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Title: Preliminary Results from the PrimEx-II experiment at Jefferson Lab

Properties of the neutral pion, as the lightest hadron in Nature, are most sensitive to the basic symmetries and their partial breaking effects in the theory of the strong interaction (QCD). In particular, the po →gg decay width is primarily defined by the spontaneous chiral symmetry breaking effect (chiral anomaly) in QCD. The next order corrections to the anomaly have been shown to be small and are known to a 1% precision level. The PrimEx Collaboration at JLab has developed and performed two Primakoff type experiments to measure the po →gg decay width with a similar precision. The published result from the PrimEx-I experiment, G(p0 →gg ) = 7.82±0.14 (stat.)±0.17 (syst.) eV, was a factor of two more precise than the average value quoted in PDG-2010 [1]. The second experiment was performed in 2010 with a goal of 1.4% total uncertainty to address the next-to-leading-order theory calculations. The preliminary results from the PrimEx-II experiment are presented and discussed in this note.
  1. NCA&T, Greensboro, NC; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-PHY-15-2158; DOE/OR/23177-3846
DOE Contract Number:
AC05-06OR23177; PHY-1506388; PHY-1205962; PHY-0079840
Resource Type:
Resource Relation:
Journal Name: Proceedings of Science; Journal Volume: CD15; Conference: Chiral Dynamics (CD15) : Pisa, Italy, June 29-July 3, 2015
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States