A. Beretvas

Branching ratio and asymmetry for Xi 0--> Lambda gamma.

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.

Level 3 system at CDF

Abstract Level 3 uses 32-bit microprocessors installed in VME crates to execute FORTRAN filter algorithms. The system is integrated into the CDF FASTBUS data acquisition network which is designed to support event rates of 100 Hz into level 3. Filter algorithms access event data in the same detector bank format as used for off-line analysis.

Electron identification using a synchrotron radiation detector

Abstract A xenon filled multiwire proportional chamber was used to detect synchrotron radiation from high energy electrons traversing the field of a standard spectrometer magnet. Signals from the chamber were used to achieve an electron trigger with a pion rejection of ∼ 17 and an average electron detection efficiency of 81%. Off-line analysis of the chamber signals increased the pion rejection to 59 with an electron efficiency of 77%.

The CDF Level 3 trigger

Abstract We discuss the architecture, operation, and performance of the Level 3 trigger used in the Fermilab CDF experiment in 1988–1989. This trigger used an on-line computer farm of 58 Motorola 68020 processors operating in parallel. The on-line programs were written mainly in Fortran and run in an environment similar to that used for off-line analysis.

Integration of the ACP Multiprocessor Farm with the CDF FASTBUS Data Acquisition System

The Collider Detector Facility collaboration at Fermilab is developing a three level on-line event filtering system for high speed data acquisition. The third level of the trigger uses the Fermilab Advanced Computer Program system of parallel processors in VME crates which are managed by a MicroVAX II and are interfaced to the FASTBUS data acquisition system. In section 1, the author briefly describes the Collider Detector Facility and the goals of the trigger system. Section 2 is a short discussion of the first two levels of the trigger. In section 3, he describes the hardware components of the Level 3 trigger and Section 4 is devoted to hardware test and results. Section 5 concludes this paper with a summary of on-line test and results of the Level 3 trigger system.

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. Xi. sup 0 r arrow. Lambda. gamma

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 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.

Two-jet invariant 0 mass distribution at √s=1.8 TeV

We present the dijet invariant-mass distribution in the region between 60 and 500 GeV, measured in 1.8-TeV {ital {bar p}p} collisions in the Collider Detector at Fermilab. Jets are restricted to the pseudorapidity interval {vert bar}{eta}{vert bar}{lt}0.7. Data are compared with QCD calculations; axigluons are excluded with 95% confidence in the region 120{lt}{ital M}{sub {ital A}}{lt}210 GeV for axigluon width {Gamma}{sub {ital A}}={ital N}{alpha}{sub s}{ital M}{sub {ital A}}/6, with {ital N}=5.