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The ongoing and planned experimental activities with direct reference to light unflavoured pseudoscalar mesons motivate a new theoretical study regarding their properties. An overview including details on new precise calculations is presented.
In high energy collisions saturation and multiple collisions are most easily accounted for in transverse coordinate space, while analyses in momentum space have been more suitable for calculating properties of exclusive final states. In this paper I describe an extension of Mueller's dipole cascade model, which attempts to combine the good features of both these descriptions. Besides saturation it
We extend our earlier work on the massive O(N) non-linear sigma model to other observables. We derive expressions at leading order in the large N expansion at all orders in the loop expansion for the decay constant, vacuum expectation value, meson meson scattering and the scalar and vector form factors. This is done using cactus diagram resummation using a generalized gap equation and other recurs
In this Letter we analyze the relation between the triple-pomeron and Good-Walker formalism's for diffractive excitation in DIS and hadronic collisions. In both approaches gap events are interpreted as the shadow of absorption into inelastic channels. We here argue that the two formalisms are just different views of the same phenomenon. We first demonstrate how this relation works in a simple toy
The medium-induced one-gluon radiation spectrum off a massive quark-antiquark (q (q) over bar) antenna traversing a colored QCD medium is calculated in this contribution. The gluon spectrum off the antenna computed at first order in the opacity expansion is collinear finite but infrared divergent, which is different from the result obtained from an independent emitter which is both infrared and co
We present a consistent way of combining associated weak boson radiation in hard dijet events with hard QCD radiation in Drell-Yan-like scatterings. This integrates multiple tree-level calculations with vastly different cross sections, QCD- and electroweak parton-shower resummation into a single framework. The new merging strategy is implemented in the PYTHIA event generator and predictions are co
It is well known that spectroscopic measurements suffer from an interference known as stray light, causing spectral distortion that reduces measurement accuracy. In severe situations, stray light may even obscure the existence of spectral lines. Here a novel general method is presented, named Periodic Shadowing, that enables effective stray light elimination in spectroscopy and experimental result
Adopting the hypothesis about the exact cancellation of vacuum condensates contributions to the ground state energy in particle physics to the leading order in graviton-mediated interactions, we argue that the observable cosmological constant can be dynamically induced by an uncompensated quantum gravity correction to them after the QCD phase transition epoch. To start with, we demonstrate a possi
We consider the diffractive Drell-Yan process in proton-(anti) proton collisions at high energies in the color dipole approach. The calculations are performed at forward rapidities of the leptonic pair. The effect of eikonalization of the universal "bare" dipole-target elastic amplitude in the saturation regime takes into account the principal part of the gap survival probability. We present predi
We present a formalism which modifies the Mueller Dipole Model such that it incorporates energy-momentum conservation and also important colour suppressed effects. We implement our formalism in a Monte Carlo simulation and compare the results to inclusive data from HERA and the Tevatron, where we see that there is a good agreement between the data and our model.
We calculate the one-loop effective action of the SU(2) Yang-Mills theory for center-vortex configurations, both in 3D and 4D. We find that in both cases there are minima of the effective action, corresponding to vortices of the transverse size approximately 4/g(3)(2) and 1.7/Lambda((MS) over bar), respectively. The values of the effective actions at the minima are negative, suggesting that the Eu
HERA provides a unique possibility to investigate the dependence of multiple interactions on transverse interaction sizes through variation of the photon virtuality Q2. In order to observe effects of multiple interactions at Q2 substantially different from zero we have to look into regions of phase space where resolved processes dominate over direct ones. The forward jet production at small values
The Lund dipole model DIPSY is based on BFKL evolution and saturation. It can be applied to collisions between electrons, protons, and nuclei. In this paper, I present some recent results for exclusive final states in inelastic collisions, a method to generate final states in diffractive excitation, and some results for collisions with nuclei.
We add the Wess-Zumino-Witten term to the N = 3 massive nonlinear sigma model and study the leading logarithms in the anomalous sector. We obtain the leading logarithms to six loops for pi(0) -> gamma*gamma* and to five loops for y*pi pi pi. In addition we extend the earlier work on the mass and decay constant to six loops and the vector form factor to five loops. We present numerical results for
A derivation for a polarized CCFM evolution equation which is suitable to describe the scaling behavior of the unintegrated polarized gluon density is given. We discuss the properties of this polarized CCFM equation and compare it to the standard CCFM equation in the unpolarized case.
A semiclassical description of structure functions in DIS at small x is presented. It gives an intuitive picture of the transition from the Double Leading Log approximation at large Q(2), to the powerlike dependence on x in the BFKL region at limited Q(2). Formal derivations from perturbative QCD, e.g. in the BFKL or the CCFM formalisms, are technically complicated, and therefore such an intuitive
We derive a partition function for the Lund fragmentation model and compare it with that of a classical gas. For a fixed rapidity “volume” this partition function corresponds to a multiplicity distribution which is very close to a binomial distribution. We compare our results with the multiplicity distributions obtained from the JETSET Monte Carlo for several scenarios. Firstly, for the fragmentat
