arXiv subjects

G. Penner

Publications and source records attributed to G. Penner.

14 recordsLinked to original sources

arXiv2005

Coupled-channel analysis of the $ω$-meson production in $πN$ and $γN$ reactions for c.m. energies up to 2 GeV

The pion- and photon induced reactions for the final states $γN$, $πN$, $2πN$, $ηN$, and $ωN$ are studied within a coupled-channel effective Lagrangian approach in the energy region from the pion threshold up to 2 GeV. To investigate the role of the nucleon resonances in the different reactions we include all known states with spin-$\foh$,-$\fth$, and -$\ffh$ and masses below 2 GeV. We find a strong contribution from the $D_{15}(1675)$ resonance to the $πN \to ωN$ reaction. While the $F_{15}(1680)$ state only slightly influences the $ω$ meson production in the $πN$ scattering its role is enhanced in the $ω$ photoproduction due to the large electromagnetic coupling of this resonance. We predict the beam asymmetry $Σ_X$ to be a negative in the $γp \to ωp$ reaction near to the threshold. Above the 1.85 GeV the asymmetry is found to change its sign and becomes positive at forward directions. The presented findings can be experimentally tested at GRAAL, CLAS, and CB-ELSA facilities.

nucl-th↗

arXiv2004

Spin-5/2 resonance contributions to the pion-induced reactions for energies $\sqrt{s}\leqslant$2.0 GeV

The spin-$\ffh$ resonance effects are studied within the coupled channel effective Lagrangian model for baryon resonance analysis. We extend our previous hadronic calculations to incorporate the $D_{15}$, $F_{15}$, $D_{35}$, $F_{35}$ states. While the effect of the spin-$\ffh$ resonances to the $ηN$, $K Λ$, and $K Σ$ reactions are small, the contribution to the $ωN$ is found to be important. The results for the 'conventional' and Pascalutsa-like spin-$\ffh$ descriptions are discussed. \PACS{{11.80.-m},{13.75.Gx},{14.20.Gk},{13.30.Gk}}

nucl-th↗

arXiv2003

Vector meson production and nucleon resonance analysis in the Giessen coupled-channel model

We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states $γN$, $πN$, $2πN$, $ηN$, $KΛ$, $KΣ$, and $ωN$ for energies from the nucleon mass up to $\sqrt s = 2$ GeV. In this analysis we find strong evidence for various higher lying resonances as, e.g., the $P_{13}(1900)$. The $ωN$ production mechanism is dominated by large $P_{11}(1710)$ and $P_{13}(1900)$ contributions.

nucl-th↗

arXiv2003

Spin-5/2 resonance effects in a coupled channel nucleon resonance analysis

Spin-$\ffh$ resonance contributions in pion-nucleon scattering are investigated within the coupled channel $K$-matrix approach for c.m. energies up to $\sqrt s=$ 2 GeV. All previously studied $πN$, $2πN$, $ηN$, $K Λ$, $K Σ$, and $ωN$ final states are included. We find a significant improvement of $χ^2$ in almost all channels by inclusion of the spin-$\ffh$ states. The obtained coupling parameters are discussed.

hep-ph↗

arXiv2002

Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV I: pion-induced results and hadronic parameters

We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states gamma N, pi N, 2 pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass up to sqrt(s) = 2 GeV. In this analysis we find strong evidence for the resonances P_{31}(1750), P_{13}(1900), P_{33}(1920), and D_{13}(1950). The omega N production mechanism is dominated by large P_{11}(1710) and P_{13}(1900) contributions. In this first part, we present the results of the pion-induced reactions and the extracted resonance and background properties with emphasis on the difference between global and purely hadronic fits.

nucl-th↗

arXiv2002

Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV II: photon-induced results

We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states gamma N, pi N, 2 pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass up to sqrt(s) = 2 GeV. In this analysis we find strong evidence for the resonances P_{31}(1750), P_{13}(1900), P_{33}(1920), and D_{13}(1950). The omega N production mechanism is dominated by large P_{11}(1710) and P_{13}(1900) contributions. In this second part we present the results on the photoproduction reactions and the electromagnetic properties of the resonances. The inclusion of all important final states up to sqrt(s) = 2 GeV allows for estimates on the importance of the individual states for the GDH sum rule.

nucl-th↗

arXiv2002

Pi N -> Omega N in a Coupled-Channel Approach

We describe the pi N -> omega N cross section from threshold to a center of mass energy of 2 GeV in a unitary coupled-channel model and analyze it in terms of rescattering and resonance excitations. The amplitude is mainly composed of D13, P13, and P11 contributions, where the D13 dominates over the complete considered energy range. We also outline the generalization of the standard partial-wave formalism necessary for the decomposition of the omega N final state.

nucl-th↗

arXiv2002

What is the Correct pi^- p -> omega n Cross Section at Threshold?

