Photoproduction of ω-Mesons at ELSA and the role of azimuthal asymmetries

Measurements of ω photoproduction of the Crystal-Barrel/TAPS experiment at the ELSA accelerator of Bonn University are presented which used linearly polarized tagged photon beam from threshold to Eγ = 1700MeV. The azimuthal asymmetries ∑and ∑πindicate s-channel resonance contributions on top of the established t-channel exchange processes. These findings are further enhanced by a very first measurement of the G-asymmetry which, in addition to the polarized photon beam, also requires a longitudinally polarized proton target. An intuitive interpretation of the specific sensitivity of the azimuthal asymmetries to the reaction mechanisms involved is given.     

Analysis of the Photoproduction of η-Mesons on Protons in a Resonance Energy Range

A model of the photoproduction of -mesons on protons with energies from the reaction threshold to 2.5 GeV takes into account contributions to the amplitude of eleven nucleon resonances: S ₁₁(1535), S ₁₁(1650), P ₁₁(1440), P ₁₃(1720), D ₁₃(1520), D ₁₅(1675), F ₁₅(1680), F ₁₇(1990), G ₁₇(2190), G ₁₉(2250), and H ₁₉(2220) and of the background component comprising the nucleon pole and the exchange by vector mesons in the t-channel. Recent experimental data on cross sections and -asymmetry of the pp process measured from the reaction threshold to 1.1 GeV are used as a criterion of correctness of the model. Starting from photon energies of 1.7 GeV and higher, the cross section of the process depends strongly on the contribution of the -meson, that is, on the mechanism of action of vector mesons on the photoproduction amplitude and constants of vector meson coupling with -mesons and nucleons. The calculated cross sections and -asymmetry of the pp process at energies exceeding 1.4 GeV do not contradict the available experimental data.     

Photoproduction of Mesons off the Deuteron Quasifree and Coherent Processes

Photoproduction of mesons off the deuteron has been investigated at a tagged photon beam of the Bonn ELSA accelerator with the combined Crystal Barrel - TAPS electromagnetic calorimeter for incident photon energies up to 2.5 GeV. The mesons have been detected in coincidence with recoil protons, neutrons and deuterons. This allow the measurement of meson production reactions off the quasifree nucleons bound in the deutron, as well as the coherent production off the deuteron. The comparison of quasifree proton reactions to free proton reactions can confirm or invalidate possible nuclear effects on the extracted cross section reactions. Furthermore the isospin composition of a resonance can be estimated from the comparison of quasifree proton and neutron reactions. The quasifree photoproduction of the η＇ and π°η mesons off nucleons and the coherent photoproduction of π°η--pairs off the deuteron are discussed.     

π 0 and η Photoproduction on the Deuteron at ELPH, Tohoku University

Baryon spectroscopy is important to understand Quantum Chromodynamics at low energies. In this purpose, a series of π ⁰ and η photoproduction experiments was carried out with an electro-magnetic calorimeter FOREST at Research Center for Electron Photon Science, Tohoku University. The incident tagged bremsstrahlung photon energy ranges from 550 to 1,150 MeV. The differential and total cross sections obtained for π ⁰ and η photoproduction processes on the proton are consistent with the SAID and MAID calculations. The analysis of π ⁰ and η photoproduction on the neutron is underway.     

Photoproduction of the Θ~+ and its vector and axial-vector structure

We present recent investigations on the vector and axial-vector transitions of the baryon antide-cuplet within the framework of the self-consistent SU(3) chiral quark-soliton model, taking into account the 1/N_c rotational and linear ms corrections. The main contribution to the electric-like transition form factor comes from the wave-function corrections. This is a consequence of the generalized Ademollo-Gatto theorem. It is also found that in general the leading-order contributions are almost canceled by the rotational 1/N_c corrections. The results are summarized as follows: the vector and tensor K*NΘ coupling constants, g_(K*NΘ)=0.74-0.87 and f_(K*NΘ) = 0.53-1.16, respectively, and F_(Θ→KN)=0.71 MeV, based on the result of the KNΘ coupling constant g_(KnΘ) = 0.83. We also show the differential cross sections and beam asymmetries, based on the present results. We also discuss the connection of present results with the original work by Diakonov, Petrov, and Polyakov.     

