The resummation of inter-jet energy flow for gaps-between-jets processes at HERA

We calculate resummed perturbative predictions for gaps-between-jets processes and compare to HERA data. Our calculation of this non-global observable needs to include the effects of primary gluon emission (global logarithms) and secondary gluon emission (non-global logarithms) to be correct at the leading logarithm (LL) level. We include primary emission by calculating anomalous dimension matrices for the geometry of the specific event definitions and estimate the effect of non-global logarithms in the large $N_c$ limit. The resulting predictions for energy flow observables are consistent with experimental data.Comment: 31 pages, 4 figures, 2 table

A GLOBAL QCD STUDY OF DIRECT PHOTON PRODUCTION

A global QCD analysis of the direct photon production process from both fixed target and collider experiments is presented. These data sets now completely cover the parton $x$ range from 0.01 to 0.6, thereby providing a stringent test of perturbative QCD and parton distributions. Previous detailed studies of direct photons emphasized fixed target data. We find most data sets have a steeper $p_t$ distribution than the QCD prediction. Neither global fits with new parton distributions nor improved photon fragmentation functions can resolve this problem since the deviation occurs at different $x$ values for experiments at different energies. A more likely explanation is the need for additional broadening of the $k_t$ of the initial state partons. The magnitude and the possible physical origin of this effect are investigated and discussed.Comment: 8 page Latex file using epsf.sty for figures. 6 eps figures submitted separately in uuencoded file

Photoproduction of J/psi mesons at high energies in parton model and k_t-faktorization approach

We consider J/psi meson photoproduction on protons at high energies at the leading order in alpha_s using conventional parton model and k_t-factorization approach of QCD. It is shown that in the both cases the colour singlet mechanism gives correct description for experimental data from HERA for the total cross section and for the J/psi meson z-spectrum at realistic values of a c-quark mass and meson wave function at the origin Psi (0). At the same time our predictions for p_t-spectrum of J/psi meson and for p_t dependence of the spin parameter alpha obtained in k_t-factorization approach are very different from the results obtained in conventional parton model. Such a way the experimental study of a polarized J/psi meson production at the large p_t should be a direct test of BFKL gluons.Comment: LaTeX2e, 11 pages plus 8 fig. using epsfig.st

W boson production at hadron colliders: the lepton charge asymmetry in NNLO QCD

We consider the production of W bosons in hadron collisions, and the subsequent leptonic decay W->lnu_l. We study the asymmetry between the rapidity distributions of the charged leptons, and we present its computation up to the next-to-next-to-leading order (NNLO) in QCD perturbation theory. Our calculation includes the dependence on the lepton kinematical cuts that are necessarily applied to select W-> lnu_l events in actual experimental analyses at hadron colliders. We illustrate the main differences between the W and lepton charge asymmetry, and we discuss their physical origin and the effect of the QCD radiative corrections. We show detailed numerical results on the charge asymmetry in ppbar collisions at the Tevatron, and we discuss the comparison with some of the available data. Some illustrative results on the lepton charge asymmetry in pp collisions at LHC energies are presented.Comment: 37 pages, 21 figure

The fully differential single-top-quark cross section in next-to-leading order QCD

We present a new next-to-leading order calculation for fully differential single-top-quark final states. The calculation is performed using phase space slicing and dipole subtraction methods. The results of the methods are found to be in agreement. The dipole subtraction method calculation retains the full spin dependence of the final state particles. We show a few numerical results to illustrate the utility and consistency of the resulting computer implementations.Comment: 37 pages, latex, 2 ps figure

When the boundaries are blurred: the significance of feminist methods in research

This article focuses on the ways that the author’s somewhat in-between position as both an outsider/researcher and an insider/ex-political Iranian activist now in exile has contributed to the process of research on Iranian women exiles in the Netherlands and the United States. Feminist attention on life stories as a method, and feminist anthropologists’ attention to particularity, involvement and reflexivity give the author the space, and inspire her, to explore the issue of positioning. This makes it possible for her to engage with the issues of home, identity and belonging, not only as a scholar but also as a woman in exile. In this way, the reflexivity resulting from this involvement enables her to reevaluate her own identity, sense of belonging, and life in exile, next to rethinking these essential themes within the social sciences on the theoretical level. The blurred boundary of the self and the other in her research has its moments of complication, but in the end, these complicated moments seem to be not only necessary but rewarding, in many ways

The neutrino cross section and upward going muons

The charged current cross section for neutrinos with energy of a few GeV is reanalysed. In this energy range the cross section for the lowest multiplicity exclusive channels is an important fraction of $\sigma_{CC}$ and the approximation of describing the cross section with deep inelastic scattering formulae may be inaccurate. Possible consequences of our reanalysis of the cross section in the interpretation of the data obtained by deep underground detectors on $\nu$--induced upward going muons (both stopping and passing) are discussed.Comment: 9 pages, REVTEX, 1 uu-encoded compressed file with 3 figure

Ioffe-time distribution of quarks in the photon

We have analysed the Ioffe-time distribution of quarks in virtual photons using Operator Product Expansion of the correlation function that determines the matrix element of the corresponding quark string operator. The distribution for a transversally polarised photon admits a spectral representation which can be continued to the on-shell region $p^2 =0$. The resulting model Ioffe-time distribution turns out to be larger than parametrisations of the available $F_2^{\gamma}$ data. This result is linked to the slope of the quark distribution at the origin, which comes out too large as well.Comment: 12 pages, LaTex, one uuencoded figur