Timelike and spacelike QCD characteristics of the e^+e^- annihilation process

We consider the Adler D-function, which is defined in the spacelike region, and the annihilation ratio smeared, according to the Poggio, Quinn, and Weinberg method, which is determined for timelike argument. We show that the method of the nonperturbative a-expansion allows one to describe these Euclidean and Minkowskian characteristics of the process of annihilation down to the lowest energy scales. Received: 23 November 1999 / Published online: 6 March 2000     

Next-to-leading-order QCD correction to e(+)e(-)-->J/psi+eta(c) at sqrt[s]=10.6 GeV

One of the most challenging open problems in heavy quarkonium physics is the double charm production in e+e- annihilation at B factories. The measured cross section of e+e- --> J/psi + eta(c) is much larger than leading order (LO) theoretical predictions. With the nonrelativistic QCD factorization formalism, we calculate the next-to-leading order (NLO) QCD correction to this process. Taking all one loop self-energy, triangle, box, and pentagon diagrams into account, and factoring the Coulomb-singular term into the cc bound state wave function, we get an ultraviolet and infrared finite correction to the cross section of e+e- --> J/psi + eta(c) at sqrt[s] = 10:6 GeV. We find that the NLO QCD correction can substantially enhance the cross section with a K factor (the ratio of NLO to LO) of about 1.8-2.1; hence, it greatly reduces the large discrepancy between theory and experiment.     

QCD JET IN POLARIZED e+e－ ANNIHILATION

Following perturbative QCD theory, the two-jet and three-jet angular distributions in polarized e⁺e^－ annihilation is computed using the dimensional regularization scheme. The azimuthal inhomogeneity caused by the polarization is discussed. We also compute the exact formulae of dependence on ε´,δ to the second order and discuss the correction to G.Sterman and S.Weinberg's result.     

Higgs-boson pairproduction ine + e − reactions

We calculate the production cross section of Higgs-boson pairs ine ⁺ e ^? annihilation. In this reaction the lowest order contribution comes from one loop graphs. We study the behaviour of the cross section as a function of the energy, the Higgs-boson mass and the scattering angle.     

Radiative muon pair production in high-energy electron-positron annihilation process

The lowest order radiative correction to the differential cross section of process of muon pair production with the emission of a hard photon at high energy electron-positron annihilation are calculated. Taking into account the emission of additional soft and hard photon, the cross section can be put in the form of the Drell-Yan process in leading logarithmical approximation. Applying the crossing transformation, we obtain the cross section of the radiative electron-muon high-energy scattering process. Virtual and soft photon emission contributions of the nonleading form are tabulated for several typical kinematical points. The limit of the small invariant mass of a muon pair is in agreement with our previous analysis.     

Cross sections for five jet production above theW + W − threshold ine + e − annihilation

We describe the calculation of five jet production from theW ⁺ W ^– intermediate state ine ⁺ e ^– annihilation in lowest order QCD. Some results for integrated cross-sections are presented.     

On the decay of θ mesons in charmonium models

We derive a new formula for the decay rate of the ψ mesons by properly treating the dependence of lowest order electromagnetic annihilation on the quark-antiquark bound state wave function. Results are presented for currently used non-relativistic potentials models for charmonium. In all cases substantial corrections to previous estimates from commonly used formulas occur. Our results are of relevance also for hadronic decay via gluons in QCD and weak decay of pseudoscalar mesons.     

The Gribov-Lipatov relation in QCD

We analyse and calculate the structure functions of both deep inelastic leptoproduction ande ⁺ e ^? annihilation in QCD and in the parton model in a way which brings out the similarities and differences between the two situations. In particular we give a probability interpretation of the Gribov-Lipatov relation for quarks in QCD. The relation does not hold for hadronic structure functions but we determine its modified consequences for this case. A generalised Drell-Yan conjecture is also discussed and verified to lowest order in QCD.     

Low mass dielectrons at LHC energy

We study the thermal production of low mass dielectrons in central nucleus-nucleus collisions at LHC energy. We assume initial quark-gluon plasma production, followed by a first order quark-hadron phase transition and subsequent hadronization; the expansion of the system is described by Bjorken's hydrodynamical model. In the quark-gluon plasma, we include both the basisq annihilation process and lowest order QED and QCD corrections. In the hadronic phase, we consider pion annihilation as well as pion scattering with virtual bremsstrahlung leading to dielectron production. Our results are then compared to dielectron rates from ⁰ and Dalitz decays. We conclude that it will be rather difficult to disentangle the quark-gluon plasma contributions from competing dielectron production processes.     

Nonperturbative, Unitary Quantum-Particle Scattering Amplitudes from Three-Particle Equations

We here use our nonperturbative, cluster decomposable relativistic scattering formalism to calculate photon–spinor scattering, including the related particle–antiparticle annihilation amplitude. We start from a three-body system in which the unitary pair interactions contain the kinematic possibility of single quantum exchange and the symmetry properties needed to identify and substitute antiparticles for particles. We extract from it a unitary two-particle amplitude for quantum–particle scattering. We verify that we have done this correctly by showing that our calculated photon–spinor amplitude reduces in the weak coupling limit to the usual lowest order, manifestly covariant (QED) result with the correct normalization. That we are able to successfully do this directly demonstrates that renormalizability need not be a fundamental requirement for all physically viable models.     

