Studying the production mechanisms of light meson resonances in two-pion photoproduction

Il Nuovo Cimento A (1965-1970), 1968

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Physical Review C, 2012

The details of the analysis of the near-threshold bump structure in the forward differential cross section of the φ-meson photoproduction to determine whether it is a signature of a resonance, together with more extensive results, are presented. The analysis is carried out in an effective Lagrangian approach which includes Pomeron and (π, η) exchanges in the t channel, and contributions from the sand u-channel excitations of a postulated nucleon resonance. In addition to the differential cross sections, we use the nine spin-density matrix elements as recently measured, instead of the φ-meson decay angular distributions which depend only on six spin-density matrix elements as was done before, to constrain the resonance parameters. We conclude that indeed the nonmonotonic behavior, along with the other experimental data as reported by LEPS, can only be explained with an assumption of the excitation of a resonance of spin 3/2, as previously reported. However, both parities of (±) can account for the data equally well with almost identical mass of 2.08 ± 0.04 GeV and width of 0.501 ± 0.117 and 0.570 ± 0.159 for 3/2 + and 3/2 − , respectively. The ratio of the helicity amplitudes A 1 2 /A 3 2 calculated from the resulting coupling constants differs in sign from that of the known D13(2080). More experimental data on single and double polarization observables are needed to resolve the parity. We further find that with an assumption of large values of the OZI-evading parameters xOZI = 12 for J P = 3/2 − and xOZI = 9 for J P = 3/2 + , the discrepancy between the recent experimental data on ω-meson photoproduction and theoretical model can be considerably reduced. We argue that the large value of xOZI indicates that the postulated resonance contains non-negligible amount of strangeness content.

Physical Review C, 2002

A partial-wave analysis of single-pion photoproduction data has been completed. This study extends from threshold to 2 GeV in the laboratory photon energy, focusing mainly on the influence of new measurements and modeldependence in the choice of parameterization employed above the two-pion threshold. Results are used to evaluate sum rules and estimate resonance photo-decay amplitudes. These are compared to values obtained in the MAID analysis.

The exclusive reaction γp → pπ + π − was studied in the photon energy range 3.0 -3.8 GeV and momentum transfer range 0.4 < −t < 1.0 GeV 2 . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was about 20 pb −1 . The reaction was isolated by detecting the π + and proton in CLAS, and reconstructing the π − via the missing-mass technique. Moments of the di-pion decay angular distributions were derived from the experimental data. Differential cross sections for the S, P , and D-waves in the M π + π − mass range 0.4 − 1.4 GeV were derived performing a partial wave expansion of the extracted moments. Besides the dominant contribution of the ρ(770) meson in the P -wave, evidence for the f0(980) and the f2(1270) mesons was found in the S and D-waves, respectively. The differential production cross sections dσ/dt for individual waves in the mass range of the above-mentioned mesons were extracted. This is the first time the f0(980) has been measured in a photoproduction experiment.

Physical Review D, 2009

The exclusive reaction γp → pπ + π − was studied in the photon energy range 3.0 -3.8 GeV and momentum transfer range 0.4 < −t < 1.0 GeV 2 . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was about 20 pb −1 . The reaction was isolated by detecting the π + and proton in CLAS, and reconstructing the π − via the missing-mass technique. Moments of the di-pion decay angular distributions were derived from the experimental data. Differential cross sections for the S, P , and D-waves in the M π + π − mass range 0.4 − 1.4 GeV were derived performing a partial wave expansion of the extracted moments. Besides the dominant contribution of the ρ(770) meson in the P -wave, evidence for the f0(980) and the f2(1270) mesons was found in the S and D-waves, respectively. The differential production cross sections dσ/dt for individual waves in the mass range of the above-mentioned mesons were extracted. This is the first time the f0(980) has been measured in a photoproduction experiment.

Physical Review C, 1997

The role of dynamics in spin observables for pseudoscalar meson photoproduction is investigated using a density matrix approach in a multipole truncated framework. Extraction of novel rules for γp → π + n, K + Λ and ηp reactions based on resonance dominance, and on other broad and reasonable dynamical assumptions, are discussed. Observables that are particularly sensitive to missing nucleonic resonances predicted by quark-based approaches, are singled out.

Journal of Otolaryngology - Head &amp; Neck Surgery, 1972

Physical Review Letters, 2006

The photoproduction of the ! meson has been studied at GRAAL from threshold up to a photon energy of 1.5 GeV. The differential cross sections and beam asymmetries have been measured precisely at all angles. The total cross section is also obtained. Systematic enhancements of the differential cross section at large angles and nonzero beam asymmetries at intermediate angles provide clear evidence for s-and u-channel resonant processes. The data are compared to the results of hadron and quark models.

CONFERENCE ON THEORETICAL PHYSICS AND NONLINEAR PHENOMENA (CTPNP) 2019: Excursion from Vacuum to Condensed Matter, 2020

meson photoproduction on the nucleon was investigated by using the effective Lagrangian approach at the tree level. We consider the leading contributions to the amplitude, which are Born term, vector-meson term, and resonance term. The resonances listing up to spin-5/2 (20 resonances) are taken from Particle Data Group which is updated at January 19th, 2019. The unknown values of the model parameter are extracted from fitting to around 1082 experiment data. We also calculate the differential cross section to compare the model predictions with the experiment data. And the last, we analyze the graphics quantitatively at several cos .

Physical Review C, 2021