We describe an experiment that has set new limits on the time reversal invariance violating D coefficient in neutron ␤ decay. The emiT experiment measured the angular correlation ͗J͘•(p e ϫp p ) using an octagonal symmetry that optimizes electron-proton coincidence rates. The result is Dϭ͓Ϫ0.6Ϯ1.2(stat)Ϯ0.5(syst)͔ ϫ10 Ϫ3 . This improves constraints on the phase of g A /g V and limits contributions to T violation due to leptoquarks. This paper presents details of the experiment, data analysis, and the investigation of systematic effects.

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We describe an apparatus used to measure the triple-correlation term ͑D n • p e ϫ p ͒ in the beta decay of polarized neutrons. The D coefficient is sensitive to possible violations of time reversal invariance. The detector has an octagonal symmetry that optimizes electron-proton coincidence rates and reduces systematic effects. A beam of longitudinally polarized cold neutrons passes through the detector chamber, where a small fraction undergo beta decay. The final-state protons are accelerated and focused onto arrays of cooled semiconductor diodes, while the coincident electrons are detected using panels of plastic scintillator. Details regarding the design and performance of the proton detectors, beta detectors, and the electronics used in the data collection system are presented. The neutron beam characteristics, the spin-transport magnetic fields, and polarization measurements are also described.

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