[Primex2] [EXTERNAL] an abstract to DNP meeting

[Gan, Liping]

Dear colleagues,

The attached file below is my abstract to DNP fall meeting. I would appreciate very much for your comments and suggestions by Monday (June 28). Thank you!

Best regards,
Liping



Precision Measurement of the π0 Lifetime
Liping Gan
(University of North Carolina Wilmington)
On behalf of the PrimEx-II collaboration
As the lightest and the simplest hadron, π0 plays a crucial role in our understanding of the symmetry structure of low-energy QCD. The π0→γγ decay width offers a fundamental test of the QCD predictions based on the chiral anomaly and spontaneous chiral symmetry breaking. The theoretical calculations over the past two decades have reached 1% precision in the decay amplitude of π0 into two photons. The experimental measurement of this parameter with a comparable accuracy provides a stringent test of QCD. The PrimEx collaboration at Jefferson Lab has developed and performed two experiments (PrimEx I&II) to measure the π0 radiative decay width via the Primakoff effect. The published result, Γ(π0→γγ)=7.802±0.052±0.105 eV,  has a 1.5% total uncertainty. It agrees to the leading-order chiral anomaly and is about 2σ lower than the high-order QCD predictions. The details of measurement and the physics impact will be discussed.

Thanks to NSF for support of PHY-0079840 (MRI ) and PHY-1812396.


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