Using data collected with the L3 detector near the Z resonance, corresponding to an integrated luminosity of 150pb-1, the branching fractions of the tau lepton into electron and muon are measured to be B(tau->e nu nu) = (17.806 +- 0.104 (stat.) +- 0.076 (syst.)) %, B(tau->mu nu nu) = (17.342 +- 0.110 (stat.) +- 0.067 (syst.)) %. From these results the ratio of the charged current coupling constants of the muon and the electron is determined to be g_mu/g_e = 1.0007 +- 0.0051. Assuming electron-muon universality, the Fermi constant is measured in tau lepton decays as G_F = (1.1616 +- 0.0058) 10^{-5} GeV^{-2}. Furthermore, the coupling constant of the strong interaction at the tau mass scale is obtained as alpha_s(m_tau^2) = 0.322 +- 0.009 (exp.) +- 0.015 (theory).
First DSYS error is experimental, the second is from theory.
An updated analysis using about 1.5 million events recorded at $\sqrt{s} = M_Z$ with the DELPHI detector in 1994 is presented. Eighteen infrared and collinear safe event shape observables are measured as a function of the polar angle of the thrust axis. The data are compared to theoretical calculations in ${\cal O} (\alpha_s^2)$ including the event orientation. A combined fit of $\alpha_s$ and of the renormalization scale $x_{\mu}$ in $\cal O(\alpha_s^2$) yields an excellent description of the high statistics data. The weighted average from 18 observables including quark mass effects and correlations is $\alpha_s(M_Z^2) = 0.1174 \pm 0.0026$. The final result, derived from the jet cone energy fraction, the observable with the smallest theoretical and experimental uncertainty, is $\alpha_s(M_Z^2) = 0.1180 \pm 0.0006 (exp.) \pm 0.0013 (hadr.) \pm 0.0008 (scale) \pm 0.0007 (mass)$. Further studies include an $\alpha_s$ determination using theoretical predictions in the next-to-leading log approximation (NLLA), matched NLLA and $\cal O(\alpha_s^2$) predictions as well as theoretically motivated optimized scale setting methods. The influence of higher order contributions was also investigated by using the method of Pad\'{e} approximants. Average $\alpha_s$ values derived from the different approaches are in good agreement.
The weighted value of ALPHA-S from all the measured observables using experimentally optimized renormalization scale values and corrected for the b-mass toleading order.
The value of ALPHA-S derived from the JCEF and corrected for heavy quark mass effects. The quoted errors are respectively due to experimental error, hadronization, renormalization scale and heavy quark mass correction uncertainties.
Energy Energy Correlation EEC.
Infrared and collinear safe event shape distributions and their mean values are determined using the data taken at five different centre of mass energies above M Z with the DELPHI detector at LEP. From the event shapes, the strong coupling α s is extracted in O ( α s 2 ), NLLA and a combined scheme using hadronisation corrections evaluated with fragmentation model generators as well as using an analytical power ansatz. Comparing these measurements to those obtained at M Z , the energy dependence (running) of α s is accessible. The logarithmic energy slope of the inverse strong coupling is measured to be d α −1 s d log (E cm ) =1.39±0.34( stat )±0.17( syst ) , in good agreement with the QCD expectation of 1.27.
Moments of the (1-THRUST) distributions at cm energies 133, 161, 172 and 183 GeV.
Moments of the Thrust Major distributions at cm energies 133, 161, 172 and 183 GeV.
Moments of the Thrust Minor distributions at cm energies 133, 161, 172 and 183 GeV.
We extract a set of values for the Gross-Llewellyn Smith sum rule at different values of 4-momentum transfer squared ($Q^{2}$), by combining revised CCFR neutrino data with data from other neutrino deep-inelastic scattering experiments for $1 < Q^2 < 15 GeV^2/c^2$. A comparison with the order $\alpha^{3}_{s}$ theoretical predictions yields a determination of $\alpha_{s}$ at the scale of the Z-boson mass of $0.114 \pm^{.009}_{.012}$. This measurement provides a new and useful test of perturbative QCD at low $Q^2$, because of the low uncertainties in the higher order calculations.
