Observation of Parity Violation in the Omega-minus -> Lambda + K-minus Decay

The alpha decay parameter in the process Omega-minus -> Lambda + K-minus has been measured from a sample of 4.50 million unpolarized Omega-minus decays recorded by the HyperCP (E871) experiment at Fermilab and found to be [1.78 +/- 0.19(stat) +/- 0.16(syst)]{\times}10^{-2}. This is the first unambiguous evidence for a nonzero alpha decay parameter, and hence parity violation, in the Omega-minus -> Lambda + K-minus decay.Comment: 10 pages, 7 figure

HyperCP: A high-rate spectrometer for the study of charged hyperon and kaon decays

The HyperCP experiment (Fermilab E871) was designed to search for rare phenomena in the decays of charged strange particles, in particular CP violation in $\Xi$ and $\Lambda$ hyperon decays with a sensitivity of $10^{-4}$. Intense charged secondary beams were produced by 800 GeV/c protons and momentum-selected by a magnetic channel. Decay products were detected in a large-acceptance, high-rate magnetic spectrometer using multiwire proportional chambers, trigger hodoscopes, a hadronic calorimeter, and a muon-detection system. Nearly identical acceptances and efficiencies for hyperons and antihyperons decaying within an evacuated volume were achieved by reversing the polarities of the channel and spectrometer magnets. A high-rate data-acquisition system enabled 231 billion events to be recorded in twelve months of data-taking.Comment: 107 pages, 45 Postscript figures, 14 tables, Elsevier LaTeX, submitted to Nucl. Instrum. Meth.

Measurement of the asymmetry in the decay Ω̄+→Λ̄K+→p̄π+K+

The asymmetry in the p̄ angular distribution in the sequential decay Ω̄+→Λ̄K+→p̄π+K+ has been measured to be ᾱΩᾱΛ=[+1.16±0.18(stat)±0. 17(syst)]×10-2 using 1.89×106 unpolarized Ω̄+ decays recorded by the HyperCP (E871) experiment at Fermilab. Using the known value of αΛ, and assuming that ᾱΛ=-αΛ, ᾱΩ=[-1.81±0.28(stat)±0.26(syst)]×10-2. A comparison between this measurement of ᾱΩᾱΛ and recent measurements of αΩαΛ made by HyperCP shows no evidence of a violation of CP symmetry. © 2006 The American Physical Society

New measurement of ξ- → Λπ- decay parameters

A study on the measurement of φ≡ using a sample of 144×106 ≡- →λπ- decays having an average polarization of 3.7% was presented. The polarized ≡-'s were produced by directing an 800 geV÷c proton beam onto a 2 mm ×2 mm× 60 mm cu target at angles of +3 and -3 mrad. The results were shown to be a 2.9× improvement over the best previous mesurements. It was shown that CP violation in charged ≡→λπ decays are not suppressed by a vanishing final phase shift difference

Search for CP violation in hyperon decays.

Direct CP violation in nonleptonic hyperon decays can be established by comparing the decays of hyperons and anti-hyperons. For Xi decay to Lambda pi followed by Lambda to p pi, the proton distribution in the rest frame of Lambda is governed by the product of the decay parameters alXi alLam. The asymmetry A_Xi Lambda, proportional to the difference of alXi alLam of the hyperon and anti-hyperon decays, vanishes if CP is conserved. We report on an analysis of a fraction of 1997 and 1999 data collected by the Hyper CP (E871) collaboration during the fixed-target runs at Fermilab. The preliminary measurement of the asymmetry is AXiLam = [ -7 pm 12(rm stat) pm 6.2(rm sys) ] times 10-4, an order of magnitude better than the present limit

Examining CP symmetry in strange baryon decay

Non-conservation of CP symmetry can manifest itself in non-lepton ichyperon decays as a difference in the decay parameter between the strange-baryon decay and its charge conjugate. By comparing the decay distribution in the $\Lambda$ helicity frame for the decay sequence $\Xi- \to \Lambda \pi-$,$\Lambda \to p \pi-$with that of $\overline Xi+$ decay, E756 at Fermilab did not observe any CP-odd effect at the $10-2$ level. The status of a follow-up experiment, HyperCP (FNAL E871), to search for CP violation in charged $\Xi-\Lambda$ decay with a sensitivity of $10-4$is also presented

Examining CP symmetry in strange baryon decay

Non-conservation of CP symmetry can manifest itself in non-lepton ichyperon decays as a difference in the decay parameter between the strange-baryon decay and its charge conjugate. By comparing the decay distribution in the $\Lambda$ helicity frame for the decay sequence $\Xi- \to \Lambda \pi-$,$\Lambda \to p \pi-$with that of $\overline Xi+$ decay, E756 at Fermilab did not observe any CP-odd effect at the $10-2$ level. The status of a follow-up experiment, HyperCP (FNAL E871), to search for CP violation in charged $\Xi-\Lambda$ decay with a sensitivity of $10-4$is also presented