We derive the light-front wave function (LFWF) representation of the γ * γ * → η c (1S) , η c (2S) transition form factor F (Q 2 1 , Q 2 2 ) for two virtual photons in the initial state. For the LFWF, we use different models obtained from the solution of the Schrödinger equation for a variety of cc potentials. We compare our results to the BaBar experimental data for the η c (1S) transition form factor, for one real and one virtual photon. We observe that the onset of the asymptotic behaviour is strongly delayed and discuss applicability of the collinear and/or massless limit. We present some examples of two-dimensional distributions for F (Q 2 1 , Q 2 2 ). A factorization breaking measure is proposed and factorization breaking effects are quantified and shown to be almost model independent. Factorization is shown to be strongly broken, and a scaling of the form factor as a function ofQ 2 = (Q 2 1 + Q 2 2 )/2 is obtained.

In this work, we present a thorough analysis of η c (1S, 2S) quarkonia hadroproduction in k ⊥ -factorisation in the framework of the light-front potential approach for the quarkonium wave function. The off-shell matrix elements for the g * g * η c (1S, 2S) vertices are derived. We discuss the importance of taking into account the gluon virtualities. We present the transverse momentum distributions of η c for several models of the unintegrated gluon distributions. Our calculations are performed for four distinct parameterisations for the cc interaction potential consistent with the meson spectra. We compare our results for η c (1S) to measurements by the LHCb collaboration and present predictions for η c (2S) production.

In this work, we present a thorough analysis of scalar P-wave χ Q0 , Q = c, b quarkonia electromagnetic form factors for the γ * γ * → χ Q0 couplings, as well as their hadroproduction observables in k ⊥-factorisation using the light-front (LF) potential approach for the quarkonium wave function. The electromagnetic form factors are presented as functions of photon virtualities. We discuss the role of the Melosh spin-rotation and relativistic corrections estimated by comparing our results with those in the standard nonrelativistic QCD (NRQCD) approach. Theoretical uncertainties of our approach are found by performing the analysis with two different unintegrated gluon densities and with five distinct models of the QQ interaction potentials consistent with the meson spectra. The results for the rapidity and transverse momentum distributions of χ Q0 produced in highenergy pp collisions at √ s = 13 TeV are shown.

We discuss an application of dynamical multi-parton interaction model, tuned to measurements of underlying event topology, for a description of destroying rapidity gaps in the jet-gap-jet processes at the LHC. We concentrate on the dynamical origin of the mechanism of destroying the rapidity gap. The cross section for jet-gap-jet is calculated within LL BFKL approximation. We discuss the topology of final states without and with the MPI effects. We discuss some examples of selected kinematical situations (fixed jet rapidities and transverse momenta) as distributions averaged over the dynamics of the jet-gap-jet scattering. The color-singlet ladder exchange amplitude for the partonic subprocess is implemented into the PYTHIA 8 generator, which is then used for hadronisation and for the simulation of the MPI effects. Several differential distributions are shown and discussed. We present the ratio of cross section calculated with and without MPI effects as a function of rapidity gap in between the jets.

We discuss how to calculate cross sections as well as rapidity, transverse momentum and energy distributions of ν τ and ν τ produced from the direct D ± s → ν τ /ν τ and chain D ±τ decays in p+ 96 Mo scattering with proton beam E lab = 400 GeV i.e. at √ s NN = 27.4 GeV. The τ decays are simulated with the help of the TAUOLA code and include multiple decay channels of τ in amounts proportional to their branching ratios. In our calculations we include D ± s from charm fragmentation c → D + s andc → D − s as well as those from subleading fragmentation of strange quarks/antiquarks s → D − s ands → D + s . The s =s asymmetry of the strange quark content of proton is included. The different contributions to D ± s and ν τ /ν τ are shown explicitly.We discuss and quantify a not discussed so far effect of asymmetries for production of ν τ and ν τ caused by subleading fragmentation mechanism and discuss related uncertainties. A potential measurement of the asymmetry is discussed. Estimates of a number of observed ν τ /ν τ in the ν τ /ν τ + 208 Pb reaction, with 2m long target are given with the help of the NuWro program. We refer also to the production of the high-energy (anti)neutrinos in the atmosphere. † also at