New sum rules for polarized deep inelastic scattering

Relations between the structure functions g₁ and g₂ of polarized DIS are derived in the leading perturbative QCD approximation, starting with the sum rules for twist-3 parton correlation functions which follow from gauge invariance and the equation of motion of the quark fields. For the first moments they coincide with the approximate relations proposed earlier by Wandzura and Wilczek as well as Bukhvostov, Kuraev and Lipatov.     

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.     

Radiative corrections to the structure functions and sum rules in polarized dis

The one-loop NLO radiative corrections (RC) to the observables in polarized DIS using assumption that a quark is an essential massive particle are considered. If compared with classical QCD formulae the obtained results are identical for the unpolarized and different for polarized sum rules, that can be explained as the influence of the finite quark mass effects on NLO QCD corrections. The explicit expression for one-loop NLO QCD contribution to the structure function g ₂ is presented.     

Constraints on penguins from hadronic sum rules

We have derived an upper bound on the K-π transition amplitude of the penguin operator using hadronic sum rules. Combined with an anomalous-commutator contribution, this sets lower and upper limits on the physical K → 2π amplitude of the penguin operator. Applying this result to CP-violating effects, we find that the Gilman-Hagelin lower limit on ?′/? decreases by an order of magnitude.     

New contributions to heavy quark sum rules

We analyze new contributions to the theoretical input in heavy quark sum rules and we show that the general theory of singularities of perturbation theory amplitudes yields the method to handle these specific features. In particular we study the inclusion of heavy quark radiation by light quarks at and of non-symmetric correlators at . Closely related with this is that we also propose a solution to the construction of moments of the spectral densities at where the presence of massless contributions invalidates the standard approach. We circumvent this problem through a new definition of the moments, providing an infrared safe and consistent procedure. Received: 11 February 2002 / Revised version: 14 March 2002 / Published online: 22 May 2002     

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.     

A numerical study of resonance contributions to nuclear sum rules

The modified form of the nuclear sum rule which was proposed by Berggren is applied to a simple solvable problem and it is demonstrated, within the confines of that problem, that the continuum contribution to the sum rule is often dominated by the contribution from a few resonances, just as Berggren had anticipated. It is further shown that the bound, virtual and resonant states of the Hamiltonian considered form a complete set of states in terms of which the internal region of space can be expanded.     

Light quark masses from scalar sum rules

In this work, the mass of the strange quark is calculated from QCD sum rules for the divergence of the strangeness-changing vector current. The phenomenological scalar spectral function which enters the sum rule is determined from our previous work on strangeness-changing scalar form factors [1]. For the running strange mass in the scheme, we find . Making use of this result and the light quark mass ratios obtained from chiral perturbation theory, we are also able to extract the masses of the lighter quarks and . We then obtain and . In addition, we present an updated value for the light quark condensate. Received: 18 October 2001 / Revised version: 22 January 2002 / Published online: 12 April 2002     

Revisiting hidden-charm pentaquarks from QCD sum rules

We revisit hidden-charm pentaquark states P_c(4380) and P_c(4450) using the method of QCD sum rules by requiring the pole contribution to be greater than or equal to 30% in order to better that the one-pole parametrization is valid. We find two mixing currents, and our results suggest that P_c(4380) and P_c(4450) can be identified as hiddencharm pentaquark states having J~P= 3/2~-and 5/2~+, respectively. However, there still exist other possible spin-parity assignments, such as J~P = 3/2~+ and J~P = 5/2~-, which must be clarified in further theoretical and experimental studies.     

TheA 1 width from Weinberg's sum rules

The Weinberg sum rules have been successfully exploited to obtain the width of A₁(1080) meson. Agreement with experiment is good.     

Compressibility of hadrons from operator sum rules

Monopole sum rules for ar ² transition operator are discussed for baryons and mesons. From these, the energy of the compression modes can be directly related to the hadronic compressibility. From the systematics of excited hadrons the compressibility of baryons is found to be in the order of 1.3 GeV, quite close to that of mesons in the light and strange quark sector. Experiments will be very important to study the compression modes in different hadron systems.The author is indepted to the Institute of Nuclear Theory (INT Seattle) for the invitation to the program N ^* Excitations and the Structure of the Nucleon where basic ideas of the paper have been discussed. In particular, discussion with O. Bohigas, B.K. Jennings, and J. Wambach is gratefully acknowledged.     

Nucleon charge radius from QCD sum rules

The proton and neutron electric radii are calculated within QCD using the sum rules method for processes with small momentum transfers. The agreement with experimental values is good for the proton radius and somewhat poorer for the neutron one due to the numerical smallness.     

Self-consistent mean-field theory,progenitor sum rules,and the giant dipole resonance

Self-consistent mean-field theory gives an expression for the giant dipole resonance energy which depends on κ (the enhancement of the dipole sum rule by exchange currents). The value of κ needed to fit the GDR is much smaller than that obtained from the integrated photoabsorption cross section, in Suzuki's treatment. A corrected treatment which resolves this discrepancy is given here.     

Evaluation of the Skyrme parameter from QCD sum rules

The dimensionless parameter of the Skyrme lagrangian is evaluated by two methods. In one a combination of sum rules for the nucleon and the pion is used, in the other only baryonic sum rules. e = 5−8 and e = 5−7 is found, respectively, in agreement with the phenomenological value e = 5.45. To leading order in the operator-product expansion the analytical expression of e does not depend on the chiral-symmetry-breaking parameters.     

Infrared renormalons and the relations between the Gross-Llewellyn Smith and the Bjorken polarized and unpolarized sum rules

It is demonstrated that the infrared renormalon calculus indicates that the QCD theoretical expressions for the Gross-Llewellyn Smith sum rule and for the Bjorken polarized and unpolarized ones contain an identical negative twist-4 1/Q² correction. This observation is supported by the consideration of the results of calculations of the corresponding twist-4 matrix elements. Together with the indication of the similarity of the perturbative QCD contributions to these three sum rules, this observation leads to simple new theoretical relations between the Gross-Llewellyn Smith and Bjorken polarized and unpolarized sum rules in the energy region Q² ≥ 1 GeV². The validity of this relation is checked using concrete experimental data for the Gross-Llewellyn Smith and Bjorken polarized sum rules.     

Limits on anomalous top couplings from Z pole physics

We obtain constraints on possible anomalous interactions of the top quark with the electroweak vector bosons arising from the precision measurements at the Z pole. In the framework of SU(2)_L ⊗ U(1)_Y chiral Lagrangians, we examine all effective CP-conserving operators of dimension five which induce fermionic currents involving the top quark. We constrain the magnitudes of these anomalous interactions by evaluating their one-loop contributions to the Z pole physics. Our analysis shows that the operators that contribute to the LEP observables get bounds close to the theoretical expectation for their anomalous couplings. We also show that those which break the SU(2)_C custodial symmetry are more strongly bounded.