Search for narrow resonances in $\pi p$ elastic scattering from the EPECUR experiment

The analysis of high-precision ${\pi }^{\pm }p\to {\pi }^{\pm }p$ cross-sectional data from the EPECUR Collaboration based on the multichannel $K$-matrix approach is presented. The sharp structures seen in these data are studied in terms of both opening thresholds and new resonance contributions. Some prominent features are found to be due to the opening $K\mathrm{\Sigma }$ channel. However, a complete description of the data is improved with the addition of two narrow resonant structures at $W\sim 1.686$ and $W\sim 1.720\mathrm{GeV}$. These structures are interpreted as manifestations of $S_{11}$ and $P_{11}$ resonances. The underlying nature of the observed phenomena is discussed.

Figure 1

${\pi }^{+}p$ elastic scattering. Red solid lines correspond to the present calculations. Dashed lines indicate the XP15 solution. Vertical arrows shows positions where structures in ${\pi }^{-}p$ scattering were observed.

Figure 2

${\pi }^{-}p$ elastic scattering. Red solid lines correspond to the present calculations. Dashed lines lines are the XP15 solution.

Figure 3

Total cross section for $\pi p\to K\mathrm{\Sigma }$. (a) ${\pi }^{-}p\to K^0{\mathrm{\Sigma }}^0$, (b) ${\pi }^{-}p\to K^{+}{\mathrm{\Sigma }}^{-}$, and (c) ${\pi }^{+}p\to K^{+}{\mathrm{\Sigma }}^{+}$. The data are from Ref. [39]. Red solid lines are from the present work.

Figure 4

${\pi }^{-}p$ elastic scattering with added resonances. The red solid line gives the present calculation.

Figure 5

Comparison of the measured and calculated ${\pi }^{-}p\to \eta n$ total cross sections. The red solid line presents the calculations from this work. The black dashed line indicates the $S$-wave contribution.

Figure 6

${\pi }^{-}p\to K\mathrm{\Lambda }$ differential cross section. Red solid lines indicate present calculations.

Figure 7

Energy dependence of ${\pi }^{-}p\to K\mathrm{\Lambda }$ differential cross section. Red solid line indicates present calculations.