Sökresultat

The hadronic decays of the τ lepton can be used to determine the effective charge ατ(m τ 2,) for a hypothetical τ lepton with a mass in the range 0

Dressed Gluon Exponentiation (DGE) is used to calculate the thrust and the heavy-jet mass distributions in e + e - annihilation in the two-jet region. We perform a detailed analysis of power corrections, taking care of the effect of hadron masses on the meas

We investigate the relation between a postulated skeleton expansion and the conformal limit of QCD. We begin by developing some consequences of an Abelian-like skeleton expansion, which allows one to disentangle running-coupling effects from the remaining skeleton coefficients. The latter are by construction renormalon free, and hence hopefully better behaved. We consider a simple ansatz for the e

We calculate the potential between two static quarks in QCD using modified boundary conditions for the perturbative expansion. Through a change of the Feynman prescription we effectively add a "sea" of gluons to the asymptotic states with energies below a given scale A. We find that the standard result for the static potential gets corrections of order A 2/Q 2 both at small and large momentum tran

The thrust distribution in e+e- annihilation is calculated exploiting its exponentiation property in the two-jet region t=1-T≪1. We present a general method (DGE) to calculate a large class of logarithmically enhanced terms, using the dispersive approach in renormalon calculus. Dressed Gluon Exponentiation is based on the fact that the exponentiation kernel is associated primarily with a single gl

The interaction potential V(Q2) between static test charges can be used to define an effective charge αv(Q2) and a physically based renormalization scheme for quantum chromodynamics and other gauge theories. In this paper we use recent results for finite-mass fermionic corrections to the heavy-quark potential at two loops to derive the next-to-Ieading order term for the Gell-Mann-Low function of t

A new model for hadronic string reinteractions based on a generalised area law is presented. The model describes both the hadronic final states in e+ e- annihilation and the diffractive structure function in deep inelastic scattering. The model also predicts a shift in the W-mass reconstructed from hadronic decays of W-pairs of the order 65 MeV.

We show that the asymmetry in the fractional energy of charm versus anticharm jets produced in high energy diffractive photoproduction is sensitive to the interference of the Odderon (C=-) and Pomeron (C=+) exchange amplitudes in QCD. We predict the dynamical shape of the asymmetry in a simple model and estimate its magnitude to be of the order 15% using an Odderon coupling to the proton which sat

The conventional definition of the running coupling (Formula presented) in quantum chromodynamics is based on a solution to the renormalization group equations which treats quarks as either completely massless at a renormalization scale μ above their thresholds or infinitely massive at a scale below them. The coupling is thus nonanalytic at these thresholds. In this paper we present an analytic ex

Membrane processes are often competing directly with conventional separation processes. The aim of this study is to highlight the potentials of combinations of membrane processes and conventional separation processes by the means of hybrid processes and process synergies. The concepts of hybrid processes and process synergies will be introduced and defined supported by industrial examples, e.g.

Physics and programming aspects are discussed for a Fortran 77 Monte Carlo program to simulate complete events in deep inelastic lepton-nucleon scattering. The parton level interaction is based on the standard model electroweak cross sections, which are fully implemented in leading order for any lepton of arbitrary polarization, and different parametrizations of parton density functions can be use

In the last half of the twelfth century, canon law established the rule that a marriage could be declared invalid if the consent had been given through force or fear. This ruling was a natural consequence of the insistence on free consent as the only requirement for a valid marriage. It did, however, entail a number of both practical and theoretical problems. It could be difficult to prove force a

The differences between two standard Monte Carlo models, LEPTO and ARIADNE, for deep inelastic scattering at small-χ is analysed in detail. It is shown that the difference arises from a 'unorthodox' suppression factor used in ARIADNE which replaces the normal ratio of parton densities. This gives rise to a factor that qualitatively is similar to what one would expect from BFKL dynamics for some ob

A program to simulate the production of heavy quarks through the boson-gluon fusion process in e±p collisions is presented. The full electroweak structure of the electron-gluon interaction is taken into account as well as the masses of the produced heavy quarks. Higher order QCD radiation is treated using initial and final state parton showers, and hadronization is performed using the Lund string

The Monte Carlo generator MAJOR 1.5 simulates the production and decay of heavy Majorana neutrinos via lepton mixing or exchange of 'light' right-handed W-bosons in deep inelastic scattering, i.e. e±p → NX → e±W∓X or veZX. Physics and programming aspects are described in this manual.

We show that the 'orthogonal' characteristics of the observed rapidity gaps and large forward energy flows in deep inelastic scattering at HERA, can be described within a single framework. Our Monte Carlo model is based on perturbative QCD matrix elements and parton showers together with Lund string model hadronization, but has in addition a new mechanism for soft colour interactions which modifie

The direct charmonium and bottomonium production rate observed at high [Formula presented] in [Formula presented] collisions at the Fermilab Tevatron is factors of 10 larger than predictions based on conventional perturbative QCD. We show that this excess can be accounted for by our model for soft color interactions, previously introduced to describe in a novel way the large rapidity gap events ob