在γp→pη新的精确束流不对称性Σ数据中对pη'尖点的观测。

Observation of the pη^{'} Cusp in the New Precise Beam Asymmetry Σ Data for γp→pη.

作者信息

Afzal F, Wunderlich Y, Anisovich A V, Bayadilov D, Beck R, Becker M, Blanke E, Brinkmann K-Th, Ciupka S, Crede V, Dieterle M, Dutz H, Elsner D, Friedrich S, Frommberger F, Gridnev A, Gottschall M, Grüner M, Gutz E, Hammann C, Hannappel J, Hartmann J, Hillert W, Hoff J, Hoffmeister P, Honisch C, Jude T, Kalinowsky H, Kalischewski F, Keshelashvili I, Klassen P, Klein F, Klempt E, Koop K, Kroenert P, Krusche B, Lang M, Lopatin I, Mahlberg P, Meißner U-G, Messi F, Metag V, Meyer W, Mitlasóczki B, Müller J, Müllers J, Nanova M, Nikonov K, Nikonov V, Novinskiy V, Novotny R, Piontek D, Reicherz G, Richter L, Rönchen D, Rostomyan T, Salisbury B, Sarantsev A, Schaab D, Schmidt C, Schmieden H, Schultes J, Seifen T, Sokhoyan V, Sowa C, Spieker K, Stausberg N, Thiel A, Thoma U, Triffterer T, Urban M, Urff G, van Pee H, Walther D, Wendel Ch, Wiedner U, Wilson A, Winnebeck A, Witthauer L

机构信息

Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Germany.

National Research Centre "Kurchatov Institute", Petersburg Nuclear Physics Institute, Gatchina, Russia.

出版信息

Phys Rev Lett. 2020 Oct 9;125(15):152002. doi: 10.1103/PhysRevLett.125.152002.

DOI:10.1103/PhysRevLett.125.152002

PMID:33095637

Abstract

Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W=1748 MeV to W=2045 MeV). The data cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη^{'} threshold [E_{γ}=1447 MeV (W=1896 MeV)]. The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N(1895)1/2^{-} nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.

摘要

报告了在质子上产生η介子的光致产生过程中，标记光子能量在1130至1790 MeV（质量范围从W = 1748 MeV至W = 2045 MeV）时的束流不对称性Σ数据。这些数据覆盖了整个立体角，便于进行精确的矩分析。首次观察到极化可观测量中的强尖点效应，这是在pη′阈值[Eγ = 1447 MeV（W = 1896 MeV）]处分支点奇点的效应。最新的BnGa分波分析纳入了新的束流不对称性数据，并给出了N(1895)1/2⁻核子共振的有力迹象，证明了纳入所有奇点对于正确确定分波和共振参数的重要性。