The first measurement of the elementary process $\mu^- p \rightarrow \nu_{\mu} n \gamma$ is reported. A photon pair spectrometer was used to measure the partial branching ratio ($2.10 \pm 0.22) \times 10^{-8}$ for photons of k > 60 MeV. The value of the weak pseudoscalar coupling constant determined from the partial branching ratio is $g_p(q^{2}=-0.88m_{\mu}^2) = (9.8 \pm 0.7 \pm 0.3) \cdot g_a(0)$, where the first error is the quadrature sum of statistical and systematic uncertainties and the second error is due to the uncertainty in $\lambda_{op}$, the decay rate of the ortho to para $p \mu p$ molecule. This value of g_p is $\sim$1.5 times the prediction of PCAC and pion-pole dominance.Comment: 13 pages, RevTeX type, 3 figures (encapsulated postscript), submitted to Phys. Rev. Let

Charge symmetry breaking in n p elastic scattering at 347 MeV has been measured with high precision.

The Doppler-shift attenuation method was used to obtain the following mean lifetimes (in psec) for the indicated nuclear levels: 10 C(3.36), r=0.155 ±0.025; 10 B(3.59), r=0.150±0.015; 10 Be(3.37), r=0.189 ±0.020; 10 B (2.15), r= 2.7_ 0 .4 +0 -8 . A limit of r <30 fsec is obtained for 10 B (1.74), which is a factor of 8 greater than, and therefore consistent with, the lifetime computed from the analog 0 decay of 10 C. Transition strengths obtained from the 10 B(2.15) and 10 B(3.59) lifetimes are in good agreement with the effectiveinteraction calculations of Cohen and Kurath, as modified by Warburton et at. The 10 C(3.36) and 10 Be(3.37) states decay by analog E2 transitions: 2 + , r=l-»0 + , T=1, with 7%=±l, whose strengths are well described by calculations of Kurath's for an effective charge €«= € p =0.5. An upper limit was obtained for the corresponding transition 5.17 ->1.74 in 10 B(r*=0) which is consistent (factor of 4 greater) with the analog strengths observed in the T e -ztl nuclei.

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A nonzero difference of the analyzing powers due to charge symmetry breaking has been measured with high precision in np elastic scattering at a neutron beam energy of 347 MeV. The neutron beam and proton target were alternately polarized for the measurements of A n and A p . A mirror-symmetric detection system was used to cancel geometry-related systematic errors. From fits of the measured asymmetry angular distributions over the range of 53.4°р cm р86.9°, the difference in the zero-crossing angles of the analyzing powers was determined to be 0.438°Ϯ0.054°(stat.)Ϯ0.051°(syst.) in the center-of-mass system. Using the experimentally determined slope of the analyzing power dA/dϭ(Ϫ1.35Ϯ0.05)ϫ10 Ϫ2 deg Ϫ1 ͑c.m.͒, this is equivalent to ⌬AϵA n ϪA p ϭ͓59Ϯ7(stat.)Ϯ7(syst.)Ϯ2(syst.)͔ϫ10 Ϫ4 . The shape of ⌬A() in the vicinity of the zero-crossing angle has also been extracted. Predictions of nucleon-nucleon interaction models based on meson exchange agree well with the results. ͓S0556-2813͑98͒06404-8͔PACS number͑s͒: 13.75. Cs, 11.30.Hv, 13.88.ϩe, 21.45.ϩv ͗P beam ϩ P target ͘•⌬A͑͒ϩ͑ P beam Ϫ P target ͒•͗A͑ ͒͘. ͑3͒However, at the zero-crossing angle, the second term and associated systematic errors disappear. Rather than measuring ⌬A directly at the zero-crossing angle, the difference of the individual zero-crossing angles, where the respective analyzing powers cross zero,