We study the decays of the charmonium resonances $J/\psi$ and $\psi(3686)$ to the final states $\Xi^{-}\bar\Xi^{+}$, $\Sigma(1385)^{\mp}\bar\Sigma(1385)^{\pm}$ based on a single baryon tag method using data samples of $(223.7 \pm 1.4) \times 10^{6}$ $J/\psi$ and $(106.4 \pm 0.9) \times 10^{6}$ $\psi(3686)$ events collected with the BESIII detector at the BEPCII collider. The decay $\psi(3686)\rightarrow\Sigma(1385)^{\mp}\bar\Sigma(1385)^{\pm}$ is observed for the first time, and the measurements of the other processes, including the branching fractions and angular distributions, are in good agreement with and much more precise than the previously published results. Additionally, the ratios $\frac{{\cal{B}}(\psi(3686)\rightarrow\Xi^{-}\bar\Xi^{+})}{{\cal{B}}(J/\psi\rightarrow\Xi^{-}\bar\Xi^{+})}$, $\frac{{\cal{B}}(\psi(3686)\rightarrow\Sigma(1385)^{-}\bar\Sigma(1385)^{+})}{{\cal{B}}(J/\psi\rightarrow\Sigma(1385)^{-}\bar\Sigma(1385)^{+})}$ and $\frac{{\cal{B}}(\psi(3686)\rightarrow\Sigma(1385)^{+}\bar\Sigma(1385)^{-})}{{\cal{B}}(J/\psi\rightarrow\Sigma(1385)^{+}\bar\Sigma(1385)^{-})}$ are determined.
The number of the observed events $N_\rm{obs.}$, efficiencies $\epsilon$, $\alpha$ values, and branching fractions ${\cal B}$ for $\psi\rightarrow\Xi^{-}\bar\Xi^{+}$, $\Sigma(1385)^{\mp}\bar\Sigma(1385)^{\pm}$. Only statistical uncertainties are indicated.
We have measured the partial width and forward-backward charge asymmetry for the reaction e + e - →Z 0 →μ + μ - (γ). We obtain a partial width Γ μμ of 83.3±1.3(stat)±0.9(sys) MeV and the following values for the vector and axial vector couplings: g v =−0.062 −0.015 +0.020 and g A =−0.497 −0.005 +0.005 . From our measurement of the partial width and the mass of the Z 0 boson we determine the effective electroweak mixing angle, sin 2 θ w =0.232±0.005, and the neutral current coupling strength parameter, ϱ =0.998±0.016.
No description provided.
Forward backward charge asymmetry.
No description provided.
We use the reaction e+e−→μ+μ−, in the Mark J detector at the DESY high-energy e+e− collider PETRA, to test the standard electroweak theory and find good agreement. We also set limits on the parameters of several extended gauge theories.
CROSS SECTION MEASUREMENT RELATIVE TO PREDICTED QED CROSS SECTION.
FORWARD-BACKWARD ASYMMETRY. THE SYSTEMATIC ERROR IN THE ASYMMETRY IS <0.5 PCT.
ANGULAR DISTRIBUTIONS NOT GIVEN IN PAPER. SUPPLIED BY E.DEFFUR.
None
DATA ARE CORRECTED FOR TWO-PHOTON AND TAU PRODUCTION EFFECTS, ACCEPTANCE AND QED RADIATIVE EFFECTS UP TO ORDER ALPHA**3. THERE IS ALSO A 6 PCT NORMALISATION ERROR NOT INCLUDED. THE OVERALL AVERAGE VALUE OF R FROM THIS DATA IS 3.88 +- 0.04 +- 0.22.
No description provided.
SEE PRL 55, 665 FOR MOST RECENT VALUES OF THE MU+ MU- CROSS SECTIONS.
The measurement of the nonelectromagnetic forward-backward charge asymmetry in the reaction e+e−→μ+μ− at s∼34.6 GeV and in the angular region 0<|cosθ|<0.8 is reported. With a systematic error less than 1%, we observe an asymmetry of (-8.1±2.1)%. This is in agreement with the standard electroweak theory prediction of (-7.6±0.6)%. The weak-current coupling constants are also reported.
SEE PRL 55, 665 FOR DISTRIBUTIONS AT 34.6 GEV AND ABOVE.
SEE PRL 55, 665 FOR CROSS SECTION VALUES AND FORWARD BACKWARD ASYMMETRY.
No description provided.
Forum