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An Experimental Test of Exchange Degeneracy in the Reactions $\pi^+ p \to K^+ \Sigma^+$, $\pi^+ p \to K^+ \Sigma^+$ (1385) and Their Line Reversed Partners

Berglund, A. ; Buran, T. ; Carlson, P.J. ; et al.

Nucl.Phys.B 166 (1980) 25-61, 1980.

Inspire Record 143535 DOI 10.17182/hepdata.34526

A description is given of an experimental study of exchange degeneracy (EXD) in hypercharge-exchange reactions using the line-reversed partners π + p→K + Σ + (K − p→ π − Σ + ) and π + p→ K + Σ + (1385) (K − p→ π − Σ + (1385)) at incident momenta of 7.0 and 10.1 GeV/ c . Both pairs of reaction were measured in the same apparatus, with particular care being taken to minimize relative normalization errors. For the Σ production reactions we present high statistics measurements of the differential cross sections and polarizations from t ′=0 to large t . The general trends of the data agree with naive expectations from weak EXD. The cross-section difference in the extreme forward direction at the higher momentum is consistent with zero and there is a general reduction in the cross-section differences going from the lower to the higher momentum. The polarizations are approximately equal in magnitude and of opposite sign between the two reactions. On the other hand, the data do not agree with the detailed predictions of EXD. The slope for the positive reaction is systematically steeper in the forward region than for the negative reaction and there is a complex s and t dependence for the cross-section differences including a cross-over at t ⋍ −0.8( GeV /c) 2 . For the Σ(1385) production reactions, we present differential cross-section measurements in the forward region (| t |<0.3(GeV/ c ) 2 ). The cross-section differences are substantial and essentially constant over the s and t ranges studied.

2 data tables

Table 1

THESE RESULTS WERE BRIEFLY REPORTED IN A. BERGLUND ET AL., PL 73B, 369 (1978), THE RECORD OF WHICH INCLUDES THE TABULATED DATA.

Table 2

THE RESULTS AT 10.1 GEV WERE FIRST PUBLISHED IN A. BERGLUND ET AL., PL 60B, 117 (1975), THE RECORD OF WHICH INCLUDES THE TABULATED DATA.

The Reactions K- p --> pi-+ Sigma+- (1385) at 4.2-GeV/c

The Amsterdam-CERN-Nijmegen-Oxford collaboration Holmgren, S.O. ; Aguilar-Benitez, M. ; Barreiro, F. ; et al.

Nucl.Phys.B 119 (1977) 261-291, 1977.

Inspire Record 110408 DOI 10.17182/hepdata.35566

The reactions K − p→ π − Σ + (1385) and K − p→ π + Σ − (1385) are studied at 4.2 GeV c incident momentum using data from a high statistics bubble chamber experiment corresponding to ∼80 events/μb. The total and differential cross sections are presented. Amplitude analyses are performed and the complete Σ ± (1385) helicity spin density matrices are extracted. The results are compared with the predictions of the additive quark model and exchange degeneracy. A substantial cross section is observed for the reaction K − p→ π + Σ − (1385) in the forward direction, which implies exotic meson quantum numbers in the t -channel. One possible interpretation of this process provides an explanation for the small but significant violations of the additive quark model predictions observed in the reaction K − p→ π − Σ + (1385) at low four-momentum transfer. In the backward direction unnatural parity exchange is shown to give a larger contribution to K − p→ Σ − (1385) π + than natural parity exchange.

11 data tables

Table 1

Axis error includes +- 5/5 contribution.

Table 2

Axis error includes +- 5/5 contribution.

Table 3

Axis error includes +- 5/5 contribution.

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A Study of the Line Reversed Hypercharge Exchange Reactions pi+ p --> K+ Sigma+ (1385) and K- p --> pi- Sigma+ (1385) at 10-GeV/c

Berglund, A. ; Buran, T. ; Carlson, P.J. ; et al.

Phys.Lett.B 60 (1975) 117-120, 1975.

Inspire Record 100190 DOI 10.17182/hepdata.27751

We present results on the differential cross-sections for the reactions π + p → K + Σ + (1385) and K − p → π − Σ + (1385) at 10 GeV/ c . For the first time, the same equipment has been used in measuring both reactions, in order to obtain good relative normalization. In the region of low t ( t min to −0.3 (GeV/ c ) 2 ) the two differential cross-sections have similar shape, and show a sharp forward dip indicating a dominant helicity flip contribution. However, the magnitudes of the cross-sections are significantly different, indicating substantial exchange degeneracy breaking. We find the ratio of the integrated cross-sections for the reactions K − p → π − Σ + (1385) and π + p → K + Σ + (1385) over the range −0.3 < t ′ < 0.0 (GeV/ c ) 2 to be 2.0 ± 0.2.

2 data tables

Table 1

TMIN = -0.013 GEV**2.

Table 2

TMIN = +0.012 GEV**2.