The reactions e + e − →γγγ and e + e − →γγγγ have been studied at center-of-mass energies between 35 and 46.8 GeV with an integrated luninosity of about 130 pb −1 accumulated with the CELLO detector at PETRA. The measurements are compared to QED calculations up to third and fourth orders of perturbation theory. Excellent agreement is observed.
No description provided.
The azimuthal dependence of the flow of hadronic energy about the momentum-transfer direction in charged-current deep-inelastic neutrino-nucleon scattering is used to study gluon emission and the transverse momentum 〈kT〉 of partons confined inside the nucleon. A 7-standard-deviation azimuthal asymmetry is observed indicating an average 〈kT〉=0.303±0.041 GeV/c.
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In the analysis of the reactione+e−→e+e−KS0Ks0 clear evidence for exclusive γγ→f2′ resonance production is observed. The productΓγγ ·B(f2′→K\(\bar K\)) is measured to be 0.10−0.03−0.02+0.04+0.03 keV independent of ana priori assumption on the helicity structure. Our data are consistent with a pure helicity 2 contribution and we derive an upper limit for the ratioΓγγ(0)/Γγγ. The absence of events in the mass region around 1.3 GeV clearly proves destructivef2−a2 interference and allows to measure the relative phases betweenf2,a2 andf2′. Upper limits on the production of the glueball candidate statesf2(1720) andX(2230) as well as theKS0KS0-continuum are given.
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We have measured the W transverse momentum distribution ( p T W ) using a sample of 323 W → eν and W → μν events produced in proton-antiproton collisions at the CERN collider. In the present letter we extend the study of the distribution up to p T W ∼- m W and compare to leading and higher order QCD. This comparison is a precise test of QCD with hadron colliders and the inclusive spectrum gives good agreement over a large range of p T W . However we observed two events at very large p T W (∼- 100 GeV/ c ) in which the W candidate recoils against an energetic di-jet system. Both events have a very large missing transverse energy and a jet-jet mass compatible with the W mass. In a separate analysis, a topologically similar event has been observed in which a high-mass di-jet system is balanced by a large missing transverse energy which could be interpreted as Z 0 → ν ν decay. We cannot easily explain these three events in terms of explicit second-order QCD calculations. However we cannot exclude at this stage the possibility that they are the result of non-gaussian fluctuations in the response of UA1 calorimetry or a statistical fluctuation in the data.
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The interaction of 800-GeV protons in nuclear emulsion has been investigated. The multiplicities and angular distributions of charged particles emitted by both the projectile and the target nucleus have been measured for 1718 inelastic events and are compared with the data obtained in proton-emulsion collisions at 67, 200, and 400 GeV. The target excitation is found to be independent of energy while the production of secondary particles continues to increase with incident proton energy.
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A comparison is made between the properties of the final state hadrons produced in 280 GeV μp interactions and ine+e− annihilation. The Lund model of hadroproduction is used as an aid in understanding the differences observed. The hadron distributions from μp ande+e− interactions are consistent with the quark parton model assumption of environmental independence, provided that the differences in heavy quark production and hard QCD effects in the two processes are taken into account. A comparison with aK+p experiment is also made. Values are also determined for the Lund model parameters σq = 0.410 ± 0.002 ± 0.020 GeV and σ′ = 0.29−0.15 −0.13+0.09+0.10 GeV, controlling the transverse momenta in fragmentation and intrinsic transverse momenta of the struck quark respectively.
With respect to the virtual photon axis.
With respect to the sphericity axis.
With respect to the thrust axis.
We compare the particle flow in the event plane of three-jet qq¯g (quark-antiquark-gluon) events with the particle flow in radiative annihilation events qq¯γ (quark-antiquark-photon) for similar kinematic configurations. In the angular region between quark and antiquark jet, we find a significant decrease in particle density for qq¯g as compared to qq¯γ. This effect is predicted in QCD as a result of destructive interference between soft-gluon radiation from quark, antiquark, and hard gluon.
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A sample of two-jet events from the UA1 experiment at the CERN $p \bar{p}$ Collider has been used to study the fragmentation of high-energy quark and gluon jets into charged hadrons. Compared with lower-energy jets observed in $e^+ e^−$ and $pp$ collisions, the fragmentation function measured in the present experiment is softer (i.e. peaked to smaller values of z) and the mean internal transverse momentum is larger, mainly because of the effects of the QCD scaling violations. Using our knowledge of the quark and gluon structure functions in the proton, together with the QCD matrix elements, a statistical separation of quark and gluon jets is achieved within the present experiment. The fragmentation function for the gluon jets is found to be softer, and the angular spread of the fragmentation products larger, than is the case for quark jets.
No description provided.
The multiplicities per event of π ± and K ± are measured separately for e + e - annihilation into c c , b b , and light quark pairs at E cm=29 GeV. The K ± multiplicity is higher for heavy quark events than for light quark events. The π ± multiplicity and the π ± scaled differential cross section at low x = E beam/ E beam are found to be higher for b b events than for other events.
Numerical values requested from authors. Data given separately for (b bbar), (c cbar) and light quark jets.
Measured multiplicities for (b bbar) jets.
Measured multiplicities for (c cbar) jets.
Using the ARGUS detector at the DORIS II e+e− storage ring at DESY, we have obtained evidence for a new charmed resonance which decays into D*±(2010)π∓. The observed mass and width are 2420±6 MeV/c2 and 70±21 MeV/c2, respectively. The fragmentation function is found to be hard, as expected for a state containing a leading charm quark produced by nonresonant e+e− annihilation.
No description provided.
Estimated production cross section obtained by comparison with observed D*(2010) production rate.
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