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The novel sources of CP violation observed in charged χ and λ hyperon decays were investigated. A comparison of the p and p̄ angular distributions in the hyperon decays was made using a subset of the data from the HyperCP experiment (E871) at Fermilab. A possible source of bias was found to be a momentum-dependent differential loss of events due to interactions of the χ- and χ̄+ decay products. The obtained result was observed to be stable with respect to time, χ momentum, and secondary-beam intensity, The results show that differences between the χ- and χ+ production angles could cause a bias due to production polarization differences.
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.
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.
The ATLAS detector has been built to study the reactions produced by the Large Hadron Collider (LHC). ATLAS includes a system of liquid argon calorimeters for energy measurements. The electronics for amplifying, shaping, sampling, pipelining, and digitizing the calorimeter signals is implemented on a set of front-end electronic boards. The front-end boards are installed in crates mounted between the calorimeters, where they will be subjected to significant levels of radiation during LHC operation. As a result, all components used on the front-end boards had to be subjected to an extensive set of radiation qualification tests. This paper describes radiationtolerant designs, radiation testing, and radiation qualification of the front-end readout system for the ATLAS liquid argon calorimeters.
The ATLAS detector has been designed for operation at CERN's Large Hadron Collider. ATLAS includes a complex system of liquid argon calorimeters. This paper describes the architecture and implementation of the system of custom front end electronics developed for the readout of the ATLAS liquid argon calorimeters.
The ATLAS detector has been designed for operation at CERN's Large Hadron Collider. ATLAS includes a complex system of liquid argon calorimeters. The electronics for amplifying, shaping, sampling, pipelining, and digitizing the calorimeter signals is implemented on the Front End Boards (FEBs). This paper describes the design, implementation and production of the FEBs and presents measurement results from testing performed at several stages during the production process.
We present a detailed examination of the heavy flavor properties of jets produced at the Fermilab Tevatron collider. The data set, collected with the Collider Detector at Fermilab, consists of events with two or more jets with transverse energy E(T)>or equal to15 GeV and pseudorapidity \eta\< or equal to1.5. The heavy flavor content of the data set is enriched by requiring that at least one of the jets (lepton- jet) contains a lepton with a transverse momentum larger than 8 GeV/c. Jets containing hadrons with heavy flavor are selected via the identification of secondary vertices. The parton-level cross sections predicted by the HERWIG Monte Carlo generator program are tuned within theoretical and experimental uncertainties to reproduce the secondary-vertex rates in the data. The tuned simulation provides new information on the or...
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