ABSTRACT
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 ρ, δ, and P(µ)(π)ξ tests the standard model in a purely leptonic process and provides improved limits for relevant extensions to the standard model. Specifically, for the generalized left-right symmetric model |(g(R)/g(L))ζ|<0.020 and (g(L)/g(R))m(2)>578 GeV/c(2), both 90% C.L.
ABSTRACT
The TWIST Collaboration has measured the Michel parameter rho in normal muon decay, mu(+)--> e(+)nu(e)nu (mu). In the standard model, rho = 3/4. Deviations from this value imply mixing of left- and right-handed muon and electron couplings. We find rho=0.750 80+/-0.000 32(stat) +/- 0.000 97(syst) +/- 0.000 23, where the last uncertainty represents the dependence of rho on the Michel parameter eta. This result sets new limits on the W(L)-W(R) mixing angle in left-right symmetric models.
ABSTRACT
We report on the first determination of upper limits on the branching ratio (BR) of eta decay to pi0pi0gamma and to pi0pi0pi0gamma. Both decay modes are strictly forbidden by charge conjugation (C) invariance. Using the Crystal Ball multiphoton detector, we obtained BR(eta-->pi0pi0gamma)<5 x 10(-4) at the 90% confidence level, in support of C invariance of isoscalar electromagnetic interactions of the light quarks. We have also measured BR(eta-->pi0pi0pi0gamma)<6 x 10(-5) at the 90% confidence level, in support of C invariance of isovector electromagnetic interactions.
ABSTRACT
Recently the Crystal Ball Collaboration measured precise new data for the near-threshold reaction K(-)p-->etaLambda, which is dominated by formation of the Lambda(1670)1 / 2(-). In this Letter, we present results of a unitary, multichannel analysis that incorporates the new Crystal Ball data. For our preferred fit, we obtain mass M = 1673+/-2 MeV, width Gamma = 23+/-6 MeV, and elasticity x = 0.37+/-0.07. This elasticity is significantly larger than previously recognized. Resonance parameters of our preferred fit are in striking agreement with the quark-model predictions of Koniuk and Isgur.
ABSTRACT
Wildtype cowpea mosaic virus (CPMV) was extracted from fresh and frozen plant material by methods suitable for large-scale application. Deep freezing, crushing, and thawing in water or buffers gave 0.6+/-0.2 mg g(-1) of virus after up to 24 h. Release from sliced fresh leaves was lower at 0.14+/-0.03 mg g(-1). Homogenisation of frozen leaves for 1 min increased yield to a maximum, on average of 3.5 mg g(-1) but varying between batches from 2.2 to 4.8 mg g(-1) virus Long term storage at -80 degrees C increased subsequent yield by 2 mg g(-1) per year on average; the maximum was 10.4+/-1.9 mg g(-1) (665 days storage). Within a batch, similar yields were obtained between individual fresh plants, and from frozen versus fresh leaves. After homogenisation for 1 min, 90% of debris particles were smaller than 12 microm, half under 5 microm and 10% less than 1 microm. Homogenate (4% dry weight) was rheologically complex, exhibiting shear thinning with hysteresis at low shear rates which bears on subsequent processing. At shear rates above 200 s(-1), its apparent viscosity was 0.02 N s m(-2).
