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A New determination of alpha(s) using direct photon production cross-sections in p p and anti-p p collisions at S**(1/2) = 24.3-GeV

The UA6 collaboration Werlen, M. ; Ballocchi, G. ; Breedon, R.E. ; et al.
Phys.Lett.B 452 (1999) 201-206, 1999.
Inspire Record 496157 DOI 10.17182/hepdata.34551

Direct photon production cross sections obtained in high statistics p ̄ p and pp collisions at s =24.3 GeV at the CERN SPS are used in a next-to-leading order QCD analysis. From the cross section difference σ( p ̄ p → γX)−σ(pp → γX) and quark distributions measured in deep inelastic scattering, a determination of the strong coupling constant, α s , is performed via a measurement of Λ (4) MS . This measurement yields a value Λ (4) MS = 210±22 ( stat. )±44 ( syst. ) +105 −36 ( theo. ) MeV. The corresponding value of α s expressed at M 2 Z is α s (M 2 Z )=0.1112 ±0.0016 ( stat. ) ±0.0033 ( syst. ) +0.0077 −0.0034 ( theo. ) .

1 data table

Value of LAMBDA(MSBAR) and ALPHAS at MZ**2 deduced from the difference in the pbar and p direct photon cross sections. The second systematic error is due to the uncertainties in the theory.


Measurement of the total cross section for e+ e- --> hadrons at s**(1/2) = 10.52-GeV.

The CLEO collaboration Ammar, R. ; Baringer, Philip S. ; Bean, A. ; et al.
Phys.Rev.D 57 (1998) 1350-1358, 1998.
Inspire Record 445351 DOI 10.17182/hepdata.47132

Using the CLEO detector at the Cornell Electron Storage Ring, we have made a measurement of R=sigma(e+e- ->hadrons)/sigma(e+e- ->mu+mu-) =3.56+/-0.01+/-0.07 at ECM=10.52 GeV. This implies a value for the strong coupling constant of alpha_s(10.52 GeV)=0.20+/-0.01+/-0.06, or alpha_s(M_Z)=0.13+/-0.005+/-0.03.

2 data tables

Corrected for background and radiactive effects.

Value of ALPHAS, the strong coupling constant, from the measurement of R. CT,= ALPHAS also given evolved to the Z0 mass.


Measurement of the direct photon spectrum in Upsilon(1S) decays.

The CLEO collaboration Nemati, B. ; Richichi, S.J. ; Ross, W.R. ; et al.
Phys.Rev.D 55 (1997) 5273-5281, 1997.
Inspire Record 425927 DOI 10.17182/hepdata.52340

Using data taken with the CLEO II detector at the Cornell Electron Storage Ring, we have determined the ratio of branching fractions: $R_{\gamma} \equiv \Gamma(\Upsilon(1S) \rightarrow \gamma gg)/\Gamma(\Upsilon(1S) \rightarrow ggg) = (2.75 \pm 0.04(stat.) \pm 0.15(syst.))%$. From this ratio, we have determined the QCD scale parameter $\Lambda_{\overline{MS}}$ (defined in the modified minimal subtraction scheme) to be $\Lambda_{\overline{MS}}= 233 \pm 11 \pm 59$ MeV, from which we determine a value for the strong coupling constant $\alpha_{s}(M_{\Upsilon(1S)}) = 0.163 \pm 0.002 \pm 0.014$, or $\alpha_{s}(M_{Z}) = 0.110 \pm 0.001 \pm 0.007$.

1 data table

The ALPHAS at MZ is extrapolation from M(UPSI).


Energy dependence of the differences between the quark and gluon jet fragmentation

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Z.Phys.C 70 (1996) 179-196, 1996.
Inspire Record 403254 DOI 10.17182/hepdata.48064

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 $$←pha_s(M_Z)=0.116pm 0.003 (stat.)pm 03009 (syst.).$$

2 data tables

No description provided.

Durham and JADE algoritms were used.


