We present here the analysis of low mass dimuon events (1.8 < M μμ < 2.6 GeV / c 2 ) produced by positive and negative pion and proton beams at 200 GeV / c . Using the difference between the π - and the π + cross sections, and comparing to the Drell-Yan model, we find a K -factor of 2.47 ± 0.5. Only about 1 2 of the events can be attributed to the Drell-Yan mechanism. If the remaining events are attributed to muonic decays of D mesons we findan upper limit for the cross section of charmed meson production.
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We have studied the reactions e + e − → e + e − , e + e − → γγ , e + e − → μ + μ − , and e + e − → τ + τ − in the centre-of-mass (CM) energy range from 39.8 to 45.2 GeV using the CELLO detector at PETRA. Upper limits on the partial widths for new spin 0 bosons with masses both within and above the energy range covered are determined. No evidence for contributions of such new particles has been observed up to the highest PETRA energies in a model independent way. Under the assumptions of recently suggested models relating the existence of spin 0 bosons to the radiative width Γ τ of the Z 0 we exclude such bosons at the 95% confidence level for masses below the Z 0 -mass if Γ τ > 20 MeV.
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Figure actually gives the 95 PCT CL upper limits of the coupling constants for each process as a function of the mass of the intermediate spin zero boson.
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.
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Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=DEL++,BACK=CORRECTED,DEF=1.08 < M(P PI+) < 1.8 GEV)//RES-DEF(RES=SIG(1385P13)+-,BACK=CORRECTED,DEF=1.26 < M(LAMDA PI+-) <2.0 GEV)//RES-DEF(RES=ASIG(1385P13)+-,BACK=CORRECTED,DEF=1.26 < M(ALAMDA PI+-) < 2.0< GEV)).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=DEL++,BACK=CORRECTED,DEF=1.08 < M(P PI+) < 1.8 GEV)//RES-DEF(RES=SIG(1385P13)+-,BACK=CORRECTED,DEF=1.26 < M(LAMDA PI+-) <2.0 GEV)//RES-DEF(RES=ASIG(1385P13)+-,BACK=CORRECTED,DEF=1.26 < M(ALAMDA PI+-) < 2.0< GEV)).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=DEL++,BACK=CORRECTED,DEF=1.08 < M(P PI+) < 1.8 GEV)//RES-DEF(RES=SIG(1385P13)+-,BACK=CORRECTED,DEF=1.26 < M(LAMDA PI+-) <2.0 GEV)//RES-DEF(RES=ASIG(1385P13)+-,BACK=CORRECTED,DEF=1.26 < M(ALAMDA PI+-) < 2.0< GEV)).
The reactionsK−p→π∓Σ(1385)± are studied at an incident laboratory momentum of 8.25 GeV/c using data from a high statistics (≃180 events/μb) bubble chamber experiment. In the case of the reactionK−p→π−Σ(1385)+ an amplitude analysis is performed and the complete Σ(1385)+ spin density matrix is extracted as a function oft′. The results are compared with the predictions of the additive quark model. In the case of the reactionK−p→π+Σ(1385)− the cross-sections for forward and backward production are determined.
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We have used the momentum spectrum of leptons produced in semileptonic B-meson decays to set a 90%-confidence-level upper limit on Γ(b→ulν)Γ(b→clν) of 4%. We also measure the semileptonic branching fractions of the B meson to be (12.0±0.7±0.5)% for electrons and (10.8±0.6±1.0)% for muons.
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We report the results of a study of ρ and ω production in π+p interactions at 15.7 GeV/c. The SLAC hybrid bubble-chamber facility was used to study reactions in which neutral particles are produced. Three tantalum plates inside the 40-in. bubble chamber and a large array of lead glass downstream of the chamber provided photon detection over a large solid angle. Final states with two neutral particles have been isolated with kinematic fits in which neutral pions were reconstructed in the plates and lead glass. Data from an earlier untriggered π+p bubble-chamber experiment at 15 GeV/c were used to obtain samples of events in channels which did not trigger the hybrid system. Cross sections for ρ and ω production are given for several exclusive final states. Relative ρ and ω production rates are studied. The ratio of nondiffractive ω to ρ0 production is measured to be ω/ρ0=0.44±0.07. We estimate the inclusive ω cross section to be 1.9±0.3 mb. The results are compared to the Lund model of low-pT hadronic reactions.
OMEGA cross sections have been corrected to allow for all decay modes.
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Inclusive and semi-inclusive cross sections and distributions of γ's and π0's inK+p interactions at 70 GeV/c are presented. The results are compared to other experiments and to the Lund model for low-pT hadron collisions.
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