The distribution of total tranverse energy ΣE T over the pseudorapidity interval −1 < η < 1 and an azimuthal range Δφ =300° has been measured in the UA2 experiment at the CERN p p collider ( s = 540 GeV ) using a highly segmented total absorption caloriter. In the events with very large ΣE T (ΣE T ⪆60 GeV ) most of the transverse energy is found to be contained in small angular regions as expected for high transverse momentum hadron jets. We discuss the properties of a sample of two-jet events with invariant two-jet masses up to 140 GeV c 2 and we measure the cross section for inclusive jet production in the range of jet transverse momenta between 15 and 60 GeV c .
No description provided.
HERE ET IS ACTUALLY THE ENERGY-DENSITY=ET/DELTA OMEGA.
No description provided.
The production and properties of high transverse momentum hadron jets have been measured in the UA2 experiment at the CERN\(\bar pp\) Collider\((\sqrt s= 540 GEV)\) using a highly segmented total absorption calorimeter. The characteristics of a sample of two-jet events with invariant mass up to 200 GeV/c2 are discussed, including measurements of their fragmentation properties, angular and rapidity distributions, and the properties of the additional energy clusters accompanying the two-jet system. Cross sections for inclusive jet production in the jet transverse momentum range between 30 and 100 GeV/c and for the two-jet invariant mass distribution in the mass range from 60–200 GeV/c2 are reported.
No description provided.
The production of very large transverse momentum hadron jets has been measured in the UA2 experiment at the CERN p p Collider for s = 540 GeV using a highly segmented calorimeter. The range of previously available cross sections for inclusive jet production is extended to p T = 150 GeV and the two-jet invariant mass distribution to m jj = 280 GeV with the largely increased data sample collected during the 1983 running period. The results are compared with the predictions of QCD models.
LISTED ERRORS INCLUDE STATISTICAL AND THE PT-DEPENDENT UNCERTAINTIES. THE ADDITIONAL OVERALL SYSTEMATIC UNCERTAINTY IS 45PCT.
LISTED ERRORS INCLUDE STATISTICAL AND THE M-DEPENDENT UNCERTAINTIES. THE ADDITIONAL OVERALL SYSTEMATIC UNCERTAINTY IS 45PCT.
Jet production properties at s = 540 GeV have been measured in the UA2 detector at the CERN p p Collider. Results on the total transverse momentum of the jet system, on the parton density in the nucleon (structure function) and on the two-jet angular distributions are reported. The data are compared with QCD predictions and extrapolations from lower energy experiments.
DISTRIBUTION OF THE SCATTERING ANGLE OF THE 2-JET AXIS IN THE 2-JET COM FRAME WITH A NORMALISATION FIXED AT 1 FOR COS(THETA*) = 0.
STRUCTURE FUNCTION IS DEFINED AS F(X) WHERE D3(SIG)/DX1/DX2/DCOS(THETA) = (F(X1)/X1)*(F(X2)/X2)*D(SIG)/DCOS(THETA).
The production of very large transverse momentum ( p T ) hadron jets has been measured in the UA2 experiment at the CERN p p Collider for s =630 GeV . The inclusive jet production cross sections exhibit a p T -dependent increase with respect to the s =546 GeV data from previous Collider runs. This increase can be described both by QCD calculations and by approximate x T =2 p T /√ s scaling. No significant deviation of the data from QCD predictions is observed at very large p T , placing a lower limit on the characteristic scale Λ c of a hypothetical superstrong contact interaction responsible for the binding of preons in the quark ( Λ c >370 GeV at 95% CL).
No description provided.
The UA2 experiment, running at the CERN SPS\(\bar pp\) Collider, has performed a study of events containing three hard jets in the final state. The angular distributions of the three jets show evidence for gluon bremsstrahlung, in good agreement with a QCD model to leading order in the strong coupling constant αs. The yield of three-jet events relative to that of two-jet events provides a measure of the strong coupling constant: ;3K3/K2=0.23±0.01±0.04, whereK2 andK3 represent the contributions arising from higher order corrections in α3 to the two- and three-jet exclusive cross-sections. A detailed discussion of the systematic and theoretical uncertainties is given.
No description provided.
A measurement of the direct production of photons with high transverse momentum from\(\bar pp\) collisions at\(\sqrt s= 630\) GeV is presented. The structure of events containing a high transverse momentum photon is studied. The results support predictions from QCD theory.
The last data point is an average over the interval 60-100 GeV in which 5 events are found.
No description provided.
No description provided.
An analysis of global event-shape variables has been carried out for the reaction e + e − →Z 0 →hadrons to measure the strong coupling constant α s . This study is based on 52 720 hadronic events obtained in 1989/90 with the ALEPH detector at the LEP collider at energies near the peak of the Z-resonance. In order to determine α s , second order QCD predictions modified by effects of perturbative higher orders and hadronization were fitted to the experimental distributions of event-shape variables. From a detailed analysis of the theoretical uncertainties we find that this approach is best justified for the differential two-jet rate, from which we obtain α s ( M Z 2 ) = 0.121 ± 0.002(stat.)±0.003(sys.)±0.007(theor.) using a renormalization scale ω = 1 2 M Z . The dependence of α s ( M Z 2 ) on ω is parameterized. For scales m b <ω< M Z the result varies by −0.012 +0.007 .
The second DSYS error is the theoretical error.
In four-jet events from e + e − →Z 0 →multihadrons one can separate the three principal contributions from the triple-gluon vertex, double gluon-bremsstrahlung and the secondary quark-antiquark production, using the shape of the two-dimensional angular distributions in the generalized Nachtmann-Reiter angle θ NR ∗ and the opening angle of the secondary jets. Thus one can identify directly the contribution from the triple-gluon vertex without comparison with a specific non-QCD model. Applying this new method to events taken with the DELPHI-detector we get for the ratio of the colour factor N c to the fermionic Casimir operator C F : N c C F = 2.55 ± 0.55 ( stat. ) ± 0.4 ( fragm. + models ) ± 0.2 ( error in bias ) in agreement with the value 2.25 expected in QCD from N c =3 and C F = 4 3 .
NC, CF, and TR are the color factors for SU(3) group.
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.
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