The pi^- p -> omega n threshold cross section measured in the seventies resisted up to now a consistent theoretical description in line with experiment, mainly caused by too large Born contributions. This led to a discussion in the literature about the correctness of the extraction of these data points. We show that the extraction method used in these references is indeed correct and that there is no reason to doubt the correctness of these data.

nucl-th↗

arXiv2001

The Giessen Model - Vector Meson Production on the Nucleon in a Coupled Channel Approach

In this paper we present the extension of our unitary gauge invariant effective Lagrangian model to vector meson nucleon final states. This model already included the final states $γN$, $πN$, $2πN$, $ηN$, $K Λ$, and $K Σ$ and was developed for a simultaneous analysis of all avaible experimental data for photon- and pion-induced reactions on the nucleon. We discuss how the extension to vector meson nucleon final states is realized, outline a generalization of the standard partial wave formalism, that is applicable to any meson-/photon-baryon reaction, and show first results for $ωN$ production.

nucl-th↗

arXiv2001

Anti-Kaon Induced Reactions on the Nucleon

Using a previously established effective Lagrangian model we describe anti-kaon induced reactions on the nucleon. The dominantly contributing channels in the cm-energy region from threshold up to 1.72 GeV are included (K N, πΣ, πΛ). We solve the Bethe-Salpeter equation in an unitary $K$-matrix approximation.

nucl-th↗

arXiv2000

Role of N*(1650) in the near threshold pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions

We investigate the pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions at beam energies near their thresholds within an effective Lagrangian model, where the strangeness production proceeds via the excitation of N*(1650), N*(1710), and N*(1720) baryonic resonances. It is found that the $N^*$(1650) resonance dominates both these reactions at near threshold energies. The contributions from this resonance together with the final state interaction among the outgoing particles are able to explain the observed beam energy dependence of the ratio of the cross sections of the two reactions in the near threshold region.

nucl-th↗

arXiv2000

Nucleon Resonances in Meson Nucleon Scattering with Strangeness Production

An effective Lagrangian model in a coupled channels framework is applied to extract nucleon resonance parameters. In the K-matrix approximation, we simultaneously analyze all the available data for the transitions from pi N to five possible meson-baryon final states, pi N, pipi N, eta N, K Lambda, and KSigma, in the energy range from pi N threshold up to W = 2 GeV. In this work, we focus our efforts on the K Sigma channel. In particular, we include a set of Delta resonances around 1900 MeV: the S31(1900), P31(1910), and P33(1920) states. In most cases the parameters of nucleon resonances determined by the fits are consistent with the commonly accepted values in the literature. We find that in the low-energy region, the S11(1650), P11(1710), and P13(1720) states are important for the p(pi-,K0)Sigma0 and p(pi-,K+)Sigma- processes while the P33(1600) and D33(1700) states are significant for the pure I=3/2 reaction p(pi+,K+)Sigma+. In the high energy region, we find a D13 state at 1945 MeV which is important for the p(pi-,K0)Sigma0 reaction while the Delta resonances around 1900 MeV show up significantly in the p(pi-,K+)Sigma- and p(pi+,K+)Sigma+ processes.

nucl-th↗

arXiv2000

Missing Nucleon Resonances in Kaon Production with Pions and Photons

Resonances with strong couplings to strangeness channels are investigated in a coupled-channels framework of kaon production with pions and photons. We find evidence for an additional D13 resonance around 1900 MeV that has a significant decay width into the K Lambda final state. Such a state has been predicted in a relativistic quark model at 1960 MeV with significant gamma N and K Lambda branching ratios.

nucl-th↗

arXiv1999

Nucleon Resonances in Kaon Photoproduction

Nucleon resonances are investigated through the electromagnetic production of K-mesons. We study the kaon photoproduction process at tree-level and compare to a recently developed unitary K-matrix approach. Employing hadronic form factors along with the proper gauge prescription yields suppression of the Born terms and leads a resonance dominated process for both K-Lambda and K-Sigma photoproduction. Using new SAPHIR data we find the K+-Lambda photoproduction to be dominated by the S11(1650) at threshold, with additional contributions from the P11(1710) and P13(1720) states. The K-Sigma channel couples to a cluster of Delta resonances around W = 1900 MeV. We briefly discuss some tantalizing evidence for a missing D13 resonance around 1900 MeV with a strong branching ratio into KLambda channel.

nucl-th↗