Photoproduction of K 0 and Λ at HERA and a comparison with deep inelastic scattering

Inclusive K ⁰ and Λ photoproduction has been investigated at HERA with the H1 detector at an average photon-proton center of mass energy of 200 GeV in the transverse momentum range 0.5 < p _t < 5 GeV. The production rates as a function of p _t and center of mass rapidity are compared to those obtained in deep inelastic scattering at 〈Q ²〉 = 23 GeV². A similar comparison is made of the rapidity spectra of charged particles. The rate of strangeness photoproduction is compared with $p\bar p$ measurements. The observations are also compared with next-to-leading order QCD calculations and the predictions of a Monte Carlo model.     

Photoproduction ofρ- andω-mesons in the peripheral model

Photoproduction ofρ- andω-mesons on nucleons is considered. The possible matrix elements according to the peripheral model are constructed and the cross section is calculated,π,η,σ (ABC) and vector meson exchange is taken into account. The angular distribution for the decay pions of polarizedρ's is discussed with particular reference to peripheral production     

Photoproduction of the $\Theta^+$ and its vector and axial-vector structure

We present recent investigations on the vector and axial-vector transitions of the baryon antidecuplet within the framework of the self-consistent SU（3） chiral quark-soliton model, taking into account the 1/No rotational and linear mscorrections. The main contribution to the electric-like transition form factor comes from the wave-function corrections. This is a consequence of the generalized Ademollo-Gatto theorem. It is also found that in general the leading-order contributions are almost canceled by the rotational 1/No corrections. The results are summarized as follows： the vector and tensor K＇NO coupling constants, gK＊N= 0.74--0.87 and fk＊N =0.53--1.16, respectively, and F→KN = 0.71 MeV, based on the result of the KN coupling constant gKne =0.83. We also show the differential cross sections and beam asymmetries, based on the present results. We also discuss the connection of present results with the original work by Diakonov, Petrov, and Polyakov.     

Measurements of the mid-rapidity parity violating spin asymmetries for W ± bosons at PHENIX

The parity violating W ^± single spin asymmetry, in longitudinally polarized p + p collisions, can give us a clean way to access the $\Delta \bar u$ and $\Delta \bar d$ polarized parton distribution functions. The current status of the analysis of the 2011 data set and future prospects will be presented.     

Development of small molecules that mimic the binding of ω-conotoxins at the N-type voltage-gated calcium channel

Cone snails (Conidae) are marine predators with some extraordinary features. Their venom contains a hundred or more peptides that target numerous ion channels and receptors in mammals, including several that are involved in disease. omega-Conotoxins from fish hunting snails are 24-27 residue peptides with a rigid 4-loop cysteine framework that target the N-type voltage-gated calcium channel (VGCC). Two omega-conotoxins, MVIIA and CVID are currently in clinical development for chronic pain management (Ziconotide or Prialt, and AM336, respectively). In an attempt to develop small molecule equivalents of CVID, we defined the Calpha-Cbeta vectors of the residues believed to be important for binding to the N-type VGCC. Using these vectors, we undertook a virtual screening of virtual libraries approach to identify compounds that matched the pharmacophore. Cyclic pentapeptides containing residues of loop 2 of CVID, with one or more being a D-amino acid were designed and synthesised and were found to be active at the N-type VGCC (IC50 approximately 20 microM). Agreeing with the specificity profile of CVID, molecules were inactive at the P/Q-type VGCC.     

Direct Hard Photoproduction of J/ψ andγ in High Energy Pb-Pb and Ca-Ca Collisions at LHC

Direct hard PhotoProduction of J/ψ and γ at LHC Pb-Pb collisions with CMS energy 5.5ATeV, and Ca-Ca collisions with CMS energy 7ATeV, are discussed in the process: A+A→A+J/ψ(γ) + X. It turns out that the processes can be used to testing the gluon distribution in the nucleus, as well as to studying the mechanism of large P_t gluon and heavy quark fragmentation of J/ψ.     

