Testing gauge theories of weak interactions in the deep inelastic region

The analogs of the Adler sum rule and the Llewellyn-Smith relation for the Georgi-Glashow and Lee-Prentki-Zumino models for weak interactions, are derived. It is suggested that these could provide useful tests of the models.     

The diagrammatic structure of deep inelastic scattering in asymptotically free theories

We investigate the structure of the leading diagrams in QCD. The diagrams of a simple scalar gluon model form the basis of a generalisation to the more complicated vector gluon theory. It is found that a certain set of a generalised ladder diagrams gives the standard QCD result for the non-singlet structure function in the limit x → 1. A simple brems-strahlung model is presented which forms a useful link between QCD field theory and more intuitive parton formulations. The value of a diagrammatic treatment is that it provides an accessible approach to the discussion of other processes such as the Drell-Yan mechanism for heavy muon pair production.     

Comparison of asymptotically free theories with high-energy deep inelastic scattering data

Comparison of the predictionsof asymptotically free gauge theories on ? 1n vW₂(x, q²)|? 1n q² in the small x region with recent data on high-energy muon-hadron scattering allows a fairly direct determination of the effective coupling constant. The result is α(q²)?0.21/[1 + 0.14 1n q² (GeV²)]. This is much smaller than previous indirect estimates.     

Chiral effective field theories of the strong interactions

Effective field theories of the strong interactions based on the approximate chiral symmetry of QCD provide a model-independent approach to low-energy hadron physics. We give a brief introduction to mesonic and baryonic chiral perturbation theory and discuss a number of applications. We also consider the effective field theory including vector and axial-vector mesons.     

Absence of interaction in Lie field theories

It is shown that theories of relativistic Lie fields cannot lead to scattering or reactions, even if an infinite number of Lie fields is present.Supported in part by the National Science Foundation under Grant NSF GP 6036.     

Multi-jet event rates in deep inelastic scattering and determination of the strong coupling constant

Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant is determined evaluating the jet event rates. Values of are extracted in four different bins of the negative squared momentum transfer in the range from 40 GeV to 4000 GeV. A combined fit of the renormalization group equation to these several values results in     

Phenomenology of asymptotically free theories in deep inelastic scattering: (II). Neutrino scattering

The current neutrino inelastic charged current scattering data are shown to be in reasonable agreement with the predictions of simple four-flavour quark models with parameters determined from electroproduction. The data is consistent with the scale-breaking effects from asymptotic freedom that are included in the calculations. We discuss the uncertainty in the neutrino predictions coming from different parametrizations of electroproduction, the ambiguous extrapolation of the theory to low Q² and the effects of a non-zero value of R = σ_L/σ_T.     

Nonlinear two-photon interaction in a strong magnetic field

Sections of nonlinear photon-photon scattering processes and merger of photons in the nucleus (Ze) (Ze) in a strong magnetic field are computed by using a developed two-dimensional formalism. Closed expressions are obtained for the sections with a graphical illustration of the results and they are compared with the case of no external fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 16–19, June, 1988.     

Hard form factors for meson-baryon strong couplings as derived from deep inelastic lepton scattering

As stimulated by earlier attempts for obtaining theNN andN form factors from the deep inelastic lepton scattering data, we extend the analysis by taking into account effects of additional mesons including, , ,K, andK ^*, with the coupling constants fixed by the lowenergy nucleon-nucleon and hyperon-nucleon scattering data. Contrary to an earlier claim that the NN andN form factor must be very soft (e.g., with the cutoff mass less than 500 MeV in the monopole form), we find, for example, that with all form factors parametrized in the dipole form, a universal cutoff mass of 1150 MeV in the/N sector and 1400 MeV in the/ sector yields predictions in excellent agreement with recently published neutrino data on the momentum fractions carried by thes, , and¯d quarks, as well as consistent with the sea-to-valence ratio extracted from the CDHS data and the Femilab E615 experiment. Similar results can also be obtained by using exponential cutoffs for all couplings, or by using monopole forms for some vertices while retaining dipole forms for the rest. The success of the mesonexchange picture in generating the strangeness content in a proton suggests an alternative understanding of the origin of sea quarks in the proton.We wish to thank G. Garvey, K. Holinde, L.-C. Liu, M. B. Johnson, M. Strikman, A. W. Thomas and Jochen Wambach for helpful conversations. W-Y. P. Hwang wishes to acknowledge the Alexander von Humboldt Foundation for a fellowship to visit Jülich for conducting research. His research works was also supported in part by the National Science Council of the Republic of China. The work of G. E. Brown is supported in part by a Humboldt award, in part by NATO Grant RG85/0093, and in part by the U.S. Department of Energy.     

