Fundamental Neutron Physics

Nico, J. S.; Snow, W. M.

doi:10.1146/annurev.nucl.55.090704.151611

Cited by 77 publications

(83 citation statements)

References 352 publications

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“…(See Refs. [5,6,7,8] for reviews of fundamental symmetry tests in β-decay.) In this work, we study the so-called D correlation, corresponding to the triple product J · p e ×p ν , where J is nuclear polarization, and p e (p ν ) is the e ± (ν) momentum.…”

Section: Introductionmentioning

confidence: 99%

CPviolation in beta decay and electric dipole moments

Tulin

2012

Phys. Rev. D

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The T-odd correlation coefficient D in nuclear β-decay probes CP violation in many theories beyond the Standard Model. We provide an analysis for how large D can be in light of constraints from electric dipole moment (EDM) searches. We argue that the neutron EDM d n currently provides the strongest constraint on D, which is 10 − 10 3 times stronger than current direct limits on D (depending on the model). In particular, contributions to D in leptoquark models (previously regarded as "EDM safe") are more constrained than previously thought. Bounds on D can be weakened only by fine-tuned cancellations or if theoretical uncertainties are larger than estimated in d n . We also study implications for D from mercury and deuteron EDMs.

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Section: Introductionmentioning

confidence: 99%

CPviolation in beta decay and electric dipole moments

Tulin

2012

Phys. Rev. D

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“…Of the future experimental plans reviewed in Refs. [11][12][13][14][15][16][17][18][19], the claim of ultimate precision rests with the PERC experiment [20], for a sensitivity of up to 10 −4 precision.…”

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confidence: 97%

“…Alternatively, e.g., new, light degrees of freedom could appear and yield violations of the V − A law -if probed at sufficient experimental resolution. At the same time, an ongoing vigorous experimental program for precision measurements of neutron β decay observables with cold and ultracold neutrons [11][12][13][14][15][16][17] exists with an overarching goal of realizing bettered assessments of the limits of the SM. The experimental effort focuses on measurements of two general types of observables: angular correlation coefficients, which parametrize the angular correlations between the momenta of the various decay products and/or the spin of the initial state neutron or electron in the differential decay rate, and the neutron lifetime, τ .…”

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confidence: 99%

Framework for maximum likelihood analysis of neutronβdecay observables to resolve the limits of theV−Alaw

Gardner

Plaster

2013

Phys. Rev. C

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We assess the ability of future neutron β decay measurements of up to O(10 −4 ) precision to falsify the standard model, particularly the V − A law, and to identify the dynamics beyond it. To do this, we employ a maximum likelihood statistical framework which incorporates both experimental and theoretical uncertainties. Using illustrative combined global fits to Monte Carlo pseudodata, we also quantify the importance of experimental measurements of the energy dependence of the angular correlation coefficients as input to such efforts, and we determine the precision to which ill-known "second-class" hadronic matrix elements must be determined in order to exact such tests.

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“…The HWI in general and the NN weak interaction amplitudes in particular are scientifically interesting for several reasons [1][2][3][4][5]. Because the range for W and Z exchange between quarks is small compared to the nucleon size, HWI are first-order sensitive to quark-quark correlations in hadrons.…”

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confidence: 99%

Measurement of parity-violatingγ-ray asymmetry in the capture of polarized cold neutrons on protons

et al. 2011

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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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Fundamental Neutron Physics

Cited by 77 publications

References 352 publications

CPviolation in beta decay and electric dipole moments

CPviolation in beta decay and electric dipole moments

Framework for maximum likelihood analysis of neutronβdecay observables to resolve the limits of theV−Alaw

Measurement of parity-violatingγ-ray asymmetry in the capture of polarized cold neutrons on protons

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