Erratum: Test of Low-Energy Theorems forH1(γ→,π0)H

Abstract

In the results published in our Letter, the contributions from carbon and oxygen in the Kapton target windows were taken into account for the cross sections but they were neglected in the determination of the polarized beam asymmetries AE. The nuclei in the target windows have J ¼ 0 þ and therefore an asymmetry of AE ¼ 1 for the coherent 0 production that dominates in the threshold region. The contribution of the target-window contamination in each channel from threshold to 166 MeV is between 5% and 7% [1]. We therefore estimate the target-window contribution to the asymmetry to be 0:06 AE 0:01 in absolute units. Thus, the asymmetries should be corrected by subtracting %0:06 AE 0:01 from each datum. The published and corrected asymmetries are plotted in Fig. 1. The errors were increased by adding the 0.01 uncertainty in quadrature with the previously published values. The total and differential cross sections reported were corrected for the target-window contributions and thus remain valid. This correction to AE does not change the values of the S-wave amplitude E 0þ , the P-wave amplitude P 1 , or the P-wave combination P 23 . It will, however, modify the individual extraction of the P 2 and P 3 amplitudes. This is shown in Table I. / deg 0 π cms θ 0 20 40 60 80 100 120 140 160 180 Σ -0.3 -0.2 -0.1 -0.0 0.1 0.2 0.3 0.4 ChPT [2] DR [3] fit to the data published corrected FIG. 1. Published (filled squares) and corrected asymmetries (open squares) for E ¼ 159:5 MeV as a function of pion centerof-mass angle. The solid line is a fit to the published data, the dotted line is a prediction of ChPT [2], and the dashed line is a DR calculation [3].TABLE I. Results of the P-wave multipoles with statistical and systematic errors from a qk fit using AE pub and AE cor along with the original total and differential cross sections. Comparisons are made with predictions of ChPT [2] and a dispersion theoretical approach [3]. a AE pub AE cor ChPT DR P 1 9:44 AE 0:06 AE 0:28 9:44 AE 0:06 AE 0:28 9:14 AE 0:5 9.55 P 2 À9:48 AE 0:12 AE 0:28 À9:90 AE 0:12 AE 0:28 À9:7 AE 0:5 À10:37 P 3 11:32 AE 0:12 AE 0:34 10:96 AE 0:12 AE 0:34 10.36 9.27 P 23 10:45 AE 0:07 10:44 AE 0:07 11.07 9.84a P-wave combinations converted into the unit q  10 À3 =m 2 þ .

Threshold cusps and triangle singularities in hadronic reactions

“…(39), O(2 × 10 7 ) events need to be collected for the Υ(3S) → Υ(2S)π 0 π 0 decay. The cusp phenomena in the pion photoproduction process γp → π 0 p have been observed in experiments at Mainz [200][201][202][203] and Saskatoon [204]. Taking into account that the electric dipole amplitude for the γp → π + n reaction is much larger than that for the γp → π 0 p reaction, the presence of a cusp at the π + n threshold can be ascribed to the charge-exchange rescattering process γp → π + n → π 0 p, which has been studied long time ago [205][206][207][208][209][210][211][212].…”

Thresholdπ0photoproduction in relativistic chiral perturbation theory

“…[15] has been analyzed several times in the light of new experimental data [14,15,29,30,45,46]. Here, we fit the LECs in the same way to the experiment as in the relativistic case, allowing for a better comparison between both calculations.…”

Chiral dynamics with (non)strange quarks

“…The solid line is the theoretical prediction as discussed in the text and the data are from Ref. [2]. The cusp at the opening of the π + n threshold (E γ = 151.8 MeV) is clearly visible.…”