Related papers: Helicity-Dependent Angular Distributions for Doubl…
The reaction $\gamma p \to \pi^0 p$ is investigated in the energy range above the resonance region. The amplitudes include the leading Regge singularities in the cross-channel and correctly describe the differential cross section for beam…
We studied the photoproduction of $\psi^{\prime}$ in the forward regions in polarized $\gamma p$ collisions at relevant HERA energies. We found that this reaction is very effective to test the color-octet mechanism which is based on the…
Using the helicity formalism, we calculate the combined angular distribution function of the two gamma photons ($\gamma_1$ and $\gamma_2$) and the electron ($e^-$) in the triple cascade process…
New results on the single-differential and fully-integrated cross sections for the process $\gamma_{v} p \rightarrow p' \pi^{+} \pi^{-}$ are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory.…
Differential cross sections for the reaction $\gamma p \to p \pi^0$ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged photon beam with energies from 0.675 to 2.875 GeV. The results reported here possess…
$\gamma\gamma\to\gamma Z$ scattering at the Photon Linear Collider is considered. Explicit formulas for helicity amplitudes due to $W$ boson loops are presented. It is shown that the $Z\gamma$ pair production will be easily observable at…
We consider the reaction g+d -> pi+d in a wide energy range around and above the eta-meson photoproduction threshold at backward CM angles of the outgoing pion. Our theoretical analysis is essentially motivated by the recent measurements of…
Measurements of double helicity asymmetries for inclusive hadron production in polarized proton-proton collisions are sensitive to spin-dependent parton distribution functions, in particular to the gluon distribution function. This study…
The cross section asymmetry Sigma has been measured for the photoproduction of pi0-mesons off protons, using polarized photons in the energy range Eg = 0.5 - 1.1 GeV. The CM angular coverage is Theta = 85 - 125 deg with energy and angle…
We present new data for the polarization observables of the final state proton in the $^{1}H(\vec{\gamma},\vec{p})\pi^{0}$ reaction. These data can be used to test predictions based on hadron helicity conservation (HHC) and perturbative QCD…
The double spin asymmetry for exclusive $J/\psi$ pair production in the polarized $p-p$ collisions at RHIC is investigated. Our study shows that the asymmetry in this process is measurable at RHIC-SPIN experiments in the near future, and,…
We report a measurement of the differential cross section of $\pi^0$ pair production in single-tag two-photon collisions, $\gamma^* \gamma \to \pi^0 \pi^0$, in $e^+ e^-$ scattering. The cross section is measured for $Q^2$ up to 30 GeV$^2$,…
Recent JLab data of the differential cross section for the reaction p(e,e'p)pi0 in the invariant mass region of 1.1 < W < 1.4 GeV at four-momentum transfer squared Q^2= 2.8 and 4.0 (GeV/c)$^2$ are analyzed with two models, both of which…
We present the results of the experimental study of the reaction of dipion production by the beam of the negative pions with momentum 1.78 GeV/c on the polarized proton and liquid hydrogen targets. The experiment covers the region of dipion…
Pion photoproduction in the $\overrightarrow\gamma\overrightarrow p \to \pi^0 p$ reaction has been measured in the FROST experiment at the Thomas Jefferson National Accelerator Facility. In this experiment, circularly polarized photons with…
The double dissociation photoproduction cross section for the process gamma p -> XY, in which the systems X and Y are separated by a large rapidity gap, is measured at large 4-momentum transfer squared |t| > 20 GeV^2 by the H1 Collaboration…
The ALICE Collaboration reports three measurements in ultra-peripheral proton$-$lead collisions at forward rapidity. The exclusive two-photon process \ggmm and the exclusive photoproduction of J/$\psi$ are studied. J/$\psi$ photoproduction…
Beam-helicity asymmetries and mass-differential cross sections have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral and mixed-charge pion pairs in the reactions $\boldsymbol{\gamma}p\rightarrow n\pi^0\pi^+$…
Differential cross sections for the reaction $\gamma p \to K^{*0} \Sigma^+$ are presented at nine bins in photon energy in the range from 1.7 to 3.0 GeV. The \kstar was detected by its decay products, $K^+\pi^-$, in the CLAS detector at…
The first data from MAX-lab in Lund, Sweden on pion production in photonuclear reactions at threshold energies, is presented. The decrease of the total yield of pi+ in gamma + 12C, 27Al reactions below 200 MeV as well as differential,…