Effective interaction of a photon with a strong laser field

The problem of nonlocality of effective interaction of radiation field with a strong classical electromagnetic field has been investigated. The interaction operator allowing one to take into account the natural nonlocality of such a process is derived from the analysis of ordered diagrams of quantum electrodynamics.     

Phenomenology of asymptotically free theories in deep inelastic scattering: (I). Electron and muon scattering

We calculate the predictions of asymptotically free theories for deep inelasric scattering using a straightforward Mellin transform technique which uses a minimum of theoretical assumptions. Parameterizing the quark and anti-quark distributions functions, we fit all the available μ and e scattering data. We investigate the sensitivity of the theory of the (almost) unknown gluon distributions and the choice of scaling variable. The best fit uses the formalism of Georgi and Politzer for the 1/Q² terms with a quark gluon coupling constant g²/4π ～ 1 at Q² = 1 (GeV/c)². (Equivalently the scale parameter Λ is 500 MeV/c.) Good fits are also found in simpler models using x, x′ or ξ as scaling variables. The best value of Λ depends strongly on the choice of scaling variable.     

Hydrogen atom in a strong laser field: Numerical simulation versus Keldysh-type theories

The dynamics of a 3D hydrogen atom in an intense laser pulse is investigated using the direct numerical integration of the nonstationary Schrödinger equation in the multiphoton regime of ionization. The results obtained are compared with the theoretical data of the strong-field approximation (SFA) method and the validity of the SFA and other Keldysh-type theories in the problem of the strong-field ionization of atoms is analyzed in a wide range of laser frequencies and intensities. The Reiss approximation (SFA) provides qualitative agreement with the numerical simulation for moderate laser intensities and reveals the channel closing phenomena during the multiphoton ionization. However, this approach is found to be inappropriate in the presence of strong fields where we numerically demonstrate the suppression of atomic ionization. The reason for the stabilization lies in the formation of a new system (dressed atom), which is not taken into account in the SFA and other Keldysh-type theories.     

Polarized deep inelastic sum rules

New sum-rules for the polarized deep inelastic neutrino-nucleon cross sections are derived by applying the Melosh transformation to matrix elements of local currents and of local limits of the first derivatives of bilocal currents.     

Spin dependence of deep inelastic diffraction

Using a perturbative model for diffractive interactions, we derive an expression for the polarized diffractive structure function in the high energy limit. This structure function is given by the interference of diffractive amplitudes with polarized and unpolarized exchanges. For the polarized exchange we consider both two-gluon and quark-antiquark amplitudes. The polarized diffractive amplitude receives sizable contributions from non-strongly ordered regions in phase space, resulting in a double logarithmic enhancement at small x. The resummation of these double logarithmic terms is outlined. We also discuss the transition from our perturbative expression to the nonperturbative region. A first numerical estimate indicates that the perturbative contribution to the spin asymmetry is substantially larger than the nonperturbative one. Received: 7 July 1999 / Published online: 14 October 1999     

Hyperfine interaction in the presence of a strong nonmonochromatic laser field

We analyse in a simple and qualitative way how the properties of electromagnetic field jointly with hyperfine interaction affect the possible coherences between Zeeman sublevels of an atomic structure. We show that in the limit of a strong and/or broadband light hyperfine structure plays no role in creation of the Zeeman coherences.     

Probabilistic model for deep inelastic reactions

Due to transport phenomena in the interaction region, the dynamical variables in deep inelastic collision do not have sharp values at the end of the interaction. In the present model, they are considered as random variables with Gaussian probabilities centered on the classical results, while the Coulomb dynamics outside the interaction domain is treated exactly. Very simple formulas are obtained for multiple-differential cross-sections. Numerical results applied to the “quasi-fission” products of the reaction⁸⁴Kr(525 MeV)+²⁰⁹Bi agree fairly well with experimental data.     

Pion fluctuation in deep inelastic scattering

The forward neutron production in the ep collisions at 300GeV measured by H1 and ZEUS Collaborations at DESY has been used to estimate the total probability for proton fluctuation into nπ⁺ and pπ⁰. The probability found is on the order of 30%. This number is compared with the numbers obtained for the probability of quark fluctuation into π⁺ from several alternative DIS processes (Gottfried sum rule, polarized structure function) and the axial-vector coupling constant, where the pion fluctuation is believed to play an important role.