Precision Determination of the Top Quark Mass

The CDF and D0 collaborations have updated their measurements of the mass of the top quark using proton-antiproton collisions at sqrt{s}=1.96TeV produced at the Tevatron. The uncertainties in each of the of top-antitop decay channels have been reduced. The new Tevatron average for the mass of the top quark based on about 1/fb of data per experiment is 170.9+-1.8GeV/c^2.Comment: 14 pages, 4 figures; LaTeX2e, 8 .eps files, uses LaThuileFPSpro.sty (included). To appear in the proceedings of the 21st Rencontres des Physique de la Vallee d'Aoste, La Thuile, March 4-10, 200

Performance of the CDF Calorimeter Simulation in Tevatron Run II

The CDF experiment is successfully collecting data from ppbar collisions at the Tevatron in Run II. As the data samples are getting larger, systematic uncertainties due to the measurement of the jet energy scale assessed using the calorimeter simulation have become increasingly important. In many years of operation, the collaboration has gained experience with GFLASH, a fast parametrization of electromagnetic and hadronic showers used for the calorimeter simulation. We present the performance of the calorimeter simulation and report on recent improvements based on a refined in situ tuning technique. The central calorimeter response is reproduced with a precision of 1-2%.Comment: 8 pages, 4 figures; LaTeX2e, 10 .eps files, uses aipproc.cls, aipxfm.sty and aip-6s.clo (included). Contribution to the Proceedings of the 12th International Conference on Calorimetry in High Energy Physics (CALOR06), June 5-9, 2006, Chicago (IL), USA. To be published by American Institute of Physics (AIP

Tests of Power Corrections for Event Shapes in e+e- Annihilation

A study of perturbative QCD calculations combined with power corrections to model hadronisation effects is presented. The QCD predictions are fitted to differential distributions and mean values of event shape observables measured in e+e- annihilation at centre-of-mass energies from 14 to 189 GeV. We investigate the event shape observables thrust, heavy jet mass, C-parameter, total and wide jet broadening and differential 2-jet rate and observe a good description of the data by the QCD predictions. The strong coupling constant alpha_S(M_Z) and the free parameter of the power correction calculations alpha_0(2 GeV) are measured to be alpha_S(M_Z) = 0.1171 +/- 0.0032/0.0020 and alpha_0(2 GeV) = 0.513 +/- 0.066/0.045. The predicted universality of alpha_0 is confirmed within the uncertainties of the measurements.Comment: 28 pages, LaTeX2e, 21 .eps-files included, accepted by Eur. Phys. J.

Study of moments of event shapes in e+e- annihilation using JADE data

Data from e+e- annihilation into hadrons collected by the JADE experiment at centre-of-mass energies between 14 GeV and 44 GeV were used to study moments of event shape distributions. The data were compared with Monte Carlo models and with predictions from QCD NLO order calculations. The strong coupling constant measured from the moments is alpha_S(M_Z) = 0.1286 +/- 0.0007 (stat) +/- 0.0011 (expt) +/- 0.0022 (had) +/- 0.0068 (theo), alpha_S(M_Z) = 0.1286 +/- 0.0072 (total error), consistent with the world average. However, systematic deficiencies in the QCD NLO order predictions are visible for some of the higher moments.Comment: JADE note 147 submitted as contributed paper to ICHEP 2004, corrected statistical error of 6 observable average and several typo

Measurement of the Strong Coupling Constant alpha_S from the Four-Jet Rate in e+e- Annihilation using JADE data

Data from e+e- annihilation into hadrons collected by the JADE experiment at centre-of-mass energies between 14 GeV and 44 GeV were used to study the four-jet rate as a function of the Durham algorithm's resolution parameter y_cut. The four-jet rate was compared to a QCD NLO order calculations including NLLA resummation of large logarithms. The strong coupling constant measured from the four-jet rate is alpha_S(M_Z) = 0.1169 +/- 0.0004 (stat) +/- 0.0012 (expt) +/- 0.0021 (had) +/- 0.0007 (theo), alpha_S(M_Z) = 0.1169 +/- 0.0026 (total error) in agreement with the world average.Comment: JADE note 146 submitted as contributed paper to ICHEP 200

A Measurement of the QCD Colour Factors using Event Shape Distributions at sqrt(s)=14 GeV to 189 GeV

Measurements of the QCD colour factors C_A and C_F and of the number of active quark flavours n_f in the process e+e- -> hadrons at high energy are presented. They are based on fits of O(alpha_S**2)+NLLA QCD calculations to distributions of the event shape observables 1-T, C, B_T and B_W measured at centre-of-mass energies from 14 GeV to 189 GeV. Hadronisation effects are approximated with power correction calculations which also depend on the QCD gauge structure. In this approach potential biases from hadronisation models are reduced. Our results for individually measured quantities are n_f = 5.64 +- 1.35, C_A = 2.88 +- 0.27 and C_F = 1.45 +- 0.27 in good agreement with QCD based on the SU(3) symmetry group where n_f=5 for the energies considered here, C_A=3 and C_F=4/3. From simultaneous fits of C_A and C_F we find C_A = 2.84 +- 0.24 and C_F = 1.29 +- 0.18, which is also in good agreement with the QCD expectation.Comment: accepted by European Journal of Physics

The resummed thrust distribution in DIS

We present preliminary results on the resummation of leading and next-to-leading logarithms for the thrust distribution in deep inelastic scattering. Our predictions, expanded to O(alpha_s^2), are compared to corresponding results from the Monte Carlo programs DISASTER++ and DISENT.Comment: 5 pages; talk presented by V. Antonelli at the UK Phenomenology Workshop on Collider Physics, September 1999, St. John's College, Durha