Using about 3.9 million hadronic Z decays from e+e- collisions recorded by the OPAL detector at LEP at centre-of-mass energies near MZ the branching ratio for the decay D_s -> tau nu_tau has been measured to be (7.0 +/- 2.1(stat) +/- 2.0 (syst))%. This result can be used to derive the decay constant of the D_s meson: f(D_s) = 286 +/- 44(stat) +/- 41(syst) MeV.
FORMFACTOR(NAME=FP,C=DECAY CONSTANT) is pseudoscalar meson decay constant.
Measurements of the individual multiplicities of pi+, pi- and pi0 produced in the deep-inelastic scattering of 27.5 GeV positrons on hydrogen are presented. The average charged pion multiplicity is the same as for neutral pions, up to approximately z= 0.7, where z is the fraction of the energy transferred in the scattering process carried by the pion. This result (below z= 0.7) is consistent with isospin invariance. The total energy fraction associated with charged and neutral pions is 0.51 +/- 0.01 (stat.) +/- 0.08 (syst.) and 0.26 +/- 0.01 (stat.) +/- 0.04 (syst.), respectively. For fixed z, the measured multiplicities depend on both the negative squared four momentum transfer Q^2 and the Bjorken variable x. The observed dependence on Q^2 agrees qualitatively with the expected behaviour based on NLO-QCD evolution, while the dependence on x is consistent with that of previous data after corrections have been made for the expected Q^2-dependence.
The measured PI0 multiplicity. Additional 9 PCT systematic error.
The measured multiplicity for charged pions, individually and the average. Additional 7 PCT systematic error.
The charged pion multiplicity as a function of x for four different z regions.
Using a prompt neutrino beam in which a nu_tau component was identified for the first time, the nu_tau magnetic moment was measured based on a search for an anomalous increase in the number of neutrino-electron interactions. One such event was observed when 2.3 were expected from background processes, giving an upper 90% confidence limit of 3.9x10^-7 Bohr magnetons.
CONST(NAME=BOHR MAGNETON) is Bohr magneton.
A precise measurement of the anomalous g value, a_mu=(g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a_mu^+=11 659 202(14)(6) X 10^{-10} (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a_mu(SM)=11 659 159.6(6.7) X 10^{-10} (0.57 ppm) and a_mu(exp)-a_mu(SM)=43(16) X 10^{-10} in which a_mu(exp) is the world average experimental value.
The anomalous G value is related to the gyromagnetic ratio by MOM(N=A_MU) =(G-2)/2.
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The photoabsorption asymmetry A1 for exclusive RHO0 production.
The photoabsorption asymmetry A1 for exclusive RHO0 production as a function of Q**2.
The photoabsorption asymmetry A1 for exclusive RHO0 production as a function of W.
We present measurements of time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurement uses a data sample of 23 million Upsilon(4S)-->B-anti-B decays collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we find events where one neutral B meson is fully reconstructed in a CP eigenstate containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay time distributions in such events. The result is sin2beta=0.34 +/- 0.20 (stat) +/- 0.05 (syst).
Standard Model predicts the time-dependent rate asymmetry as follows: A(t) = (B0(t)-BBAR0(t))/(B0(t)+BBAR0(t)) = SIN(2*BETA)*SIN(Delta(M)*t), where Delta(M) is the mass difference between the two B0 mass eigenstates. The total systematic error equals +0.50 -0.46.
The triple gauge-boson couplings involving the W are determined using data samples collected with the ALEPH detector at mean centre-of-mass energies of 183 GeV and 189 GeV, corresponding to integrated luminosities of 57 pb^-1 and 174 pb^-1, respectively. The couplings, g^Z_1, Kappa_gamma and lambda_gamma, are measured using W-pair events, single-W production and single-gamma production. Each coupling is measured individually with the other two coupling fixed at their Standard Model value. Including ALEPH results from lower energies, the 95% confidence level intervals for the deviation to the Standard Model are -0.087 < Dg^Z_1 < 0.141 -0.200 < DKappa_gamma < 0.258 -0.062 < Lambda_gamma < 0.147. Fits are also presented where two or all three couplings are allowed to vary. In addition, W-pair events are used to set limits on the C- or P-violating couplings g^V_4, g^V_5, Kappa_V, and Lambda_V, where V denotes either gamma or Z. No deviations from the Standard Model expectations are observed.
The errors included the statistical and systematic uncertainties. Deviation from SM values.
The errors included the statistical and systematic uncertainties. Combined results, lower sqrt(s) data are also included.
The errors included the statistical and systematic uncertainties. Combined results, lower sqrt(s) data are also included. Three-parameter fit.
Dijet production has been studied in neutral current deep inelastic e+p scattering for 470 < Q**2 < 20000 GeV**2 with the ZEUS detector at HERA using an integrated luminosity of 38.4 pb**{-1}. Dijet differential cross sections are presented in a kinematic region where both theoretical and experimental uncertainties are small. Next-to-leading-order (NLO) QCD calculations describe the measured differential cross sections well. A QCD analysis of the measured dijet fraction as a function of Q**2 allows both a precise determination of alpha_s(M_Z) and a test of the energy-scale dependence of the strong coupling constant. A detailed analysis provides an improved estimate of the uncertainties of the NLO QCD cross sections arising from the parton distribution functions of the proton. The value of alpha_s(M_Z), as determined from the QCD fit, is alpha_s(M_Z) = 0.1166 +- 0.0019 (stat.) {+ 0.0024}_{-0.0033} (exp.)} {+ 0.0057}_{- 0.0044} (th.).
The differential dijet cross section dsig/dZP1.
The differential dijet cross section dsig/dlog10(x).
The differential dijet cross section dsig/dlog10(xi).
Emission of intermediate mass fragments (IMFs) (Z>~3) from central collisions of 40Ar+45Sc (E/A=35–115 MeV), 58Ni+58Ni (E/A=35–105 MeV), and 86Kr+93Nb (E/A=35–95 MeV) was studied. For each system, the average number of IMFs per event increased with beam energy, reached a maximum, and then decreased. The beam energy of peak IMF production increased linearly with the combined mass of the system. The number of IMFs emitted at the peak also increased with the system mass. Percolation calculations showed a weaker dependence of the peak beam energy and the number of IMFs on the total mass of the system.
Uncertainty in EKIN is 1 PCT.
We measured the capture-fission excitation functions for the 32S+181Ta reaction and the 38S+181Ta reaction. (The radioactive 38S beam was produced by projectile fragmentation.) In the 32S-induced reaction, an incomplete fusion component was observed at high energies, with an average linear momentum transfer corresponding to the escape of an α particle. The deduced interaction barrier heights were 130.7±0.3 and 124.8±0.3 MeV for the 32S- and 38S-induced reactions, respectively. No differences between the two reactions were observed beyond a simple shift in the interaction barrier height.
A typical beam energy resolution was 0.01 TO 0.1 MeV. In the S32-induced reaction, an incomplete fussion component was observed at high energies, with an average linear momentum transfer corresponding to th e escape of an alpha patticle. The deduced interaction barrier heights were 130 .7+-0.3 and 124.8+-0.3 MeV for the S32 and S38-induced reactions respectively.
A typical beam energy resolution was 0.01 TO 0.1 MeV.
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