Photoproduction of π+ p-pairs on the 16O nucleus and isobar configurations

The yield of the ¹⁶O(γ, π⁺ p) reaction has been measured in the region of the excitation of the Δ(1232) isobar at high momentum transfers to the residual nuclear system. The experimental data are interpreted within the model taking into account manifestations of isobar configurations in the ground state of the ¹⁶O nucleus. Direct and exchange mechanisms of the production of pions with emission of one and two nucleons, which follow from the structures of the density matrices for these reactions, have been considered. The probability of the production of the Δ-isobar in the ground state of the ¹⁶O nucleus has been empirically estimated as P _Δ = 0.019 ± 0.003 ± 0.003.     

Dielectric Properties of Nuclear Matter with the ωNN Interaction at High Temperature

Based on the QHD-1 field equation, the dielectric constant of nuclear matter with the ωNN interaction has been obtained in the framework of kinetic theory. Furthermore, the characters and physical background of the dielectric constant at high temperature is analyzed in detail.     

Localization of a high-power microwaves absorption in the cylindrical plasma column at ωLH ≪ ω ≪ ωce

This paper describes experiments which make it possible to determine the place of the absorption of electromagnetic waves in a cold (T _e=5–10eV) not fully ionized plasma column at _ce/=1 and _ce/> 1.The authors wish to thank L.Bárdo for helping with the experiments.     

Photoproduction of multi-meson final states — recent results from the Crystal-Barrel/TAPS experiment at ELSA-

Multi-meson final states such as γp →pπ0π0 and γp →pπ0η have been investigated with the Crystal-Barrel/TAPS experiment at ELSA. Baryon cascades via △π and △η and also via higher mass baryon resonances are clearly observed. Based on this data and on data from other reactions a partial wave analysis has been performed from which partial decay widths of various N＊ and △＊ states into the different pπ0π0 and pπ0η decay channels have been determined, leading partly to unexpected results. In addition, polarisation observables have been investigated. The beam asymmetry X has been determined for both reactions and double polarisation data using a longitudinally polarised target and a circularly or linearly polarised photon beam has been taken. Given the angular coverage of the Crystal-Baxrel/TAPS experiment this data covers almost the full angular range and phase space. This data will provide new and important information for the partial wave analyses and bring us one step closer towards a complete experiment.     

Photoproduction of positive pions from hydrogen at large angles in the energy range 0.3–2.0 GeV

The differential cross-section for the reaction γp↦π ⁺ n was measured using the bremsstrahlung beam of the Bonn 2.5 GeV electron synchrotron. The pions were detected and momentum analysed in a multichannel magnet spectrometer. Data reduction resulted in 1278 measured cross-sections which are presented as energy distributions at six laboratory angles between 180° and 95°. The range of laboratory photon energies extended from 0.3 to 2.1 GeV. The statistical accuracy is better than 3 percent, the systematic error is about 5 percent. The data are compared with other experimental results and predictions of a phenomenological analysis. These cross-sections are the result of a measurement program which was started in the seventies. Further results will be reported in forthcoming publications. Received: 2 February 2000 / Accepted: 14 August 2001     

Conformal couplings and “azimuthal matching” of QCD pomerons

Using the asymptotic conformal invariance of perturbative QCD we derive the expression of the coupling of external states to all conformal spin p components of the forward elastic amplitude. Using the wave function formalism for structure functions at small x, we derive the perturbative coupling of the virtual photon for , which is maximal for linear transverse polarization. The non-perturbative coupling to the proton is discussed in terms of “azimuthal matching” between the proton color dipoles and the configurations of the photon. As an application, the recent conjecture of a second QCD pomeron related to the conformal spin-1 component is shown to rely upon a strong azimuthal matching of the component in –proton scattering. Received: 25 October 1999 / Revised version: 19 January 2000 / Published online: 14 April 2000