Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1504.02221

Measurement of double polarisation asymmetries in $ω$-photoproduction

H. Eberhardt·T. C. Jude·H. Schmieden·A. V. Anisovich·B. Bantes·D. Bayadilov·R. Beck·Yu. Beloglazov·M. Bichow·S. Boese·K. -Th. Brinkmann·Th. Challand·V. Crede·F. Diez·P. Drexler·H. Dutz·D. Elsner·R. Ewald·K. Fornet-Ponse·St. Friedrich·F. Frommberger·Ch. Funke·M. Gottschall·A. Gridnev·M. Gruener·E. Gutz·Ch. Hammann·J. Hannappel·J. Hartmann·W. Hillert·Ph. Hoffmeister·Ch. Honisch·I. Jaegle·D. Kaiser·H. Kalinowsky·F. Kalischewski·S. Kammer·I. Keshelashvili·V. Kleber·F. Klein·E. Klempt·K. Koop·B. Krusche·M. Kube·M. Lang·I. Lopatin·Y. Maghrbi·K. Makonyi·V. Metag·W. Meyer·J. Mueller·M. Nanova·V. Nikonov·R. Novotny·D. Piontek·S. Reeve·G. Reicherz·T. Rostomyan·S. Runkel·A. Sarantsev·St. Schaepe·Ch. Schmidt·R. Schmitz·T. Seifen·V. Sokhoyan·V. Sumachev·A. Thiel·U. Thoma·M. Urban·H. van Pee·D. Walther·Ch. Wendel·U. Wiedner·A. Wilson·A. Winnebeck
View original source ↗Read source document ↗Export metadata ↓

Abstract

The first measurements of the beam-target-helicity-asymmetries $E$ and $G$ in the photoproduction of $ω$-mesons off protons at the CBELSA/TAPS experiment are reported. $E$ ($G$) was measured using circularly (linearly) polarised photons and a longitudinally polarised target. $E$ was measured over the photon energy range from close to threshold ($E_γ= 1108$~MeV) to $E_γ= 2300$~MeV and $G$ at a single energy interval of $1108 < E_γ<1300$~MeV. Both measurements cover the full solid angle. The observables $E$ and $G$ are highly sensitive to the contribution of baryon resonances, with $E$ acting as a helicity filter in the $s$-channel. The new results indicate significant $s$-channel resonance contributions together with contributions from $t$-channel exchange processes. A partial wave analysis reveals strong contributions from the partial waves with spin-parity $J^P=3/2^+, 5/2^+$, and $3/2^-$.

Explore related subjects

nucl-ex

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

H. Eberhardt, T. C. Jude, H. Schmieden, A. V. Anisovich, B. Bantes, D. Bayadilov, R. Beck, Yu. Beloglazov, M. Bichow, S. Boese, K. -Th. Brinkmann, Th. Challand, V. Crede, F. Diez, P. Drexler, H. Dutz, D. Elsner, R. Ewald, K. Fornet-Ponse, St. Friedrich, F. Frommberger, Ch. Funke, M. Gottschall, A. Gridnev, M. Gruener, E. Gutz, Ch. Hammann, J. Hannappel, J. Hartmann, W. Hillert, Ph. Hoffmeister, Ch. Honisch, I. Jaegle, D. Kaiser, H. Kalinowsky, F. Kalischewski, S. Kammer, I. Keshelashvili, V. Kleber, F. Klein, E. Klempt, K. Koop, B. Krusche, M. Kube, M. Lang, I. Lopatin, Y. Maghrbi, K. Makonyi, V. Metag, W. Meyer, J. Mueller, M. Nanova, V. Nikonov, R. Novotny, D. Piontek, S. Reeve, G. Reicherz, T. Rostomyan, S. Runkel, A. Sarantsev, St. Schaepe, Ch. Schmidt, R. Schmitz, T. Seifen, V. Sokhoyan, V. Sumachev, A. Thiel, U. Thoma, M. Urban, H. van Pee, D. Walther, Ch. Wendel, U. Wiedner, A. Wilson, A. Winnebeck. 2015-09-01. Measurement of double polarisation asymmetries in $ω$-photoproduction. https://doi.org/10.1016/j.physletb.2015.09.049

