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Polarization of $\Lambda$ and $\bar{\Lambda}$ Produced by 800 GeV Protons

Ramberg, E.J. ; Bock, G.J. ; Coleman, R. ; et al.
Phys.Lett.B 338 (1994) 403-408, 1994.
Inspire Record 372108 DOI 10.17182/hepdata.42451

We have measured the polarization of Λ and Λ hyperons produced by 800 GeV protons on a Be target at a fixed targeting angle of 4.8 mrad. Comparison with previous data at 400 GeV production energy and twice the targeting angle shows no significant energy dependence for the Λ polarization. This is in striking contrast to the energy dependence found for σ + and Ξ − polarizations. We find no evidence for Λ polarization at 800 GeV.

2 data tables
Table 1

Errors are combined statistics and systematics.

Table 2

No description provided.


Polarization in Inclusive $\Lambda$ and $\bar{\Lambda}$ Production at Large $p_T$

Lundberg, B. ; Handler, R. ; Pondrom, L. ; et al.
Phys.Rev.D 40 (1989) 3557-3567, 1989.
Inspire Record 287809 DOI 10.17182/hepdata.23077

A study of the inclusive polarization of Λ hyperons produced by 400-GeV/c protons incident on nuclear targets has been performed at Fermilab. The polarization P of the Λ has been mapped over a large range of xF and pT to good precision for pT up to 3.8 GeV/c. The magnitude of the polarization at fixed xF rises with pT to a plateau at about 1 GeV/c, and the size of the plateau increases monotonically with xF. The Λ¯ were found to be unpolarized for pT<2.4 GeV/c. A target-nucleus dependence for the Λ polarization has been observed.

17 data tables
Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

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Spin Parameter Measurements in $\Lambda$ and $K_S$ Production

Bonner, B.E. ; Buchanan, J.A. ; Clement, J.M. ; et al.
Phys.Rev.D 38 (1988) 729-741, 1988.
Inspire Record 268865 DOI 10.17182/hepdata.23270

The Brookhaven Alternating Gradient Synchrotron polarized proton beam incident on a beryllium target was used for inclusive Λ production at beam momenta of 13.3 and 18.5 GeV/c. The beam polarization was transverse to the beam direction with magnitude 0.63 at 13.3 GeV/c and 0.40 at 18.5 GeV/c. The Λ polarization was measured and found to be in agreement with results from earlier experiments which used unpolarized proton beams. Analyzing power AN and spin transfer DNN of the Λ’s were both measured and compared with a hyperon-polarization model in which the polarization arises from a Thomas-precession effect. There is good agreement with its predictions: AN=0 and DNN=0. In particular, our measurement of 〈DNN〉=-0.009±0.015 supports the idea that the valence quarks carry all of the hadron spin, since this assumption is implicit in the model’s use of SU(6) wave functions to form final-state hadrons from beam fragments and sea quarks. The presence of substantial KS samples at both beam momenta and Λ¯’s at 18.5 GeV/c prompted a measurement of their analyzing powers, which yielded AN(KS)=-0.094±0.012 at 13.3 GeV/c beam momentum and -0.076±0.015 at 18.5 GeV/c, and AN(Λ¯)=0.03±0.10.

15 data tables
Table 1

No description provided.

Table 2

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Table 3

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