Related papers: The process p + pbar --> gamma + pi^0 within the h…
We develop an impact representation for the generalized distribution amplitude which describes the exclusive hadronization of a quark-antiquark pair to a pair of mesons. Experiments such as gamma^* gamma -> pi pi and gamma^* N -> pi pi N'…
In this paper we consider the production of proton-antiproton pairs in two-photon interactions in electron-positron and heavy-ion collisions. We try to understand the dependence of the total cross section on the photon-photon c.m. energy as…
In this paper we consider the exclusive production of proton-antiproton pairs in the interaction between two quasireal photons in $e^+e^-$ collision. The differential and total cross section of the process $\gamma \gamma \to p\bar {p}$ at a…
We investigate the possibility to constrain the pion distribution amplitude from the gamma* gamma* -> pi transition. For a surprisingly large range in the two photon virtualities we find that the transition form factor is essentially…
The nonresonant mechanism in the reactions $e^+\,e^-\to \pi^-\,p\,\bar{n}$ and $e^+\,e^-\to \pi^+\,n\,\bar{p}$ is investigated in frame of the one-photon exchange approximation. The description of the hadronic phase space and the invariant…
We report a study of $\bar p+p\to \bar p+X+Y$ at $\sqrt s=1800$ GeV, where $Y$ is a proton or system of mass-squared $M_Y^2\lesssim 8$ GeV$^2$. In a sample of events with a leading $\bar p$ of fractional momentum loss $0.035<\xi_{\bar…
We study the scaling regime of nucleon - anti-nucleon annihilation into a deeply virtual photon and a meson, bar p N -> gamma* pi. We obtain the leading twist amplitude in the kinematical region where it factorizes into an antiproton…
The exclusive reactions $\gamma p \to K^{*0} \Sigma^+(1189)$ and $\gamma p \to K^{0} \pi^{0}\Sigma^+(1189)$, leading to the p 4$\pi^{0}$ final state, have been measured with a tagged photon beam for incident energies from threshold up to…
We evaluate differential distributions for the four-body $p p \to p p \pi^+ \pi^-$ reaction which constitutes a irreducible background to three-body processes $p p \to p p M$, where $M$ are a broad resonances in the $\pi^+ \pi^-$ channel,…
We extend the k_\perp-factorization formalism for exclusive photoproduction of vector mesons to the production of electroweak Z^0 bosons. Predictions for the gamma p \to Z^0 p and p p \to p p Z^0 reactions are given using an unintegrated…
We study the exclusive production of pi pi and rho pi in hard gamma* gamma scattering in the forward kinematical region where the virtuality of one photon provides us with a hard scale in the process. The newly introduced concept of…
We investigate lepton-pair production in hard exclusive hadron-hadron collisions. We consider a double handbag (DH) mechanism in which the process amplitude factorizes in hard subprocesses, qq -> qq gamma* and qg -> qg gamma*, and in soft…
Exclusive two-pion production near threshold in the collision of a highly virtual photon with a real one offers a new possibility to unravel the partonic content of hadrons. We explain the dynamics of this regime, i.e. the separation of the…
We calculate the differential cross section and single-polarization observables for the reaction $\gamma p \to \Phi p$ within perturbative QCD, treating the proton as a quark-diquark system. The phenomenological couplings of gauge bosons to…
The gamma -> 3 pi form factor was calculated in a simple-minded constituent model with a constant quark mass parameter, as well as in the Schwinger-Dyson approach. The comparison of these and various other theoretical results on this…
{We investigate the photoproduction process $ p \gamma \rightarrow \Lambda_{c}^{+} \overline{D^{0}}$ within the handbag approach, which we assume to be the dominant mechanism at energies well above the production threshold and in the…
We derive the minimal Fock-state expansions of the pion and the photon wave functions in light-cone formalism, then we calculate the pion-photon and the photon-pion transition form factors of $\gamma ^{\ast}\pi ^{0}\to \gamma $ and $\gamma…
Ultraperipheral collisions (UPCs) of ions provide new opportunities to study the quarkonium production mechanism in photon-photon scattering. In this paper, we investigate the exclusive process $\gamma+\gamma\to J/\psi+\gamma$ up to…
In this work, we calculate the total cross sections and the center-of-mass frame angular distributions of the charmonium production plus a light meson by the low energy $p\bar{p}$ interaction. The results of $p\bar{p}\to \pi^0 \Psi$ with…
We discuss the evaluation of the transition form factor (TFF) $F^{\gamma*\gamma\pi^0}(Q^2)$ by means of QCD theory and by state-space reconstruction from topological data analysis. We first calculate this quantity in terms of quark-gluon…