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A. T. Goritschnig

Publications and source records attributed to A. T. Goritschnig.

10 recordsLinked to original sources
arXiv2014

Hard Excluseive $Φ$ and $J/Ψ$ Photoproduction off a Proton

We study the photoproduction of the vector mesons $Φ$ and $J/Ψ$ off a proton in the kinematical regime of large energies and scattering angles within the framework of perturbative QCD. Our investigations are based on the hard scattering approach. This means that the hadrons are replaced by their valence Fock states and scattering on the partonic level is described by tree graphs in which the large transferred momentum is redistributed between the valence partons via the exchange of hard gluons. We find that the unpolarized photoproduction cross sections are dominated by Compton-scattering-like graphs in which the photon couples to the proton, whereas vector-meson-dominance-like graphs, in which the photon fluctuates into the heavy quark-antiquark pair which then exchanges two gluons with the proton, play a minor role. We give explicit predictions for unpolarized scattering cross sections and compare them with experimental data where possible.

hep-ph↗
arXiv2014

Timelike deeply virtual Compton scattering with a linearly polarized real (or quasi-real) photon beam

We calculate timelike virtual Compton scattering amplitudes in the generalized Bjorken scaling regime and focus on a new polarization asymmetry in the scattering process with a linearly polarized photon beam in the medium energy range, which will be studied intensely at JLab12 experiments. We demonstrate that new observables help us to access the polarized quark and gluon generalized parton distributions $\tilde H(x, ξ, t)$ and $ \tilde E(x, ξ, t)$.

hep-ph↗
arXiv2014

Timelike Compton scattering with a linearly polarized photon beam

We study the timelike virtual Compton scattering process with a linearly polarized photon beam, in the generalized Bjorken scaling region and in the medium energy range which will be studied intensely at JLab12 experiments. We define new observables and show how they should help to access the polarized quark and gluon generalized parton distributions.

hep-ph↗
arXiv2013

Production of heavy meson pairs in $p\bar{p}$ collisions within a double handbag approach

We study the pair-production of heavy mesons in proton-antiproton annihilations within a perturbative QCD-motivated framework. In particular we investigate $p \bar{p} \rightarrow \overline{D^0} D^0$ within a double handbag approach, where a hard subprocess factorizes from soft hadronic matrix elements. The soft matrix elements can be parametrized by transition distribution amplitudes, which are off-diagonal in flavor space. The transition distribution amplitudes are modelled as overlaps of light-cone wave functions. We obtain rather robust model results for $p \bar{p} \rightarrow \overline{D^0} D^0$ cross sections, which are expected to be measured at the future $\bar{\text{P}}\text{ANDA}$ detector at GSI-FAIR.

hep-ph↗
arXiv2013

Double handbag description of proton-antiproton annihilation into a heavy meson pair

We propose to describe the process $ p \bar{p} \,\to\, \bar{D^0} D^0$ in a perturbative QCD motivated framework where a double-handbag hard process $ u d \bar u \bar d \to \bar{c} c$ factorizes from transition distribution amplitudes, which are quasi forward hadronic matrix elements of $Ψ_q Ψ_q Ψ_c $ operators, where q denotes light quarks and c denotes the heavy quark. We advocate that the charm-quark mass acts as the large scale allowing this factorization. We calculate this process in the simplified framework of the scalar diquark model and present the expected cross sections for the PANDA experiment at GSI-FAIR.

hep-ph↗
arXiv2009

Proton-Antiproton Annihilation into a Lambda_c-Antilambda_c Pair

The process p-pbar -> Lambda_c-Antilambda_c is investigated within the handbag approach. It is shown that the dominant dynamical mechanism, characterized by the partonic subprocess u-ubar -> c-cbar factorizes in the sense that only the subprocess contains highly virtual partons, a gluon to lowest order of perturbative QCD, while the hadronic matrix elements embody only soft scales and can be parameterized in terms of helicity flip and non-flip generalized parton distributions. Modelling these parton distributions by overlaps of light-cone wave functions for the involved baryons we are able to predict cross sections and spin correlation parameters for the process of interest.

hep-ph↗
arXiv2009

$p\bar{p} \to Λ_c \barΛ_c$ within a Handbag Picture -- Cross Section and Spin Observables

We study the process $p\bar{p} \to Λ_c \barΛ_c$ within the generalized parton picture. Our starting point is the double handbag diagram which factorizes into soft generalized parton distributions and a hard subprocess amplitude for $u \bar{u} \to c \bar{c}$. Our cross-section predictions may become interesting in view of forthcoming experiments at FAIR in Darmstadt.

hep-ph↗
arXiv2008

$p\bar{p} \to Λ_c \barΛ_c$ within the generalized parton picture - first results

We study proton-antiproton annihilation into $Λ_c \barΛ_c$ pairs within the generalized parton picture. Our starting point is the double handbag diagram which is shown to factorize into soft generalized parton distributions for the $p \to Λ_c$ (and $\bar{p} \to \barΛ_c$) transition and a hard subprocess amplitude for $u \bar{u} \to c \bar{c}$. Thereby the mass of the charm quark is taken as the hard scale so that our results are not restricted to large scattering angles and/or incredibly large energies. Modelling the generalized parton distributions for the $p\to Λ_c$ transition by an overlap of simple quark-diquark light-cone wave functions we make first predictions for $p\to Λ_c$ transition form factors and unpolarized $p\bar{p} \to Λ_c \barΛ_c$ cross sections. Our findings may become interesting in view of forthcoming experiments at FAIR in Darmstadt.

hep-ph↗