High Statistics Measurement of Polarization in $\pi^- p \to K^0 \Lambda$ at 3-{GeV}/$c$ and 5-{GeV}/$c$

Snyder, A. ; Ambats, I. ; Meyer, W.T. ; et al.
Phys.Rev.D 21 (1980) 599, 1980.
Inspire Record 8072 DOI 10.17182/hepdata.24173

We have measured the polarization of the Λ hyperon produced in the reaction π−p→K0Λ at 3 and 5 GeV/c, for four-momentum transfers t′ out to 1.6 GeV2, by observing the parity-violating decay Λ→pπ−. With an increase in statistical power by a factor of 3 to 4 over the best previous experiments in this energy range, we confirm earlier observations that the polarization is small and positive below t′=0.4 GeV2, becoming large and positive for larger values of t′. In particular, at 5 GeV/c for all t′ between 0.8 and 1.6 GeV2 the polarization is consistent with a value of - 1.

2 data tables

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Cross-Sections of Strange Particle Production in pi- p Interactions at 5-GeV/c

Budagov, Yu.A. ; Vinogradov, V.B. ; Volodko, A.G. ; et al.
Yad.Fiz. 25 (1977) 1195-1200, 1977.
Inspire Record 124565 DOI 10.17182/hepdata.19039

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1 data table

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Differential cross-sections in pi- p ---> k0 lambda0 and pi- p ---> k0 sigma0 from 3 to 6 gev/c

Ward, C.E.W. ; Ambats, I. ; Lesnik, A. ; et al.
Phys.Rev.Lett. 31 (1973) 1149-1152, 1973.
Inspire Record 83757 DOI 10.17182/hepdata.21372

We have measured the differential cross sections for the associated-production reactions π−p→K0Λ0 and π−p→K0Σ0 at 3, 4, 5, and 6 GeV/c, with a total of over 40 000 events. We find that both reactions have exponential forward peaks for −t≲0.4 (GeV/c)2, with no indication of forward-direction flattening or turnover; the slopes of the forward peaks show little if any variation with momentum; and the two cross sections are equal within experimental error from −t=1.2 (GeV/c)2 out to at least −t=2.0 (GeV/c)2.

5 data tables

INTERCEPT AND SLOPE FROM FIT TO D(SIG)/DT (PRESUMABLY FOR -TP < ABOUT 0.4 GEV**2).

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A MEASUREMENT OF POLARIZATION IN pi- p ---> K0 LAMBDA0 AT 5-GeV/c

Ward, C.E.W. ; Ambats, I. ; Lesnik, A. ; et al.
Phys.Lett.B 48 (1974) 471-473, 1974.
Inspire Record 80559 DOI 10.17182/hepdata.27997

We have measured the Λ° polarization in π − p→ K°Λ° at 5 GeV / c , using a data sample of 3709 events. The polarization is positive for small t , passes through zero near t = −0.3 (GeV/ c ) 2 , and becomes large and negative at larger t , consistent with a value of −1.0 for t between −0.7 and −1.6(GeV/ c ) 2 .

1 data table

THE AUTHORS FEEL THAT THE POLARIZATIONS > 1 IN ABSOLUTE VALUE ARE PROBABLY DUE TO STATISTICS RATHER THAN SYSTEMATIC ERRORS.


Cross-Sections and Polarizations in the Reactions pi- p --> Lambda K0 and pi- p --> Lambda K* (890) Near the Backward Direction, from 3-GeV/c to 6-GeV/c

Ward, C.E.W. ; Ambats, I. ; Lesnik, A. ; et al.
Phys.Rev.D 16 (1977) 2041, 1977.
Inspire Record 4930 DOI 10.17182/hepdata.24506

We have measured the differential cross sections and Λ polarizations in the reactions π−p→ΛK0 and π−p→ΛK*0 (890) near the backward direction, at 3, 4, 5, and 6 GeV/c. Data equal to several times the world's total sample above 2 GeV/c were recorded. Both reactions are characterized by cross sections falling rapidly with beam momentum, and by large positive Λ polarizations for u′ between 0.0 and 0.6 GeV2. Analysis of π−p→ΛK0 yields an effective Regge trajectory consistent with antishrinkage of the backward peak. Separation into amplitudes of definite-parity-naturality exchange shows the reaction to be dominated by unnatural-parity exchange. The energy behavior of this exchange is, however, not consistent with a single linear baryon Regge trajectory or exchange-degenerate pair of trajectories. An apparent normalization discrepancy between data on π−p→ΛK0 of a CERN-ETH group and other high-statistics data including that of this experiment is discussed.

10 data tables

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Measurement of the Polarization in the Forward Peak of pi- p --> K0 Lambda at 5-GeV/c

Beusch, W. ; Borghini, M. ; Lauper, S. ; et al.
Nucl.Phys.B 99 (1975) 53-60, 1975.
Inspire Record 89729 DOI 10.17182/hepdata.31783

The π − p→K 0 λ polarization has been measured at 5 GeV/ c in the range 0<− t <1.4 (GeV/ c ) 2 . The polarization is small for − t ⪅0.4 (GeV/ c ) 2 , becoming negative at the higher values of − t .

1 data table

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Measurement of the Differential Cross-Section and the Spin-Correlation Parameters P,A, and R in the Backward Peak of pi- p --> K0 Lambda at 5-GeV/c

Astbury, P. ; Gallivan, J. ; Jafar, J. ; et al.
Nucl.Phys.B 99 (1975) 30-52, 1975.
Inspire Record 98667 DOI 10.17182/hepdata.31861

We present measurements for the baryon-exchange reaction π − p→ Λ K 0 at 5 GeV/ c over the range − u <2(GeV/ c ) 2 . The differential cross section is obtained from events produced on a liquid hydrogen target. These data are combined with events produced on a butanol polarized target and the parameters P , A , and R are then determined from an analysis of the decay angular distribution of the forward-going Λ. From our data it is possible to determine the magnitudes and the relative phase of the two invariant amplitudes A ′ and B . The consequences for the ratio B / A ′ are discussed in detail.

4 data tables

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THE ERRORS QUOTED IN D(SIG)/DU DO NOT INCLUDE THE ERROR ASSIGNED TO THE OVERALL U-INDEPENDENT CORRECTIONS FACTOR (4.62 +- 0.36), OR OTHER POSSIBLE NORMALIZATION ERRORS.

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