance. As a result, we obtain approximately the same form of the pion WF by two different methods and for two different ansatzes of non-local quark condensates. We predict the mass of the π′-resonance and obtain the form of its WF.     

QCD Calculation ofK^0 - \bar K^0 mixing from three-point function sum rules

We calculate theB parameter for \(K^0 - \bar K^0 \) mixing in the framework of QCD sum rules for a three-point function involving pseudoscalar currents, and contrast our results with other calculations. We findB=0.5±0.1±0.2, where the first error reflects uncertainties in the various QCD parameters and the second one is an estimate of uncalculated three-loop radiative and higher order quark mass corrections.     

DecayB \to Dl\bar v from QCD sum rules

\(B \to Dl\bar v\) form factor is calculated using 3-point QCD sum rules.     

Ds0DK vertex in QCD sum rules

We calculate the form factors and the coupling constant in the D_s0DK vertex in the framework of QCD sum rules. We evaluate the three point correlation functions of the vertex considering both D and K mesons off-shell. The form factors obtained are very different but give the same coupling constant.     

QCD sum rules versus experiment

We show the compatibility of Shifman, Vainshtein and Zakharov (SVZ) sum rules with the sum rules involving the electro-magnetic mass difference of pions and the axial form factor in radiative π^± decay. In spite of good agreement between them, QCD sum rules are unable to explain clearly the experimental data of τ-decay in the axial channel.     

QCD sum rules: charmonium

The dimensiond=4 gluon condensateφ ₁ is determined from an analysis of charmonium, taking model dependent estimates ofd=6.8 condensates into account. ForS-waves, there is a compatibility region, where both these and model dependent higher state corrections to ground state dominance are small, enablingφ ₁ to be determined from a fit to the data. ForP-waves the estimated higher dimension contributions are large in the region of ground state dominance, and noφ ₁ determination is possible. Theφ ₁ value obtained from the fit to theS-wave ratios is 3 5 times bigger than that obtained by RRY using the plateau method. The methods are compared for the vector current. We show that the higher state correction used by RRY does not fit the data; and that the plateau method is much more sensitive to thed=6.8 condensates than the ratio used here. When reasonable estimates of both these and the higher state corrections are taken into account, there is compatibility between the two methods.     

B0-B(-)0 mixing beyond factorization in QCD sum rules

We present a calculation of the B0-B(-)0 mixing matrix element in the framework of QCD sum rules for three-point functions. We compute alpha(s) corrections to a three-point function at the three-loop level in QCD perturbation theory, which allows one to extract the matrix element with next-to-leading order (NLO) accuracy. This calculation is imperative for a consistent evaluation of experimentally measured mixing parameters since the coefficient functions of the effective Hamiltonian for B0-B(-)0 mixing are known at NLO. We find that radiative corrections violate factorization at NLO; this violation is under full control and amounts to 10%. The resulting value of the B parameter is found to be B(B)(m(b))=1+0.1(PT)-0.05(non-PT).     

Thermal QCD sum rules study of vector charmonium and bottomonium states

We calculate the masses and leptonic decay constants of the heavy vector quarkonia, J/ψ and ϒ mesons at finite temperature. In particular, considering the thermal spectral density as well as additional operators coming up at finite temperature, the thermal QCD sum rules are acquired. Our numerical calculations demonstrate that the masses and decay constants are insensitive to the variation of temperature up to T ≅ 100 MeV, however after this point, they start to fall altering the temperature. At deconfinement temperature, the decay constants attain roughly to 45% of their vacuum values, while the masses are diminished about 12%, and 2.5% for J/ψ and ϒ states, respectively. The obtained results at zero temperature are in good consistency with the existing experimental data as well as predictions of the other nonperturbative models.     

Elastic and proton-dissociative \rho^0 photoproduction at HERA

Elastic and proton-dissociative photoproduction (, , respectively, with ) has been studied in interactions at HERA for photon-proton centre-of-mass energies in the range GeV and for GeV, where is the square of the four-momentum transfer at the proton vertex; the results on the proton-dissociative reaction are presented for masses of the dissociated proton system in the range . For the elastic process, the invariant mass spectrum has been investigated as a function of . As in fixed target experiments, the resonance shape is asymmetric; this asymmetry decreases with increasing , as expected in models in which the asymmetry is ascribed to the interference of resonant and non-resonant production. The cross section has been studied as a function of ; a fit to the resonant part with the form gives . The resonant part of the cross section is b at GeV. The dependence of the cross section can be described by a function of the type with (stat.) (syst.) GeV and (stat.) (syst.) GeV. The dependence has also been studied as a function of and a value of the slope of the pomeron trajectory GeV has been deduced. The spin density matrix elements , and have been measured and found to be consistent with expectations based on -channel helicity conservation. For proton-dissociative photoproduction in the mass range, the distributions of the two-pion invariant mass, and the polar and azimuthal angles of the pions in the helicity frame are the same within errors as those for the elastic process. The distribution has been fitted to an exponential function with a slope parameter GeV. The ratio of the elastic to proton-dissociative photoproduction cross section is . Received: 3 December 1997 / Online publication: February 26, 1998     

Three-body nuclear interactions in the QCD sum rules

The QCD sum rules used to calculate the characteristics of single-particle nucleons are reviewed briefly. The contribution from three-body forces to the nucleon self-energies are calculated.     

QCD sum rules at finite temperature

Finite energy and Laplace transform QCD sum rules atT0 are analyzed, and predictions for vacuum condensates are compared with the low temperature expansion of the energy density and pressure. Results show a serious disagreement which indicates a breakdown of the FESR programme already at dimension four, and which invalidates Laplace transform sum rules, at least in their straightforward extension to finite temperature.     

Symmetry energy from QCD sum rules

We review the symmetry energy in the context of AdS/CFT correspondence. After constructing D -brane configurations corresponding to dense system in boundary theory, we calculate the symmetry energy by solving DBI action of D branes in confining and deconfining phase. We conclude that the density dependence of the symmetry energy has scaling law, whose power depends only on the dimensionality of the branes and space-time.     

QCD sum rules with finite masses

The concept of QCD sum rules is extended to bound states composed of particles with finite mass such as scalar quarks or strange quarks. It turns out that mass corrections become important in this context. The number of relevant corrections is analyzed in a systematic discussion of the IR- and UV-divergencies, leading in general to a finite number of corrections. The results are demonstrated for a system of two massless quarks and two heavy scalar quarks.We wish to thank Dr. Lech Mankiewicz for very helpful discussions. This work was supported by DFG (G. Hess program).