Search results for "Photoproduct"
showing 10 items of 511 documents
"Table_T07" of "Threshold ��0 photoproduction on transverse polarised protons at MAMI"
2022
Target asymmetry T for c.m. cos(Theta_pi0)= 0.423
"Table_T17" of "Threshold ��0 photoproduction on transverse polarised protons at MAMI"
2022
Target asymmetry T for c.m. cos(Theta_pi0)= -0.966
"Table_T01" of "Threshold ��0 photoproduction on transverse polarised protons at MAMI"
2022
Target asymmetry T for c.m. cos(Theta_pi0)= 0.996
"Table_T02" of "Threshold ��0 photoproduction on transverse polarised protons at MAMI"
2022
Target asymmetry T for c.m. cos(Theta_pi0)= 0.966
"Table 1" of "Virtual Compton scattering under pi0 threshold at Q**2 = 0.33-GeV**2: Preliminary results."
1999
No description provided.
Determination of the pole position of the lightest hybrid meson candidate
2019
Mapping states with explicit gluonic degrees of freedom in the light sector is a challenge, and has led to controversies in the past. In particular, the experiments have reported two different hybrid candidates with spin-exotic signature, pi1(1400) and pi1(1600), which couple separately to eta pi and eta' pi. This picture is not compatible with recent Lattice QCD estimates for hybrid states, nor with most phenomenological models. We consider the recent partial wave analysis of the eta(') pi system by the COMPASS collaboration. We fit the extracted intensities and phases with a coupled-channel amplitude that enforces the unitarity and analyticity of the S-matrix. We provide a robust extracti…
New Results on Charm Production at HERA
2014
The copious production of charm quarks at HERA yielded measure- ments of the charm contribution to the proton structure and of the charm mass and fragmentation parameters of charmed hadrons. Several measure- ments of charm production in deep inelastic scattering from the H1 and ZEUS collaborations as well as combined data are presented. They provide a powerful vindication of the form of the gluon density in the proton de- rived from scaling violations of inclusive deep inelastic scattering data. A QCD fit to the charm data leads to a measurement of the charm mass and provides precise predictions e.g. for W and Z production at the LHC. In ad- dition, charm fragmentation fractions in photopro…
Spin alignment and violation of the OZI rule in exclusive ω and ϕ production in pp collisions
2014
Exclusive production of the isoscalar vector mesons $\omega$ and $\phi$ is measured with a 190 GeV$/c$ proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable $x_{F}$ of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on $x_{F}$ and on the invariant mass $M_{p\mathrm{V}}$ of the system formed by fast proton $p_\mathrm{fast}$ and vector meson $V$ is discussed in terms of diffractive production of $p_\mathrm{fast}V$ resonances in competition with central production. The measurement of the spin density matrix element $\rho_{00}$ of the vector mesons…
Gluon imaging using azimuthal correlations in diffractive scattering at the Electron-Ion Collider
2021
We study coherent diffractive photon and vector meson production in electron-proton and electron-nucleus collisions within the Color Glass Condensate effective field theory. We show that electron-photon and electron-vector meson azimuthal angle correlations are sensitive to non-trivial spatial correlations in the gluon distribution of the target, and perform explicit calculations using spatially dependent McLerran-Venugopalan initial color charge configurations coupled to the numerical solution of small $x$ JIMWLK evolution equations. We compute the cross-section differentially in $Q^2$ and $|t|$ and find sizeable anisotropies in the electron-photon and electron-$\mathrm{J}/��$ azimuthal co…
Finite-energy sum rules in eta photoproduction off a nucleon
2016
The reaction ${\gamma}N \to {\eta}N$ is studied in the high-energy regime (with photon lab energies $E_{\gamma}^{\textrm{lab}} > 4$ GeV) using information from the resonance region through the use of finite-energy sum rules (FESR). We illustrate how analyticity allows one to map the t-dependence of the unknown Regge residue functions. We provide predictions for the energy dependence of the beam asymmetry at high energies.