Measurement of the forward - backward asymmetry in e+ e- ---> b anti-b and the b quark branching ratio to muons at TRISTAN using neural networks

The AMY collaboration Ueno, K. ; Kanda, S. ; Olsen, S.L. ; et al.
Phys.Lett.B 381 (1996) 365-371, 1996.
Inspire Record 418709 DOI 10.17182/hepdata.38513

The forward-backward asymmetry in e + e − → b b at s = 57.9 GeV and the b-quark branching ratio to muons have been measured using neural networks. Unlike previous methods for measuring the b b forward-backward asymmetry where the estimated background from c -quark decays and other sources are subtracted, here events are categorized as either b b or non- b b events by neural networks based on event-by-event characteristics. The determined asymmetry is −0.429 ± 0.044 (stat) ± 0.047 (sys) and is consistent with the prediction of the standard model. The measured B B mixing parameter is 0.136 ± 0.037 (stat) ± 0.040 (sys) ± 0.002 (model) and the measured b-quark branching ratio to muons is 0.122 ± 0.006 (stat) ± 0.007 (sys).

1 data table

Measurement of charm production in two photon processes using inclusive lepton events at TRISTAN

The AMY collaboration Aso, T. ; Miyata, H. ; Sasaki, T. ; et al.
Phys.Lett.B 363 (1995) 249-258, 1995.
Inspire Record 401053 DOI 10.17182/hepdata.38520

Measurements of open charm production in photon-photon collisions made with the AMY detector at TRISTAN are reported. Charmed hadrons were identified by detecting the high momentum muons or electrons from their semileptonic decays. The data sample corresponds to an integrated luminosity of 275 pb −1 at an average center of mass energy of 58 GeV. Results are presented in the form of cross sections of inclusive leptons from charm for both muons and electrons. The measured cross section is 1.8 standard deviations higher than theoretical predictions based on the direct and photon-gluon fusion process, where the mass of charm quark is assumed to be 1.6 GeV.

3 data tables

Measurement of alpha(s) using NLLA + O (alpha-s**2) in e+ e- annihilation at s**(1/2) = 58-GeV

The AMY collaboration Kim, D.Y. ; Kang, J.S. ; Myung, S.S. ; et al.
Phys.Lett.B 420 (1998) 233-240, 1998.
Inspire Record 455114 DOI 10.17182/hepdata.28221

A measurement of the strong coupling constant α S is presented using hadronic events produced in e + e − annihilations at s =58.0 GeV from the AMY detector at TRISTAN. The measurement is based on comparisons of the distributions of thrust, heavy jet mass, total jet broadening, wide jet broadening, and energy-energy correlations with QCD calculations resummed up to next-to-leading-logarithms matched with the O ( α S 2 ) perturbative calculation. Combining the results of the individual evaluations, we find α S (58 GeV )=0.132±0.006 .

1 data table

No description provided.


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

The AMY collaboration Lee, K.B. ; Sagawa, H. ; Chung, Y.S. ; et al.
Phys.Lett.B 313 (1993) 469-474, 1993.
Inspire Record 356468 DOI 10.17182/hepdata.51361

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 α s is determined by fits to the prediction of the Next-to-Leading Logarithm Parton-Shower model. The measured value of α s (57.9 GeV ) = 0.134 -0.005 +0.006 .

1 data table

No description provided.


A measurement of the photon structure function F2(gamma) at Q**2 = 6.8-GeV**2.

The AMY collaboration Kojima, T. ; Nozaki, T. ; Abe, K. ; et al.
Phys.Lett.B 400 (1997) 395-400, 1997.
Inspire Record 441558 DOI 10.17182/hepdata.28320

The photon structure function F 2 γ has been measured at an average Q 2 value of 6.8 GeV 2 using data collected by the AMY detector at the TRISTAN e + e − collider. The measured F 2 γ is compared with several QCD-based parton density models.

1 data table

No description provided.


OBSERVATION OF ANOMALOUS PRODUCTION OF MUON PAIRS IN e+ e- ANNIHILATION INTO FOUR LEPTON FINAL STATES

The AMY collaboration Ho, Y.H. ; Kurihara, Y. ; Omori, T. ; et al.
Phys.Lett.B 244 (1990) 573-579, 1990.
Inspire Record 294829 DOI 10.17182/hepdata.51362

We report results of a study of four-lepton final states produced in e + e − collisions at center-of-mass energies from 50 to 61.4 GeV using the AMY detector at the TRISTAN collider. For the cases where two or three charged tracks are produced at large angles relative to the beam direction, the cross sections agree with QED. However, we observe an excess of e + e − → e + e − μ + μ − events with four tracks at wide angles and with dimuon mass less than 1.0 GeV / c 2 .

1 data table

No description provided.


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

The AMY collaboration Takashimizu, N. ; Sasaki, T. ; Miyata, H. ; et al.
Phys.Lett.B 384 (1996) 96009331 481-486, 1996.
Inspire Record 419685 DOI 10.17182/hepdata.38328

The inclusive cross section for the production of charmed D<sup loc="post">∗±</sup> mesons in two-photon processes is measured with the AMY detector at the TRISTAN e<sup loc="post">+</sup>e<sup loc="post">−</sup> collider. D<sup loc="post">∗±</sup> mesons are 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<sup loc="post">−1</sup> at a center-of-mass energy of 58 GeV is used to determine a cross section σ(e<sup loc="post">+</sup>e<sup loc="post">−</sup> → e<sup loc="post">+</sup>e<sup loc="post">−</sup>D<sup loc="post">∗±</sup>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.

2 data tables

No description provided.

Reduced acceptance region to compare with the TOPAZ results.


New limits on the masses of the selectron and photino

The AMY collaboration Sugimoto, Y. ; Abe, K. ; Fujii, Y. ; et al.
Phys.Lett.B 369 (1996) 86-92, 1996.
Inspire Record 403978 DOI 10.17182/hepdata.38437

A study of e + e − annihilations into final states containing a single energetic photon with no accompanying particles is made at a center of mass energy of 57.8 GeV. The measured cross section is consistent with expectations from standard model processes and is used to set limits on the masses of the scalar electron and photino particles predicted by supersymmetry theories. If the photino is assumed to be massless, the 90% confidence level lower limit on the mass of the degenerate scalar electron is 65.5 GeV. If the results of all the single photon experiments are combined, this lower limit increases to 79.3 GeV.

1 data table

No description provided.


A Determination of alpha-s in e+ e- annihilation at s**(1/2) = 57.3-GeV

The AMY collaboration Li, Y.K. ; Sagawa, H. ; Bodek, A. ; et al.
Phys.Lett.B 355 (1995) 394-400, 1995.
Inspire Record 406129 DOI 10.17182/hepdata.6546

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.

6 data tables

The data are compared to the predictions of Monte-Carlo.

Using the p-scheme for jet clustering.

Using the E-scheme for jet clustering.

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A High Q**2 measurement of the photon structure function F2(gamma)

The AMY collaboration Sahu, S.K. ; Ebara, S. ; Nozaki, T. ; et al.
Phys.Lett.B 346 (1995) 208-216, 1995.
Inspire Record 392701 DOI 10.17182/hepdata.38361

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.

3 data tables

No description provided.

No description provided.

Errors contain both statistics and systematics.