First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen

D Blyth; J Fry; N Fomin; R Alarcon; L Alonzi; E Askanazi; S Baeßler; S Balascuta; L Barrón-Palos; A Barzilov; J D Bowman; N Birge; J R Calarco; T E Chupp; V Cianciolo; C E Coppola; C B Crawford; K Craycraft; D Evans; C Fieseler; E Frlež; I Garishvili; M T W Gericke; R C Gillis; K B Grammer; G L Greene; J Hall; J Hamblen; C Hayes; E B Iverson; M L Kabir; S Kucuker; B Lauss; R Mahurin; M McCrea; M Maldonado-Velázquez; Y Masuda; J Mei; R Milburn; P E Mueller; M Musgrave; H Nann; I Novikov; D Parsons; S I Penttilä; D Počanić; A Ramirez-Morales; M Root; A Salas-Bacci; S Santra; S Schröder; E Scott; P-N Seo; E I Sharapov; F Simmons; W M Snow; A Sprow; J Stewart; E Tang; Z Tang; X Tong; D J Turkoglu; R Whitehead; W S Wilburn; NPDGamma Collaboration

doi:10.1103/PhysRevLett.121.242002

First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen

Phys Rev Lett. 2018 Dec 14;121(24):242002. doi: 10.1103/PhysRevLett.121.242002.

Authors

D Blyth^{1

2}, J Fry^{3

4}, N Fomin^{5

6}, R Alarcon¹, L Alonzi³, E Askanazi³, S Baeßler^{3

7}, S Balascuta^{1

8}, L Barrón-Palos⁹, A Barzilov¹⁰, J D Bowman⁷, N Birge⁵, J R Calarco¹¹, T E Chupp¹², V Cianciolo⁷, C E Coppola⁵, C B Crawford¹³, K Craycraft^{5

13}, D Evans^{3

4}, C Fieseler¹³, E Frlež³, I Garishvili^{5

7}, M T W Gericke¹⁴, R C Gillis^{4

7}, K B Grammer^{5

7}, G L Greene^{5

7}, J Hall³, J Hamblen¹⁵, C Hayes^{5

16}, E B Iverson⁷, M L Kabir^{13

17}, S Kucuker^{5

18}, B Lauss¹⁹, R Mahurin²⁰, M McCrea^{13

14}, M Maldonado-Velázquez⁹, Y Masuda²¹, J Mei⁴, R Milburn¹³, P E Mueller⁷, M Musgrave^{5

22}, H Nann⁴, I Novikov²³, D Parsons¹⁵, S I Penttilä⁷, D Počanić³, A Ramirez-Morales⁹, M Root³, A Salas-Bacci³, S Santra²⁴, S Schröder^{3

25}, E Scott⁵, P-N Seo^{3

26}, E I Sharapov²⁷, F Simmons¹³, W M Snow⁴, A Sprow¹³, J Stewart¹⁵, E Tang^{6

13}, Z Tang^{4

6}, X Tong⁷, D J Turkoglu²⁸, R Whitehead⁵, W S Wilburn⁶; NPDGamma Collaboration

Affiliations

¹ Arizona State University, Tempe, Arizona 85287, USA.
² High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
³ University of Virginia, Charlottesville, Virginia 22904, USA.
⁴ Indiana University, Bloomington, Indiana 47405, USA.
⁵ University of Tennessee, Knoxville, Tennessee 37996, USA.
⁶ Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
⁷ Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
⁸ Horia Hulubei National Institute for Physics and Nuclear Engineering, Magurele 077125, Romania.
⁹ Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000, Mexico.
¹⁰ University of Nevada, Las Vegas, Nevada 89154, USA.
¹¹ University of New Hampshire, Durham, New Hampshire 03824, USA.
¹² University of Michigan, Ann Arbor, Michigan 48109, USA.
¹³ University of Kentucky, Lexington, Kentucky 40506, USA.
¹⁴ University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.
¹⁵ University of Tennessee, Chattanooga, Tennessee 37403 USA.
¹⁶ Physics Department, North Carolina State University, Raleigh, North Carolina 27695, USA.
¹⁷ Mississippi State University, Mississippi State, Mississippi 39759, USA.
¹⁸ Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
¹⁹ Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
²⁰ Middle Tennessee State University, Murfreesboro, Tennessee 37132, USA.
²¹ High Energy Accelerator Research Organization (KEK), Tukuba-shi, 305-0801, Japan.
²² Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
²³ Western Kentucky University, Bowling Green, Kentucky 42101, USA.
²⁴ Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
²⁵ Saarland University, Institute of Experimental Ophthalmology, Kirrberger Str. 100, Bldg. 22, 66424 Homburg/Saar, Germany.
²⁶ Triangle Universities Nuclear Lab, Durham, North Carolina 27708, USA.
²⁷ Joint Institute for Nuclear Research, Dubna 141980, Russia.
²⁸ National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.

PMID: 30608729
DOI: 10.1103/PhysRevLett.121.242002

Abstract

We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.0±1.4(stat)±0.2(syst)]×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=[2.6±1.2(stat)±0.2(syst)]×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=[-7.4±3.5(stat)±0.5(syst)]×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.