Photoproduction Of Heavy Vector Mesons Research Articles

Near threshold heavy vector meson photoproduction at LHC and EicC

The exclusive J/Psi and Upsilon photoproduction in fixed - target collisions at the LHC and ep(A) collisions at the Electron ion collider in China (EicC) is investigated considering different models for the treatment of the vector meson production at low energies, close to the threshold. Results for the total cross sections and associated distributions are presented. We predict a large number of J/Psi events at the LHC in the rapidity range covered by the LHCb detector. For the EicC, our predictions point out that a detailed analysis of the near threshold J/Psi and Upsilon photoproduction is feasible. Moreover, our results indicate that the modeling of the near threshold vector meson production can be constrained by future experimental analyzes at the LHC and EicC.

Nuclear form factor of xenon from photoproduction of vector mesons in Xe-Xe ultraperipheral collisions at the LHC

Using the Gribov-Glauber model for photon-nucleus scattering and a generalization of the vector meson dominance model for the hadronic structure of the photon, we calculate cross sections of light and heavy vector meson photoproduction in ultraperipheral Xe-Xe collisions at 5.44 TeV at the Large Hadron Collider. Analyzing the momentum transfer distribution in this process, we examine the feasibility to extract the nuclear isoscalar form factor of Xe isotopes, which are needed in searches for dark matter with Xenon-based detectors.

Heavy Vector Meson Photoproduction in Ultra-peripheral Collisions at the LHC

Heavy Vector Meson Photoproduction in Ultra-peripheral Collisions at the LHC

Photoproduction of heavy vector mesons in ultra-peripheral Pb–Pb collisions

Ultra-peripheral Pb-Pb collisions, in which the two nuclei pass close to each other, but at an impact parameter greater than the sum of their radii, provide information about the initial state of nuclei. In particular, heavy vector meson production, where the particle mass sets a hard scale, proceeds in such collisions by photon-gluon interactions, and gives access to nuclear PDFs. The ALICE collaboration has published measurements of J/ψ and ψ(2S) photoproduction in ultra-peripheral collisions in LHC Run 1 at forward (J/ψ) and mid-rapidity, and has obtained a substantially larger data set in 2015 from LHC Run 2, allowing much more detailed studies of the production mechanism to be performed. In particular, the increased energy and more detailed measurements in the forward region in Run 2 give access to significantly lower values of Bjorken-x than in previous studies. In this talk, the latest available results from Run 2 will be given.

Exclusive heavy vector meson photoproduction in hadronic collisions at the LHC: Predictions of the color glass condensate model for Run 2 energies

In this letter we update our predictions for exclusive $J/\Psi$ and $\Upsilon$ photoproduction in proton-proton and nucleus - nucleus collisions at the Run 2 LHC energies obtained with the color dipole formalism and considering the impact parameter Color Glass Condensate model (bCGC) for the forward dipole - target scattering amplitude. A comparison with the LHCb data on rapidity distributions and photon - hadron cross sections is presented. Our results demonstrate that the current data can be quite well described by the bCGC model, which takes into account nonlinear effects in the QCD dynamics and reproduces the very precise HERA data, without introducing any additional effect or free parameter.

Exclusive photoproduction ofJ/ψin proton-proton and proton-antiproton scattering

Protons and antiprotons at collider energies are a source of high-energy Weizsaecker-Williams photons. This may open a possibility to study exclusive photoproduction of heavy vector mesons at energies much larger than possible at the HERA accelerator. Here we present a detailed investigation of the exclusive J/{psi} photoproduction in proton-proton (Relativistic Heavy Ion Collider, CERN LHC) and proton-antiproton (Tevatron) collisions. We calculate several differential distributions in t{sub 1}, t{sub 2}, y, {phi}, as well as transverse momentum distributions of J/{psi}'s. We discuss correlations in the azimuthal angle between outgoing protons or proton and antiproton as well as in the (t{sub 1},t{sub 2}) space. Differently from electroproduction experiments, here both colliding beam particles can be a source of photons, and we find large interference terms in azimuthal-angle distributions in a broad range of rapidities of the produced meson. We also include the spin-flip parts in the electromagnetic vertices. We discuss the effect of absorptive corrections on various distributions. Interestingly, absorption corrections induce a charge asymmetry in rapidity distributions, and are larger for pp reactions than for the pp case. The reaction considered here constitutes an important nonreduceable background in recently proposed searches for odderon exchange.