No description provided.
Total GLS integral and ALPHAS for each bin in Q2. Systematic errors are correlated in different Q2 bins. The second DSYS error in ALPHAS is due to the uncertainty in the theory.
ALPHAS extrapolated to the Z0 mass. The second DSYS error is due to the uncertainty in the theory.
We have studied the structure of hadronic events with a hard, isolated photon in the final state (e + e − → Z → hadrons + γ) in the 3.6 million hadronic events collected with the L3 detector at centre-of-mass energies around 91 GeV. The centre-of-mass energy of the hadronic system is in the range 30 GeV to 86 GeV. Event shape variables have been measured at these reduced centre-of-mass energies and have been compared with the predictions of different QCD Monte Carlo programs. The event shape variables and the energy dependence of their mean values are well reproduced by QCD models. We fit distributions of several global event shape variables to resummed O (α s 2 ) calculations to determine the strong coupling constant α s over a wide range of energies. We find that the strong coupling constant α s decreases with increasing energy, as expected from QCD.
No description provided.
No description provided.
No description provided.
We present a study of the structure of hadronic events recorded by the L3 detector at LEP at the center of mass energies of 161 and 172 GeV. The data sample corresponds to an integrated luminosity of 21.25 pb −1 collected during the high energy runs of 1996. The distributions of event shape variables and the energy dependence of their mean values are well reproduced by QCD models. From a comparison of the data with resummed O ( α s 2 ) QCD calculations, we determine the strong coupling constant at the two energies. Combining this with our earlier measurements we find that the strong coupling constant decreases with increasing energy as expected in QCD.
No description provided.
Average jet multiplicity using JADE algorithm.
Average jet multiplicity using Durham algorithm.
The hadronic fragmentation functions of the various quark flavours and of gluons are measured in a study of the inclusive hadron production from Z 0 decays with the DELPHI detector and are compared with the fragmentation functions measured elsewhere at energies between 14 GeV and 91 GeV. A large scaling violation is observed, which is used to extract the strong coupling constant from a fit using a numerical integration of the second order DGLAP evolution equations. The result is α s ( M Z ) = 0.124 −0.007 +0.006 (exp) ± 0.009(theory) where the first error represents the experimental uncertainty and the second error is due to the factorization and renormalization scale dependence.
SIG(Q=BQ, Q=CQ, Q=UDS) corresponds to BQ, CQ, and U,D,S quarks fragmentation into charged hadron.
alpha_s was evaluated from the scaling violation of the fragmentation func tions. The data from other experiments are used for the fitting procedure.
We present a study of the structure of hadronic events recorded by the L3 detector at center-of-mass energies of 130 and 136 GeV. The data sample corresponds to an integrated luminosity of 5 pb −1 collected during the high energy run of 1995. The shapes of the event shape distributions and the energy dependence of their mean values are well reproduced by QCD models. From a comparison of the data with resummed O (α s 2 ) QCD calculations, we determine the strong coupling constant to be α s (133 GeV) = 0.107 ± 0.005(exp) ± 0.006(theor).
Mean values of the event shape variables.
Mean charged particle multiplicity.
The value of alpha_s from the fits to the event shape variables : thrust (THRUST), scale heavy jet mass (MH**2/S), total jet broadening (BT)and wide jet broadening (BW). The last value is combined result (COMBINED). The second systematic error is due to uncertainties in the theory.
