Diphoton production in gluon fusion at small transverse momentum

We discuss the production of photon pairs in gluon-gluon scattering in the context of the position-space resummation formalism at small transverse momentum. We derive the remaining unknown coefficients that arise at $O(\alpha_S)$, as well as the remaining $O(\alpha_S^2)$ coefficient that occurs in the Sudakov factor. We comment on the impact of these coefficients on the normalization and shape of the resummed transverse momentum distribution of photon pairs, which comprise an important background to Higgs boson production at the LHC.Comment: 11 pages, 3 figures; minor changes, additional referenc

Diffractive Interactions: Theory Summary

I review various theory issues in diffraction that have been presented and discussed in the working group on diffractive interactions, and a few points concerning the comparison of theory with data.Comment: 9 pages, 3 figures. Talk given at the 7th International Workshop on Deep Inelastic Scattering and QCD (DIS 99), Zeuthen, Germany, 19-23 April 199

Next-to-leading order QCD corrections to hadron+jet production in pp collisions at RHIC

We compute the next-to-leading order QCD corrections to the spin-independent and spin-dependent cross-sections for the production of a single-hadron accompanied by an opposite jet in hadronic collisions. This process is being studied experimentally at RHIC, providing a new tool to unveil the polarized gluon distribution Delta g. We perform a detailed analysis of the phenomenological impact of the observable at NLO accuracy and show that the preliminary data by the STAR collaboration confirms the idea of a small gluon polarization in the 0.05<x<0.3 range.Comment: 16 pages, 11 Figures included. Minor typos correcte

Trends in commuter and leisure travel in The Netherlands 1991-2001 - Mode choice and travel time

Data collected over recent years indicates that there has been an increase in the average distance of trips made, in the Netherlands (e.g. in 1985 the average trip made was 8.7 km, in 2000 the average trip length was 10.6 km (Harms, 2003)). This paper uses a multi-level approach to look at the micro and macro level factors that affect the travel behaviour of individuals for commuting and leisure in the Netherlands over the last 10 years. A strong influence on the travel behaviour of an individual comes from the context of the household they belong to, the household operates with the context of the residential area in which they live, and all our behaviour is affected by our temporal location. The behaviour of individuals can be considered as dependent on context, and these contextual influences can be envisaged as nested. The multi-level approach allows us to simultaneously consider the impact of individual factors (such as gender), household factors (such as household income), and municipality level factors (such as local population density) and at the same time look at trends across time in commuting and leisure travel behaviour. The advantage of the multi-level approach is that it allows a wholistic approach, where not only aggregate or individual data is used to explain travel behaviour but both levels’ explanatory contributions are included in analyses conducted.

Global analysis of fragmentation functions for pions and kaons and their uncertainties

We present new sets of pion and kaon fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either pions or kaons identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions without the need of non trivial flavor symmetry assumptions. The resulting sets are in good agreement with all data analyzed, which cover a much wider kinematical range than in previous fits. An extensive use of the Lagrange multiplier technique is made in order to assess the uncertainties in the extraction of the fragmentation functions and the synergy from the complementary data sets in our global analysis.Comment: 28 pages, 25 figure

Transverse Momentum Distribution Through Soft-Gluon Resummation in Effective Field Theory

We study resummation of transverse-momentum-related large logarithms generated from soft-gluon radiations in soft-collinear effective field theory. The anomalous dimensions of the effective quark and gluon currents, an important ingredient for the resummation, are calculated to two-loop order. the result at next-to-leading-log reproduces that obtained using the standard method for deep-inelastic scattering, Drell-Yan process, and Higgs production through gluon-gluon fusion. We comment on the extension of the calculation to next-to-next-to-leading logarithms.Comment: 13 pages, one figur

Monte Carlo calculations of energy depositions and radiation transport. Volume 1 - Validation of COHORT codes

Monte Carlo codes for IBM 7090 digital computer to calculate radiation heating in propellant tanks, and radiation environment about nuclear rocket stag

Effects of gravitational darkening on the determination of fundamental parameters in fast rotating B-type stars

In this paper we develop a calculation code to account for the effects carried by fast rotation on the observed spectra of early-type stars. Stars are assumed to be in rigid rotation and the grid of plane-parallel model atmospheres used to represent the gravitational darkening are calculated by means of a non-LTE approach. Attention is paid on the relation between the apparent and parent non-rotating counterpart stellar fundamental parameters and apparent and true vsini parameters as a function of the rotation rate Omega/Omega_c, stellar mass and inclination angle. It is shown that omission of gravitational darkening in the analysis of chemical abundances of CNO elements can produce systematic overestimation or underestimation, depending on the lines used, rotational rate and inclination angle. The proximity of Be stars to the critical rotation is re-discussed by correcting not only the vsini of 130 Be stars, but also their effective temperature and gravity to account for stellar rotationally induced geometrical distortion and for the concomitant gravitational darkening effect. We concluded that the increase of the vsini estimate is accompanied by an even higher value of the stellar equatorial critical velocity, so that the most probable average rate of angular velocity of Be stars attains Omega/Omega_c ~ 0.88.Comment: 20 pages, 16 figures. Submitted for publication in A&

A New Fracture Function Approach to QCD Initial State Radiation

Ordinary fracture functions, describing hadrons production in the deep inelastic scattering target fragmentation region, are generalized to account for the production of hadrons in arbitrary number, thus offering a renewed framework for dealing with QCD initial state radiation. We also propose a new jet-like observable which measures beam remnants and low-$p_{\perp}$ scattering fragments and derive its QCD evolution equations by using Jet Calculus. Possible implications for semi-inclusive deep inelastic scattering and hadron-hadron reactions are shortly discussed.Comment: 10 pages, 5 figures, revtex