Soft gluon corrections to hard quark-quark scattering sub-processes

We sum the double-logarithmic contributions in all orders to quark-(anti) quark scattering and annihilation amplitudes. The Born cross sections are multiplied by correction factors, which are large in certain kinematical regions. We discuss the difference of the large p_⊥ cross sections in proton-proton and proton-antiproton scattering and the away-side energy flux distribution out of the trigger plane.     

Simulation of QCD jets: The choice of the cutoff

In view of the simulation ofe ⁺ e ^? annihilation events corresponding to QCD multi-jet final states, we examine the dependence of the results on the value of the cutoff, which delimits the perturbative from the non-perturbative regimes. We do this by studying in some detail related effects for the lowest order perturbative contributions (including single gluon emission). We conclude that event simulation is considerably affected by the choice of the cutoff. Up to energies where only two and three jet configurations are dominant, though, this does not prevent from having quantitative tests of QCD, if suitable kinematical cuts are applied.     

Radiative corrections in nucleon time-like form factors measurements

The completely general radiative corrections to lowest order, including the final- and initial-state radiations, are studied in proton-antiproton annihilation into an electron-positron pair. Numerical estimates have been made in a realistic configuraton of the PANDA detector at FAIR for the proton time-like form factors measurements.     

Jets from heavy quarks ine + e − annihilation

The quark mass effects in the jet structure ine ⁺ e ^? annihilation into hadrons are studied in the lowest nontrivial O(α _s ) order of QCD perturbation theory.     

HIGH-ORDER CRANKING CALCULATION IN THE INTERACTING BOSON MODEL AND INTERACTING BOSONFERMION MODEL

Considering that the IBM and IBFM cranking calculations in the lowest order of angular frequency can give reasonably good estimates for the moment of inertia,we extend them to study the dependence of the moment of inertia on the higher order terms.We find that the analytic expressions for the correction terms can be derived.Numerical calculations for ¹⁵⁴Gd and ¹⁶¹Er are performed and compared with experiment.The Hamiltonian is taken from a microscopic approach.Calculated results show that the properties of higher order terms depend on the deformation of rotating system but the correction yields only limited effect when ω is small.     

Low-energy gluon to the vacuum polarization of heavy quarks

We calculate a correction to the effective electromagnetic current at low energies, induced by a heavy-quark loop, and determine the analytic structure of the vacuum polarization function at small q ², for which an explicit expression is given to the O(α _s ³ ) order of perturbation theory. Implications to the high-precision analysis of experimental data on heavy-quark production in e ⁺ e ^? annihilation are discussed.     

SU(3) analysis of annihilation contributions and CP violating relations in B\to P P decays

Several methods proposed to measure the angle in the KM unitarity triangle assumed that the tree contribution to is purely due to annihilation contributions and is negligibly small. This assumption has to be tested in order to have a correct interpretation of the experimental data. In this paper we show that using SU(3) symmetry, the smallness of the tree contribution can be tested in a dynamic model-independent way. We also derive several relations between CP violating rate differences for decays without assuming the smallness of the annihilation contributions. These relations provide important tests for the standard model of CP violation. Received: 5 January 1999 / Revised version: 4 March 1999 / Published online: 18 June 1999     

Lattice calculation of the lowest-order hadronic contribution to the muon anomalous magnetic moment

We present a quenched lattice calculation of the lowest order [O(alpha(2))] hadronic contribution to the anomalous magnetic moment of the muon which arises from the hadronic vacuum polarization. A general method is presented for computing entirely in Euclidean space, obviating the need for the usual dispersive treatment which relies on experimental data for e(+)e(-) annihilation to hadrons. While the result is not yet of comparable precision to those state-of-the-art calculations, systematic improvement of the quenched lattice computation to this level is straightforward and well within the reach of present computers. Including the effects of dynamical quarks is conceptually trivial; the computer resources required are not.     

Quantum corrections for Boltzmann equation

We present the lowest order quantum correction to the semiclassical Boltzmann distribution function, and the equation satisfied by this correction is given. Our equation for the quantum correction is obtained from the conventional quantum Boltzmann equation by explicitly expressing the Planck constant in the gradient approximation, and the quantum Wigner distribution function is expanded in powers of Planck constant, too. The negative quantum correlation in the Wigner distribution function which is just the quantum correction terms is naturally singled out, thus obviating the need for the Husimi’s coarse grain averaging that is usually done to remove the negative quantum part of the Wigner distribution function. We also discuss the classical limit of quantum thermodynamic entropy in the above framework. Supported by the National Natural Science Foundation of China (Grant No. 10404037) and the Scientific Research Fund of GUCAS (Grant No. 055101BM03)     

符合多普勒展宽谱的源修正研究

测量了Ti,Ni,Cu,Al以及Si的符合多普勒展宽谱。对于Ni的多普勒展宽谱,采用最小二乘法拟合得出其中的源强度。给出了源修正前后湮没量子在Si中的多普勒展宽谱,讨论了源成分的影响。用高斯-抛物线模型拟合多普勒展宽谱,将多普勒展宽谱中自由电子的湮没贡献和束缚电子的湮没贡献分开,进而探讨了只对束缚电子的湮没贡献做源修正的方法。In the present work, Coincidence Doppler Broadening （CDB） measurements have been performed for five elements i.e. Ti, Ni, Cu, Al and Si. As to the CDB spectra of Ni, we obtained the annihilation fraction of positron-electron pairs in the source by least square fitting. After source correction, spectra for Si are also given to indicate the influence of source components. CDB spectra were simulated with Gauss-Parabola model to separate annihilation contribution of core electrons from outermost electrons. Furthermore, a new source correction method, i.e. source correction will be done only in the contribution of core electron, has been presented