Three jet events arising from decays of the Z boson, collected by the DELPHI detector, were used to measure differences in quark and gluon fragmentation. Gluon jets were anti-tagged by identifying b quark jets. Unbiased quark jets came from events with two jets plus one photon. Quark and gluon jet properties in different energy ranges were compared for the first time within the same detector. Quark and gluon jets of nearly the same energy in symmetric three jet event topologies were also compared. Using three independent methods, the average value of the ratio of the mean charged multiplicities of gluon and quark jets is $$< r >=1.241 pm 0.015 (stat.)pm 0.025 (syst.).$$ Gluon jets are broader and produce fragments with a softer energy spectrum than quark jets of equivalent energy. The string effect has been observed in fully symmetric three jet events. The measured ratio Rγ of the charged particle flow in the qq̅ inter-jet region of the qq̅g and qq̅γ samples agrees with the perturbative QCD expectation. The dependence of the mean charged multiplicity on the hadronic center-of-mass energy was analysed in photon plus n-jet events. The value for αs(MZ) determined from these data using a QCD prediction with corrections at leading and next-to-leading order is $$←pha_s(M_Z)=0.116pm 0.003 (stat.)pm 03009 (syst.).$$
No description provided.
Durham and JADE algoritms were used.
We have compared a new QCD calculation by Clay and Ellis of energy-energy correlations (EEC’s) and their asymmetry (AEEC’s) in e+e− annihilation into hadrons with data collected by the SLD experiment at SLAC. From fits of the new calculation, complete at O(αs2), we obtained αs(MZ2)=0.1184±0.0031(expt)±0.0129(theory) (EEC) and αs(MZ2)=0.1120±0.0034(expt)±0.0036(theory) (AEEC). The EEC result is significantly lower than that obtained from comparable fits using the O(αs2) calculation of Kunszt and Nason.
The data are compared to the predictions of Monte-Carlo. Two values of ALPHA_S are corresponded the two theoretical models used in the comparison.
We present a comparison of the strong couplings of light ($u$, $d$, and $s$), $c$, and $b$ quarks determined from multijet rates in flavor-tagged samples of hadronic $Z~0$ decays recorded with the SLC Large Detector at the SLAC Linear Collider. Flavor separation on the basis of lifetime and decay multiplicity differences among hadrons containing light, $c$, and $b$ quarks was made using the SLD precision tracking system. We find: $\alpha_s{_{\vphantom{y}}}~{uds}/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 0.987 \pm 0.027({\rm stat}) \pm 0.022({\rm syst}) \pm 0.022({\rm theory})$, $\alpha_s{_{\vphantom{y}}}~c/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 1.012 \pm 0.104 \pm 0.102 \pm 0.096$, and $\alpha_s{_{\vphantom{y}}}~b/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 1.026 \pm 0.041 \pm 0.041\pm 0.030.$
No description provided.
The strong coupling alpha_s(M_Z^2) has been measured using hadronic decays of Z^0 bosons collected by the SLD experiment at SLAC. The data were compared with QCD predictions both at fixed order, O(alpha_s^2), and including resummed analytic formulae based on the next-to-leading logarithm approximation. In this comprehensive analysis we studied event shapes, jet rates, particle correlations, and angular energy flow, and checked the consistency between alpha_s(M_Z^2) values extracted from these different measures. Combining all results we obtain alpha_s(M_Z^2) = 0.1200 \pm 0.0025(exp.) \pm 0.0078(theor.), where the dominant uncertainty is from uncalculated higher order contributions.
Final average value of alpha_s. The second (DSYS) error is from the uncertainty on the theoretical part of the calculation.
TAU is 1-THRUST.
RHO is the normalized heavy jet mass MH**2/EVIS**2.
We have determined the strong coupling $\as$ from a comprehensive study of energy-energy correlations ($EEC$) and their asymmetry ($AEEC$) in hadronic decays of $Z~0$ bosons collected by the SLD experiment at SLAC. The data were compared with all four available predictions of QCD calculated up to $\Oa2$ in perturbation theory, and also with a resummed calculation matched to all four of these calculations. We find large discrepancies between $\as$ values extracted from the different $\Oa2$ calculations. We also find a large renormalization scale ambiguity in $\as$ determined from the $EEC$ using the $\Oa2$ calculations; this ambiguity is reduced in the case of the $AEEC$, and is very small when the matched calculations are used. Averaging over all calculations, and over the $EEC$ and $AEEC$ results, we obtain $\asz=0.124~{+0.003}_{-0.004} (exp.) \pm 0.009 (theory).$
Statistical errors only.
