Gnome model and deep-inelastic lepton-nucleon structure functions

We investigate the gnome model for hadrons, a nonet scheme which has been proposed as an alternative to the quark model and which avoids certain well-known difficulties of the latter concerning fractional charge, spin and statistics. It is found that the gnome model gives the same results as the quark model for semi-leptonic decay and electromagnetic transition matrix elements. The bounds for deep-inelastic lepton-nucleon structure functions are not as restrictive as the ones from the quark model if only SU(2) invariance is imposed. SU(3) invariance together with duality gives more restrictiven bounds.     

Charm structure functions and gluon shadowing effects with the AdS/CFT model

By means of the UGD function extracted from an AdS/CFT inspired saturation model, the charm and bottom structure functions are studied in fixed-order perturbation theory. It is shown that the theoretical results are in good agreement with the recent HERA data. Then, this UGD function is also used to investigate net-kaon rapidity distribution in Au+Au collisions at RHIC energies and the theoretical results fit well to the BRAHMS data. In the end of this paper, we give the predicted results for nuclear charm structure function at very small x where the popular shadowing parameterizations are invalid.     

Quark charges and colour gluon mass from deep-inelastic bremsstrahlung

We derive sum rules for the structure functionV(x) for the ‘three-photon’ processe ^±+p→e ^±+γ+X which can distinguish between various colour models below colour threshold, independently of the quark and gluon distributions. A careful study of the sum rule forV(x) in the broken colour gauge theory model can in principle be used to determine the colour gluon mass. Invoking the specific assumptions of the dominance ofp-type quarks and neglecting the sea of quark-antiquark pairs, we also obtain bounds forV(x) in terms ofvW ₂ (x) which can distinguish between various colour models below colour threshold.     

Quark antisymmetrization and deep-inelastic scattering II. Nuclear structure functions

We consider the effects of quark antisymmetrization for nuclear structure functions. Antisymmetrizing the naive folding of nuclear wave functions in terms of nucleons and the nucleon wave function in terms of quarks, introduces additional contributions. Using the calculated results on quark three-momentum distributions, we calculate the effects on the deep-inelastic structure functions for s- and p-wave nuclei. The effects of quark antisymmetrization turn out to be small.     

The pomeron structure in DIS and gluon recombination effects

A formalism for diffractive deep inelastic scattering is presented based on the concept of a pomeron structure function. Assuming the pomeron to be essentially a gluonic object with the small size indicated by its small interaction cross-sections, we show that the QCD evolution of its structure function exhibits large screening corrections due to gluon recombinations at small-χ. With a gluon-to-quark conversion appropriate at small-χ, diffractiveep cross-sections are obtained giving large enough statistics at HERA to distinguish between QCD evolution governed by the conventional Altarelli-Parisi equations and by the non-linear Gribov-Levin-Ryskin equation.     

Twist-4 gluon recombination corrections for deep inelastic structure functions

We calculate twist-4 coefficient functions for the deep inelastic structure function F₂(x,Q²) associated to 4-gluon operator matrix elements for general values of the Bjorken variable x and study the numerical effect on the slope ∂F₂(x,Q²)/∂logQ². It is shown that these contributions diminish the strongly rising twist-2 terms towards small values of x.     

Higher-twist effects in deep-inelastic scattering

Non-scaling, non-factorizing 1/Q² contributions to cross sections are derived for semi-inclusive deep-inelastic scattering, ?N → ?′πX. These higher twist terms are dominant at large z = p_π · p_N/Q · p_N. They provide unusual (1 ? y) terms in the cross section. as well as asymmetries in the azimuthal angle dependence. Calculations are also presented for the quark to pion fragmentation function D_π(z, Q²).     

Longitudinal-transverse separations of deep-inelastic structure functions at low Q2 for hydrogen and deuterium

We report on a study of the longitudinal to transverse cross section ratio, R=sigmaL/sigmaT, at low values of x and Q2, as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Laboratory Hall C spanning the four-momentum transfer range 0.06相似文献   

Analytic expression for the joint x and Q2 dependences of the deep-inelastic structure functions

We obtain a good analytic fit to the joint Bjorken-x and Q2 dependences of ZEUS data on the deep-inelastic structure function F(2)(p)(x,Q2). At fixed virtuality Q2, as we showed previously, our expression is an expansion in powers of ln(1/x) that satisfies the Froissart bound. Here we show that for each x, the Q2 dependence of the data is well described by an expansion in powers of lnQ2. The resulting analytic expression allows us to predict the logarithmic derivatives (partial differential(n)F(2)(p)/(partial differentiallnQ2)n)x for n=1,2 and to compare the results successfully with other data. We extrapolate the proton structure function F(2)(p)(x,Q2) to the very large Q2 and the very small x regions that are inaccessible to present-day experiments and contrast our expectations with those of conventional global fits of parton distribution functions.     

Quark and gluon fragmentation functions into photons

The fragmentation functions of quarks and gluons into photons are studied beyond the Leading Logarithm approximation. We address the nature of the initial conditions of the evolution equation solutions and study problems related to factorization scheme invariance. The possibility of measuring these distributions in LEP experiments is discussed, and a comparison with existing data is made. Received: 28 May 1997 / Published online: 20 February 1998     

Nuclear effects in the structure functions

By using a relativistic framework and accurate nuclear spectral function the structure functions F_2A andF _3A of deep inelastic charged lepton and neutrino scattering are calculated in nuclei and results are presented.     

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.     

Soft gluon radiation in Higgs boson production at the LHC

We examine the contributions of soft gluons to the Higgs production cross section at the LHC in the Standard Model and its minimal supersymmetric extension. The soft gluon radiation effects of this reaction share many features with the Drell-Yan process, but arise at lowest order from a purely gluonic initial state. We provide an extension of the conventional soft gluon resummation formalism to include a new class of contributions which we argue to be universal, and resum these and the usual Sudakov effects to all orders. The effect of these new terms is striking: only if they are included, does the expansion of the resummed cross section to next-to-leading order reproduce the exact result to within a few percent for the full range of Higgs boson masses. We use our resummed cross section to derive next-to-next-to-leading order results, and their scale dependence. Moreover, we demonstrate the importance of including the novel contributions in the resummed Drell-Yan process.