P -wave excited baryons from pion- and photo-induced hyperon production

Abstract

Abstract. We report evidence for N (1710)P11, N (1875)P11, N (1900)P13, ∆(1600)P33, ∆(1910)P31, and ∆(1920)P33, and find indications that N (1900)P13 might have a companion state at 1970 MeV. The controversial ∆(1750)P31 is not seen. The evidence is derived from a study of data on pion-and photo-induced hyperon production, but other data are included as well. Most of the resonances reported here were found in the Karlsruhe-Helsinki (KH84) [1] and the Carnegie-Mellon (CM) [2] analyses but were challenged recently by the Data Analysis Center at GWU [3]. Our analysis is constrained by the energy independent πN scattering amplitudes from either KH84 or GWU. The two πN amplitudes from KH84 or GWU, respectively, lead to slightly different πN branching ratios of contributing resonances but the debated resonances are required in both series of fits.

Measurement of the Transverse Target and Beam-Target Asymmetries inηMeson Photoproduction at MAMI

“…By adding all contributions in quadrature, a total systematic uncertainty of less than 6% is obtained. Figure 2 shows our results for T and F asymmetries together with previous data for T [13] and various theoretical predictions [4,6,8,10] for different bins in the incoming photon energy as a function of the η meson polar angle in the center-of-mass system, θ Ã η . The main inconsistencies with the existing data [13] are in the near threshold region.…”

Coupled-channel analysis ofKΣproduction on the nucleon up to 2.0 GeV

“…While the two γp → K + 0 datasets published respectively by the CLAS [6] and SAPHIR collaborations [13] are not very consistent in the backward angles, the newly measured data by the CLAS group [8] agree well with the former CLAS data [6] and LEPS data [1][2][3]. In the Bonn-Gatchina isobar partial wave analysis of these data, the evidence for the P 13 (1900) resonance, which is not favored by diquark models, is reported [22][23][24][25], while the P 31 (1750) state found both in the Juelich [42] and Giessen coupled-channel models [30,31] plays no role. Keeping these problems in mind, we perform a new combined analysis by taking into account all new measurements from CLAS and CBELSA groups, etc.…”

“…Strangeness electroproduction on the proton was also accurately measured by the CLAS [15] and A1 groups [16]. However, on theoretical side, most of the calculations [17][18][19][20][21] are based on the previous database, and the very recent data are not yet included in the analysis except for the Bonn-Gatchina partial wave analysis [22][23][24][25][26][27]. So it is meaningful to perform a full coupled-channel calculation based on the updated database combining both the πN and γ N data.…”

Partial wave analysis

“…We always quote errors which cover all solutions or we discuss different classes of solutions in which the number and the properties of some resonances may differ [44][45][46][47][48][49].…”

“…Before 2006, data on photoproduction added information on the helicity couplings of resonances listed in the RPP, but the resonances were introduced into the respective analyses with fixed masses and widths. Early results of the BnGa group using data on photoproduction from the CB-ELSA experiment [65][66][67][68] were not yet included in the RPP [44,69] or not yet used to define particle properties [30,70] The BnGa group was the first one which combined pion and photoproduced reactions in a coupled channel fit, fitted masses and widths freely and searched systematically for new resonances [46][47][48][49]. In this way, the baryon resonances dismissed in the Arndt et al analysis [15] could be re-established [46].…”