Statistical errors only.
ALPHAS from the EEC O(ALPHAS**2) measurement.
We report on the measurement of the leptonic and hadronic cross sections and leptonic forward-backward asymmetries at theZ peak with the L3 detector at LEP. The total luminosity of 40.8 pb−1 collected
Results from 1990 data. Additional systematic uncertainty of 0.3 pct.
Results from 1991 data. Additional systematic uncertainty of 0.15 pct.
Results from 1992 data. Additional systematic uncertainty of 0.15 pct.
We have determined the strong coupling αs from measurements of jet rates in hadronic decays of Z0 bosons collected by the SLD experiment at SLAC. Using six collinear and infrared safe jet algorithms we compared our data with the predictions of QCD calculated up to second order in perturbation theory, and also with resummed calculations. We find αs(MZ2)=0.118±0.002(stat)±0.003(syst)±0.010(theory), where the dominant uncertainty is from uncalculated higher order contributions.
The second systematic error comes from the theoretical uncertainties.
A determination of the hadronic fragmentation functions of the Z 0 boson is presented from a study of the inclusive hadron production with the DELPHI detector at LEP. These fragmentation functions were compared with the ones at lower energies, thus covering data in a large kinematic range: 196 ⩽ Q 2 ⩽ 8312 GeV 2 and x (= P h E beam ) > 0.08 . A large scaling violation was observed, which was used to extract the strong coupling constant in second order QCD: α s ( M Z ) = 0.118 ± 0.005. The corresponding QCD scale for five quark flavours is: Λ (5) MS = 230 ± 60 MeV .
No description provided.
Extraction of strong coupling constant ALP_S and the LAMQCD)MSBAR values.
A new measurement of αs is obtained from the distributions in thrust, heavy jet mass, energy-energy correlation and two recently introduced jet broadening variables following a method proposed by Cata
Thrust distribution corrected for detector acceptance and initial state photon radiation.
Heavy jet mass (RHO) distribution (THRUST definition) corrected for detect or acceptance and initial state photon radiation.
Heavy jet mass (RHOM) distribution (MASS definition) corrected for detectoracceptance and initial state photon radiation.
We present a study of the global event shape variables thrust and heavy jet mass, of energy-energy correlations and of jet multiplicities based on 250 000 hadronic Z 0 decays. The data are compared to new QCD calculations including resummation of leading and next-to-leading logarithms to all orders. We determine the strong coupling constant α s (91.2 GeV) = 0.125±0.003 (exp) ± 0.008 (theor). The first error is the experimental uncertainty. The second error is due to hadronization uncertainties and approximations in the calculations of the higher order corrections.
Measured EEC distribution corrected for detector effects and photon radiation. Errors are combined statistical and systematic uncertainties.
Measured average jet multiplicities for the K_PT algorithm. All numbers are corrected for detector effects and photon radiation. Errors are combined statistical and systematic uncertainties.
Value of strong coupling constant, alpha_s, determined from the data. First error is experimental, the second is theoretical.
Distributions of event shape variables obtained from 120600 hadronicZ decays measured with the DELPHI detector are compared to the predictions of QCD based event generators. Values of the strong coupling constant αs are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions. The final result, αs(MZ), is based on second order perturbation theory and uses two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model.
Experimental differential Thrust distributions.
Experimental differential Oblateness distributions.
Experimental differential C-parameter distributions.
