We have measured the inclusive $D~{*\pm}$ production cross section in a two-photon collision at the TRISTAN $e~+e~-$ collider. The mean $\sqrt{s}$ of the collider was 57.16 GeV and the integrated luminosity was 150 $pb~{-1}$. The differential cross section ($d\sigma(D~{*\pm})/dP_T$) was obtained in the $P_T$ range between 1.6 and 6.6 GeV and compared with theoretical predictions, such as those involving direct and resolved photon processes.
Numerical values supplied by R. Enomoto.
No description provided.
Measurements of the forward-backward asymmetry of e + e − → cc events were carried out at a mean √s energy of 57.95 GeV at TRISTAN, KEK. The cc events were tagged either by the full-reconstruction of D ∗± or the inclusive P T spectrum of π s ± from D ∗± → D 0 ( D 0 )π s ± . The forward-backward asymmetry was measured to be A FB c = −0.49 −0.13 +0.14 (stat.) ± 0.06 (syst.), consistent with the standard model.
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The strong coupling constant α s was determined from analyses of the thrust, heavy jet mass and, differential 2-jet rate, using e + e - hadronic events at s = 58 GeV with the TOPAZ detector at TRISTAN. The NLLjet Monte Carlo simulation (NLLjet) and analytic formulae based on resummation up to the next-to-leading logarithms combined with O ( α 2 s ) calculations were used to evaluate α s . The average α s values at Q 2 = (58 GeV) 2 from the analyses are α s = 0.125 ± 0.009 for NLLjet and α s = 0.132 ± 0.008 for the resummed analytic formulae.
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The exact definition for Y23 see text.
We have investigated the properties of jet production in almost real γγ collisions at √ s =58 GeV with the TOPAZ detector at the TRISTAN e + e − collider. The data were analyzed with a jet-clustering method based on a cone algorithm. The jet rate shows evidence for a hard scattering effect of the hadronic constituents of a photon (resolved photon processes). We have also observed a substantial energy flow in the small-angle region, which is additional evidence for resolved photon processes. We present the transverse momentum dependence of the inclusive jet and two-jet cross sections and compare them with different model predictions.
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We carried out the energy scan between E CM = 58 and 60 GeV at the TRISTAN e + e − collider to search for the possible narrow resonance suggested by the L3 experiment at LEP. The total cross sections are measured for γγ, multihadron, e + e − and μ + μ − production at ten energy points covering this energy range almost uniformly. The results are in good agreement with the Standard Model predictions, and 95% confidence level upper limits are set to Γ ee × BR of the hypothetical scalar and tensor resonances.
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The process e + e − → μ + μ − and e + e − have been studied in the energy range s =52−61.4 GeV , using the TOPAZ detector at TRISTAN. From an integrated luminosity of L = 74.0 pb −1 , lowest-order cross sections and forward-backward asymmetries are measured to be 〈σ μμ 〈 = 25.4±0.9±1.2 pb , 〈A μμ 〉 = (−32.2±3.1±1.1)%, 〈σ ττ 〉 = 27.1±1.1±1.2 pb , 〈A ττ 〉 = (−33.9±4.9±1.0)% , at an average energy of s 〉=57.87 GeV . From the measured assymetry we derive axial vector couplings of a c a μ =0.96±0.09±0.01,and a c a τ =1.01±0.14±0.01±. These results are consistent with standard model expectations. Lower limits in the range 2–5 TeV (95%CL)are placed on compositeness scale parameters for leptons.
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Additional 4.6 pct systematic uncertainty.
Additional 4.4 pct systematic uncertainty.
The process e + e − →e + e − μ + μ − has been studied in single-tag and double-tag configurations using the TOPAZ detector at TRISTAN. The data correspond to the integrated luminosity of 45.3pb − at center-of-mass energies ranging from 52 to 61.4 GeV. The observed events in both configurations have shown a good agreement with QED predictions in order α 4 . Although the AMY group reported an excess of e + e − →e + e − μ + μ − events in double-tag mode at low muon invariant mass region less than 1.0 GeV/c 2 , we did not observed such excess in our data.
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An experimental study of b-quark jets using high- p T electrons was carried out at √ s =58 GeV with the TOPAZ detector at the e + e − collider TRISTAN at KEK. The forward-backward charge asymmetry of the b-quark was obtained to be A b b ̄ =−0.55±0.27( stat. )±0.07( syst. ) , consistent with the standard model prediction. Also, such jet properties of the b-quark as the average charged multiplicity and the rapidity of charged particles were analyzed. In order to purify the b-quark event samples in this analysis, only events with backward-going electrons or forward-going positrons were used. The energy dependence of these jet properties was studied by making comparisons with the results of the DELCO experiment at the PEP collider (√ s =29 GeV) at SLAC.
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Mean values of jet properties for b-jet sample.
We have collected 122 multi-hadronic inclusive muon events with the TOPAZ detector at 〈 s 〉 = 58.27 GeV with ∫ L d t=40.61 pb −1 . From this event sample we derived the differential cross section for B-hadron productions and determined B-hadron forward-backward asymmetry (A b b ) to be A b b = −0.71 ± 0.34 ( stat ) +0.07 −0.08 ( syst ) . A fit to the differential cross section, after correcting for the effect of B 0 B 0 mixing, yielded the axial-vector coupling constant of the b-quark ( a b ): a b = −1.79 +0.34 −0.32 (stat) +0.15 −0.14 (syst). We also set a 90% confidence level limit of χ <0.37 on the B 0 B 0 mixing parameter.
Observed differential cross section.
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We have measured the total e + e − hadronic annihilation cross section at the center of mass energies between 50.0 GeV and 61.4 GeV with the TOPAZ detector at TRISTAN. The full electroweak radiative corrections (up to O(α 3 )) were applied to the data which were analysed together with the published data from PEP and PETRA. We then determined the standard model parameters, M z (the mass of the Z), sin w 2 θ (the Weinberg angle) and Λ MS (the QCD scale parameter) by comparing the experimental data with the prediction of the standard model. The best fit values are M z = 89.2 −1.8 +2.1 GeV/c 2 , sin 2 θ w = 0.233 −0.025 +0.035 and Λ MS = 0.327 −0.206 +0.275 GeV. A constraint is obtained on the heavy top quark mass through the radiative corrections if we take the SLC value of M z (91.1 GeV / c 2 ).
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