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PROWSE 1958

Prowse, D.J.; Baldo-Ceolin, M.;
Anti-Lambda Hyperon
Phys. Rev. Lett. 1 (1958) 179;

Summary
An event has recently been found in an emulsion stack exposed to a 4.6 ± 0.3 BeV π^–-meson beam at the Berkeley Bevatron which is interpreted as the decay of an anti-lambda hyperon, anti-Λ^o. The threshold for production with a free nucleon is 4.73 BeV and extends down to ~ 4.3 BeV with a bound nucleon, the production reaction being of the type π^– p → Λ^o anti-Λ^o n The side of the stack was exposed to a beam of 10⁶ π mesons per sq cm, the intensity falling off by a factor of 10³ in a distance of 8 in. across the emulsion sheets. The emulsions were scanned for stopping π⁺ mesons and these were followed back to their origins if it appeared that they were produced in the region of high π^–-meson flux. Most tracks which were successfully traced back came from primary π^–-meson stars but 3 traced back to decaying K⁺ mesons and one to a "V'' type event. The other branch of the "V'' event was traced after 3 cm range into a large star from which 3 shower particles were emitted. The visible energy in this star is 783 MeV including the rest masses of the 3 shower particles which were all identified as π mesons; one was arrested and decayed into a μ meson, the other two were identified by the Δ g^* vs Δ R and by the vs g^* methods. (Extracted from the introductory part of the paper.).

Accelerator LBL Detectors EMUL

Related references
More (earlier) information appears in
M. Baldo-Ceolin and D. J. Prowse, Bull.Am.Phys.Soc. 3 (1958) 163;
See also
W. H. Barkas et al., Nuovo Cim. 8 (1958) 186;
G. Alexander and R. H. W. Johnston, Nuovo Cim. 5 (1957) 263;

Data comments
One event.

Reactions

	π– nucleus anti-p π+ X	4.6 GeV (Tlab)	cs, mass
	π– p n Λ anti-Λ	4.6 GeV (Tlab)	cs, mass
	anti-Λ anti-p π+

Particles studied

anti-Λ

ex, mass

Record comments
First evidence for the anti-Λ.

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