We present a study of energy-energy correlations based on 83 000 hadronic Z 0 decays. From this data we determine the strong coupling constant α s to second order QCD: α s (91.2 GeV)=0.121±0.004(exp.)±0.002(hadr.) −0.006 +0.009 (scale)±0.006(theor.) from the energy-energy correlation and α s (91.2 GeV)=0.115±0.004(exp.) −0.004 +0.007 (hadr.) −0.000 +0.002 (scale) −0.005 +0.003 (theor.) from its asymmetry using a renormalization scale μ 1 =0.1 s . The first error (exp.) is the systematic experimental uncertainly, the statistical error is negligible. The other errors are due to hadronization (hadr.), renormalization scale (scale) uncertainties, and differences between the calculated second order corrections (theor.).
Statistical errors are equal to or less than 0.6 pct in each bin. There is also a 4 pct systematic uncertainty.
ALPHA_S from the EEC measurement.. The first error given is the experimental error which is mainly the overall systematic uncertainty: the first (DSYS) error is due to hadronization, the second to the renormalization scale, and the third differences between the calculated and second order corrections.
ALPHA_S from the AEEC measurement.. The first error given is the experimental error which is mainly the overall systematic uncertainty: the first (DSYS) error is due to hadronization, the second to the renormalization scale, and the third differences between the calculated and second order corrections.
We have studied the energy-energy angular correlations in hadronic final states from Z 0 decay using the DELPHI detector at LEP. From a comparison with Monte Carlo calculations based on the exact second order QCD matrix element and string fragmentation we find that Λ (5) MS =104 +25 -20 ( stat. ) +25 -20( syst. ) +30 00 ) theor. ) . MeV, which corresponds to α s (91 GeV)=0.106±0.003(stat.)±0.003(syst.) +0.003 -0.000 (theor). The theoretical error stems from different choices for the renormalization scale of α s . In the Monte Carlo simulation the scale of α s as well as the fragmentation parameters have been optimized to described reasonably well all aspects of multihadron production.
Data requested from the authors.
Values of LAMBDA-MSBAR(5) and ALPHA-S(91 GeV) deduced from the EEC measurements. The second systematic error is from the theory.
We present a study of jet multiplicities based on 37 000 hadronic Z 0 boson decays. From this data we determine the strong coupling constant α s =0.115±0.005 ( exp .) −0.010 +0.012 (theor.) to second order QCD at √ s =91.22GeV.
Errors are combined statistical and systematic uncertainties.
No description provided.
The production rates for 2-, 3-, 4- and 5-jet hadronic final states have been measured with the DELPHI detector at the e + e − storage ring LEP at centre of mass energies around 91.5 GeV. Fully corrected data are compared to O(α 2 s ) QCD matrix element calculations and the QCD scale parameter Λ MS is determined for different parametrizations of the renormalization scale ω 2 . Including all uncertainties our result is α s ( M 2 Z )=0.114±0.003[stat.]±0.004[syst.]±0.012[theor.].
Corrected jet rates.
Second systematic error is theoretical.
We present data on energy-energy correlations (EEC) and their related asymmetry (AEEC) ine+e− annihilation in the centre of mass energy range 12<W≦46.8 GeV. The energy and angular dependence of the EEC in the central region is well described byOαs2 QCD plus a fragmentation term proportional to\({1 \mathord{\left/ {\vphantom {1 {\sqrt s }}} \right. \kern-\nulldelimiterspace} {\sqrt s }}\). BareO(α)s2 QCD reproduces our data for the large angle region of the AEEC. Nonperturbative effects for the latter are estimated with the help of fragmentation models. From various analyses using different approximations, we find that values for\(\Lambda _{\overline {MS} } \) in the range 0.1–0.3 GeV give a good description of the data. We also compare analytical calculations in QCD for the EEC in the back-to-back region to our data. The theoretical predictions describe well both the angular and energy dependence of the data in the back-to-back region.
Correlation function binned in cos(chi).
Correlation function binned in cos(chi).
Correlation function binned in cos(chi).
None
No description provided.
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