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Abstract In the kinematic region where three particles i, j, k are collinear, the multi-parton scattering amplitudes factorise into a product of a triple collinear splitting function and a multi-parton scattering amplitude with two fewer particles. These triple collinear splitting functions contain both iterated single unresolved contributions, and genuine double unresolved contributions. We make this explicit by rewriting the known triple collinear splitting functions in terms of products of two-particle splitting functions, and a remainder that is explicitly finite when any two of {i, j, k} are collinear. We analyse all of the single unresolved singularities present in the remainder.

In the kinematic region where three particles i, j, k are collinear, the multi-parton scattering amplitudes factorise into a product of a triple collinear splitting function and a multi-parton scattering amplitude with two fewer particles. These triple collinear splitting functions contain both iterated single unresolved contributions, and genuine double unresolved contributions. We make this explicit by rewriting the known triple collinear splitting functions in terms of products of two-particle splitting functions, and a remainder that is explicitly finite when any two of {i, j, k} are collinear. We analyse all of the single unresolved singularities present in the remainder. [ABSTRACT FROM AUTHOR]

In this paper, a special kind of Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations is introduced. Since it is not possible to solve DGLAP integral equations analytically, the numerical solutions of these equations can be of interest. Here, the Tau spectral method is used for solving this integral equation and offer an approximate solution. Finally, this solution is compared with solution obtained experimentally for Q0² = 0:35GeV². [ABSTRACT FROM AUTHOR]

In this informal memoir, the author describes his passage through a golden age of elementary particle physics. It includes not only his career trajectory as a theoretical physicist but also his excursions into experimental physics and particle accelerator theory. While his successes are highlighted, some unsuccessful efforts are included in the narrative as well. Those "losers" were arguably as pleasurable as the less-frequent "winners." Since retirement, the author has become interested in gravitation theory and cosmology—a new golden age. This activity is also briefly described. [ABSTRACT FROM AUTHOR]

The inclusive spectrum of the charged particles, π 0- and η -mesons produced in the pp collisions at LHC energies were analyzed by fitting them with exponential functions. It was found the spectra were composed of several p T regions, which could be characterized by the length of the regions L K c and two free fitting parameters a K c and b K c . The study of the L K c dependences of the parameters a K c and b K c and of the energy dependencies of the L K c , a K c and b K c showed that the regions can be classified into two groups depending on the values of the L K c , a K c and b K c . The values of the L K c and b K c for the first group don't depend on colliding energy and the type of the particles (though the values of a K c increase linearly with energy) whereas the characteristics in the second group of regions show strong dependencies. It was found that the ratio of the length for the η -mesons to one for the π 0-mesons is approximately equal to the ratio of their mass: 〈 L η 〉 : 〈 L π 0 〉 ≅ m η : m π 0 . Assuming that the values of the L K c are directly proportional to the string tension the result could be considered as evidence in favor of parton string fragmentation dynamics. The increase in the lengths for the η -mesons' regions is accompanied by an increase of the values for the parameter b k c . It can mean that the η -mesons were produced at smaller values of α S compared with that for π 0-mesons. The results show that for the first group of regions the lengths of the regions are ∼ 3–5 times greater than the lengths of neighboring, lower p T regions. For the second group of regions the lengths of the regions are ∼ 1–2 times greater than the lengths of neighboring lower p T region. In the framework of the string fragmentation and hadronization dynamics, this could mean that the particles in the group I of regions are produced through previous-generation strings decays into ∼ 3–5 strings while those in group I I originate from previous-generation strings decays into ∼ 2 strings. [ABSTRACT FROM AUTHOR]

In this paper, the results of investigation of single and pair production of J / Ψ mesons in the D0 experiment at the Tevatron accelerator are considered. The contributions of single and double parton interactions to the total cross section of the pair production J / Ψ of mesons are estimated for the first time. With the help of these measurements, the effective cross section of double parton interactions σeff was calculated. [ABSTRACT FROM AUTHOR]

Measurements of charged jet production with respect to the second-order harmonic event plane, quantified as v 2 ch jet , in s NN = 2.76 TeV Pb–Pb collisions are presented. The contribution of hydrodynamic flow to the underlying event energy is corrected for on a jet-by-jet basis. Remaining effects from instrumental resolution and regional fluctuations in the energy density of the underlying event are corrected for by unfolding. Significant v 2 ch jet is observed in semi-central collisions. Qualitative agreement is found with v 2 c h + e m j e t of jets reconstructed from charged and neutral fragments and v 2 of single charged particles, as well as with predictions from the JEWEL Monte Carlo model. [ABSTRACT FROM AUTHOR]

We present the QCD models based on the hadronization of final states of e+e- annihilations, in 60 GeV centre of mass energy in the AMY detector at the KEK collider TRISTAN. To achieve this, we first find the jet axis by using the momentum tensor and diagonilizing it for each event. The models under consideration are the Webber, the Matrix Elements and the Parton Shower. In most cases our results are consistent with the models. Our results are also consistent with those obtained from other experiments.

Abstract: In the first LHC 2009 and 2010 runs the ALICE experiment collected about 10 at and more than 20 at bench for the pQCD description of hard scattering phenomena at the highest center of mass energy p + p collisions ever recorded. These data are used to study the universality of the charged hadron invariant yields measured by the ALICE experiment in terms of scaling. Leading particle associated yield is used to study the angular correlations. A comparison of per-trigger yield in and data samples is presented. An increasing role of the soft QCD radiation is deduced from the slope of the associated particle yield in the region perpendicular to the leading particle. [Copyright &y& Elsevier]

Flavour equilibration for a thermally equilibrated but chemically non-equilibrated quark-gluon plasma is presented. Flavour equilibration is studied enforcing baryon number conservation. In addition to the usual processes like single additional gluon production gg ⇆ ggg and its reverse and quarkantiquark pair production by gluon pair fusion gg ⇆ qiqi- and reverse thereof, processes like quark-flavour interchanging qiqi- ⇆ qjqj is also considered. The degree of equilibration is studied comparatively for various reactions/constraints that are being considered. [ABSTRACT FROM AUTHOR]

The nucleons (protons and neutrons) are by far the most abundant form of matter in our visible Universe; they are composite particles made of quarks and gluons, the fundamental quanta of Quantum Chromo Dynamics (QCD). The usual interpretation of the nucleon dynamics in high energy interactions is often limited to a simple one-dimensional picture of a fast moving nucleon as a collection of co-linearly moving quarks and gluons (partons), interacting accordingly to perturbative QCD rules. However, massive experimental evidence shows that, in particular when transverse spin dependent observables are involved, such a simple picture is not adequate. The intrinsic transverse motion of partons has to be taken into account; this opens the way to a new, truly 3-dimensional (3D) study of the nucleon structure. A review of the main experimental data, their interpretation and understanding in terms of new transverse momentum dependent partonic distributions, and the progress in building a 3D imaging of the nucleon is presented. [ABSTRACT FROM AUTHOR]

The determination of parton distribution functions in the nucleon and nuclei is important for obtaining precise hadron-reaction cross-sections, from which any new exotic signature could be found. We show that a future neutrino factory could provide important information on the parton distributions. First, a recent effort concerning the parametrization of nuclear parton distributions is explained. It suggests that the factory should be important for determining unknown behavior of valence-quark distributions in nuclei at small x. Second, the facility could be used for understanding nucleon spin structure and isospin violation in the parton distributions. [Copyright &y& Elsevier]