Related Experiment Video
Updated: Jun 19, 2026

Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
New precise measurement of the pion weak form factors in pi+-->e+ nugamma decay
M Bychkov1, D Pocanić, B A Vandevender
1Department of Physics, University of Virginia, Charlottesville, Virginia 22904-4714, USA. mab3ed@virginia.edu
Abstract:
We have measured the pi+-->e+ nugamma branching ratio over a wide region of phase space, based on a total of 65 460 events acquired using the PIBETA detector. Minimum-chi2 fits to the measured (E(e+), E(gamma) energy distributions result in the weak form factor value of F(A)=0.0119(1) with a fixed value of F(V)=0.0259. An unconstrained fit yields F(V)=0.0258(17) and F(A)=0.0117(17). In addition, we have measured a=0.10(6) for the dependence of F(V) on q2, the e+ nu pair invariant mass squared, parametrized as F(V)(q2)=F(V)(0)(1+aq(2)). The branching ratio for the kinematic region E(gamma)>10 MeV and theta(e(+)gamma)>40 degrees is measured to be B(expt)=73.86(54)x10(-8). Earlier deviations we reported in the high-E(gamma)-low-E(e+) kinematic region are resolved without a tensor term. We also derive new values for the pion polarizability alpha(E)=2.78(10)x10(-4) fm3 and neutral pion lifetime tau(pi0)=(8.5+/-1.1)x10(-17) s.
More Related Videos
Related Concept Videos
Determination of Pi Terms
The theorem indicates that the number...
Nuclear Overhauser Enhancement (NOE)
Types of Radioactivity
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)
Atomic Nuclei: Nuclear Magnetic Moment
Nuclear Stability
To hold positively charged protons together in the...

