Status of the NPDGamma experiment

Fry, J. R.; Alarcón, R.; Allen, Robert R.; Askanazi, Evan; Balascuta, S.; Barrón‐Palos, L.; Baeßler, S.; Barzilov, Alexander; Blessinger, C.; Blyth, David; Bowman, J. D.; Calarco, J. R.; Chupp, T. E.; Coppola, C. E.; Crawford, Christopher; Craycraft, K.; Dabaghyan, M.; Evans, David; Favela, José F; Fieseler, C.; Fomin, N.; Fox, W.; Freedman, S. J.; Frlež, E.; Fu, Changbo; García, C.; Garishvili, I.; Gillis, R. C.; Grammer, Kyle B.; Greene, Geoffrey L.; Hamblen, J.; Hayes, C.; Hersman, F. W.; Ichihara, T.; Iverson, Erik B.; Jones, G. L.; Kabir, Latiful; Kucucker, S.; Lauss, B.; Li, Y.; Mahurin, R.; Maldonado-Velázquez, M.; McCrea, Mark; Masuda, Y.; Mei, Jia‐Wei; Milburn, R. H.; Mitchell, G. S.; Mueller, P. E.; Muto, S.; Musgrave, M.; Nann, H.; Novikov, Ivan; Page, S. A.; Parsons, Donald Kent; Počanić, D.; Penttilä, S. I.; Ramsay, W. D.; Salas-Bacci, A.; Santra, S.; Seo, P. N.; Sharapov, É. I.; Sharma, M.; Simmons, F. Blair; Smith, T. B.; Snow, W. M.; Stuart, J.; Tang, Elise; Tang, Zhaowen; Thomison, Jack; Tong, Xin; Vanderwerp, J.; Waldecker, S. J.; Wilburn, W. S.; Xu, W.; Yuan, V. W.; Zhang, Y.

doi:10.1007/s10751-016-1376-4

Cited by 7 publications

(7 citation statements)

References 15 publications

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“…In addition to the above results, we expect to have a new constraint from NPDGamma in hand soon. NPDGamma data taking is finished and the statistical uncertainty of the result has been given as approximately 13 ppb [3]. Current efforts are focused on measuring and subtracting potential systematic effects, including an asymmetry associated with aluminum in the target window.…”

Section: Experimental Constraints On Large-n C Lecsmentioning

confidence: 99%

“…These results helped motivate the NPDGamma effort. The Collaboration has worked toward its goal of measuring h 1 π since approximately 2000, beginning with an earlier version of the experiment at LANSCE [20], then moving to the SNS to exploit the high-intensity cold neutron beamline that became available there [1,2,3]. The goal has been to reach a sensitivity corresponding to A γ ∼ 10 −8 [21], verifying the 18 F result and possibly pushing beyond, to a detection of h 1 π .…”

Section: Introductionmentioning

confidence: 99%

“…The creation of a high-intensity cold neutron beamline at the Spallation Neutron Source (SNS) as well as upgrades at NIST will enable a new generation of experiments. Results from the first experiment performed at the SNS, the NPDGamma Collaboration's measurement of the gamma ray asymmetry A γ ( np → dγ), should be announced soon [1,2,3]. Furthermore, the feasibility of a new kind of "measurement"evaluation of PNC NN scattering amplitudes from lattice QCD -has been demonstrated [4].…”

Section: Introductionmentioning

confidence: 99%

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A New Paradigm for Hadronic Parity Nonconservation and Its Experimental Implications

Gardner

Haxton

Holstein

2017

Annu. Rev. Nucl. Part. Sci.

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For decades the primary experimental goal in studies of hadronic parity nonconservation (PNC) has been the isolation of the isovector weak nucleon-nucleon interaction, expected to be dominated by long-range pion exchange and enhanced by the neutral current. In mesonexchange descriptions this interaction together with an isoscalar interaction generated by ρ and ω exchange dominate most observables. Consequently these two amplitudes have been used to compare and check the consistency of the field's experiments. Yet to date, despite sensitive searches like that performed with 18 F, no evidence for isovector hadronic PNC has been found. Here we argue, based on recent large-N c treatments and new global analyses, that the emphasis on isovector hadronic PNC was misplaced. Large-N c provides an alternative and theoretically better motivated simplification of effective field theories (EFTs) of hadronic PNC, separating the five low-energy constants (LECs) into two of leading order (LO), and three others that are N 2 LO. This scheme pivots the isospin coordinates we have traditionally used, placing one dominant axis in the isoscalar plane, and a second along the isotensor direction. We show that this large-N c LEC hierarchy accurately describes all existing data on hadronic PNC. In particular, the null result found in 18 F reflects its dependence on an N 2 LO observable. We discuss opportunities to further test the predicted large-N c hierarchy of LECs, illustrating the kind of analyses experimentalists can use to better constrain the LO theory and to determine the size of N 2 LO corrections. This formalism -combined with a new wave of experiments that will be performed at the SNS cold neutron beam line and the recent demonstration that lattice QCD can now be applied to PNC NN scattering -could lead to rapid progress in the next five years. We discuss the impact of anticipated new results, including NPDGamma and a lattice QCD calculation of isotensor PNC. We also describe future experiments that can yield more precise values of the LO LECs and help isolate the N 2 LO ∼ 10% corrections.

