Articles you may be interested inAn all-optical scalar and vector spin-exchange relaxation-free magnetometer employing on-off pump modulation

The NPDGamma collaboration reports results from the first phase of a measurement of the parity violating up-down asymmetry Aγ with respect to the neutron spin direction of γ-rays emitted in the reaction n + p → d + γ using the capture of polarized cold neutrons on the protons in a liquid parahydrogen target. One expects parity-odd effects in the hadronic weak interaction (HWI) between nucleons to be induced by the weak interaction between quarks. Aγ in n + p → d + γ is dominated by a ∆I = 1, 3 S1 − 3 P1 parity-odd transition amplitude in the n-p system. The first phase of the measurement was completed at the Los Alamos Neutron Science Center spallation source (LANSCE) with the result Aγ = (−1.2 ± 2.1 stat. ± 0.2 sys.) × 10 −7 . We also report the first measurement of an upper limit for the parity allowed left right asymmetry in this reaction, with the result Aγ,LR = (−1.8 ± 1.9 stat. ± 0.2 sys.) × 10 −7 . In this paper we give a detailed report on the theoretical background, experimental setup, measurements, extraction of the parity-odd and parity-allowed asymmetries, analysis of potential systematic effects, and the LANSCE results. The asymmetry has an estimated size of 5 × 10 −8 and the aim of the NPDGamma collaboration is to measure it to 1 × 10 −8 . The second phase of the measurement will be performed at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory.

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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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