The time dependence of muon spin relaxation has been measured in high purity aluminum and silver samples in a longitudinal 2 T magnetic field at room temperature, using time-differential musr. For times greater than 10 ns, the shape fits well to a si
ngle exponential with relaxation rates of $lambda_{textrm{Al}} = 1.3 pm 0.2,(textrm{stat.}) pm 0.3,(textrm{syst.}),pms$ and $lambda_{textrm{Ag}} = 1.0 pm 0.2,(textrm{stat.}) pm 0.2,(textrm{syst.}),pms$.
The TWIST Collaboration has completed a new measurement of the energy-angle spectrum of positrons from the decay of highly polarized muons. A simultaneous measurement of the muon decay parameters {rho}, {delta}, and (P_{mu}){xi} tests the Standard Mo
del (SM) in a purely leptonic process and provides improved limits for relevant extensions to the SM. Specifically, for the generalized left-right symmetric model |(g_R/g_L){zeta}|<0.020 and (g_L/g_R)m_2> 578 GeV/c^2, both 90% C.L.
The TWIST experiment has made a precision measurement of three of the decay parameters in muon decay. The newest results are rho = 0.75014 +-0.00017(stat) +-0.00044(sys) +-0.00011(eta) and delta = 0.75067 +-0.00030(stat) +-0.00067(sys). Together with
previously published results, improved constraints on possible extensions of the electroweak Standard Model are derived.
