We have measured gluon splitting into bottom quarks, g→b b ̄ , in hadronic Z 0 decays collected by SLD between 1996 and 1998. The analysis was performed by looking for secondary bottom production in 4-jet events of any primary flavor. 4-jet events were identified, and in each event a topological vertex-mass technique was applied to the two jets closest in angle in order to identify them as b or b ̄ jets. The upgraded CCD-based vertex detector gives very high B -tagging efficiency, especially for B hadrons with the low energies typical of this process. We measured the rate of g→b b ̄ production per hadronic event, g b b ̄ , to be (2.44±0.59(stat.)±0.34(syst.))×10 −3 .
No description provided.
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.
We report values of $R = \sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-)$ for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.
Measured values of R.
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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.
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).
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.
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 process e^+e^- -> Z gamma gamma -> q q~ gamma gamma is studied in 0.5 fb-1 of data collected with the L3 detector at centre-of-mass energies between 130.1 GeV and 201.7 GeV. Cross sections are measured and found to be consistent with the Standard Model expectations. The study of the least energetic photon constrains the quartic gauge boson couplings to -0.008 GeV-2 < a_0/\Lambda^2 < 0.005 GeV-2 and -0.007 GeV-2 < a_c/\Lambda^2 < 0.011 GeV-2, at 95% confidence level.
No description provided.
The results are presented for more more restrictive phase space.
CONST(NAME=LAMBDA_NEW) is New Physics scale. COUPLING(NAME=A0,AC) are quartic gauge boson couplings of the effective Lagrangians (see paper for details).
The formation and subsequent decay of nuclei excited via the annihilation of 1.22-GeV antiprotons have been investigated at the low energy antiproton ring (LEAR). Both neutrons and charged products, from protons up to fission fragments and heavy residues, were detected over a solid angle of 4π by means of the Berlin neutron ball (BNB) and the Berlin silicon ball (BSiB), respectively. All events associated with an inelasticity greater than 10 MeV were recorded, a condition fulfilled for 100% of the annihilation events. The distributions of excitation energy (E*) of the transient hot nuclei have been investigated for a large range of target nuclei, E* being determined event by event from the total multiplicity of light particles. The average excitation energies are about twice as large as for annihilations at rest, and range from 2.5 MeV/nucleon for the Cu target to 1.5 MeV/nucleon for the U target, in good agreement with the predictions of an intranuclear-cascade model. The distributions extend to E*>8 MeV/nucleon for Cu and E*>5 MeV/nucleon for Au, with cross sections exceeding 1% of σreac. Thanks to the capability of determining E* for all events, largely irrespective of their mass partitions, the probabilities of the different decay channels at play could be estimated as a function of E*. The data show the prevalence of fission and evaporation up to E*=4–5 MeV/nucleon for Au and U. The fission probability Pfis was measured for the first time over the full range of E*. The reproduction of the data by statistical models is reasonable, provided that the ratio af/an is adjusted for the different targets and a transient time shorter than 1×10−21 s is considered. The experiment has allowed the fission probability to be investigated as functions of the associated neutron and light-charged particle multiplicities. The intermediate-mass fragment multiplicities rise smoothly with E* up to about 1 unit at E*=1 GeV for Au and U, with no indication of significant contribution from another process than evaporation. Heavy residues have been measured quite abundantly at the highest E*, with most of their kinetic energy arising from the recoil effects in the evaporation stage. Overall, the data allow a coherent picture to be established, consistent with the hot nucleus retaining conventional decay properties.
No description provided.
No description provided.
No description provided.
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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