Parity violation in the scattering of 15 MeV protons by hydrogen

Nagle, D. E.; Bowman, J. D.; Hoffman, C. M.; McKibben, J.L.; Mischke, R. E.; Potter, J. M.; Frauenfelder, Hans; Sorenson, L.

doi:10.1063/1.31768

Cited by 25 publications

(17 citation statements)

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“…The interpretations of these experiments depend on shell model estimates of quite complicated polarizabilities (Cs) or suppressed mixing matrix elements ( 21 Ne), and there are reasons to believe the associated errors could be large [5]. The plot also omits hadronic PNC constraints established in experiments on neutron spin rotation in 4 power for the capture of polarized protons on deuterium [43], on the circular polarization of γ-rays produced in the capture of unpolarized neutrons on deuterium nd → tγ [57], and on the γ-ray asymmetry from the capture of polarized neutrons on deuterium [58] . The first three experiments established upper bounds that are not sufficiently restrictive to impact our analysis.…”

Section: Experimental Constraints and 2d Reductionsmentioning

confidence: 99%

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 and 2d Reductionsmentioning

confidence: 99%

A New Paradigm for Hadronic Parity Nonconservation and Its Experimental Implications

Gardner

Haxton

Holstein

2017

Annu. Rev. Nucl. Part. Sci.

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“…This last correction was given by ys, where y is the sensitivity to transverse polarization and E is the spatial first moment of the beam polarization distribution x and y are particle coordinates at the collimator, R,(x, y) and R,(x, y) are the transverse polarization components for a given beam helicity, and B(x, y) represents the intensity of the beam. It can be seen that a transverse component of polarization that averages to zero can produce a spurious parity signal (4,33).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…A recent calculation has used Regge theory predictions, there is a contrast between the situation at low to calculate the contribution to the asymmetry from parity nonenergies and that at higher energies. Measurements (3,4) of conservation in the nucleon wave function (20). The result is AL = +2.1 X lop6 with an estimated error of 30%, but this scattering (1) or triple-scattering (2) geometries.…”

Section: Theoretical and Experimental Backgroundmentioning

confidence: 95%

Parity nonconservation in proton scattering at higher energies

Mischke¹

1988

Can. J. Phys.

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Parity-nonconservation experiments In the scattering of longitudinally polarized protons at incident proton momenta of 1.5 and 6 GeV/c are examined. These experiments indicate a change w~th energy of the total cross section correlated with proton helicity that was unexpected. This energy dependence is due to the strong part of the Interaction and may indicate the role of a diquark component In the nucleon. New experiments at higher energies are needed to confirm such a model. Future experiments can benefit from an analysis of sources of systematic error that have been encountered In the experiments discussed here.Des exptriences sur la non-conservation de la pant6 dans la diffusion de protons polarises longltudinalement pour des protons incidents de 1,5 et 6 GeV/c sont examinees. Ces exptriences indiquent un changement de la section efficace totale en fonction de I'energie par rapport a I'hClicitC du proton qui n'ttait pas attendu. Cette dtpendance en Cnergle est due i la partie forte de I'lnteraction et peut ~ndiquer le r6le de la composante diquark dans le nuclton. De nouvelles experiences a des energies plus tlevees sont dtsirables pour confirmer un tel modele. Des experiences futures peuvent bCnCficier de l'analyse des sources d'erreurs systtmatiques qui ont Ct C rencontrees dans l'experience discutte ici Can J Phys 66,495 (1988) [Traduit par la @ue]

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“…The first measurements of A, were made at 15 MeV proton energy, using the polarized beam of the tandem accelerator at Los Alamos (2,3). Protons scattered by a 6 bar H2 target were detected in scintillation detectors (1 bar = 100 kPa).…”

Section: Introductionmentioning

confidence: 99%

“…= (1 + 4) x lop7, was reported as a letter in 1974. The final result (3) was presented at the Symposium on High Energy Physics with Polarized Beams and Polarized Targets in 1978: [2] A,(15 MeV) = (-1.…”

Section: Introductionmentioning

confidence: 99%

Parity violation in proton scattering: low energy region

Haeberli¹

1988

Can. J. Phys.

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Measurements of the parity-violating longitudinal analyzing power, A,, in the scattering of low-energy protons (Ep < 50 MeV) are reviewed. The experiments are based on the determination of the relative scattering cross sections a+ and a-for incident protons of positive and hegative helicity, respect~vely. The first results were reported from Los Alamos, where a significant analyzing power [ A z = (-1.7 ? 0.8) X was found for p-p scattering at 15 MeV. All other results are for a proton energy near 45 MeV, primarily by the group working at Schweizerisches Instrtut fiir Nuklearforschung, which recently reported a new, very accurate result for p-p scattering of A, = (-1.50 -C 0.22) X A review is presented of the methods that have been developed by this group over the last 10 years to reduce systematic errors in the determination of A, to a few times lop9.On passe en revue les mesures du pouvoir d'analyse longitudinal A, qui ne respectent pas la paritt dans la diffusion de protons i basses tnergies (Ep < 50 MeV). Les expkriences sont bastes sur la dttermination des sections efficaces relatives de diffusion a + et a-pour des protons incidents d'helicitt positive et ntgative. Les premiers rtsultats furent rapportts par Los Alamos, o t~ un pouvoir d'analyse significatif [ A , = (-1.7 2 0,8) X fut trouve pour la diffusion p-p a 15 MeV. Tous les autres rksultats sont ii une energie des protons de prks de 45 MeV, obtenus prlncipalement par le groupe travaillant a Schweizerisches Institut fiir Nuklearforschung, qui a rkcemment rapport6 un nouveau resultat trks prkcis pour la diffusion p-p de A, = (-1,50 2 0,22) X lo-'. On prtsente une revue des mithodes qui ont CtC dtvelopptes par ce groupe durant les 10 dernikres anntes pour rtduire les erreurs systtmatiques dans la determination de A: it quelques-parties dans [Traduit par la revue] Can 1. Phys 66. 485 (1988)

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Parity violation in the scattering of 15 MeV protons by hydrogen

Cited by 25 publications

References 0 publications

A New Paradigm for Hadronic Parity Nonconservation and Its Experimental Implications

A New Paradigm for Hadronic Parity Nonconservation and Its Experimental Implications

Parity nonconservation in proton scattering at higher energies

Parity violation in proton scattering: low energy region

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