S.K. Sahu

Measurements of the inclusive jet cross section in photon-photon interactions at TRISTAN

Abstract We present cross section measurements for inclusive jet production in almost-real photon-photon interactions at TRISTAN using the AMY detector. The results are compared with leading-order QCD calculations for different parameterizations of the parton density in the photon.

A high-Q2 measurement of the photon structure function F2γ

Abstract The photon structure function F 2 γ has been measured at average Q 2 values of 73 and 390 GeV 2 using data collected by the AMY detector at the TRISTAN e + e − collider. F 2 γ is observed to be increasing as ln Q 2 . The x -dependence of F 2 γ , where x is the momentum fraction carried by the parton inside the photon, is also measured. The measurements are compared with several parton density models.

Measurement of D-*+/- production in two-photon processes at TRISTAN

The inclusive cross section for the production of charmed D*(+/-) mesons in two-photon processes is measured with the AMY detector at the TRISTAN e(+)e(-) collider. D*(+/-) mesons ate identified from the distribution of charged-particle transverse momenta relative to the jet axis. A data sample corresponding to an integrated luminosity of 176 pb(-1) at a center-of-mass energy of 58 GeV is used to determine a cross section sigma(e(+)e(-) --> e(+)e(-)D*(+/-)X) = 270 +/- 49(stat) +/- 38(syst) pb. The results are compared with theoretical expectations based on the Vector Meson Dominance, direct quark-parton model, and resolved photon processes.

Measurement of αs from the moment of particle momenta within jets from e+e- annihilation

We present a study of the third moment of the inclusive momentum distribution of particles within jets produced by e+e- annihilation at TRISTAN. In this analysis, the QCD coupling strength alpha(s) is determined by fits to the prediction of the Next-to-Leading Logarithm Parton-Shower model. The measured value of alpha(s) (57.9 GeV) = 0.134(-0.005)+0.006.

A measurement of Bose-Einstein correlations in e+e− annihilation at TRISTAN

Abstract Using e+e− annihilation events accumulated with the AMY detector at the TRISTAN collider, we have studied the Bose-Einstein correlations in the distributions of like-sign charged tracks. As reference samples we used the opposite-sign charged track pairs and mixed pairs, which are like-sign pairs synthesized from tracks belonging to different events. The results of the different reference samples give approximately 0.45 for the correlation strength and approximately 0.65 fm for the source size. Previous measurements of these parameters in e+e− annihilation at energies from CESR to LEP show remarkably flat dependence on s . Our results conform well with this picture.

Measurements of cross section and charge asymmetry for e+e− → μ+μ− and e+e− → τ+τ− at s = 57.8 GeV

Abstract With data corresponding to 142 pb−1 accumulated at s = 57.8 GeV by the AMY detector at TRISTAN we measure the cross section of the reactions e+e− → μ+μ− and e+e− → τ+τ− and the symmetry in the angular distributions. For the lowest order cross section we obtain σμμ = 27.54 ± 0.65 ± 0.95 pb and σττ = 28.27 ± 0.87 ± 0.69 pb, and for the forward-backward asymmetry, Aμμ = 0.303 ± 0.027 ± 0.008 and Aττ = −0.291 ± 0.040 ± 0.019. These measurements agree with the standard model. Assuming e−μ−τ univrsality we extract the vector and axial coupling constants | gν| = 0.00 ± 0.09 and |gA| = 0.476 ± 0.024. A fit of data to composite models places lower bounds (95% confidence level) on the compositeness scale of 2–4 TeV.

Search for anomalous γγ production at TRISTAN

We report on measurements of the total cross section for e+e- --> gammagamma for center-of-mass energies between 57.4 and 59.5 GeV, using the AMY detector at the TRISTAN collider. We set new limits on the production of a possible new s-channel resonance decaying into photon pairs.

A DETERMINATION OF ALPHA(S) IN E(+)E(-) ANNIHILATION AT ROOT-S=57.3 GEV

Abstract We present a study of differential two jet ratios in multi-hadronic final states produced by e + e − annihilation in the AMY detector at TRISTAN. The data are compared to the predictions of the next-to-leading logarithm parton-shower (NLL PS) Monte Carlo and the O ( α s 2 ) matrix element QCD models. We determine the strong coupling strength α s (57.3 GeV) = 0.130 ± 0.006.

A determination of αs in e+e− annihilation at GeV

Abstract We present a study of differential two jet ratios in multi-hadronic final states produced by e + e − annihilation in the AMY detector at TRISTAN. The data are compared to the predictions of the next-to-leading logarithm parton-shower (NLL PS) Monte Carlo and the O ( α s 2 ) matrix element QCD models. We determine the strong coupling strength α s (57.3 GeV) = 0.130 ± 0.006.

A determination of αs in e+e− annihilation at s=57.3 GeV

Abstract We present a study of differential two jet ratios in multi-hadronic final states produced by e + e − annihilation in the AMY detector at TRISTAN. The data are compared to the predictions of the next-to-leading logarithm parton-shower (NLL PS) Monte Carlo and the O ( α s 2 ) matrix element QCD models. We determine the strong coupling strength α s (57.3 GeV) = 0.130 ± 0.006.