Exclusive photoproduction of a heavy vector meson in QCD

The process of exclusive heavy vector meson photoproduction, gamma p -> V p, is studied in the framework of QCD factorization. The mass of the produced meson, V = Upsilon or J/Psi, provides a hard scale for the process. We demonstrate, that in the heavy quark limit and at the one-loop order in perturbation theory, the amplitude factorizes in a convolution of a perturbatively calculable hard-scattering amplitude with the generalized parton densities and the nonrelativistic QCD matrix element <O_1>_V. We evaluate the hard scattering amplitude at one-loop order and compare the data with theoretical predictions using an available model for generalized parton distributions.

Diffractive heavy vector meson production from the BFKL equation

Diffractive heavy vector meson photoproduction accompanied by proton dissociation is studied for arbitrary momentum transfer. The process is described by the non-forward BFKL equation, for which a complete analytical solution is found, giving the scattering amplitude. The impact of non-leading corrections to the BFKL equation is also analysed. Results are compared to the HERA data on J/psi production.

Photoproduction of heavy vector mesons at HERA – a test field for diffraction

Exclusive diffractive photoproduction of heavy vector mesons (V=\(\phi, J/\psi\), and \(\Upsilon\)) at HERA is studied in a model employing a dipole Pomeron exchange (P) with an inelastic \(\gamma PV\) vertex. The model is fitted to the data on \({\mathrm{d}\sigma/\mathrm{d}t}\), B, and \(\sigma_{\mathrmel}\) for \(Q^2=0\) and beyond the threshold region. The elastic cross sections for both \(\phi\) and \(J/\psi\) photoproduction show a moderate increase within the HERA energy region. The flattening of the slope B(s) (indicating little or no shrinkage) for \(J/\psi\) is not correlated with the slope of the Pomeron trajectory. Estimates for \(\Upsilon\) photoproduction at HERA are given.

Photoproduction of heavy vector mesons at HERA – a test field for diffraction

Exclusive diffractive photoproduction of heavy vector mesons (V=phi, J/psi and Upsilon) at HERA is studied in a model employing a dipole Pomeron exchange (P) with an inelastic gamma-P-V vertex. The model is fitted to the data on dsigma/dt, B and elastic sigma for Q^2=0 and beyond the threshold region. The elastic cross sections for both phi and J/psi photoproduction show a moderate increase within the HERA energy region. The flattening of the slope B(s) (little or no shrinkage) for J/psi is not correlated with the slope of the Pomeron trajectory. Estimates for Upsilon photoproduction at HERA are given.

Diffractive photoproduction of heavy vector mesons

Photoproduction of vector mesons is considered within the context of a quark model. The conventional vector-dominance predictions for photoproduction are a consequence of the model at high energies. At lower energies the model predicts a strong energy dependence in (dsigma/dt)/sub t//sub min/ for heavy vector mesons as observed.

Photoproduction of heavy vector mesons: The ϒ(9.4)

The predictions based on the vector meson dominance model (VMD) and the tensor-coupled pomeron for the photoproduction of heavy vector mesons are revised, and corrections to the model are proposed as suggested by the experimental data for the light vector mesons and the ψ (3100). In particular, the string model is used to predict the Regge trajectories of the heavy vector mesons (ψ, ϒ, …) which results in a correction to the predicted heavy vector meson-nucleon total cross section in agreement with the ψ data. The q 2 dependence of VMD is also discussed. The cross section for the photoproduction of the ϒ (9.4) is estimated within this framework.

Associated multiparticle production and intra-nuclear cascading

In the existing experiments on multiparticle production off nuclei it is difficult to distinguish between intra-nuclear cascading of secondaries and the other mechanisms of production which give important information on the short-time development of hadronic interactions. It is argued that by selecting nuclear interactions with no or little shadowing one can unambiguously establish the existence (or lack) of intra-nuclear cascading. It is suggested that investigation of associated particle production in the photoproduction of heavy vector mesons from nuclei and in inelastic lepton-nucleus interactions is a promising method of analyzing intranuclear cascading.