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A. Sarantsev

Publications and source records attributed to A. Sarantsev.

26 records · Page 2Linked to original sources
arXiv2012

Well-established nucleon resonances revisited by double-polarization measurements

The first measurement is reported of the double-polarization observable G in photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid angle. G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon. The observable is highly sensitive to contributions from baryon resonances. The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of the long-lasting efforts to understand γp -> pπ 0 as the simplest photoproduction reaction, surprisingly large differences between the new data and the latest predictions are observed which are traced to different contributions of the N (1535) with spin-parity J^P = 1/2^- and N (1520) with J^P = 3/2^- . In the third resonance region, where N (1680) with J^P = 5/2^+ production dominates, the new data are reasonably close to the predictions.

nucl-ex↗
arXiv2011

The f2(1565) in pbar-p -> (omega-omega)pizero interactions at rest

Data are presented on the reaction pbar-p -> omega-omega-pizero at rest from the Crystal Barrel detector. These data identify a strong signal due to f2(1565) -> omega-omega. The relative production from initial pbar-p states 3P2, 3P1 and 1S0 is well determined from omega-omega decay angular correlations; P-state annihilation dominates strongly. A combined fit is made with data on pbar-p -> 3pizero at rest, where f2(1565) -> pizero-pizero is observed.

hep-ex↗
arXiv2010

Some indication for a missing chiral partner eta_4 around 2 GeV

The high-lying mesons in the light quark sector previously obtained from the partial wave analysis of the proton-antiproton annihilation in flight at 1.9 - 2.4 GeV region at CERN reveal a very high degree of degeneracy. This degeneracy can be explained as due to an effective restoration of both SU(2)_L * SU(2)_R and U(1)_A symmetries combined with a principal quantum number n + J. In this case there must be chiral partners for the highest spin states in the 2 and 2.3 GeV bands presently missing in the data. Here we reanalyze the Crystal Barrel data and show an indication for existence of the missing $4^{-+}$ state around 2 GeV. This result calls for further experimental search of the missing states both in the proton-antiproton annihilation and in the production reactions.

hep-ph↗
arXiv2010

Photoproduction of meson pairs: First measurement of the polarization observable I^s

The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Fits using Bonn-Gatchina partial wave analysis demonstrate that the new polarization observables carry significant information on the contributing partial waves.

nucl-ex↗
arXiv2009

Photoproduction of $η$ and $η\prime$ Mesons off Protons

Total and differential cross sections for $η$ and $η^\prime$ photoproduction off the proton have been determined with the CBELSA/TAPS detector for photon energies between 0.85 and 2.55 GeV. The $η$ mesons are detected in their two neutral decay modes, $η\toγγ$ and $η\to 3π^0\to 6γ$, and for the first time, cover the full angular range in $\rm cos θ_{cm}$ of the $η$ meson. These new $η$ photoproduction data are consistent with the earlier CB-ELSA results. The $η^\prime$ mesons are observed in their neutral decay to $π^0π^0η\to 6γ$ and also extend the coverage in angular range.

nucl-ex↗
arXiv2005

Photoproduction of Baryons Decaying into N pi and N eta

A combined analysis of photoproduction data on γp to πN, eta N was performed including the data on K Lambda and K Sigma. The data are interpreted in an isobar model with s--channel baryon resonances and pi, rho,(omega), K, and K^* exchange in the t--channel. Three baryon resonances have a substantial coupling to eta N, the well known N(1535)S_{11}, N(1720)P_{13}, and N(2070)D_{15}. The inclusion of data with open strangeness reveals the presence of further new resonances, N(1840)P_{11}, N(1875)D_{13} and N(2170)D_{13}.

hep-ex↗
arXiv2005

Partial wave decomposition of pion and photoproduction amplitudes

Partial wave amplitudes for production and decay of baryon resonances are constructed in the framework of the operator expansion method. The approach is fully relativistically invariant and allow us to perform combined analyses of different reactions imposing directly analyticity and unitarity constraints. All formulas are given explicitly in the form used by the Crystal Barrel collaboration in the (partly forthcoming) analyses of the electro-, photo- and pion induced meson production data.

hep-ph↗