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Measurements of $γ_v p \to π^+ π^-p'$ Cross Sections with the CLAS12 Detector for $Q^2$ from 2.4-8.0 GeV$^2$ and $W$ from 1.4-2.1 GeV

This paper reports exclusive cross sections for the $ep \to e'π^+π^-p'$ reaction using the CLAS12 detector at Jefferson Laboratory. The extractions of fully integrated and nine single-differential cross sections are presented for the first time for photon virtualities $Q^2$ from 2.4 to 8.0 GeV$^2$ and center-of-mass energies $W$ from 1.4 to 2.1 GeV, which covers a large part of the nucleon resonance region. These data considerably extend the kinematic reach of previous measurements from CLAS that covered $Q^2$ up to 5.0 GeV$^2$. Exclusive $γ_v p \to π^+ π^-p'$ cross section measurements are of particular importance for the extraction of $γ_vpN^*$ resonance electrocouplings across the $N^*$ spectrum, especially in the mass range above 1.6 GeV where several resonances decay preferentially to the $ππN$ final states. The electrocouplings with extended $Q^2$ coverage expected from these new data will enable an improved understanding of the emergence of $N^*$ mass and structure in the transition from the strongly coupled toward the perturbative QCD regime.

nucl-ex↗
arXiv2026

Direct measurement of Enhanced octupole collectivity in 148Dy

Excited states in $^{148}_{~66}$Dy were populated via $β^+/EC$ decay of $^{148m}$Ho using the GRIFFIN spectrometer at the TRIUMF ISAC-I facility. A combined measurement of the mean lifetime of the $3_1^-$ level using the Generalized Centroid Difference (GCD) method and branching fraction of the $3_1^-\rightarrow0_1^+$ $γ$-ray decay has been performed. From these results, an enhanced electric octupole $B(E3;3_1^-\rightarrow0_1^+)$ transition strength of 46(3)~W.u. has been determined in $^{148}_{~66}$Dy. This is the largest measured value across the closed neutron shell at $N=82$ and provides direct evidence of enhanced octupole collectivity beyond $Z=64$. The evolution of the $B(E3; 3^-_1 \rightarrow 0^+_1)$ strength along the $N=82$ isotonic chain is compared with quasiparticle random-phase approximation (QRPA) calculations using the SkI3 and SkM$^*$ Skyrme energy-density functionals, as well as with large-scale shell-model (SM) calculations. This result extends the boundaries of enhanced octupole collectivity far from the so-called `octupole magic numbers' $Z=56$ and $N=88$.

nucl-ex↗
arXiv2026

First observation of the fine structure of the Pygmy Dipole Resonance in a nucleus away from stability via the $β^-$ decay of $^{92}$Rb to $^{92}$Sr

A comprehensive $γ$-ray spectroscopy study of excited states in $^{92}$Sr populated via $β^-$ decay of $^{92}$Rb ($J^π=0^-$, $Q_β=8095(6)$~keV) was performed with the GRIFFIN spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high $γ$-ray efficiency of the GRIFFIN spectrometer combined with the intense rubidium beams produced allowed for 864 $γ$-ray transitions to be placed in the level scheme with 190 excited levels populated, most of them identified for the first time. The excitation energies of low-spin states in $^{92}$Sr are well reproduced by large-scale Shell Model calculations up to 5~MeV. The $β$-feeding intensities are in very good agreement with results from a recent study employing Modular Total Absorption Spectroscopy, indicating a significant suppression of the Pandemonium effect. The experimental picture reveals the energy level dependence of log~$ft$ values in unprecedented detail. These log~$ft$ values are well reproduced by Multiple-Commutator Model calculations that identify the features in the excited levels' wavefunctions that enable the population of high-lying levels with a low effective Q-value that belong to the Pygmy Dipole Resonance.

nucl-ex↗