Direct photon production in anti-p p and p p interactions at s**(1/2) = 24.3-GeV

The UA6 collaboration Sozzi, G. ; Ballocchi, G. ; Bernasconi, A. ; et al.
Phys.Lett.B 317 (1993) 243-249, 1993.
Inspire Record 358422 DOI 10.17182/hepdata.28782

Inclusive direct photon invariant cross sections have been measured in both p p and pp collisions at √ s = 24.3 GeV at the CERN SPS, permitting the first measurement of the difference of the p p and pp cross sections. The direct photon cross section in p p collisions has been found to be systematically larger than that in pp collisions, which indicates a significant contribution of the q q annihilation term as predicted by theoretical calculations.

4 data tables

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Determination of alpha-s from the scaling violation in the fragmentation functions in e+ e- annihilation

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Phys.Lett.B 311 (1993) 408-424, 1993.
Inspire Record 355937 DOI 10.17182/hepdata.48411

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 .

2 data tables

No description provided.

Extraction of strong coupling constant ALP_S and the LAMQCD)MSBAR values.


Determination of alpha-s using the next-to-leading log approximation of QCD

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Z.Phys.C 59 (1993) 21-34, 1993.
Inspire Record 354909 DOI 10.17182/hepdata.50115

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

7 data tables

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.

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Determination of $alpha_{s}$ in second order {QCD} from hadronic $Z$ decays

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adami, F. ; et al.
Z.Phys.C 54 (1992) 55-74, 1992.
Inspire Record 333272 DOI 10.17182/hepdata.14603

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.

9 data tables

Experimental differential Thrust distributions.

Experimental differential Oblateness distributions.

Experimental differential C-parameter distributions.

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An Improved measurement of alpha-s (M (Z0)) using energy correlations with the OPAL detector at LEP

The OPAL collaboration Acton, P.D. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 276 (1992) 547-564, 1992.
Inspire Record 321657 DOI 10.17182/hepdata.29245

We report on an improved measurement of the value of the strong coupling constant σ s at the Z 0 peak, using the asymmetry of the energy-energy correlation function. The analysis, based on second-order perturbation theory and a data sample of about 145000 multihadronic Z 0 decays, yields α s ( M z 0 = 0.118±0.001(stat.)±0.003(exp.syst.) −0.004 +0.0009 (theor. syst.), where the theoretical systematic error accounts for uncertainties due to hadronization, the choice of the renormalization scale and unknown higher-order terms. We adjust the parameters of a second-order matrix element Monte Carlo followed by string hadronization to best describe the energy correlation and other hadronic Z 0 decay data. The α s result obtained from this second-order Monte Carlo is found to be unreliable if values of the renormalization scale smaller than about 0.15 E cm are used in the generator.

2 data tables

Value of LAMBDA(MSBAR) and ALPHA_S.. The first systematic error is experimental, the second is from theory.

The EEC and its asymmetry at the hadron level, unfolded for initial-state radiation and for detector acceptance and resolution. Errors include full statistical and systematic uncertainties.


Properties of multi - hadronic events with a final state photon at s**(1/2) = M (Z0)

The OPAL collaboration Acton, P.D. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 54 (1992) 193-210, 1992.
Inspire Record 322027 DOI 10.17182/hepdata.14650

The properties of final state photons in multihadronic decays of theZ0 and those of the recoiling hadronic system are discussed and compared with theoretical expectations. The yield of two and three jet events with final state photons is found to be in good agreement with the expectation from a matrix element calculation ofO(ααs. Uncertainties in the interpretation of the theoretical calculation do not yet permit a final assessment of events with just one reconstructed jet. Comparing the rates of two jet events with a photon to those of three jet events in the inclusive multihadronic sample, the strong coupling constant in second order is determined asαs\((M_{Z^0 } )\)=0.122±0.010, taking into account only the statistical and experimental systematic errors. It is found that an abelian model of the strong interaction does not describe the data. The comparison of the total yield and the jet rates with QCD shower programs shows better agreement with the ARIADNE model than with the JETSET model. Both programs are found to describe well the photon properties and the properties of the residual hadronic event.

4 data tables

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