C. James

Polarization of inclusively produced hyperons

We report here polarization results from a series of Fermilab experiments from the years 1974 through 1980, with some preliminary data from a high pT polarization experiment completed in February 1982. The Λ polarization has a remarkably simple and interesting behavior when expressed as a function of xF and pT.

Branching ratio and asymmetry for 0

We have measured the branching ratio {Gamma}({Xi}{sup 0}{r arrow}{Lambda}{gamma})/{Gamma}({Xi}{sup 0}{r arrow}{Lambda}{pi}{sup 0}) to be (1.06{plus minus}0.12(stat){plus minus}0.11(syst)){times}10{sup {minus}3}. In 670 000 {Lambda}{gamma} candidates we found 116{plus minus}13 {Xi}{sup 0}{r arrow}{Lambda}{gamma} decays (background subtracted). These compare with 29 510 {Xi}{sup 0}{r arrow}{Lambda}{pi}{sup 0} events reconstructed from the {Lambda}{gamma}{gamma} sample. Monte Carlo studies gave the relative acceptances for the two processes. The helicity of the {Lambda} yielded the product of asymmetry parameters {alpha}({Lambda}{r arrow}{ital p}{pi}{sup {minus}}){alpha}({Xi}{sup 0}{r arrow}{Lambda}{gamma})=0.27{plus minus}0.28, which implies {alpha}({Xi}{sup 0}{r arrow}{Lambda}{gamma})=0.43{plus minus}0.44, where the uncertainty is all statistical.

Branching ratio and asymmetry for Ξ 0 →Λγ

We have measured the branching ratio {Gamma}({Xi}{sup 0}{r arrow}{Lambda}{gamma})/{Gamma}({Xi}{sup 0}{r arrow}{Lambda}{pi}{sup 0}) to be (1.06{plus minus}0.12(stat){plus minus}0.11(syst)){times}10{sup {minus}3}. In 670 000 {Lambda}{gamma} candidates we found 116{plus minus}13 {Xi}{sup 0}{r arrow}{Lambda}{gamma} decays (background subtracted). These compare with 29 510 {Xi}{sup 0}{r arrow}{Lambda}{pi}{sup 0} events reconstructed from the {Lambda}{gamma}{gamma} sample. Monte Carlo studies gave the relative acceptances for the two processes. The helicity of the {Lambda} yielded the product of asymmetry parameters {alpha}({Lambda}{r arrow}{ital p}{pi}{sup {minus}}){alpha}({Xi}{sup 0}{r arrow}{Lambda}{gamma})=0.27{plus minus}0.28, which implies {alpha}({Xi}{sup 0}{r arrow}{Lambda}{gamma})=0.43{plus minus}0.44, where the uncertainty is all statistical.

Production polarization and magnetic moment of anti-XI+ anti-hyperons produced by 800-GeV/c protons

The polarization of {bar {Xi}}{sup +} hyperons produced by 800-GeV/{ital c} protons in the inclusive reaction {ital p}+Be{r arrow}{bar {Xi}}{sup +}+{ital X} has been measured. The average polarization of the {bar {Xi}}{sup +}, at a mean {ital x}{sub {ital F}}=0.39 and {ital p}{sub {ital t}}=0.76 GeV/{ital c}, is {minus}0.097{plus minus}0.012{plus minus}0.009. The magnetic moment of the {bar {Xi}}{sup +} is 0.657{plus minus}0.028{plus minus}0.020 nuclear magneton.

Search for polarization in

Inclusive hyperon production by 400 GeV protons at Fermilab has shown that the hyperons are produced with significant polarization. However no polarization has been seen for Λ’s produced at these energies. In this paper we present the results of a searcch for Ξ0 polarization.