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Section: Experimental Constraints On Large-n C Lecsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A New Paradigm for Hadronic Parity Nonconservation and Its Experimental Implications

Gardner

Haxton

Holstein

2017

Annu. Rev. Nucl. Part. Sci.

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“…Hadronic parity violation is a unique probe of the non-perturbative strong coupling limit of QCD. The NPDGamma Collaboration just presented preliminary results on the long range weak meson coupling h 1 π [52], which will finally test theoretical predictions [53,54,55]. The n+ 3 He experiment at SNS continues this study, and a new n+ 4 He apparatus is under construction for NIST [56].…”

Section: Fundamental Neutron Physicsmentioning

confidence: 83%

Cold and Ultra-cold Neutrons as Probes of New Physics

Konrad¹,

Abele²

2017

Proceedings of the 26th International Nuclear Physics Conference — PoS(INPC2016)

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Despite the great success of the Standard Model, many key questions in particle physics, astrophysics, and cosmology are unanswered. In particular, more than 95 % of the universe consists of unknown dark matter and dark energy. Today, a major goal of particle physics is to look for evidence of new physics beyond the Standard Model. Collider searches for new physics are well suited to the direct production of new high-mass particles, whereas low-energy precision experiments search for traces that new particles leave in known processes. Direct and indirect evidence of new physics are highly complementary. High-precision experiments with extremely slow, cold and ultra-cold neutrons address some of the unanswered questions, for instance, on the nature of the fundamental forces and underlying symmetries, the origin, evolution, and fate of the universe, or on the nature of the gravitational force at very small distances. For example, the limit on the electric dipole moment of the neutron constrains the CP violating phases, the lifetime of the neutron determines the relative helium abundance in the universe, and neutrons bouncing over a mirror probe dark matter and dark energy. New facilities and technological developments now give window for significant improvement in precision by one to two orders of magnitude. In this paper, we will give an overview of current and planned facilities and experiments, as well as an overview of some of the applications of neutrons to astrophysics, cosmology, and physics beyond the Standard Model.

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“…Unfortunately, h 1 π contributes only to the proton-proton scattering at the subleading order, leading to a large uncertainty on the extraction h 1 π = (1.1 ± 2.0) × 10 −6 . More promising is the extraction of h 1 π from the upcoming measurement of the gamma-ray asymmetry in the neutron capture on the proton by the NPDGamma Collaboration [42,43].…”

Section: Arxiv:171109342v2 [Nucl-th] 23 Apr 2018mentioning

confidence: 99%

Novel Soft-Pion Theorem for Long-Range Nuclear Parity Violation

2018

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The parity-odd effect in the standard model weak neutral current reveals itself in the long-range parity-violating nuclear potential generated by the pion exchanges in the ΔI=1 channel with the parity-odd pion-nucleon coupling constant h_{π}^{1}. Despite decades of experimental and theoretical efforts, the size of this coupling constant is still not well understood. In this Letter, we derive a soft-pion theorem relating h_{π}^{1} and the neutron-proton mass splitting induced by an artificial parity-even counterpart of the ΔI=1 weak Lagrangian and demonstrate that the theorem still holds exact at the next-to-leading order in the chiral perturbation theory. A considerable amount of simplification is expected in the study of h_{π}^{1} by using either lattice or other QCD models following its reduction from a parity-odd proton-neutron-pion matrix element to a simpler spectroscopic quantity. The theorem paves the way to much more precise calculations of h_{π}^{1}, and thus a quantitative test of the strangeness-conserving neutral current interaction of the standard model is foreseen.

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Status of the NPDGamma experiment

Cited by 7 publications

References 15 publications

A New Paradigm for Hadronic Parity Nonconservation and Its Experimental Implications

A New Paradigm for Hadronic Parity Nonconservation and Its Experimental Implications

Cold and Ultra-cold Neutrons as Probes of New Physics

Novel Soft-Pion Theorem for Long-Range Nuclear Parity Violation

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