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NC, CF, and TF are the color factors for SU(N) group. For SU(3) they are equal to: NC = 3, CF = 4/3, and TF = 1/2.
From 2540 Z 0 → τ + τ − events, we determine the inclusive decay branching fractions of the τ -lepton into one and three charged particles to be 0.856 ± 0.006 (stat.) ± 0.003 (syst.) and 0.144 ± 0.006 (stat.) ± 0.003 (syst.), respectively. The leptonic branching fractions are measured to be 0.175 ± 0.008 (stat.) ± 0.005 (syst.) for τ → μν μ ντ and 0.177 ± 0.007 (stat.) ± 0.006 (syst.) for τ → eν e ν τ . We determined the τ lifetime both from three-prong decays using the decay length and from one-prong decays using the impact parameter. The results from the two independent methods agree and yield a combined value of [0.309 ± 0.023 (stat.) ± 0.030 (syst.)] × 10 −12 s.
ALPHAS extracted from the ratio of the branching fractions.
The ratio of the branching fractions for p p →K + K − and p p →π + π − was determined with the CPLEAR detector, by stopping antiprotons in a gaseous hydrogen target at 15 bar pressure. It was found to be BR(K + K − )/BR( π + π − )=0.205± 0.016. The fraction of P-wave annihilation at rest at this target density was deduced to be (38±9)%.
CONST is the fraction of P-wave annihilation in gaseous hydrogen at pressu re of 15 bar. In the SIG/SIG the statistical and systematic errors are added qu adratically.
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.
The study of the J ψ transverse momentum distribution in oxygen-uranium reactions at 200 GeV/nucleon shows that 〈 P T 〉 and 〈 P T 2 〉 increase with the transverse energy of the reaction. Muon pairs in the mass continuum do not exhibit the same behaviour. The comparison of the J ψ production rates in central and peripheral collisions shows a significant diminution for low P T central events.
Two parametrization of the D(SIG)/D(PT) are used: first is : PT*exp(-SLOPE*PT**CONST(C=PT)) and second is : PT*exp(-2*MT/CONST(C=MT)).
D(SIG)/D(PT) is parameterized as PT*exp(-SLOPE*PT**CONST).
D(SIG)/D(PT) is parameterized as PT*exp(-SLOPE*PT**CONST).
Calorimeter measurements of dσ de t for pp, dd, pα , and αα collisions at S nn =31.5 GeV are presented for the pseudorapidity interval | η cm | ⩽ 0.7, extending over eight decades to E t ⩾ 30 GeV. The data are compared with models that predict nuclear cross sections directly from pp data, under the assumption of independent nucleon scatters.
The distributions are fitted D(SIG)/D(ET)=CONST*ET**POWER*EXP(-SLOPE*ET).
Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentumpT. The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty≃0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. ThepT distributions depend weakly on the multiplicity.
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In an experiment performed at Fermilab we have studied the production of high p t hadron jets from 400 GeV/ c pp interactions. A large solid-angle, towered calorimeter was used to trigger and reconstruct the jet events. We report results for inclusive single-jet production and compare those results with QCD predictions and results obtained at the ISR and the SPS Collider.
The invariant distribution is fitted to CONST*(1/PT**POWER)*(1-XT)**POWER.
Inclusive cross sections are presented for 2π and 3π systems with large longitudinal x at the highest intersecting storage ring energies (s=53 GeV for 2π; s=53 and 62 GeV for 3π). The ratio π+π−π−π− rises sharply with increasing x similar to the ratio K+K−, as expected in a quark-model interpretation.
The differential cross section is fitted by the equation : E*D3(SIG)/D3(P) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
The differential cross section is fitted by the equation : E*D3(SIG)/D3(P) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
We present an analysis, in the framework of the triple Regge model, of our recent experimental results on the reaction p+p→p+X between 50 and 400 GeV.
The cross sections is fitted in the framework of the triple Regge model. The symbols P and R in the (C=...) denote pomeron and reggeon, respectively. For fit I and II the authors used conventional trajectories alpha(P) = 1 +0.25*T, alpha(R) = 0.5 + T. Fit II is restricted to data with (1 - M(P=4)**2/S) > 0.84. In fit III they use alpha(R) = 0.2 + T for the RRP term. Fit IV is like fit I with additional fixed (pion pion P) term.
The cross sections is fitted in the farmework of the triple Regge model. The symbols P and R in teh (C=...) denote pomeron and reggeon, respectively. CONST(C=C) and SLOPE are from the replacement of the RRP term by the exponential one : CONST(C=C)*(SLOPE*(1-x)). See text for detail.
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