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The ideas presented in an earlier note on the relationship between the quark fragmentation distributions as measured in leptoproduction and the one particle distributions in the mesonic fragmentation regions of hadronic interactions are carried further to photoproduction and to the baryon fragmentation distributions. The results are as before interpreted in terms of a simple additive quark model w
The renormalization of chiral perturbation theory is carried out to next-to-next-to-leading order in the meson sector. We calculate the divergent part of the generating functional of Green functions of quark currents to O(p6) for chiral SU(n), involving one- and two-loop diagrams. The renormalization group equations for the renormalized low-energy constants of O(p6) are derived. We compare our res
Over the years, many jet clustering algorithms have been proposed for the analysis of hadronic final states in e+e- annihilations. These have somewhat different emphasis and are therefore more or less suited for various applications. We here review some of the most used and compare them from a theoretical and experimental point of view.
We present our studies of four-jet double parton scattering production in proton-nucleus collisions within the framework of the pythia8 event generator. We demonstrate that double absorptive processes in pA generated by the Angantyr model in pythia8 give an enhancement of the total double parton scattering cross section similar to the predictions by Strikman and Treleani in 2001. Additionally, we
In this work, we consider expressions for the masses and decay constants of the pseudoscalar mesons in SU(3) chiral perturbation theory. These involve sunset diagrams and their derivatives evaluated at p2=mP2 (P=π, K, η). Recalling that there are three mass scales in this theory, mπ, mK and mη, there are instances when the finite part of the sunset diagrams do not admit an expression in terms of e
This paper contains some new results on the hadronic light-by-light contribution (HLbL) to the muon g − 2. The first part argues that we can expect large effects from disconnected diagrams in present and future calculations by lattice QCD of HLbL. The argument is based on the dominance of pseudo-scalar meson exchange. In the second part, we revisit the pion loop HLbL contribution to the muon anoma
This talk includes a short introduction to Chiral Perturbation Theory in the meson sector concentrating on a number of recent developments. I discuss the latest fit of the low-energy constants. Finite volume corrections are discussed for the case with twisted boundary conditions for form-factors and first results at two-loops for three flavours for masses. The last part discusses the extension to
We give a short introduction to the calculation of the leading chiral logarithms, and present the results of the recent evaluation of the LLog series for the nucleon mass within the heavy baryon theory. The presented results are the first example of LLog calculation in the nucleon ChPT. We also discuss some regularities observed in the leading logarithmical series for nucleon mass.
We study the Effective Field Theory of three QCD-like theories, which can be classified by having quarks in a complex, real or pseudo-real representations of the gauge group. The Lagrangians are written in a very similar way so that the calculations can be done using techniques from Chiral Perturbation Theory (ChPT). We calculated the vacuum-expectation-value, the mass and the decay constant of ps
In this paper the Poisson bracket algebra for the open massless relativistic string in the one-space-and one-time-dimensional case is considered. In order to characterize the orbit of the system the directrix function, i.e., the orbit of one of the endpoints of the string, is used. It turns out that the Poisson bracket algebra is of a very simple form in terms of the parameters of the directrix fu
We discuss a scenario in which the diphoton enhancement at Mγγ=750 GeV, observed by the ATLAS and CMS collaborations, is a neutral technipion π0. We consider two distinct minimal models for the dynamical electroweak symmetry breaking. In a first one, two-flavor vectorlike technicolor (VTC) model, we assume that the two-photon fusion is a dominant production mechanism. We include γγ→π0 and producti
Using the color dipole formalism we study production of Drell-Yan (DY) pairs in proton-nucleus interactions in the kinematic region corresponding to LHC experiments. Lepton pairs produced in a hard scattering are not accompanied with any final state interactions leading to either energy loss or absorption. Consequently, dileptons may serve as more efficient and cleaner probes for the onset of nucl
Top quark pairs production and decay are considered in the framework of the smeared-mass unstable particles model. The results are in good agreement with the previous ones in the literature. Suggested approach significantly simplifies calculations compared to the standard perturbative one.
We calculate cross-section of the near-threshold three-boson production at the ILC with an account of their instability and a principal part of NLO corrections. The calculations are fulfilled within the framework of the model of unstable particles with smeared mass. We show that the contribution of finite width (instability) is large in the resonance Higgs-mass range and should be taken into accou
Heavy long-lived quarks, i.e. charm and bottom, are frequently studied both as tests of QCD and as probes for other physics aspects within and beyond the standard model. The long lifetime implies that charm and bottom hadrons are formed and observed. This hadronization process cannot be studied in isolation, but depends on the production environment. Within the framework of the string model, a maj
This talk is about the hadronic light-by-light contribution to the muon anomalous magnetic moment, mainly our old work but including some newer results as well. It concentrates on the model calculations. Most attention is paid to pseudo-scalar exchange and the pion loop contribution. Scalar, a1-exchange and other contributions are shortly discussed as well. For the π0-exchange a possible large can
The recent experimental measurement of the muon g−2 at Fermilab National Laboratory, at a 4.2σ tension with the Standard Model prediction, highlights the need for further improvements on the theoretical uncertainties associated to the hadronic sector. In the framework of the operator product expansion in the presence of a background feld, the short-distance behaviour of the hadronic light-by-light
