Abstract
The K2K experiment, using a fine-grained detector in a neutrino beam of energy 〈E〉∼1.3 GeV has observed two-track events that can be interpreted as a coherent reaction νμ+N→μ−+N+π+(N=C12) or an incoherent process νμ+(p,n)→μ−+π++(p,n), the final nucleon being unobserved. The data show a significant deficit of forward-going muons in the interval Q2≲0.1 GeV2, where a sizeable coherent signal is expected. We attempt an explanation of this effect, using a PCAC formula that includes the effect of the non-vanishing muon mass. A suppression of about 25% is caused by a destructive interference of the axial vector and pseudoscalar (pion-exchange) amplitudes. The incoherent background is also reduced by 10–15%. As a consequence the discrepancy between theory and observation is significantly reduced.
Submitted Version (
Free)
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call