arXiv subjects

S. Kluth

Publications and source records attributed to S. Kluth.

29 records · Page 2Linked to original sources

arXiv2004

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.

hep-ex↗

arXiv2003

Jet physics in e+e- annihilation from 14 to 209 GeV

Results from the study of jets in hadronic final states produced in e+e- annihilation at sqrt(s)=14 to 209 GeV are discussed. Precise measurements of the strong coupling alpha_S at many points of sqrt(s) provide convincing evidence for the running of alpha_S as expected by QCD. Several measurements of the running b-quark mass m_b(M_Z) are combined yielding m_b(M_Z)=(2.92+-0.03(stat.)+-0.31(syst.)) GeV and compared with low energy results. Strong evidence for the running of the b-quark mass is found. Experimental investigations of the gauge structure of QCD are reviewed and then combined with the results for the colour factors C_A=2.89+-0.01(stat.)+- 0.21(syst.) and C_F=1.30+-0.01(stat.)+-0.09(syst.) and correlation coefficient rho=0.82. The uncertainties on the colour factors are below 10% and the agreement with the QCD expectation C_A=3 and C_F=4/3 is excellent.

hep-ex↗

arXiv2003

QCD Studies with Resurrected Jade Data

We report on recent studies of QCD performed using reanalysed e+e- annihilation data recorded at centre of mass energies 14<sqrt(s)<44 GeV by the JADE experiment operated 1979 to 1986 at the PETRA e+e- collider at DESY, Hamburg, Germany. The data for some event shape observables are compared to modern Monte Carlo event generators using parameter values obtained from LEP 1 data. The distribution of ln(1/x) with x=2p/sqrt(s) and p the momentum of a charged hadron is measured and compared to QCD predictions. Fits of O(alpha_S^2)+NLLA (resummed) QCD predictions combined with power corrections to event shape data including for the first time the sqrt(s)=14 and 22 GeV data samples are discussed.

hep-ex↗

arXiv2002

KANGA(ROO): Handling the micro-DST of the BaBar Experiment with ROOT

A system based on ROOT for handling the micro-DST of the BaBar experiment is described. The purpose of the Kanga system is to have micro-DST data available in a format well suited for data distribution within a world-wide collaboration with many small sites. The design requirements, implementation and experience in practice after three years of data taking by the BaBar experiment are presented.

physics.comp-ph↗

arXiv2001

Tests of hard and soft QCD with e+e- Annihilation Data

Experimental tests of QCD predictions for event shape distributions combining contributions from hard and soft processes are discussed. The hard processes are predicted by perturbative QCD calculations. The soft processes cannot be calculated directly using perturbative QCD, they are treated by a power correction model based on the analysis of infrared renormalons. Furthermore, an analysis of the gauge structure of QCD is presented using fits of the colour factors within the same combined QCD predictions.

hep-ex↗

arXiv2001

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.

hep-ex↗

arXiv2001

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.

hep-ex↗

arXiv2001

Measurement of the longitudinal and transverse cross-section in e^+e^- annihilation at sqrt(s)=35-44 GeV

An investigation of the polar angle distribution of charged hadrons is presented using data taken by the JADE experiment at the PETRA e^+e^- collider at centre-of-mass energies of 35 and 44 GeV. From fits to the polar angle distribution the longitudinal, sigma_L, and transverse, sigma_T, cross-section relative to the total hadronic are determined at an average energy scale of 36.6 GeV. The results are sigma_L/sigma_tot = 0.067 +/- 0.013, sigma_T/sigma_tot = 0.933 -/+ 0.013 where total errors are given and the results are exactly anti-correlated. Using the next-to-leading order QCD prediction for the longitudinal cross-section, the value alpha_S(36.6 GeV) = 0.150 +/- 0.025 of the strong coupling constant is obtained in agreement with the world average value of alpha_S evolved to an energy scale of 36.6 GeV.

hep-ex↗

arXiv2001

Experimental Studies of Power Corrections

We present recent results from experimental studies of power corrections in the model of Dokshitzer, Marchesini and Webber using data from the process e+e- -> hadrons at several centre-of-mass energies. Fitted O(alpha_S^2)+NLLA QCD predictions combined with power corrections to model hadronisation effects successfully describe differential distributions and mean values of event shape observables. The fit results for the strong coupling constant and the free parameter of the power correction calculations from the various observables are consistent with each other within the uncertainties. The same fits are further employed to study the gauge structure of QCD by additionally varying the QCD colour factors in the fits. The results are consistent with QCD based on the SU(3) symmetry group. A new measurement of the transverse cross section is shown using reanalysed data of the former JADE experiment at DESY and its implications for power correction are discussed.

hep-ex↗

arXiv2001

Multijet Final States in e+e- Annihilation

We review the current status of analyses of multijet final states in e+e- annihilation. Results for jet observables from LEP 1, LEP 2 and from the reanalysis of the PETRA experiment JADE will be presented. A determination of the b-quark mass using jet observables will be discussed and tests of power correction models will be shown. Finally determinations of the QCD colour factors from an analysis of event shape distributions at several energy points using power corrections will be discussed.

hep-ex↗

arXiv1997

A Study of Event Shapes and Determinations of alpha_s using data of e^+e^- Annihilations at sqrt{s} = 22 to 44 GeV

Data recorded by the JADE experiment at the PETRA e^+e^- collider were used to measure the event shape observables thrust, heavy jet mass, wide and total jet broadening and the differential 2-jet rate in the Durham scheme. For the latter three observables, no experimental results have previously been presented at these energies. The distributions were compared with resummed QCD calulations (O(alpha_s^2)+NLLA), and the strong coupling constant alpha_s(Q) was determined at different energy scales Q=sqrt{s}. The results, α_s(22 GeV) = 0.161 ^{+0.016}_{-0.011}, α_s(35 GeV) = 0.143 ^{+0.011}_{-0.007}, α_s(44 GeV) = 0.137 ^{+0.010}_{-0.007}, are in agreement with previous combined results of PETRA albeit with smaller uncertainties. Together with corresponding data from LEP, the energy dependence of alpha_s is significantly tested and is found to be in good agreement with the QCD expectation. Similarly, mean values of the observables were compared to analytic QCD predictions where hadronisation effects are absorbed in calculable power corrections.

hep-ex↗